GS450 troubleshooting (compression)


New Member
I have been working off and on with my 1981 Suzuki GS450L Scrambler project. I have cleaned and jetted carbs, I have replaced the ignition system with a Dyna S ignition made for the GS400, and wired up according to "brick house builds" on youtube the way he did the GS450 scrambler he built. Have replaced the plugs and wires as well (copper wires). I did a valve adjustment, and no matter what i do, i cannot get it to stay running more than a few minutes. it heats up and shuts off and will barely start and run after that until cool again.

So I did a compression test (cold) and got ~100psi on the right and ~115 on the left cylinder. I could not get it to start this morning and decided to give the starter a rest. i assume that a warm test is more important, and would need to be over 150 from things i have seen, but the differential on my test should mean something right? Is there something else that i should look at before tearing it apart?

I plan on rechecking the valve shims one more time before i pull the head, as if i get to that i will be looking at a 500cc conversion and more money spent on the bike. I have GS500 jug, pistons, carbs, and cams already though.

Thanks for reading my rambling, and for any advice you can add!


New Member
What do you mean by jetted carbs? Did you change the jets and if so why did you do that? Air intake or exhaust mods?


Over 1,000 Posts
Compression test at WOT? Make sure you don't get the valves to tight. If you found them very tight (.001 or zero lash) to begin with, there is a chance an exhaust valve is burnt. 100 and 115 is very low, but it should run.

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