Working on my buddy's 2007 650 (not EFI). Came in to the shops with a complaint of hard starting, low idling for a few seconds, then dies. Adjusted the valves to spec as they were way out. Seemed to solve the problem. He took it home, ran it a few days, then brought it back with a complaint of hard starting, running a few seconds, then quits and will not start back up. Rechecked valve clearances thinking one may have slipped again. Not the case. I can go to it "cold", half choke it and it will start and run for 15-20 seconds, then die out. Will crank and crank, maybe pop a little or run for a few seconds, then quit. When it will do this, it idles VERY slowly. Then it will crank but not restart. Plugs are not fouled, unit is well cared for. fuel is fresh.

Thoughts? Got me stumped!! HELP!

Thanks!

Tom

 

Did some more investigation into this problem and found an intake leak where the rear carb seats into the manifold. Fixed that problem and now starts right up.
The remaining problem is the intermittent backfiring from primarily the rear carb. I was able to capture the problem on the attached video. I'm wondering if I still have a valve adjustment issue, although it now idles fine. Watch, listen, and please comment...THANKS

 

I thought by posting here with a tell tale video someone would be able to suggest something. So far no responses but several lookers at the question. Anyone out there have an idea? My plan for tomorrow is to reassemble the air box and filter; see if this evens it out. Trying to arrive at a definite fix before reassembling the whole machine and find out I have to tear it down again...

Any suggestions, PLEASE????????????????

 

Does atv run the same with the air box and filter assembled? new plugs? charging rate okay? Have you check compression? Have you done an leakdown test yet?Have the carbs been cleaned good? Sorry for all the questions just some Ideals for you?

 

Well, after combing through the top end of the engine, I found a hose with a small hole in it. Could hear air sucking from it with a mechanic's stethoscope. Repaired the hose and reassembled the unit. Runs fine now! Thanks for the feedback...just like an automobile, these things are sometimes hard to diagnose.


Tom

 

Congrats....yea your rite sometimes its tuff...