Topic: Starter binding and kick starter locked after engine rebuild '75 cb750

[75750zoom]

I recently had my engine rebuilt to address a low oil pressure problem.  When I received the bike, I was able to ride it home.  When I tried to crank the bike the next morning, the electric starter appeared to be binding (i.e. the motor would engage but not turn) and the kick starter was locked.  I fully rebuilt and tested the starter and tested the solenoid.  Both are fine.  It appears that the assembly is locked somewhere within the transmission/kick start assembly.  Does anyone have any ideas on how to trouble shoot without pulling the engine and splitting the case again?  My guess at this point is that something was incorrectly assembled in the kick start assembly (i.e. a loose component) which allowed me to ride the bike home but eventually lodged somewhere within the engine and locking the transmission.  Any thoughts?! 

[grcamna2]

How does the motor turn over when you put the bike on the centerstand & remove all your spark plugs and put her in 5th gear and try rolling the motor over ?? While doing this slowly,try using the kick starter w/ one hand as the motor is slowly rotating...maybe a missing shim in the kickstart assembly?

[Ernest T]

What type of bike?  On the CB400F You can remove the kickstart mechanism without splitting the cases by removing the clutch case.  I'd assume it's the same way on the other CBs. 

I don't think that is the issue though as it is a ratcheting mechanism and shouldn't interfere with with the motor turning over.

[75750zoom]

its a 1975 cb750.  Unfortunately it appears to be dead locked. (pulled the plugs, 5th gear, rear tire locked and will not turn the motor over)

[75750zoom]

I could be wrong, but I don't think I can remove the kickstart mechanism as the majority of components sit on the other side of the kick start spindle inside the case.  I'm in the process of removing the clutch assembly but I think at this point I will not be able to access the kick start assembly without cracking the case.  I'm wondering if somehow the kickstarter pawl or stop pin is loose and floating around?

[grcamna2]

Have you tried calling the rebuilder ?

[75750zoom]

yep.  he thinks its internal but is perplexed as well given it ran and then developed this issue.
I'm going to pull the engine next weekend and begin the process of looking for the issue.

[grcamna2]

Thanks for keeping us posted...I'd like to know more about it.

[75750zoom]

Update: Alright, I think I've removed the majority of variables and unfortunately the binding issue still exists.  As a last ditch effort I pulled the rotor and inspected the starter clutch assembly.  All are in great working order.  Given that 1) the kick starter is still locked, 2) the engine can turn freely (as a reminder I did ride the bike home 80 miles from the shop where the work was done)  3) the starter and solenoid are in good working order and 4) the engine transmission assembly is locked when it is in gear but rolls freely when the clutch is engaged, I'm moving on to removing the engine and inspecting the kickstart gear.  I'll document via pictures and post as I go.  I picked up Mark Paris' fantastic book "my cb750 book" and will be referencing it frequently given this will be my first time splitting a case.  A big thanks to Mark for compiling such a great book.   We need more of this quality of work in repair manuals these days!  Any recommendations along the way are welcome as I'm definitely only a shade tree mechanic.  Surgery begins!

[75750zoom]

I thought I'd start the picture log with day 1, prior to ripping it apart.  It's taken me two years to get it to this point.  The low oil pressure problem was my last gremlin.  Ironically it looks as though I'll be coming full circle!  However at least the tear down process will be much cleaner this time around!

[phil71]

how do you know the engine can turn freely exactly? From what I'm reading here, if your only evidence that the crank can turn is that it was running when you shut it off, it seems possible you rode it with no oil pressure (by product of an ineffective repair), and it just seized after you shut it down. Had you ridden it any longer, it probably would have soft-seized while running.

[75750zoom]

Good point.  Previously I had put an additional oil pressure gauge on the engine to supplement the idiot light.  When I rode the bike home, I was consistently running 60 plus psi and 20 psi at idle.  I also checked it when I pulled into the drive way that evening to ensure that the oil pressure problem was no longer existent. The other indicator that is leading me to believe that it is something with the kickstart assembly is that when I picked up the bike after the rebuild, I noticed that the kick starter was stuck and the assembly was seized.  After shuffling it around a bit, I was able to crank it and rode home.  This leads me to believe that something is binding.  Very strange though that the problem existed, disappeared, and then reappeared.  The other theory is that the bike is haunted . 

[phil71]

it's possible.. i've seen it on 350 & 360 twins a lot.  I think the kicker and the electric start are on opposite sides of the transmission. For instance, you can't kick a 750 with the clutch engaged, but you can electric start it. If the kicker is bound, it SHOULD only bind the transmission side, which means if you pull the clutch, the electric start ought to go, or.. at the very least, you'd be able to turn it at the alternator side with a breaker bar.
If both those tests still yield a stuck reciprocating assembly, the starter clutch could be the culprit, but i've NEVER seen that.
Since you do know you had oil pressure when you parked it.. all things being equal, if it wasn't making any noises, the engine should still be okay. x-ed fingers.

[75750zoom]

You are correct.  The kicker and the electric start are on opposite side of the transmission.  Unfortunately when I pull in the clutch the electric start is still bound.  Fingers crossed as well as I'm hoping its just an assembly issue and no damage was done!

[madmtnmotors]

Did you have the clutch upgraded to the later model clutch pack when it was rebuilt? The later model clutch packs are thicker and do not play well with early model clutch covers. Pull your clutch cover and inspect the clutch hub for scoring/gouging and inspect the inside of the clutch cover. Specifically, check the screw boss on the inside of the clutch cover (where the outer tin cover screws are) closest to the kicker shaft. The early covers have a deeper boss at this location and will interfere with the clutch hub when the thicker, later model clutch packs are used. This also applies when using the earlier clutch covers on the later model engines. Been there, done that. You can remove about 1/4" of material from the inside of this screw boss to eliminate the interferece. This modification will only be required if there appears to be interference at this location. You may have other issues, especially since you were able to ride it home. The problem I had with this clutch cover interference prevented the bike from turning over at all.

[cbr954]

The kickstarter has a pawl that is held back by a spring. The pawl catches on the large gear that meshes to the clutch hub and that turns the engine over.  That big gear also drives the oil pump.  Pulling in the clutch has no affect on the kick starter.  The only way to service the kickstart parts is to split the cases.  I think the spring may be broke or the pawl assembly was reassembled incorrect.  If the kickstarter didn't work right when you picked it up from the rebuilder, I would see what they would do for you because they never should have let it leave the shop in that condition.  IMO

[the technological J]

it's possible.. i've seen it on 350 & 360 twins a lot.  I think the kicker and the electric start are on opposite sides of the transmission. For instance, you can't kick a 750 with the clutch engaged, but you can electric start it. If the kicker is bound, it SHOULD only bind the transmission side, which means if you pull the clutch, the electric start ought to go, or.. at the very least, you'd be able to turn it at the alternator side with a breaker bar.

im not sure what you mean here... are you sure you meant 750 and not 550?

[scottly]

If the kickstarter didn't work right when you picked it up from the rebuilder, I would see what they would do for you because they never should have let it leave the shop in that condition.  IMO

1+ Take it back. If you paid for work that wasn't done properly, they should either fix it or refund your money. IMHO

[the technological J]

Absolutely.......
+1

[cbstevef]

Did you ever figure out a solution to your bike problem? unfortunately, I am experiencing something very similar!