Mine is a 1986 Moto 4 225. Due to the previous owners leaving the quad outdoors in the rain, my carb was terribly corroded and pitted inside...

The choke lever is on the dash where it can collect rainwater. The rain gets inside the choke cable there and runs downhill, inside the cable housing, and then dumps into the carb at the Enrichment Circuit Plunger.

Numerous soakings and cleanings did nothing to lean out my quad, as the interior walls of the Enrichment Circuit Plunger's cylinder were hopelessly pitted and would not allow the (new) o-rings to seal... gas was constantly leaking from the Enrichment Circuit (choke), making the engine run very very rich.

My fix was a new generic carb, modified and jetted for my machine. Without posting an actual link, you can find these on eBay for about 40 bucks shipped, under the keywords MIKUNI VM26 30MM CARBURETOR CRF XR 100 200 250 CARB ATV PIT DIRT BIKE QUAD . (copy-n-paste the keywords to Google, then click on one of the eBay links)



The distance between the mounting bolt holes in the intake flange was off by a few millimeters, so I milled them wider into slots, then simply used nuts and bolts to bolt it up. Make sure the carb is centered left-to-right.

I had to fiddle with the throttle slide cap to make it work with the YFM's throttle cable, drilling out the center hole so that the cable housing's steel tube would fit through the cap.

Also, I went up one size on the pilot jet for easier cold starts. This carb has a true choke on the airbox side of the carb body, with a Choke Lever on the carb itself, so I removed the choke cable from the quad entirely.

With the benefit of hindsight, I should have taken photos in order to post an illustrated 'How-To' here.

It now runs perfectly... fast start, smooth idle, good power and acceleration. All is well.

 

I didn't even think about that thanks that may save us about 170

 

The carb says Mikuni and Japan on the sides, and the jets have the Mikuni 'Square Within A Square' trademark stamped on them, so Mikuni jets from Jets R Us, etc. drop right in.

Mine shipped from China, so these things might be Chinese rip-offs, or maybe made there legally under license... I have no idea. But they're cheap and well-made and take genuine Mikuni parts, making them a snap to calibrate.

Let 'er rip.

 

the old man just confirmed that unfortunately our carb is just plain shot LAME

 

busted pin, totally pitted, etc, he listed tons, said he rigged it to run so he could ride it a little in the sand on the flats, but thats about it first gear only high throttled, gotta stand on the brake, and squeeze the heck outta the hand brake just to keep it from going, well at least we have time to get a new carb before our riding season gets here

 

If you decide to run with the above-mentioned carb, please feel free to drop me a line here if you have any questions. I still have the Moto 4, and I check this forum most every day.

 

I have a 88 moto 4 YFM 225U. I would Assume this should work for me as well?

My carb is just dumping gas, and I can not find a rebuild kit anywhere.

The pitting is horrendous. It was running great, and then lots and lots of fuel. It idles fine, and then any extra throttle, and lots and lots of fuel.


At least it died at high RPM having fun.

 

Nearly all the stock YFM carb parts can be found individually on Bike Bandit dot com. If you want to change the jetting from stock, individual jets can be had from Jets R Us dot com.

That is, if your carb's worth rebuilding. After having spent nearly a hundred bucks on all the parts for mine, I found that my carb body was too pitted to run correctly. It was just too far gone.

Hence the Chinese replacement carb mentioned above.

 

After tearing into mine further....I think a full replacement is the only way to go.

Mine has a intake opening of 37mm, outlet flange side of 29mm, and a flange center to center of 53mm. This seems like the only route at this point.

 

That was my assessment for mine as well. To get the carb to mate up to the intake, I milled the carb flange mounting holes all the way out, making them open-ended slots.... allowing the 48mm (bolt hole center-to-center) new carb to fit the 53mm (bolt hole center-to-center) YFM intake.