[Cpoppell29]

New here but I just replaced piston head and rings on my 07 Honda foreman 500, new gaskets and all but no I have a crank no start issue and could use some insite, I opened the drain valve on the carb and gas came out, shot either in it and just cranks till it backfires out the intake. New spark plug, rings, piston head and valve seals.... any help? Thanks

 

[retro]

Did the motor run before you replaced those topend parts? What was wrong with it, the reason why you rebuilt the topend?

Assuming that the camshaft timing is correct, most likely the valves are way out of adjustment, too tight. Did you readjust the valves after you put it together? Did you have the motor on the compression stroke (not the exhaust stroke) when you adjusted valves?

Other possibilities are a stuck/bent valve, a broken valve spring, etc.

A compression test should measure about 64 PSI at starter cranking speed with the throttle held open.

Welcome to the forums!

 

[SamUK]

As above, check the timing, check valve clearances also you don’t mention a spark?

 

[Cpoppell29]

Engine was running before removal was smoking very bad so I assumed rings were gone and I was correct. I didn’t adjust the valves when I set everything back together. Has spark as well. Just no “pop” to it at all. Would you happen to know the valve specs ?

 

[retro]

Valve clearance is .006" on both valves, cold motor. See the attachment.

What in the world are you doing replacing a topend on a motor you know nothing about without a service manual? You can get one free from the manuals forum:

https://www.hondaatvforums.net/foru...nual-help/50817-service-manual-downloads.html

Have fun!

 

[Cpoppell29]

Would the valves being out of adjustment let the compression off to soon as well? Just wondering if I should adjust the valves before running the compression check

 

[LedFTed]

if the valves are adjusted to tight, you will lose compression. if the valve is burnt same thing. did ya just throw new rings in, and take care or the cylinder as well?
an old rule of thumb, was if ya do the valves on dont do the bottom, or, if the do the cylinder an dont do the valves, ya will have problems.. i cant say i always abided by it though. this was with car an truck engines. dont know if it applies to atv.
i dont know why it would backfire through the intake, except for timing, or intake valve.
you can still run a compression test, before ya adjust the valves, just to clear your mind an be sure. i think your going to find, what was said above in the other posts.
i forgot to ask,, was there a carbon buildup on the valves, or stems??
the 1st. time i replaced valves on an engine, no one told me i was supposed to re seat them. boy, was i in for a surprise :smile

 

[Cpoppell29]

I don’t think there was any way I coulda messed the timing up honestly? All I did was remove the head and the liner remove the piston head and put on new piston head with new rings and reassembled everything back to normal.

 

[LedFTed]

go ahead an do a compression check, then go from there. i dont think it would hurt anything. wait for some other replies if ya want. im not an expert on honda atv engines, an will gladly admit it. see what some others think 1st is most best.