[Osure]

2009 Grizzly 700 the oil chain guide was bad chain was slapping. it was running but would back fire every now and then so My son took it apart.
He put new chain guide and piston and rings in it. It started really hard when he got it running again after starting it a few times he smoked the starter....then a second one ... then a battery. then it would not start.
Then he said F it and handed it to me to fix
I took it down to timing chains as he replaced them to. checked timing chains and set valves. check to make sure the little decompression ball was still in it but still will not run.

Ps still hard to turn over also.

I am running out of ideas or a direction to try

 

[reogem]

Do you have a factory service manual? You can down load one from GC member and site Vendors website 501Parts

If you are confident that all the parts have been fit properly, it doesn't seem so, recheck the timing and the decompression pin and lever.

However it seems that the engine will need to be torn back down to insure that the piston and rings have been install to spec. You may need to consider taking it to a reputable ATV engine builder.

 

[Ridgway81432]

Welcome from Colorado.
Oil chain guide? for the oil pump? the thing #12?

https://www.partzilla.com/catalog/yamaha/atv/2009/grizzly-700-fi-4wd-yfm7fgyb/oil-pump

I think you had a problem with timing chain wear before this project started and now you have more problems. If the original timing chain was worn/stretched then a new chain alone probably didn't fix anything so the engine is not in proper time now and that's what can cause hard starting and backfiring.
Its easy to check but hard to write about, with the piston at t.d.c. there should be wiggle in the rocker arm(s) for the lash, then when you use a wrench/socket to wiggle the crank by hand there should not any delay in the cam moving to move the rocker.
X-2 on a f.s.m. above and you may have problems with the new piston/rings installation. As it doesn't work now I suggest a complete do over to know what is the problem now.