2001 YZ426F carb questions. NEED HELP!

Hey everyone, I am going threw my buddys yz426 and am cleaning the carb and I noticed that there is this hole in the carb that im not to sure if it is a puncture hole or just made that way. Its a keihin fcr mx 39. When I pulled the bowl off and removed the float there was a hard red/brownish line of dried goop coming from the hole. Also I know im beating a dead horse but I need some advice as far as jetting this sucker. All the info I seem to find contradicts each other so im lost. Haha. I live in iowa. Elevation is 750-1000ft and we ride in 70-90F. Any input will be greeaaattlyyy appreciated. BRAP ON!!





Looks to be normal.....couldn't tell you where the goop came from without taking the carb apart. Does it look like sealant or rusty bad gas/varnish?

What type of issuses are you having? Stock jetting should be close .......with attention being payed to the accel pump timing and duration.


I don't believe its varnish from dried fuel. Id have to guess its some kind of sealant cause it it ROCK hard. I took that pic after it sat in our parts wash at my work for 2 hours. So i didn't know if previous owner made that hole somehow and tried fixing it with some sort of sealant. Jetting is stock and I'm going to be doing the BK carb mod. Thanks for the help! BRAP ON!!

Did you remove the TPS sensor from the carb before you soaked it? How did you reset it? Soaking in really strong solvent may have attacked the gasket between the upper and lower main body halves. DON'T separate the two parts to look, as there is no known replacement for it. I believe JD Jetting has one for the later FCR-MX. It may or may not fit yours.

Check the condition of the seal on the engine side of the slide between the slide and the vacuum release plate. Also, be sure the release plate is not installed upside down.

I suspended the carb in our parts wash. Its the kind where its a bowl sitting on top of a drum with a pump that pumps solvent out of either a brush or a flex tube with a nozzle on the end. And i used the nozzle to stream fluid onto the area. I did not remove the TPS because it looks like a pain to reset in the service manual. The solvent we use at my work is not highly concentrated. I was asking about jetting because all last summer his bike seemed to be realllly boggy down low (thats why i will be doing BK mod and seemed to be lacking mid to top end pull. So i didnt know if jetting could be the issue. Ps: had new complete top end when he purchased it. Came with paperwork for proof

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