83cc upgrade - removing airbox

I have a walbro carb with a 95 main jet.. I took my air box off and put the uni-filter directly on the outlet side of the carb.. It runs great.


Bill

builditright - what did you do with the other hose that comes off of the valve cover?

shadowwalker - this hose is just for blowoff oil from inside the valve cover right? any excess just goes into the airbox and stays there?

This is fine as long as you don't run at wot for extended periods of time. However, leaving it hanging and running wot will have oil leaking out of this tube. That's why I suggested zip tying it as high up on the frame as possible so that when the throttle is released the pressure will drop and allow oil to drain back down the tube to the valve cover.

I also looked at my carb that I'm putting the new jet in. Do all of the 139QMB stock cards have an air/fuel adjustment screw?

If so, I'm assuming it is underneath this small copper colored cover.

I believe that screw is the air screw just for the idle. There's really no need to adjust it because you use the idle gas mixture screw that right next to it to make any idle mixture fine adjustments.

The strange thing is I just picked it up to take the float bowl cover off of it, and there are no heads on the screws where I would take the cover off. Like they've been ground or cut off. No idea how I can change the main jet. Anyone seen this before?

I saw some info on adding a catch canister, at the least I plan to add a PCV valve.

Drill into the plug just enough to get through then thread a screw into it and use a pair of pliers to pull it out. Be careful not to damage the a/f screw head that is underneath.

Thanks for the tips, I'll give that a shot. Any ideas on the 4 screws that hold the float bowl cover on? Those look like screws that had the heads cut off. On the other end there is just a little bit of the screw sticking out. Should I take a similar approach with those?

Here is a quick tutorial on how to change the jet

www.monstergy6.com/tech_center_carburetor_jetting.htm

Absolutely no problem mounting the uni directly to the carb, we all do it.

This carb is obviously from a manufacturer who has been screwed over by the EPA before. The capped F/A screw is one of those obscure laws that has been recently used to confiscate whole shipments of Chinese bikes. The only purpose of this, and it's quite plain the heads were stripped on purpose, is the manufacturer figured if the EPA really considered the idle mix screw a threat, imagine what kind of emissions harm could be done if the consumer was allowed to change the jets! I'm sure this was done to head off the possibility of more confiscations and fines.

A stripped head screw removal set hopefully will help you out. I don't know the screws that are in the carb, but I'm sure the threads could be matched at most hardware stores. If all else fails, aftermarket stock carbs are fairly inexpensive and don't come with these hassles.

Ha, yeah if the heads were ground off the jets that would add another hassle. I'm first going to try to get a stripped screw remove and get them out. If that doesn't work, I may drill and try to re-tap. It is aluminum after all so it would be pretty easy. Then I will see what I find inside. If it all fails or I end up messing it up, I'll just get a new carb.

But I also have never seen anything like this on any carb before...

I'll post pics and let you guys know how it goes.

I was just able to get them out. Drilled into them a little ways, maybe 1/8 of an inch (as deep as it looked like the top of the head sat), then used the backout bits and got all 3 out. Ended up besting the edge off on of them, but it will be fine if I put a washer of it before I put some screws back in. Just have to go to the hardware store now and find the right size threads to go back in. I also got the cap that was pushed in over the A/F screw, by drilling slightly into the aluminum and a little into the brass - just enough to get somethin in to pop it out. I'll post pictures tomorrow. But man, that's a weird setup, never seen that before. I was told some old car carburetors back in the day used to have caps on them like that.