For those that haven't read my intro, I just picked up a few K bikes.  I have no prior knowledge of these bikes, and am learning along the way.  As I start my process of getting the K100's up and running, I'm concentrating first on my Fairing bike.  I'm trying to diagnose a no start issue.  Here's what I have so far.

-Using a new Battery, so that's not the problem
-Pulled starter out to see it visually rotating, so that's not the problem
-Pulled out Spark Plugs to view Pistons, as well as the Crank Case Cover (CCC) to view crank.  Motor turns over by putting bike in gear and rotating rear wheel.  So motor is not froze up.
-Alternator Fins are turning when motor is being turned over by hand, nothing froze up there either.

So I'm coming back to thinking it's a Sprag Clutch issue.  After searching the interwebs and this website, I stumbled upon photos that 88 (member on these forums) posted up.  He describes being able to clean the Sprag, with access to the "3 holes" that you can see after taking the CCC off.  

After attempting this yesterday, I can still NOT find these holes, even with rotating the engine.  I reached out to 88 for some help, who contacted another member on these forums, with a 1984 RT.  That member could also not locate the holes as described.  

Not knowing a lot, I believe that the 1984 K100 may have the older "3 Roller Starter Clutch" setup.  Perhaps that setup does not have the 3 holes, like the Sprag Clutch setup.  This got me thinking:

1) Can anyone else with a 1985+ (Sprag Clutch) find these holes described?
2) Is it possible I have a 1985 Frame, with an older 1983-1984 Engine?

Any insight would be appreciated, as I'd love to get this solved and the bike fired up!

Here is a diagram of what I'm talking about:

You say you have a no start problem.  Please describe it more.  A no start problem can be interpreted many ways.

I am assuming the starter is running, but it isn't turning the engine.  

There is a technique for temporarily getting the sprag to work called the "Back Spin".  Roll the bike backwards in 5th with the clutch in and then pop it out.  This should jar the sprags so they will engage the starter. 

What I did was to dump an entire can of SeaFoam cleaner in the crankcase.  When the engine starts I ran it for about 50 miles and did an oil change.  You may want to just let the engine run in your garage  since you don't know how well it will run.  Three or four 15 minute sessions in the garage and then drain the oil and change the filter.  With any luck, it should start okay after the backspin, and the SeaFoam treatment will clean out the crap that is making the sprags stick.

I should have been more clear on the no start.

Yes, the starter motor is spinning, but the motor is not turning over. Haven’t even got to seeing about spark/fuel, just yet. Trying to resolve the motor not turning over with the starter first.

We haven’t tried the rolling backwards trick yet. I’m picturing you physically rolling the bike backwards, at a good speed and popping the clutch in 5th. Is that what you’re saying? I guess the only way to know if that works, is to then use the starter to see if I can get the motor to turn over?

Once we actually get it running, we’ll do some sort of sea foam cleaning, and changing to a full synthetic oil.

Anyone have any experience with NOT finding the holes in the Sprag Clutch?

Sent from Topic'it App

Yes, just roll it back a couple feet.  Best done as a two man job.

I am 'the other member' who went looking for those holes and couldn't find them. On the engine just below the oil filler cap is the engine number. The first 4 digits give the time of manufacture. Mine are 3284 which was week 32 of 1984. I couldn't find the holes one day when I went at it for the fun of it...bike parked on patio, lovely sunny day and no real urge for a taking bike out mostly because I had covered almost 1,000 miles during the week. So I decided to clean it and then decided to puil the crank case cover off.

I didn't investigate further but no matter what way I looked in I could see no holes despite excellent instruction from 88. I actually came to the conclusion the case castings differed and that was the reason I couldn't see any holes.

Still interested in following this up as the RT is about to get a new MAF and FPR.

92KK 84WW Olaf wrote: Mine are 3284 which was week 32 of 1984. I couldn't find the holes

The three holes you find on early -85 models and on.

Inge K. wrote:

92KK 84WW Olaf wrote: Mine are 3284 which was week 32 of 1984. I couldn't find the holes

The three holes you find on early -85 models and on.

................... well its back to the drawing board then

at least now I know I looked properly....

92KK 84WW Olaf wrote:I am 'the other member' who went looking for those holes and couldn't find them. On the engine just below the oil filler cap is the engine number. The first 4 digits give the time of manufacture. Mine are 3284 which was week 32 of 1984. I couldn't find the holes one day when I went at it for the fun of it . . .

