bmx 90cc cranks but wont start, my lil boy was riding it and it was running good. he got a lil daring and took a turn to fast and rolled it, it was still running when i got to it so i hit the kill on the remote, he was ok so i then checked the quad, turned it over and it was ok, but it would start or do anything... like it had no battery... so i took it apart and checked it out.. now it will crank but not start...sounds like no compression and its backfiring through the carb. i checked vavles, spark, new plug, exhaust, and have come up with nothing... not much pressure out of exhaust when cranking, plz help hes dying to get back on it... thanks....

 

Welcome to the forum hondamxerd!

Only thing I can think of is maybe the float got knocked out of adjustment during the roll over.... Id pull the carb and have a look..

Not sure what caused it to not have any electrical power after it flipped...A short in the remote kill maybe?

 

thanks ill check the carbs internals real quick, wonder why it sounds like no compression?

 

Your Welcome...I dont know.... cant imagine it got knocked out of time rolling over.. But you never know..

 

carb looks good clean float appears to be in good shape, still backfiring tho, timing, idk, like i said it was running on its side when i got there... it didnt run for long like that i was only bout 30 yds from it when it happened, and i hit the remote kill asap...it really wasnt a hard rollover, thanks for your help and the fast replies... idk this thing hasnt been run much prolly bout 4 -6 hours on it total...but it was running great before he wrecked, no problems starting at all

 

Strange....What was it that you found to get it to turn over again? (to get past the no battery symptoms)

 

lol, dunno really, it still does it occasionally, i cant find a short or anything, have checked all connections and grounds...

 

Have you actually unbolted the frame grounds and checked to see if paint was scraped off?

Maybe check for continuity thru the ground wires looking for resistance?

I am just tossing ideas out as I think of them..

 

no i havnt tried that, but i will...do you know how to check the timing on that quad, im leaning more n more toward that, it has good spark, fuel, doesnt seem like a lot of compression, and backfiring through the carb, sounds like timing, but its really hard for me to imagine it is since it was running after it was rolled.... also i pulled the valve caps and cranked they are moving so im guessing the valves are fine...