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1978 gs 750e cafe racer rebuild

  • Thread starter Thread starter drivera84
  • Start date Start date
240punk said:
Check spring length per manual and the valve guides for wear.
Check valve clearances as well.
Click to expand...


is this all on cliffs page?

this would be the first time I do this so I will need detailed info on how to do this....If someone has done this before and has pics it would be great.

thanks to all you guys for your help...if it werent for this forum I wouldnt be doing this for sure!
 
It may not be on Cliffs site itself but likely he has a link for a downloadable shop manual which will have all tolerances and specs in it.

Inspect for rust, surface rust can be ok as long as it's not pitted the metal on moving/wear surfaces. Cam lobes, bearings, journals, just about any moving part needs to be free of pitting.

I'd be concerned about rust in the crank bearings. These are roller bearing motors, and of course any pitting on a bearing surface is bad but, roller bearings will pit with even the slightest amount of rust. A tiny pit will quickly grow.

With you being unsure how the motor is internally, I'd suggest breaking the entire thing down. Ive cracked a motor open before that I thought was a goner looking at the jugs. But the rings sealed, no water made it into the bottom end or not enough to do damage, and since those parts are in constant contact with oil, they tend to become a bit impregnated with it and makes them somewhat less vurlnerable.
I have a few spare motors laying about that are no good except for parts. If you need valves or such, let me know.
 
pete said:
That's as good an idea as any. WD40 isn't going to be a huge help, but maybe combined with diesel it'll be ok.

Remove the timing cover which is on the right side case cover. That should give you access to the end of the crankshaft which is where you should attempt to turn it from.

At least that's how it is for my 450 but I'm pretty sure the bigger ones are the same...
Click to expand...

Hi guys, i took the left side cover tonight...it was pretty clean inside. This is the cover where the stator is located. I noticed a bolt right in the center and figured this would turn the crankshaft....i tried moving it and it felt like i was loosening the bolt. Am i turning the right bolt?

My bad....just noticed I took off the wrong cover....
 
Last edited:
Hi guys,

I took the other cover off...there was a "double bolt?" i turned it and the crankshaft moved just a bit...i tried to rotate it the other way and the bolt began unskrewing.

Im sorry to sound like a complete newbie but I am...


What am i doing wrong?
 
Turning it the wrong way?
Use the 19mm ignition side bolt. On the end of the crank, on the right side of the engine if you were sitting on it. Small round cover. Remove it. Don't force anything if it really feels like it doesn't want to go.

Pulling a spark plug or four out will help too, as you won't be turning the engine against the compression that way. Motor spins clockwise (forward) from that side.
 
TheCafeKid said:
Turning it the wrong way?
Use the 19mm ignition side bolt. On the end of the crank, on the right side of the engine if you were sitting on it. Small round cover. Remove it. Don't force anything if it really feels like it doesn't want to go.

Pulling a spark plug or four out will help too, as you won't be turning the engine against the compression that way. Motor spins clockwise (forward) from that side.
Click to expand...


The whole head is removed...so compression is not an issue, I have a seized piston. Ive tried everything to loosen it up but nothing.

I have time...so Ill just keep spraying on liquid wrench (penetrating oil) and diesel in the crankcase and in the cylinder.

You told me to no force anything...did you mean to remove the engine cover or to turn the crankshaft bolt?

Ill post new pics when I can..

thanks!
 
240punk said:
I don't suggest doing this but I would hammer down on the piston.
Click to expand...


LOL ive been tempted to do so....

Ive tried banging it lightly with a wooden block so as not to ruin it...I still hope that maybe I can save it....both outer pistons are on the up position, so I dont really know which one or if both are seized. When dissasembling it I managed to pull the cam up a little bit, enough to relese the two inner pistons. So now I cant pull the cam out nor push it back in...
 
Under that timing cover on the right of the engine where you say there's a double bolt, that 19mm is the one to use to turn the crankshaft like The Cafe Kid says.

The safest thing is just to turn it clockwise, and use a good socket or wrench that won't slip off.

If the pistons move a little then stop, I'd probably stop trying to force it, flip the engine, and split the cases to see what else is siezing it up.

And just be warned that I'm no guru, just trying a common sense approach... there may be better methods... :rolleyes:
 
hi guys,

Ive been trying to get these pistons to move....nothing!

I have a bearing puller that I think might work...what do you think?
 
Just had a thought... is it in gear? That will make it harder as you'll be trying to move the gearbox as well...

Not sure how the bearing puller will help?
 
pete said:
Just had a thought... is it in gear? That will make it harder as you'll be trying to move the gearbox as well...

Not sure how the bearing puller will help?
Click to expand...


Im not sure if it is in gear Pete, the rear wheel is stuck so I cant really move it to tell. I push the shift lever varios times down until it doesnt click anymore and just slightly up....I think it is in neutral but I am not sure.

I havnt tried the bearing puller, but I figure I can get the claws to attach to the jugs. Then put a piece of wood ontop of the piston and skrew the center of the puller see if the piston moves.
 
I think if it was me at this point I'd be pulling that sucker out, flipping her over, and splitting the crank cases...

If you can't move the wheel or the pistons then I reckon it probably is in gear and worst case scenario is the gearbox is in the same state as the pistons.

I think I'd want to know sooner rather than later what I'm dealing with...
 
pete said:
I think if it was me at this point I'd be pulling that sucker out, flipping her over, and splitting the crank cases...
Click to expand...

how do I do this? :S

I dont want to just start taking it appart without really knowing what I an unskrewing....Im sorry to sound so ignorant
 
Have you got a service manual? It will go through the process.

It'll be quite different between your 750 and my 450 so I'm not sure what to look out for, but getting the bottom crank case cover off should be reasonably straight forward I would think.
 
I would think if you used a gear/bearing puller the way you described, you would only break the fins on the jugs. Fins do not take leverage side ways at all.
 
Thanks for the heads up HD...i was thinking the same thing....

I think its time to flip er over and take her appart from the bottom!

At this point i feel like I am getting in over my head and abilities...hopefully with the manual and you guys I will be able to put it back together...
 
Mate I'd never done more than change oil and spark plugs when I rebuilt my 450's engine and the only difference between that and yours is that there's twice as many cylinders.

Take your time, measure things properly, and you'll be done before you know it ;)
 
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