My puritanical roots inhibit me from having that much fun.

Discerning those holes on an oily assembly within such a small space must be challenging. If they don't exist on your model then you're left with few options. One is to do a disassembly using these fine instructions. Another is to do this exciting procedure.

If I were trying to start a bike that had clean fuel and a working ignition, I'd try popping the clutch in fourth or fifth gear during a downhill roll; that is, if I had a way to get it uphill after a disappointment.

Consider trying to fabricate a variation of this helpful tool. It should work.

Went back to look today... no holes on the fairing bike.  Decided to pull the Crank case cover off the Frankenstein bike:




Right there in my face!

So, it seems that the Fairing bike does NOT have a Sprag Clutch.  Which lead me to check both the VIN on the frames.  I ran these on Realoem.com to find:

Fairing Bike: K100RT 84, USA, Production Date 08/1984
Frankenstein Bike: K100RT 84, USA, Production Date 11/1984

However, both titles I have in hand say that the bikes are 1985 Model year.  Could this be, especially with these build dates?  Does the Fairing bike build date make sense that it would have the older Roller Clutch, and NOT the Sprag Clutch like the Frankenstein?


Of course this is all assuming the motors have not been swapped out, of either bike, at any point.  I do not know how to read the numbers on the motors, so I posted them up here:

Fairing Bike:



Frankenstein Bike:




We also tried the Roll Back trick, to shock the Roller/Sprag clutch..... no go on that.

Any advice is appreciated.  If in fact I have to take apart the Fairing bike to gain access to the Roller Clutch, should we do the frame off approach, or the one listed above?  Should we fix the Roller Clutch, or replace it with a full Sprag clutch setup?

3384 is 1984 model year. Fairing bike

4984 is 1985 model year. Frankenstein bike

As a matter of interest mine is 3284 and does not have the holes.

IngeK will correct me if I am wrong and I will have to buy him a beer.

Forgive me for questioning this, but the sprag clutch is accessed behind the intermediate housing and nowhere near the crank case cover. Removing the CCC to access the sprag clutch does not make any sense, but I've been wrong before, and on more than one occasion too. The image in post #10 appears to be the output shaft which runs off the crankshaft, and not the sprag gear. Power is not driven directly off the end of the crankshaft, but via the output shaft. BTW the "box-o-rocks" rattle associated more with later K1200 motors is caused by shims wearing on the output shaft and can be remedied by measuring and replacing the shims. 
Does the bike run when it is bump started? My K100RS is an '87 with a sprag that would stick from time to time. Even after removing it and giving it a good clean, after a short run I had to bump start it to get going as the starter motor would spin but not engage. At a recommendation I read here somewhere, I changed to diesel oil and have never had a problem since. Fully synthetic oil is not very compatible with O-rings in these old motors, and really is just a waste of money, but I'm NOT starting an oil thread...

The big toothed cog is on end of crankshaf to drive the counter rotating output shaft ?, but up high buried behind it is the sprag clutch and it takes time to adjust eyesight to the light to find it but it is visible there.

I spent an hour looking for non existent holes and was happy there was an issue on mine which was clarified by IngeK who confirmed my early K doesn't have the 3 holes.

92KK 84WW Olaf wrote:3384 is 1984 model year. Fairing bike

4984 is 1985 model year. Frankenstein bike

As a matter of interest mine is 3284 and does not have the holes.

IngeK will correct me if I am wrong and I will have to buy him a beer.

Thanks for the info here. So I’m assuming if the Fairing bike then indeed has the Roller Clutch assembly.

To repeat. the rollback technique of shocking the clutch did not work. With that being said, the only other trick we haven’t tried is actually bump starting the bike while pushing it forward. It’s been raining here, and not really an ideal time to try this however. It’s looking like we are going to have to pull apart the bike, to gain access to that roller clutch.

I’m wondering if it makes sense to clean that clutch off and reuse versus finding a used Auxiliary Shaft with all components (including newer designed Sprag Clutch) and replacing the roller clutch? Are the housings the same, that it would accept the newer style clutch?

Sent from Topic'it App

fox1486 wrote:Thanks for the info here. So I’m assuming if the Fairing bike then indeed has the Roller Clutch assembly.

