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HELP STARTING REBUILD

  • Thread starter Thread starter Anonymous
  • Start date Start date
A

Anonymous

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I have been working on a 1978 gs750 for the past 6 months. I have done a bit of work on it and it still has yet to run. I guess there is a story to this project as in all others. I got the bike from a freind for $100. It hasnt run in a year. Prio to him giving up on it it ran but started hard, then he lost his drive chain, after sitting for some time he replaced the chain and tried to restart it but eventually gave up.

Now for my experience, I checked compression and it didnt show any. Then since I wanted to learn how to rebuild a bike I pulled the engine apart. Following a Clymer manual. The motor is back together and I am showing a compression of 50 psi. I do not get it. I did new rings,gaskets, seated the valves and timed it per Haynes. The only things I can thionk of is the timing is not right (1 exhaust pointed to gasket surface (front of emgine), 20 pins to intake 3 marking) or the timing chain is stretched to the point where it no longer works (I would imaging the stretch would have to be alot). I have been tring to start it and get nothing not even a sputter with starting fluid. I have spark, checked the petcock. I do not know where to turn next. To sum up I got about 300+ into it now and do not have a clue where to go next. I know I need new points and a timing plate, new battery, and need to kreeme the tank but before I get all the parts on order I would like to have some hope that the bike will runn someday. Can anyone give me a direction to find out why the compression is bad. :?
 
If you're only getting 50psi something is out, and cam timing is the most likely culprit. Cam chains don't stretch badly enough to affect timing, so I'd check the timing marks again. The arrow on the exhaust cam must be pointing forward and PARALLEL with the gasket face. The arrow 2(exhaust) and arrow 3(inlet) must be twenty pins apart counting the arrows as pin one and pin twenty. Good luck.
 
Update some problems found

Update some problems found

Update, I checked the cam position three times and verified TDC using a micrometer through the spark plug hole. It is OK with 1 horizontal and forward and 20 pins betwean 2 and 3.

I did find other mistakes. So far I have found that I checked the compression incorrectly. Without the throttle open also I checked my valve clearance which I would have thought wouldnt have changed but it did. I have no clearance on the intake side. Thus the compression may be affected by leaky intakes. Anyone know where to find a suzuki valve tool in order to replace the shims. How about shims where do you get those.

Ron I will check the other ignition items and pull apart the carbs as we discussed. Guy Thanks for the timing check.

Thanks for all the help,
Mark
 
You can make a tool to hold the valves down out of a small open ended spanner. You'll need to cut and grind it several times to get it to work right. Took me twenty minutes to fabricate it. You won't have to replace all the shims. Some of them can be swapped with each other, and with luck you'll only need one or two.
 
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