Honda XR100

shaggyzr2

shaggyzr2

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Joined
Dec 26, 2011
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Age
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Location
Central Wisconsin
I know this isn't a Yamaha but I'm totaly lost here and need help, maybe someone can help me. I have an 85 Honda XR100R. It had been sitting for a long time so I went through the carb, replaced the plug, put in some fresh gas, adjusted the valves and got it running. It idles fine but when I hit the gas it dogs out but eventually catches up, when I run it on half choke it runs a little better but still not like it should. I picked up a brand new aftermarket carb off Ebay, installed it and still runs the same. Anyone have any idea what could be going on here?
 

How's the fuel supply coming out of the tank? Pull the line off of the carb and turn the petcock to the "on" and "reserve" position. Is there a good stream running out? If not, there should be a petcock screen in the tank. Did they put an inline filter on it? How's the air filter?
Process of elimination .....
 
Fuel supply is good, tried it with the petcock on and on reserve. Air filter looks good, I even tried running it without the filter and ran the same. It smokes alot so I'm guessing that the rings are worn, would worn rings have anything to do with it?
 
Not going to run good at all without decent compression. Have you done a comp. test on it?
 
Strange.........Was it a fuel screw or air? This is a brand new carb on it? Does it start easy? or alot of kicks? Do the rpm's slowly drop or drop right down to below idle and then come up to idle speed after you rev it?
Always tough diagnosing over the computer.
 
Not exactly sure if its a fuel or air screw, the carb is brand new. It starts fairly easily, maybe 2 or 3 kicks when its cold. It starts up, idles nice but when u hit the gas it bogs unless u turn the throttle very slowly, when on half choke it isnt so bad. I also noticed if you slowly work it up to about 1/4 throttle, hold it there then crack the throttle its fine. It sure seems like a carb problem but it acts the same with the new and old carb. I almost thought maybe there might be an air leak somewhere around the manifold but that all looks good.
 
Spray around the carb boot with starting fluid or carb cleaner( while it is running) .If there is an air leak you will note a change in rpm. I used some clear silicone caulk to seal the carb boot on my old Invader and it worked.
 
If it's an air screw, will be on the air filter side of the slide. If it's on the engine side of the slide, it'll be a fuel screw. If it is a fuel screw, turn it out. If it's an air screw, turn it in. It really sounds like it is running too lean.
 
I just took a look at the points, they were a little pitted, I cleaned them up with some 400 grit sand paper and it seems to run a little better now, I might try and clean them up a bit more, see how that goes, may have to try a new set of points. I will turn that fuel screw out a little too. Thanks for all the help!
 
I have the gap set. I got it running somewhat decent for now, still a little bog on bottom end but not terrible. When I get time I'll throw in a new set of points.
 
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