The sprag clutch was in use from January -84....the mod with the three holes
should been from early -85....which now seems that this can be corrected to
very late -84.

Inge K. wrote:Thanks for the info here. So I’m assuming if the Fairing bike then indeed has the Roller Clutch assembly.

The sprag clutch was in use from January -84....the mod with the three holes
should been from early -85....which now seems that this can be corrected to
very late -84.

Well again, two separate things here. According to the titles for both bikes, they are both 1985 models. But the production dates for both the frames and engines are 1984.

So I either the titles are incorrect, or the bikes are truely 85 models made in 84. Either way, the separate numbers on the engines for production dates tell a story that in week 33 of 84, they were still using the older roller clutch setup.

Sent from Topic'it App

I’m not finding a lot of info on the Roller Clutch. I’m searching the forums and google, but not finding or people are replacing these with Sprags (or if that is even possible).

If anyone can point me in that direction, it would be appreciated. Or any opinions on what they would do for a next step, besides pulling everything apart and replacing the roller for a Sprag.

Sent from Topic'it App

Model year and registration year are not the same as manufacturers must build up sales stock. September is usually the changeover.

I have memories of buying a car many years back that was a facelift updated model. One of the major updates was suspension change due to issues with the prefacelift model. After 3 months the suspension was failing and when it went back to main dealer they discovered it was assembled with the old suspension components. They changed the lot. Clearly the old stock was being used up. So an 85 model could have been assembled/manufactured anytime after September 1984......but there is often no guarantee as specific components being the old or new ones and you only discover when you take it apart.

Ok, I am correcting myself. Again... Clearly, if I had looked at it like they do in the northern hemisphere I would have picked it up, but I was looking at it upside down as we do down here, and yes, that is the sprag in post #10. Simply put, I should have gone into the shed and had a look at the bike and realised my folly. 

fox1486 wrote:I’m not finding a lot of info on the Roller Clutch. I'm searching the forums and google,  but not finding or people are replacing these with Sprags (or if that is even possible).

If anyone can point me in that direction, it would be appreciated. Or any opinions on what they would do for a next step, besides pulling everything apart and replacing the roller for a Sprag.

It is unsure whether you even have the roller clutch. The clutch might be the sprag clutch without holes in its housing. Regardless, substitution is an appropriate question for a BMW dealer like MAX in New Hampshire, USA if you can't get affirmation here. They continue to do occasional restorations of vintage BMWs so they probably have depth of experience to answer your question.

If it were my bike I'd be making fevered attempts to bump start using any means including a modified paddock roller device as shown in post #9. If it started and ran I'd be able to try the engine flush technique to liberate the components. If you can't start it, you're bound to disassemble enough to get to the offending clutch and size things up then.

At least with a K100 3 roller sprag it can be replaced with a later type that is somewhat more reliable. I have the Kawasaki Z1300 with a 3 roller sprag on the starter and that's it the end they are not to be replaced and every 20,000km they need replacing oh what joy.
It makes me realize just how much better the BMWs are in that at least upgrades are made.

RicK G wrote:At least with a K100 3 roller sprag it can be replaced with a later type that is somewhat more reliable. I have the Kawasaki Z1300 with a 3 roller sprag on the starter and that's it the end they are not to be replaced and every 20,000km they need replacing oh what joy.
It makes me realize just how much better the BMWs are in that at least upgrades are made.

And that’s the answer that I’m looking for, if they can be replaced with Sprag Type.

Sent from Topic'it App

Laitch wrote:I’m not finding a lot of info on the Roller Clutch. I'm searching the forums and google,  but not finding or people are replacing these with Sprags (or if that is even possible).

If anyone can point me in that direction, it would be appreciated. Or any opinions on what they would do for a next step, besides pulling everything apart and replacing the roller for a Sprag.
It is unsure whether you even have the roller clutch. The clutch might be the sprag clutch without holes in its housing. Regardless, substitution is an appropriate question for a BMW dealer like MAX in New Hampshire, USA if you can't get affirmation here. They continue to do occasional restorations of vintage BMWs so they probably have depth of experience to answer your question.

If it were my bike I'd be making fevered attempts to bump start using any means including a modified paddock roller device as shown in post #9. If it started and ran I'd be able to try the engine flush technique to liberate the components. If you can't start it, you're bound to disassemble enough to get to the offending clutch and size things up then.

