Starter Issues: Starter Motor or Sprag Clutch

I am having issues with the starter on my ‘82 XJ750. The starter motor seems to be turning but only catches the flywheel randomly. I shared a link to a YouTube video to hear the sound the starter is currently making. I brought the bike to a shop for a general inspection and the shop owner told me my sprag clutch was worn and needed replacement which means dropping the engine and breaking the case. I originally was thinking I just needed to rebuild the starter motor so I had ordered the rebuild kit from @chacal and was planning to do that fix. I will post a video shortly to hear the sound made. If it ends up being the sprag clutch is that fixable with basic tools? The shop owner quoted me $2700 for that fix so I didn’t think it’d be worth it to keep the bike if that’s the case.

link to video (won’t let me embed the video here): https://youtube.com/shorts/zqXUhucMSTI?feature=share

 

If it is the starter clutch you can do the work yourself, plenty of help on here. You will need a socket set, torque wrenches, spanners, torx bits for the middle gear drive bolts and the three alternator rotor bearing support bolts, rotor pulling tool available from Len on info@xj4ever and a workshop manual. Remove the gear change side crankcase cover which has four bolts and press the starter button. If the starter clutch has gone the rotor on the crank won't turn.

 

Thanks @Franz. Just to clarify, is the starter clutch = the sprag clutch? And does that not require dropping the engine out of the frame on my bike?

 

Yes sprag clutch, also called ramp clutch or starter clutch. I heard your video and I am sure the starter clutch rollers are not gripping the alternator shaft. It works as follows, although in the animation it is on the end of the crankshaft, our bikes have the starter clutch on the alternator shaft and a chain turns the crank for starting and the same chain drives the alternator rotor from the crankshaft once the engine starts. Yes you need to remove the engine and split the cases to renew the starter clutch.

 

I would suggest that before you go tearing into the crankcase that you should be confident that it is worn out springs and rollers and not something that can be dealt with without splitting the cases.

First, there have been reports of modern automotive oils with modern friction modifiers causing starter clutch to not engage - makes sense when you think about it since it depends upon a certain amount of grip (= friction). Make sure you are using an appropriate engine oil, the topic is so important that it is pinned to the top of this forum:
https://www.xjbikes.com/forums/threads/choosing-the-correct-oil-for-a-wet-clutch-motorcycle.43702/

I'm a Rotella T4 guy myself, but that's just me.

Next, as @chacal explains on xj4ever.com, there is a chance that the springs and rollers are just full of schmultz, and could possibly be cleaned and made functional again by cleaning with some solvents:
http://xj4ever.com/catalog/e-8-starterclutch.html

If you are sure you have appropriate oil and are sure that the insides of the engine are spic and span, then it may be time to crack the case and replace parts. Of course that also opens a Pandora's box of "what else should I replace as long as I'm in there?"

 

True could be gunked up well worth checking first.

 

Thanks both for your detailed replies. One thing I forgot to mention is that the bike starts up pretty easily if it is warm. On cold starts, I have to bump start it but after it’s warmed up I can hit the starter and have it fire up quickly. Additionally, the starter won’t turn at all after trying for a few seconds. Does this point me in the direction of this potentially being a starter motor issue as well?

 

@Jetfixer had the same problem with his bike, he had to replace the starter clutch. Check the starter motor first. Then what Dan advised above before stripping the motor.

 

https://xjbikes.com/forums/threads/replacing-your-starter-motor-brushes-w-pics.45727/

 

Thank you all for the advice. I’ll keep this thread updated after rebuilding the starter motor.

 

That is certainly not normal and could be either the starter itself, the battery, or poor connections. Be sure to clean all the high current connections on the battery and engine case. A slow turning starter can contribute to the starter clutch not engaging.

