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Post by backwoods on Oct 19, 2010 18:13:07 GMT -5
Hey guys
I just recently finished installing an 83cc big bore kit. I'm also going to rejet the carb at 95 (thought about 105, but that may be too much).
I've got a Uni air filter, but now I'm not sure about how I want to put it on. I thought about taking the entire air box off, and putting the filter right on the carb, but I don't know if the other small host is necessary for cooling or anything like that. I saw another post on here before but can't find it now - regarding the additional host that goes back to the intake and is used for cooling. Do you guys think I will be fine if I remove it and just run the Uni?
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Post by buiditright on Oct 19, 2010 18:18:14 GMT -5
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
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Post by shadowwalker on Oct 19, 2010 18:24:36 GMT -5
If you do remove the airbox, which you should, make sure to ziptie the vent hose from the valve cover, which is the other hose you are referring to, as high on the frame as possible to keep it from blowing oil all over. I would suggest installing one of Scrappys PCV valves in the end of the vent hose just to be on the safe side.
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Post by backwoods on Oct 19, 2010 18:38:35 GMT -5
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?
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Post by buiditright on Oct 19, 2010 18:55:04 GMT -5
I only had one that came off the valve cover and it just goes down to the ground.. It is just a vent. Bill
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Post by shadowwalker on Oct 19, 2010 19:51:08 GMT -5
I only had one that came off the valve cover and it just goes down to the ground.. It is just a vent. Bill 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.
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Post by backwoods on Oct 19, 2010 20:24:36 GMT -5
cool. I'll take the airbox off tonight and zip tie that hose up somewhere higher and grab a PCV valve from the parts store to put on it.
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Post by backwoods on Oct 19, 2010 21:09:12 GMT -5
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. Attachments:
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Post by keetarider on Oct 19, 2010 21:14:37 GMT -5
Yep. that's the A/F mix screw.
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Post by tomcas on Oct 19, 2010 22:35:48 GMT -5
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.
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Post by D-cat on Oct 19, 2010 22:57:47 GMT -5
That vent hose is meant to be under a slight vacuum for a reason. Building pressure in the crank case can be a bad thing, as well as blowing oil vapor all over the place. I know people just zip-tie them up and be done with it, but to do it right, you should install the pcv valve and have a catch canister for the oil (they can be made fairly inexpensive).
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Post by backwoods on Oct 19, 2010 23:44:44 GMT -5
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.
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Post by backwoods on Oct 19, 2010 23:50:50 GMT -5
Also, I couldn't get the brass cover off of that spot anyway. There doesn't seem to be a way to pry it off. That big cap comes off, but that's just the bolt for the other end of what the butterfly valve sits on.
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Post by shadowwalker on Oct 20, 2010 2:15:19 GMT -5
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.
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Post by mainepeace on Oct 20, 2010 3:28:21 GMT -5
The plug can be up to 3/8" thick, as in my case. I drilled it at an angle off-center then just stuck in a small screwdriver and pried it out. It had actually almost worked its way off itself. It was sticking out just enough to grab with needlenose pliers when I got it off, that is until I accidentally hit it with my finger pushing it back in! Then I had to drill it as planned.
Greg
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Post by backwoods on Oct 20, 2010 15:09:50 GMT -5
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?
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Post by shadowwalker on Oct 20, 2010 18:10:35 GMT -5
Maybe post a pic of the cutoff screws? I have never seen the floatbowl screws cut but it wouldnt surprise me. If nothing else needle nose vice grips might work.
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Post by monsterGY6 on Oct 21, 2010 12:55:09 GMT -5
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Post by backwoods on Oct 21, 2010 14:53:43 GMT -5
The issue with changing the jet though is that the float bowl cover doesn't have normal screws on it, as all the other carbs I have seen pictures of do. I think I'm going to have to get a tap-out to try to back them out, then just use normal screws when I put it back on. Does anyone happen to know the size/thread pattern of the screws in it? I'll need to get some new ones to match. I added this pic that shows the "screws" Attachments:
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Post by D-cat on Oct 21, 2010 16:18:32 GMT -5
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.
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Post by shadowwalker on Oct 21, 2010 17:07:53 GMT -5
Wow. I have never seen anything like that. I agree with Dcat. Get a new stock carb and work from there. Once you finally get that bowl off who knows? They might have ground the head off the jets so you cant remove them.
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Post by backwoods on Oct 21, 2010 17:12:36 GMT -5
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.
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Post by tomcas on Oct 21, 2010 22:25:11 GMT -5
Those screws look like rivets.
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Post by backwoods on Oct 22, 2010 1:37:31 GMT -5
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.
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Post by backwoods on Oct 22, 2010 13:56:00 GMT -5
as said previously, got the screws backed out. picked up a new 4 pack of M4 x 0.7 bolts for $0.80 at home depot. should be able to get it together this weekend. a small drill hole around the cover for the A/F cover let me pop that right off. Attachments:
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Post by backwoods on Oct 22, 2010 13:57:18 GMT -5
other pic Attachments:
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