Did they make a Sprag with no holes in the housing. I would find that a little surprising, since my other motor made in 84 has holes. I think it’s a good chance it is a Roller Clutch.

The way I look at it, I still have to take apart the driveshaft to lube the splines. I’ve never been through this bike. So while I’m there, I suppose I might as well continue on with the transmission and intermediate housing. Clean/replace the roller with a Sprag. Maybe replace the rear seal while I’m there.

Sent from Topic'it App

They can be replaced with the multi sprag type but how much or which components need to be replaced I dont know.

fox1486 wrote:

Did they make a Sprag with no holes in the housing. I would find that a little surprising,

Here you go, two sprag clutches w/o the three holes.

https://www.ebay.co.uk/itm/BMW-K100RT-SPRAG-CLUTCH-1984-84-/232686512369

https://www.ebay.com/itm/85-BMW-K100-K100RS-K-100-RS-STARTER-CLUTCH-GEAR-ASSEMBLY-/401362880664

Inge K. wrote:

fox1486 wrote:

Did they make a Sprag with no holes in the housing. I would find that a little surprising,

Here you go, two sprag clutches w/o the three holes.

https://www.ebay.co.uk/itm/BMW-K100RT-SPRAG-CLUTCH-1984-84-/232686512369

https://www.ebay.com/itm/85-BMW-K100-K100RS-K-100-RS-STARTER-CLUTCH-GEAR-ASSEMBLY-/401362880664

Interesting. I assumed the first one was a roller clutch based on the fact it is out of a 1984. But the six bolts around the clutch look identical to the diagram of the Sprag Clutch above. So perhaps they did make a Sprag with no holes. Hmmmm.

Well I took the advice others have left in this post.  I told myself, before tearing it all down to get to the Hole-Less Sprag, let's see if she'll pop start forwards.  It just so happened to be 54 degrees out today, with lots of sunshine. So I put back in the oil, spark plugs, spark plug wires, and the battery.  Took two of us to push the beast to the road.  Sprayed in some Starter Fluid into the intake, and started to run.  First couple attempts were a no go.  But then suddenly..... a sputter.  On the next attempt she started to cough.  Until the third attempt where she fired up! WOOOHOO!!!  

Pulled it back in the barn, and let it run for about 20 minutes.  Decided to run to the auto parts store, grabbed a gallon of Shell Rotella T6 Full Syn 5W-40 Diesel Oil.  Ran back, changed the oil, and let the bike run on and off for about an hour.  She purrs like a kitten (which is great news, since it was a gamble that the bike ran at all).  After that, starter seems to work!  Hopefully that resolved the issue.

Next issue seems to be a battery or alternator issue.  Noticed that when I go to restart the bike, doesn't have enough juice.  I'll be tackling that next.

Clean all the ground connections, Battery, transmission, and under the tank.  Get the spot where they connect and all the lugs nice and shiny. 

You might also want to pull the starter motor and give the brushes and commutator a cleaning.

This is what I did last spring:


I had problems with sprag clutch after winter. Sometimes didn't start and had to make a downhill start. I put ATF transmission oil and Delvac 50/50 in and let the engine warm up about 15min. RPM was like 3500-4000. I did many starts after that with pulling the bike back/forward gear in. Then new Delvac diesel oil 15W40 + filter.
After that prosedure no problems with a sprag clutch. I put also one bottle of Rislone and drove abot 1K with it. 

Today I started my bike first time after 8 months without any problems! I'm using Delvac diesel oil an it has something what keeps sprag clutch clean. I have been told!

I haven't used the Diesel oil but others here have and have had no problems. The modern synthetic oils will keep it clean and give better lubrication and longer oil life.

Lots of riders(many makes and models) in the US use Shell Rotella T6 synth.  It's made for diesel engines but I've used it a bunch in my Ks and it works fine.

I have a total of 50,000 miles running three bricks on Shell T6 Rotella 15W40.  No sprag issues at all.  I figure if a heavy duty diesel engine can run a million miles on the stuff it shouldn't hurt my brick engine.

