helping a friend / neighbor with his bike ---- i always seem to be buying a bike and fixing it for my sons or I so my friends bring me their old junk for "help" ----- i am not an expert but i know which end of the carb goes to the engine :-) --- scott

this bike will not run right -- reading through the threads i see this problem mentioned over and over but no solid solutions !! bike sat for a year or two after it started running poorly another "mechanic" looked at it got it running a little better but it still wouldnt run right so here it is at my place.

i pulled the carb ordered a carb kit, air filter, carb diaphram and got to work pulling carb apart pulled every part off the carb i could find laid it all out so i wouldnt loose anthing and dunked the body , steel and brass pieces in carb dip over night next day shoot carb spray and compressed air through all the passages new parts get here install new kit { with out new diaphram---on back order} put bike together it starts will not idle but runs mid range ok and stalls out on top end shut bike off and fuel floods out of carb into air cleaner box and engine.

later on --- diaphram arrives pull carb and strip it down 100% double check all passages and jet all look good and flow air / carb cleaner float floats seat valve good fuel shuts of with minimal pressure install new diaphram with new spring {old spring was missing other mech must have "lost it"} put everything back together choke it hit the button {yes changed the oil} fires up and idles like a new bike --- hit the gas dies, restart same thing unless i barely add fuel then it will pick up rpm ever so slightly before lean burn backfire through carb and dies ---- if i restrict 80- 90% of the carb with my hand i can rev the engine up all the way -- sounds great but still only idle with full choke and when i shut it off it pukes fuel into the carb as if the choke is stuck wide open {ZERO FUEL from non obstructed over flow}

does fuel flow up into the chamber where the diaphram is? is this where the fuel is coming from? from the marks on the old diaphram and the cover i concluded that the spring is to bo on the outside of the diaphram pushing in is this correct ? what is the problem with the bike ?????

some suggestions i have read
exhaust is clear and free from obstructions fuel is fresh and clean jet are same as what was removed needle is set to factory --- i think i have covered all the bases but something is not working right --- all this time and frustration for something i dont plan to charge the guy for let me know what you are thinking --- scott thanks a million in advance

 

Look at the parts breakdown on the carb at Cycle Parts Warehouse. Shows to be 90 model Yfm350er,may help you figure out what's wrong. Sometimes when "everyone" has worked on a carb pieces end up missing,etc! This is frustrating with time spent trying to make it work! If the owner plans on keeping it sometimes best to bite the bullet and order a new one! Plus check the valve clearance on the machine and compression test to see if any problems there. The carb isn't cheap (over $400) at Cycle Parts Warehouse,but count your time in trying to solve this too! I've replaced tampered with carbs that I just couldn't get right after too many different fingers were on em! OPT

 

thanks again for the help !!! ill fiddle with it a little more and forward your advice to the owner see what he wants to do -- i think he will end up buying a new carb before this one quit working he used it around his farm tending animals and has had it since new so 4-$500 is a good investment for something that will get used !! IMO scott

 

Have you checked and set the A/F mixture screw?

Aside from it vomitting out fuel when it shuts off, it sounds like it's getting just enough to idle on, if you restrict the air. Also verify the jets are the correct size for it. As was mentioned .. the other *mechanics* may have tried just about anything to get the bike to run, and then left it however they last tweaked it.

Also check the carb boot onto the engine as well. If that has a crack in it, the bike will suck air.

 

checked the boot looks great replaced all the jets with oem air fuel screw set to two turns out cranked it in and out several turns with no change. --- i dont know but i think it has something to do with the power valve / diaphram on the side of the carb and i think that is where the fuel pukes from if it where mine id smash it with a hammer and start over :-)

 

When there is no difference on the fuel/air screw either way you turn it's usually because some idiot before you cranked down on it and broke the small tip blocking the opening, screwing up the mixture setting from then on!! When you get frustrated enough just tell the owner! Most normal people will understand when you level with them that it needs a new carb!! Been there too! Good luck OPT