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XR100 problem

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Finally got the damn thing to run, only problem now is that it starts with full choke but when I take the choke off, it dies or when I give it gas. What could be the problem? I realize that it is 99.9% that the jets are clogged but I cleaned them out and don't believe they're a problem. Any suggestions would be helpful. Thanks

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Sounds like it's running super lean. I think your jets may still be clogged

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I just moved the needle to the middle notch, it was 1 up from the middle before. Now it doesn't start at all..

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This 1985 XL100 I recently bought did the same thing. It would run only with the choke on but when I took the choke off it would die.The needle in the carb turned out to be wore out. There was a visible piece wore off about 2/3rd of the way down the needle. If the needle doesnt look wore out-switch to a different carb. My bike now runs like a top and purrs like a kitten. Good Luck.

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I'm going to go with rdl428 on this one. I'd suggest pulling the carb and checking to make sure you can clearly see through the jets when held up to a light source. Then check the float level. Also a good idea to check valve clearance if you haven't done so in awhile.

What year is your bike?

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It's an 1984. Do I need to pull out the engine to check valve clearance? I just ordered a brand new carburetor off eBay $70 shipped, is it bad if it doesn't have a brand name?

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It's an 1984. Do I need to pull out the engine to check valve clearance? I just ordered a brand new carburetor off eBay $70 shipped, is it bad if it doesn't have a brand name?

Nope, valve clearnace check takes about 5 minutes. Put piston at TDC on compression stroke, pop off the little screw caps on top of the head and check the clearances [lots of how-to's on here, just do a quick search if you have trouble]

Next check the points:

1)Use a small point file [if you don't have one you can use a small, thin strip of sandpaper folded over so the "sand" part is on the top AND on the bottom] and gently isert it between the point contacts and file them just enough so that both contacts look shiny. [if you're using sandpaper, you'll need to open the points with a small screwdriver, push the sandpaper in between the contacts, and then drag the paper back out with the pressure of the points spring squeezing the sandpaper]This will be easier with the flywheel off, but you can still do it with it on and may take a lot of sanding before they are look nice and shiny.

2)Now you want to clean the contacts. Take a piece of white printer paper and cut 2 or 3, 1/4 inch strips. Now once agin open up the points and slide the thin strip of paper between the contacts, let the pressure of the point spring squeeze the paper, then drag the paper back out. Repeat this 7 or 8 times, tearing off the end of the paper that you just dragged through the dirty contacts, so you have a nice clean strip of paper each time.

3) Set point gap. Gap should be .012~.016

4) Check for spark [make sure you have a new spark plug or now that the one you are useing works] If no spark, use the paper again 2 or three times just to make sure they are free of debris.

If after pulling the carb and insuring it is perfectly clean and you can clearly see through both the main and pilot jets and the float level is correct and the bike still doesn't run like a top, try the new carb. Although I'm a bit leary of replacing the carb for a Chineese knock-off, you could try it, just be certain it has the correct jets installed.

Good luck, let me know how you make out! :)

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Thanks for the info Racer I appreciate it. I shall tell it how it goes.

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Also, check all around the manifold and make sure it's not cracked. An air leak will cause that too. Check it with brake cleaner or something similar.

Also, switch to a cdi ignition is an amazing cure for older XR's. That and a new carb.

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How can I switch to CDI ignition? I have an 1995 XR80R's CDI, would that be possible?

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Yea, you just need a xr100 backing plate (pricey), seal, and o-ring. Then fab up something to mount the cdi and coil.

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Ok my knock off carburetor came thru the mail and the next day I installed it onto my bike. Still doesn't start, the carburetor is getting fuel but the damn thing still won't start and I am getting frustrated. Bent valve perhaps?

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You did go through everything step by step like I'd suggested in post #8 right? Ummm......right?

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