Hi! If I understood well people experience spinning starter motor with no engine turn, when sprag clutch is blocked. Meanwhile I have a good starter motor (spins with 12 Volts when not inserted), good battery, free engine (turns by hand through rear wheel in 5th gear), apparently good sprag clutch (spins free in one direction and turns engine in the other, even if only making a big effort with a screwdriver on ignition wheel through the starter motor whole.)    But: starter motor doesn't even turn when in place (tried even other, used starter motors) and I couldn't start bike by spinning it as not enough friction even in 5th gear (slips in any gear). I am about to open it to see that clutch sprag demon.....hoping that it is the right thing.  Any ideas to help me?  Thanks     Greg

Gergely wrote:But: starter motor doesn't even turn when in place (tried even other, used starter motors) . . . 

The starter will not turn the crankshaft when the starter button is pressed while the clutch hand lever is pulled in?

"starter doesn't turn when in place"

I'd use a test light to check for power at the starter motor wire with the start button pressed.

Gergely wrote:Hi! If I understood well people experience spinning starter motor with no engine turn, when sprag clutch is blocked. Meanwhile I have a good starter motor (spins with 12 Volts when not inserted), good battery, free engine (turns by hand through rear wheel in 5th gear), apparently good sprag clutch (spins free in one direction and turns engine in the other, even if only making a big effort with a screwdriver on ignition wheel through the starter motor whole.)    But: starter motor doesn't even turn when in place (tried even other, used starter motors) and I couldn't start bike by spinning it as not enough friction even in 5th gear (slips in any gear). I am about to open it to see that clutch sprag demon.....hoping that it is the right thing.  Any ideas to help me?  Thanks     Greg

Sounds like the classic case of 'assembled the starter wrong way round'. Also remember starter has a single live connection, the earth is through the starter body to engine so if you have electrical isolation there, no start. If starter not turning at all then issue is not the sprag clutch, the starter is not getting power or is inhibited.

Laitch wrote:

Gergely wrote:But: starter motor doesn't even turn when in place (tried even other, used starter motors) . . . 

The starter will not turn the crankshaft when the starter button is pressed while the clutch hand lever is pulled in?

Starter does not turn at all, even with clutch pulled and direct 12V from a supercharged battery.

92KK 84WW Olaf wrote:

Gergely wrote:Hi! If I understood well people experience spinning starter motor with no engine turn, when sprag clutch is blocked. Meanwhile I have a good starter motor (spins with 12 Volts when not inserted), good battery, free engine (turns by hand through rear wheel in 5th gear), apparently good sprag clutch (spins free in one direction and turns engine in the other, even if only making a big effort with a screwdriver on ignition wheel through the starter motor whole.)    But: starter motor doesn't even turn when in place (tried even other, used starter motors) and I couldn't start bike by spinning it as not enough friction even in 5th gear (slips in any gear). I am about to open it to see that clutch sprag demon.....hoping that it is the right thing.  Any ideas to help me?  Thanks     Greg

Sounds like the classic case of 'assembled the starter wrong way round'. Also remember starter has a single live connection, the earth is through the starter body to engine so if you have electrical isolation there, no start. If starter not turning at all then issue is not the sprag clutch, the starter is not getting power or is inhibited.

Nothing has been serviced (dimantled and reassembled) before this issue showed up. Dismounted starter spins free when earthed to the bike frame (at any other point, not in place). When in place does not turn even with direct 12 V from a car battery. Starter makes some turn ONLY when powered and start spin is given manualy in 5th gear through rear wheel (with spark plugs removed).

Could be a case of replace starter. There may be a hidden issue, but it can do that if the brushes are bad or there is a defect in the commutator. If you have not yet opened it, mark it clearly before opening so it goes back the right way [its easy to reverse it] and have a look at the brushes. [maybe not, I see you tried different starters]. They are a service item and a replacement kit is cheap.

Second, don't dismiss a break in the cable from the relay to the starter. If you are powering it from this cable and earthing elsewhere and its working this is a high probability. If you are using a completely separate 12v supply then suspect the starter relay or the live route from the battery to the relay to the starter.  

Are you using the start button for the test using the different earth? These are also a possible fail.

If you have a meter, have a look for voltage drop if you press the start button at the times nothing happens. No voltage drop highly likely faulty start button, some voltage drop possibly a fault at the relay itself, big drop says relay is getting power but its hitting a problem after the relay.

Apart from the possible break in the feed to the starter one has to look at the earthing of the starter, possible incorrect electrical connection.

One thing, is your negative earth to the gearbox lug in place and good to go?

