XR80R Carb Adjustment

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XR80R Carb Adjustment

Post by 4Strokes » Tue May 10, 2016 6:30 pm

Topic: Carb Adjustment on XR80
Author: fireman464
Posted: 03/21/2004 8:53:53 PM

Last Year, I bought three Honda dirtbikes for my kids. Out of the three, the XR80R has been a problem from day one. I'm tired of dealing with the people at my local dealership, they are rude and they can't seem to fix the bike. In fact they claim that the bike runs fine. The problem at first, was an extreme flat spot in the throttle. After they adjusted the carb, it nows floods out real easily and, it fouls plugs like they are going out of style. When I pull the plug it's soaked with gas. My question is, what is the correct procedure for adjusting the carb? There are two screws, which one is the Idle screw and which one adjusts the mixture? Any help will be greatly appreciated. This bike is almost a year old and has probably less than 4 hours run time. My son can't ride it because we can't get it to stay running.

Reply by cyber104 on 03/22/2004 09:08:39 AM
Boy, that does sound like a drag but don't give up hope. That is a GREAT bike and once you get it straightened out you'll love it.

To answer your question...the idle screw is directly in the center of the carb directly in line with the throttle cable. The mixture screw is more toward the back and closest to the rubber boot that comes from the air box. I am currently having a minor carb issue with my son's 1990 XR80R so I don't profess to be a carb expert but if I were you I would start with the mixture screw. Pop in a new spark plug and then completely seat the mixture screw and then back it out 1.5 turns. Then run the bike for 10 minutes or so and check the plug. It should not be wet with fuel.

Do this first and report back. If the plug is consistently wet you could have a float issue or one of the jets may have actually fallen out and is laying in the float bowl. You may laugh and say that can't be it but it happened to me twice on my old Husky :-)

Good luck and you WILL get this straightened out!


Reply by ThumperTDC on 03/22/2004 12:40:22 PM
First off, welcome to the forum. The flat spot you originally described is cause from the carb running too lean. This is usually experienced right off idle, or about 1/2 throttle. Do you know what exactly they did to the carb when they adjusted it? With it flooding now after they monkeied with it, it sounds like they just increased the jet sizes. Find out what the current jetting is and compare that to the stock jetting specs. If they did rejet it, switch back to the stock jets and try messing with the mixture screw. Usually a good starting point with the mixture screw is about 2 full turns out from it being fully seated.

The only other thing I could possibly add would be since it is a year old and has very little time on it would be to remove the carb and clean it out good with carb cleaner. This way you will have something clean to work with, not having to worry about if it is varnished or not.

Just curious, but what are the other 2 bikes you got for the kids?

Reply by fireman464 on 03/23/2004 11:17:14 AM
Thanks for the replies to my message. I'm not quite sure exactly what the dealership did when they worked on the bike. The people have been complete jerks and even have denied that a problem exists. Im don't believe that the jets were replaced, the slow jet is a 35 and the main is a 95. I checked the jets, the slow jet may be clogged and I have ordered a new one. The problem is that the bike will start eventually, but it will not run for more than a minute or so. It will idle for about 5 to 10 minutes, but will cut off eventually. When I pull the plug it is either wet or dark black. Also there is a hose, possibly a vacuum line that I can't seem to find a place for. I'm not referring to the overflow on the bowl. This one is further up on the body of the carb. I have tried to adjust the mixture screws when it's running, but they don't seem to make a big difference, it still cuts off eventually. I've also changed the positon on the needle one notch down. I recall the dealer saying something about raising it one notch. The floats don't appear to be sticking either. It's getting real frustrating as my son can't ride the bike. The other two bikes are an XR50 and an XR100R and they both run great. Thanks again for your replies, if you can think of anything else, please let me know.

Reply by RB Racing on 03/23/2004 12:47:45 PM
Maybe the dealer altered the float height hence the flooding. What is the current clip position on the needle?

Reply by cyber104 on 03/24/2004 09:16:27 AM
If the slow jet was clogged you wouldn't be fouling plugs it just wouldn't idle. Change the clip position on the needle to the very top groove...this will effectively lower the needle. This will lean the bike out. I'm beginning to think that you are running too rich.

After you adjust the needle, set your air screw to 1 3/4 turns out from fully seated.

Try this, I think it may work.

I understand your frustration especially as it relates to your son. I just went thru something very similar with my son's 1990 XR80R. It was the needle that was causing the trouble!


Reply by motoram on 03/24/2004 5:25:53 PM
how many hours have you ran the engine all together? This may sound wierd but when I got my son xr80r last year the sales men had a hard time starting the bike and it started and had the same problem luckily the salesmen was along time honda guy and said when the ship these bikes they put some kind of additive in the carb. why he didn't say but he took it and drain the float bowl and tank and but new gas in it and it was great after that. He also said the tech is suppost to do this but the always forget. and that you could leave it in and run it through but it would run like crap for a while. sound wierd but it's true.

Reply by fireman464 on 04/11/2004 3:59:02 PM
Hey Guys! Just wanted to say thanks for all of your help. The problem seems to have been the float level. The bike cranks every time now. It still has a flat spot in the throttle response, but we'll live with it for now.

Reply by RB Racing on 04/13/2004 07:49:29 AM
I think your needle position is a bit of now. What position is it in?

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