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changed sprockets, now bike wont start

  • Thread starter Thread starter prem
  • Start date Start date
P

prem

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i did a sprocket and chain job on my 83 GS550L last year and it never started after that. i had it taken to a mechanic who said my pistons seized in the engine. ive decided its time to fix the bike, so i can learn and so i can get back out riding. after more examination i dont think its a piston problem. the camshaft didnt move much which is why the mechanic thought it was a piston problem. but, i did some work and the pistons do their thing just fine. the starter spins also. the bike rolls with the clutch engaged. any ideas on what i should start checking? im thinking it must be the clutch or transmission.
thanks
 
Ditch the mechanic first....
Not sure about that model, but some smaller GS bikes have a clutch push rod under the front sprocket cover. Maybe something to with that.
You say the starter spins.... as in cranks the engine?
 
it doesnt crank the engine. when i take the cover off the left side. crankshaft cover i believe, i can see the starter gear spin if i take the reduction gear out that attaches to the crankshaft
 
Could be a starter clutch issue. Hold tight. Someone more familiar should be along. Also, that gear typically has a washer on each side which are easily lost when taking the gear off. They are easily lost.
The curous thing to me is why it happened after replacing the chain.
 
With the bike in neutral, can you turn the engine over by hand using the big nut under the right side crank cover as you sit on the bike? Do not use the small bolt head. That will tell you if you have a seized engine or not. To make it easy pull the plugs.

V
 
19 MM big nut on right side of crank. Take off the cam cover and observe if a valve is stuck closed as the lobes come into contact with the shim. If it turns a little then a lobe jams against a bucket I would pull the head and see if a springs broke or whatever else could jam up a valve. And I that point I would go that one step farther and pull the jug, hone them and put new rings in.

Of course look at the pistons and cylinder walls and marks before ordering rings etc etc. Find out whats wrong and order whats needed all at once.
 
gustovh said:
With the bike in neutral, can you turn the engine over by hand using the big nut under the right side crank cover as you sit on the bike? Do not use the small bolt head. That will tell you if you have a seized engine or not. To make it easy pull the plugs.

V
Click to expand...

Yup, do this.

Also, be more clear what exactly is going on. "Some work and piston did their thing" could mean anything.

Only thing I can imagine right now that would fit somewhat of rando descriptions would be a flooded cylinder.
 
Good idea, a hydro locked cylinder will make for a bad day. Pulling the plugs and hitting the starter will t
ell that story real quick. Just don't look at the plug holes when you hit the button or you may get an eye full of fuel.​
 
gsrick said:
Good idea, a hydro locked cylinder will make for a bad day. Pulling the plugs and hitting the starter will t
ell that story real quick. Just don't look at the plug holes when you hit the button or you may get an eye full of fuel.​
Click to expand...
You might want to do this outside of your garage. Take an air hose and blow around the plugs before you pull them to make sure debris doesn't fall down inside the cylinders. Disconnect the wires that power the coils and cover the spark plug holes with rags.
 
i pulled the plugs and put zip ties in each hole. then i pulled the crank case, put a wrench to it and it turned and the zip ties went up and down nicely. i got a little resistance so i put some marvel mystery oil in for good measure. then i pulled out the gear that goes between the crank and what i believe to be the starter gear. when i pushed the starter button that little gear spun. this makes me think that the problem is not the head and might be in the clutch, clutch starter or transmission. i dont wanna pull parts apart that i dont need to.
 
so i just took the right side crank cover off and the spark plugs out. i put a 19mm wrench on it and it would only go half way around. when i put a 17mm on the left side it does the same. i had gotten it to spin all the way around last time i had it open but it was with some force. i am going to take the gas tank off, remove the valve cover and examine it.
any tips or advice on what exactly to look for, or guidance.
 
Remove the valve cover and start checking things out. Are you in time (has for some reason the cam chain skipped a tooth)? Look to see what happens when you try and turn the engine over and report back.

V
 
i had put some Marvel mystery oil in the plugs and let it sit. i went to start it and it turned a little then locked up. i took the valve cover off and everything looks alright up there but i can see where the pistons get stuck. i am taking the head off now, removing the exhaust and carbs. i have never
 
Once upon a time I heard something about clutch basket screws backing out and contacting the wall of the case. I'd check a few more things before a full teardown...
 
great video. ill do that test tomorrow. i am just curious why this would happen after a sprocket change. i did try to push start the bike after the battery drained during that job. i just cant understand why the bike drove into the garage, the sprocket and chain job went well, and it never started after that.
 
I rode my 1100L on a 2000+ mile rally, parked it in the back yard, started it the next day and rode it into my shop. That motor never ran again. Would not start. Had 30 lbs compression across the board, a shot head. Sooooo you never really know until you have done your due diligence.

V
 
i pulled the top head cover off and was able to examine to top of the pistons. everything started spinning around up and down just fine.. a little stuck in places but i cleaned the cylinder walls and it is moving great. the top of one piston had 1/4inch of thick sludge. i am thinking that could have been the problem. as i start putting it back together im trying to keep checking the cam and the timing chain. does anyone have anything else i should be checking while i put it all back together, or any great resources for cam chain timing.
thanks
 
You should check that the valves of that cylinder that had sludge on top of the piston, are not bent. Bent valves will prevent full rotations of the crank. It should be easy to check while the cylinder head is still off. I would have taken the opportunity of replacing the valve guide oil seals while the head was off, and also lightly lapping the valves in. A bent valve would be seen immediately during the lapping process.

If the head has been replaced already (sounds like it from your last post), you can measure all the valve clearances and compare the readings of the other cylinders to those of the "sludged" cylinder. A large difference means those valves are bent.
 
i did a quick check of my valves and their springs and all but one seemed fine. the one that didnt took a little force to depress, but then went just as smooth as the others. i can check anything else you recommend though. i think my cam might have also been out of time. does anyone have a diagram or information on how i can time my cam chain correctly?
thanks
 
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