92KK 84WW Olaf wrote:Could be a case of replace starter. There may be a hidden issue, but it can do that if the brushes are bad or there is a defect in the commutator. If you have not yet opened it, mark it clearly before opening so it goes back the right way [its easy to reverse it] and have a look at the brushes. [maybe not, I see you tried different starters]. They are a service item and a replacement kit is cheap.

Second, don't dismiss a break in the cable from the relay to the starter. If you are powering it from this cable and earthing elsewhere and its working this is a high probability. If you are using a completely separate 12v supply then suspect the starter relay or the live route from the battery to the relay to the starter.  

Are you using the start button for the test using the different earth? These are also a possible fail.

If you have a meter, have a look for voltage drop if you press the start button at the times nothing happens. No voltage drop highly likely faulty start button, some voltage drop possibly a fault at the relay itself, big drop says relay is getting power but its hitting a problem after the relay.

Apart from the possible break in the feed to the starter one has to look at the earthing of the starter, possible incorrect electrical connection.

One thing, is your negative earth to the gearbox lug in place and good to go?

Original starter has been service by myself with full repair kit 2years ago. It works well as other 2 starters tried when not installed.     I tried 3 installed starters with external well charged battery sources and independent direct wire feed (so 12,5 V guaranteed) and no turn.      Helping by hand on rear wheel to rotate engine, starters may do some turns.    That is why or starters (all?) are weak or engine has a bigger friction than normal. Friction on sprag clutch maybe (even if spins free on the left and engage on the right) or in any other component (spark plugs, generator and oil/water pumps already removed).

Is the independent wire feed from the bike battery?

If its not then battery is possible suspect.

If it is, then you have to be losing live current between the battery and the the starter or simply not getting good earth. You have proved that's possible, but also have not proved its caused by a wire break [or other issue in the live feed eg relay fault] or by not getting signal. 

Is your Load Shed Relay [LSR] good?

Is the starter relay getting its signal from the start button? Getting the starter to do its thing using a direct feed simply says the starter itself is good. The signal from button to relay also needs input from temperature sensor [to avoid inhibit due to thinking engine is overheated].

Some Ks [mine included] have a separate live feed from the battery to the starter relay. Is it possible this feed is not connected? If you get a short jumper and put male pins on it and install it in place of the starter relay and in the correct pins you should get the starter to turn over. If it does, you have isolated the fault as not being in the battery to starter live cable. 

The brake, clutch and choke switch are all the same on early Ks. Its possible to mix up those connections under the tank, if so then pulling clutch has no effect. You can check if pulling clutch activates choke or brake light....problem.

92KK 84WW Olaf wrote:Is the independent wire feed from the bike battery?

If its not then battery is possible suspect.

If it is, then you have to be losing live current between the battery and the the starter or simply not getting good earth. You have proved that's possible, but also have not proved its caused by a wire break [or other issue in the live feed eg relay fault] or by not getting signal. 

Is your Load Shed Relay [LSR] good?

Is the starter relay getting its signal from the start button? Getting the starter to do its thing using a direct feed simply says the starter itself is good. The signal from button to relay also needs input from temperature sensor [to avoid inhibit due to thinking engine is overheated].

Some Ks [mine included] have a separate live feed from the battery to the starter relay. Is it possible this feed is not connected? If you get a short jumper and put male pins on it and install it in place of the starter relay and in the correct pins you should get the starter to turn over. If it does, you have isolated the fault as not being in the battery to starter live cable. 

The brake, clutch and choke switch are all the same on early Ks. Its possible to mix up those connections under the tank, if so then pulling clutch has no effect. You can check if pulling clutch activates choke or brake light....problem.

I think all possible electrical problems are by passed by using direct wire from my van's battery (80Ah or similar), with van engine in operation.       If battery negative is attached with wire to bike frame and starter motor grounded to bike (touch any metallic surface of the bike), starter motor spins fast connecting positive from van battery.      When starter motor installed, does not move with the same direct 12 V.       Helping in 5th gear to start turning the engine by hand through rear wheel, some turns can be made by starter motor then. But not to do initial starting movement.

80Amp battery is a lot more cranking Amps. But the bike battery also turns starter over no problem if its not installed? 

You have same issue even after changing the starter?

Load test on bike battery? Has it been load tested? It needs a meter on it to see if you are getting a massive voltage drop.

As I read it Olaf, the starter motor doesn't turn the engine over even when using his van battery, so at this stage the bike battery, which may well be poor, is not in circuit.

