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broken starter chain 91 cb750

white water rafter

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I can't see the starter chain. It is probably broken and is in the bottom of the crank case. will I have to split the case to fix it? white water rafter 6/3/2016 9:07 am
 
My sincere apologies amc49, I mistook your reply for the reply to my previous post.

Do you bother to even read replies to your posts???

http://www.cb750.com/threads/3758-Looking-for-Advice-on-Removing-Alternator-(1991)

Wake up, the answer is still the same....................

I have been under the illusion that there is a starter drive chain because the Honda parts guy called it that. My Clymer manual and the Honda service guy refer to it as the alternator drive chain. (It doubles as a starter drive chain). So I have tried to daignose the starter clutch. In fact, it does turn only in one direction, most of the time. I was only able to get it to spin in both directions once. for about an inch. That tells me that the chain has not broken,or else it would spin both ways all the time. Your mention about the oil makes a lot of sense. I changed the oil and filter early in the restoration process. I did use 4-stroke motorcycle oil and filter, but that was 2000 miles ago. I'm thinking that the in city miles have caused sludge or grit in the oil and made the sprag clutch malfuntion. My next move is to reassemble the alternator, replace the starter,and change the oil and filter. I'm thinking there is a good chance that will fix the problem. I am still curious about the loud "clank" that I heard during the start up, after which the free wheeling began. Oh well, one puzzle at a time. Muchas gracious amc49. God bless, White Water Rafter/
 
I can understand why there is confusion, this engine is a clusterfuck. All of the parts in the 1st photo, clear to the nut #13, go on the alternator shaft. The chain goes around #4 at one end and the crankshaft at the other. The gear on the starter motor contacts gear #1 in the photo.

So, your starter spins your alternator which in turn spins the crankshaft via a little chain. :wtf:

honda-cb750-nighthawk-1991-m-usa-starter-clutch_bighu0297e0800a_7fed.jpg

Found a manual for your bike. I uploaded it to Mega.

HondaNithawk.pdf 38.8 MB

Link: https://mega.nz/#!NIJGGA7B

key: !oaX69Gf8fbiIwFl4p0kr-bT97WWdJEx91lfNwwUgrrw

After looking further into this, for fucks sake! :banghead: It appears you have to tear the engine apart to get to the start clutch?

Capture.JPG

Page 9-10 it's referring to, alt chain is 20, starter clutch is 15.

Capture1.JPG

and.....

Capture2.JPG


Now you know why mechanics hate engineers. :cussing:
 
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Looks like the alt even has a separate clutch too. Technically a primary shaft that drives no power, only alt and receives starter input. Whacky design. Lots more parts to fail.

The loud clunk says most likely the issue there, the clutch itself, when they get old they can semi-lock up to then release under load and then the loud noise. May slip after or later go back to working. If alt still driving then chain is fine. Yes, most likely cases have to split to get to clutch, although I did a 550 way back by pulling out primary to drop starter clutch into oil pan area. That one though had a wide open pan, this one if like pics shows a pretty much closed up upper above the pan, can't do it.

First pic part #3 has usually 3 rollers backed by 3 springs, you can barely see a couple of them in the pic. Part #1 then slides inside to provide a cylinder for the 3 rollers to work against, it's a common one way clutch, correct it should not slip the other way at all. When it tries to lock up but one roller because of wear slips to drop off, it makes all kinds of racket popping loose, sometimes some pretty loud bangs. The springs wear out pretty quick too and more slippage/inconsistent lockups from that too.
 
BTW, white water rafter, please forgive me, I am often a dick...........................the DNA I just can't shake.
 
Looks like the alt even has a separate clutch too. Technically a primary shaft that drives no power, only alt and receives starter input. Whacky design. Lots more parts to fail.

Are you looking at those 4 spring washers? I'm thinking it's suppose to be a torque limiter setup to prevent the chain from breaking if the alt or starter seize up. My 2 year olds toy cars use that design :laughing:
 
Yup. Alts rarely seize up, more like an inertia protection device just like the alt clutch on CBX stuff. Freakin' rotor at rpm has some mass there. It's a slipper drive clutch that under big loads slips some, they do wear out after a while.
 
Yup. Alts rarely seize up, more like an inertia protection device just like the alt clutch on CBX stuff. Freakin' rotor at rpm has some mass there. It's a slipper drive clutch that under big loads slips some, they do wear out after a while.

So if someone panic stops and doesn't pull in the clutch, they will hear loud popping sounds to sooth their nerves? LMFAO

To WWR I offer this quote from the movie Braveheart. "Stephen: [to William Wallace] The Almighty tells me he can get me out of this mess, but he's pretty sure you're fucked." :cheers:
 
Well, I did not have time to work on my bike yet, but I'm wondering if my oil change idea is just a temporary solution. How many miles can I expect from the starter clutch anyway? The bike now has 72k. The engine seems sound, no smoke, valve noise or oil consumption. WWR
 
It's not miles, it's "starts" as it's only used to start the bike. I've never had to replace one myself but it's fairly common but, it's much easier to get to on most bikes.

First you have some more troubleshooting. Put it back together except for the alternator cover and try to start it.

FYI - If the engine does not turn over and the starter and the gear on the starter are all good, you'll have to pull the engine and crack the case to fix anything else.

#1 Engine turns over. Something was stuck, either the clutch or part #5 in pic #1

#2 Engine does not turn and alternator does not spin. Starter Clutch is not engaging.

#3 Engine does not turn over but alternator does spin. See #4

#4 Remove Left crankcase cover and turn crankshaft via the nut and see if alternator turns.

#4a You turn the crank and the alternator does not spin. Either the chain is broken or one or more of the parts on the alternator shaft are stuck or have broken.

#4b You turn the crank and the alternator spins. One or more of the parts on the alternator shaft are stuck or have broken and are unable to hold up to the force starting the engine.
 
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