Honda GX390 kicks back when starting.

[RCRVRP1]

I have a Honda gx 390 that sat for a few years unused. Now when I try to start it [recoil start] it kicks back so hard it yanks the starter rope out of my hand. It did start once and ran fine.
I have checked the flywheel key and it is fine. I have checked the valve clearance and its as it should be. I pulled the crankcase cover and felt behind the cam gear to see if the little spring loaded lever was free and the spring was not broken. Seems ok. I did not remove the cam and look further.
Put it back together and it still kicks back.
What else should I be checking? Thanks.

[KE4AVB]

Either the valve clearance isn't right or the cam's decompressor is bad. Although the spring is on the lever and the lever rotates still doesn't mean the part that actually bumps the lifter isn't badly worn or broken without actually removing the cam and checking.

As for valve clearance make sure you adjust them when the decompressor isn't interfering by putting the piston 1/4" pass TDC compression stroke or using the old way of adjusting each valve independently.

BTW that kickback is something that really hurt sometimes. I only done it a few times but sprained fingers were enough make me watch out for it now.

[RCRVRP1]

Thanks for the reply.

Are you saying have the piston go down the bore 1/4" past TDC and then adjust the valves? Or get it to TDC and rotate the crank 1/4"?

Which way would they be out of adjustment to cause this, too loose or too tight?

That will be easy to try before I take the cam out for inspection.

And yes that kickback is wicked. I dread trying to start it again after the valve adjustment.

Edit. Whats "the old way of adjusting each valve independently."

Another thing... When I try to start it after adjustment if I leave the plug wire off I should be able to feel if the compression release is working by the amount of effort to crank it but without the kick back? Or is the kickback not when it fires but just compression?

[KE4AVB]

Are you saying have the piston go down the bore 1/4" past TDC and then adjust the valves? Or get it to TDC and rotate the crank 1/4"?

It is with piston 1/4" down past TDC when measured through the plug hole.

Which way would they be out of adjustment to cause this, too loose or too tight?

Too loose. Valve not opening monetarily to release some of the compression. Once running the ACR ( automatic compression release) no longer does this. It is only at startup when the ACR opens the valve. You can actually see this bumping of one valve as you hand turn the engine through two complete revs when the ACR is working properly. On some engines are this happens on the intake valve and others it is the exhaust valve.

Edit. Whats "the old way of adjusting each valve independently.

It is done by adjusting the opposite valve when the first one is fully open. IE: Intake fully open you adjust the Exhaust and vice versa.

[RCRVRP1]

Thanks, I'll check it out tomorrow and let you know the outcome.
Any others wishing to help are welcome.

[wristpin]

The "old way" assumes that the lowest point on the cam is 180degrees from the highest - which is not always true .
Better to stick with the 1/4" down the bore on the power stroke method.

[HondaG100]

That engine is on the large side for hand starting. It may help you to pull slowly until you get to the compression stroke then retract the rope before you try to start it. Do not be afraid to make your valve clearance on the relief valve a little tighter than spec if that is what is needed. I believe it is exhaust on this engine.