Not too sure I understand the relevance of trying to turn the rear wheel with his foot which allows the starter to turn a few times, so is actually trying to start the bike whilst in gear.

Mike

mike d wrote:As I read it Olaf, the starter motor doesn't turn the engine over even when using his van battery, so at this stage the bike battery, which may well be poor, is not in circuit.

Not too sure I understand the relevance of trying to turn the rear wheel with his foot which allows the starter to turn a few times, so is actually trying to start the bike whilst in gear.

Mike

Yes, actually I exclude battery problems (tried with bike's, with a spare and the van's battery full charged.)  Wire and circuit problems bypassed by direct wiring.    Sparks, oil\water pump removed for minor friction. Bike is in neutral.   No starter motor turn (tried 3). All spins when outside.     "helping" starter motor by turning engine in gear by the wheel was only a trial.  In that case starter makes some turns.

Dumb question, but that's my problem.

Are you absolutely sure the transmission is actually in neutral when you are trying to start?

I could see a situation where a clutch that is having drag issues even when pulled in and a transmission in 1st or 2nd could put enough load on the starter to prevent it from turning.

Does the rear wheel spin easily when the transmission is in neutral and the clutch is out???

Point-Seven-five wrote:Dumb question, but that's my problem.  

Are you absolutely sure the transmission is actually in neutral when you are trying to start?  

I could see a situation where a clutch that is having drag issues even when pulled in and a transmission in 1st or 2nd could put enough load on the starter to prevent it from turning.

Does the rear wheel spin easily when the transmission is in neutral and the clutch is out???

I have not experienced clutch issues. In neutral rear wheel is detached from engine (rotates free).   In 4 and 5 gear turn engine through rear wheel by hand is not easy but with reasonable force is possible.

I am still thinking on this.......starter not bolted in, turns ok either on bike or van battery as in by passing the bike systems.

Starter bolted in......does not turn ok on bike battery or on van battery.

I can see only 2 possibly issues here.

Starter is in trouble, bolting it in it can no longer turn freely...
bent shaft? [ruled out by using other spares?]
defective and unable to take the full load? [ruled out by using other spares?]

Is the starter getting current ]seems to be yes] and is it earthing properly [it earths through the body to gearbox mating surface and bolts], earthing issue is going to be common to the spares also installed? Using van battery, is the earth from this van battery connected to the frame or gear box lug?

Is the sprag clutch in trouble? Not unheard of.

Is the starter being installed correctly? Not unheard of.

Is there an old O ring stuck inside? 


Is bike in neutral trying to start it?

92KK 84WW Olaf wrote:I am still thinking on this.......starter not bolted in, turns ok either on bike or van battery as in by passing the bike systems.

Starter bolted in......does not turn ok on bike battery or on van battery.

I can see only 2 possibly issues here.

Starter is in trouble, bolting it in it can no longer turn freely...
bent shaft? [ruled out by using other spares?]
defective and unable to take the full load? [ruled out by using other spares?]

Is the starter getting current ]seems to be yes] and is it earthing properly [it earths through the body to gearbox mating surface and bolts], earthing issue is going to be common to the spares also installed? Using van battery, is the earth from this van battery connected to the frame or gear box lug?

Is the sprag clutch in trouble? Not unheard of.

Is the starter being installed correctly? Not unheard of.

Is there an old O ring stuck inside? 


Is bike in neutral trying to start it?

Tied 3 (used but working) starters - same result. Installed correctly (hard to make mistake) and no other objects observed inside (like old O-rings or similar - are all perfect on starter motors)
Earth of external battery is correctly on bike frame (when hitting positive wire on starter motor positive connection, electric spark is visible.    
Sure bike is in neutral, even spark plugs and water/oil pump removed at the end for minor friction.  

Sprag clutch is still a question, even if seems (from outside) doing it's work (left free - right turns engine).  Any other component that is working but with major friction than normal inside engine. ..(?)      

Reassuming; engine turns when 4-5 gear inserted by rear wheel and even by a screwdriver (needs a lot of power) inserted in sprag clutch cogwheel, but not with starter motors.  


PS: I had bike from only 18.000 kms (now has 60.000) and I know all maintenance history. No previous issues on internal components (engine-transmission)

Are you using jumper leads with your car battery?

Are you confident they're good?