I am repairing the old family atv it’s a 86 Yamaha Moto 4 225S.

I replaced the carburetor because it had a miss at idle.

I greased all points that needed it.

glued some cracks in a carb boot (weren’t letting air in just preventative maintenance)

changed oil and filter.

cleaner air box intake.

cleaned out air intake at front of wheeler cause there was a dirt dobbler best built in there (wasn’t affecting air intake just didn’t want any sucked in there by accident)

the carburetor I bought was from eBay but had a lot of good reviews and appears to be of good quality except I recently discovered gas leaking out the fuel bowl drain even though the screw is all the way tightened. Put some flex glue in the hole and problem solved.

It ran good ish for a while (about a day) I had to choke it while riding cause it was too lean of a fuel mixture so it has a miss to it while driving and it would jerk (idles beautifully) well today I adjusted the throttle a little to let some more gas in and now the miss is worse it dies when you give it gas while it’s in gear (reverse or forwards it doesn’t matter)

I discovered a new problem earlier... it has a knocking when accelerating now... Are these two related?

I was going to do the vacuum leak check where you spray carb cleaner on boots while it’s running to check for leaks but now it won’t even start... I tried two different spark plugs (both were old one was brand new but just old) and it fouled both of them out. I tried choke, giving it throttle, nothing works.

I got a new spark plug and it tried to fire over but still wouldn’t crank for some reason even with pushing the throttle.

Are these fixable issues? Top end rebuild? New carb? Higher octane fuel? Low compression? Or should I just drive it off a cliff...

Thanks in advance for any help this is much beyond my mechanic abilities as far as diagnosis goes and the atv isn’t worth paying someone to have it look at it.

UPDATE.

I went to spray starter fluid in it to get it to kicker over and as I went to spray I was astonished at what I found...

the air box was half full of gasoline... how does this happen?!?!?

 

Just guessing here, but sounds like your cheap aftermarket carb is leaking fuel and the float is not shutting off fuel flow. Common problem with cheap aftermarket carbs. If you want it to run correctly, stop cutting corners and fix it right. Use new and oem parts. After spending bucks on aftermarket parts, most realize that the oem parts work best.

 

I put the old carb in after cleaning it and it still runs slightly rough but it runs again. was definitely the bad carb. The only reason I got that one was it had 11 5 star reviews and I couldn’t find an oem mikuni anywhere. Where can I get these?

 

Get a good quality rebuild kit and rebuild the original. A good kit has new gaskets, needle and seat plus all the setup specs to make it new again. Take your time and do a thorough rebuild and it will be like new.

 

Do you have a kit you recommend?

these are the only ones I could find

https://www.ebay.com/itm/YAMAHA-YFM2...AAAOSwceNZTD7f


Yamaha YFM225 Carburetor Repair Kit

 

I generally use the carb number and go thru know mfgrs to get good kits made for my specific carb. I have used "Uni" in the past with good sucess, when dealing with ebay, your never sure of what you getting.

 

Those are genuinely the only two I can find I used my carb number and everything I cannot find one. The carb number is VM24SH

 

Just not sure about ebay stuff, sometimes good, sometimes not....go to "Uni filters" website, and search for carb rebuild kits. They used to make custom rebuild kits for your carb number. Always had great instructions and everything fit properly. Used them many times with great sucess.
Ebay might work, just found it to be a crapshoot to many times. Whichever route you go, a thorough cleaning is in order, complete dissassembly and cleanout is a must!! Carefull reassembly setting everything to soecs in the rebuild kit is a must.

 

"I recently discovered gas leaking out the fuel bowl drain even though the screw is all the way tightened. Put some flex glue in the hole and problem solved."

Just so everyone else knows, you never, ever, block that carb drain, it is there so if the float needle sticks, fuel can run out instead of filling the engine and airbox with fuel. You are not alone, I did a carb clean on Friday on a Moto 4 225 and found a large self tapper rammed into the end of the float bowl drain pipe. If the carb dribbles from there, turn the tap off.

 

thank you for the reply! Wish I would have known that a few days ago 🤦🏼‍♂️🤦🏼‍♂️