So rebuild starter to ensure it is OK, there is a good guide here:

https://www.xjbikes.com/forums/threads/replacing-your-starter-motor-brushes-w-pics.45727/

Do a battery load test - meter on battery and record voltage when starter is engaged. It should be above 10 volts

Share what oil you are using

When slipping try jumping across the solenoid two large wires to be sure the solenoid relay is not creating a low voltage condition to the starter and causing it to turn slowly.

 

I’m using Valvoline 20W50 Motorcycle Oil. I just got my starter rebuild kit in the mail and will be doing that rebuild in the next few days. I will update if that makes any difference with my issue.

 

You can remove the engine in a couple of hours , a floor jack , a milk crate and a long pry bar . You will need a 10 mm 12mm, 14mm, 17mm socket and wrench ...yes both . Pull exhaust system , remove the rear brake lever ( 10mm bolt) you have to remove the foot pegs 17mm bolts , and 14mm bolts , the front two 12mm bolts and two 14mm , is it is a 650/750 , remove the spring clamp from the drive shaft rubber boot . Carefully push it out with a long screwdriver, remove the four drive shaft 12mm bolts . Remove the carbs and disconnect the wiring all plugs pull ground cable out around frame . Disconnect the starter cable and engine should be ready to remove. Pictures are of the starter clutch , and of engine split . I have now done two engines granted I am an aircraft mechanic, and have multiple...make that a shitload of tools . I tried to show in my thread Dreaded Starter Clutch how I did it. A wooden pallet works great to do the engine this keeps from marring the case . The orginal engine starter clutch would slip when hot, bought another engine off a friend, got two years out of it , till recently when it went out period . I fixed orginal engine ...but it has low compression, so fixed spare engine and now it starts right up with no slipping. Take your time several large freezer bags and a sharpie keep parts separated, a cardboard box draw out pattern mark where all the bolts are located . . I bought a starter clutch repair kit off of eBay came with new springs ,cups, rollers . You will need a tube of Yamabond , probably going to need a new oil pan gasket, clutch cover gasket, left side cover gasket , xj4ever has all of these items . Your only looking at less than 200$ in parts as long as you don't have to replace the chain guide ( I gambled as mine looked good on both engines) and your time . I to tried rebuilding the starter , even put my spare starter in , I use Shell Rotella 15/40 diesel oil , for giggles tried Castrol 20/50 motorcycle oil...no help . Good luck .

 

Thanks for the walkthrough @Jetfixer! That makes me feel more comfortable about possibly having to drop the engine myself. The bike is currently in the shop getting new fork seals and front brakes. When I get it back I will attempt to tackle the starter issue first starting with the starter rebuild kit I got from @chacal. If that doesn’t fix my issue I will try out the solvents approach. I’m thinking this could be the issue as the bike starts easily once warm, just struggles and spins when cold.

 

After 30 plus years the springs loose their tension and on one of my engines one roller was galled . There is one item I forgot to mention , pulling the engine , drain the oil and leave the oil filter housing off . One thing you might try is a can of Restore for four cylinders , it is supposed help high mileage engines . Several You be tubie videos on it .

 

easy stuff first rebuild that starter
if it is your starter clutch you could consider a used motor then think about changing the sarter clutch
when your in there you may want to replace the chain guides check the chainfor wear

 

Worth noting, Jetfixer (and I) had the opposite (ish) problem as you. Cold start just fine, hot start no good.

On a cold start your oil is all drained to the sump, not on the rollers in the clutch where it can cause them to slip. The springs are cold, stiff, not hot and pliable. Cold is the ideal situation for your sprag clutch to start. The fact that you have bad cold starts and good hot starts makes me think that you should look elsewhere for your issue.

Not saying it's not your starter clutch, but I'm going through the teardown process now and it is quite a lot of work (though still doable, and admittedly my teardown turned into a full engine refresh, so a bit more involved). I would exhaust other causes first.

How many miles on your engine? And how did the problem start? Did it slowly start occurring? Did it begin after the bike sat for a while? How old is the battery? What's the sitting, cranking, and running voltage on the battery? If this were me I'd be looking at the battery and for indication of inappropriate grounding.