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jtanman

DR250S still running too rich after carb rebuild...

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Just picked up a 1990 dr250 with 11,000 miles on the odometer. The guy I got it from had it sitting in storage since 2008. It looks great. Clean motor and plastics, no missing mirrors or blinkers, and flawless stock seat cover.

Having sat for 10 years I opened up the carb and ordered a rebuild kit. The o-rings were in rough shape and the float needle’s spring was seized. Had to drill out the pilot jet. Anyway, I installed a new pilot jet, gasket/o-rings, and needle and seat. Disassembled the choke plunger and cleaned it out to ensure it was clear of debris. Thoroughly cleaned all passages I could see with carb cleaner, compressed air, and wire.

With stars in my eyes I put the carb back on and the bike started first couple of kicks and idled well, but I had to have the idle screw just about all the way in. I hopped on and went for a brief ride down the road. Within 30 seconds it started running rough and stalled. I got it going again and headed back to the house. At this point the bike refused to idle and sputtered pretty badly through the rpm range. I pulled the plug and it looked like garbage (old and black) so I gapped a new one and put it in. I also pulled off the tappet covers and checked the valve clearances. Based on my inspection all 4 were in spec. At some point I went to start it again and it fired up and ran well for a few seconds, then started to struggle again. After it died I kicked 8-9 times with no hint of a start. I pulled the new plug and it was soaked. I experimented with the mixture screw and tried running the bike with the screw turned 0 to 4 turns out at several intervals with minimal luck.

During this entire time I’ve had the air filter off, so I’m sure it’s not suffocating from any lack of air.

Any ideas? I’m trying to stay level-headed but I just might donkey-kick this thing if I can’t make any progress!

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That part were you mentioned drilling out the pilot jet is the most suspicious to me.

 

Pilot jets are so small, that even drilling them out with the correct size bit will most times result in a larger than normal hole. All it takes is a sleight wobble in the bit, and there you go, a couple of 0.0x mm's will do a hell of a lot.

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That part were you mentioned drilling out the pilot jet is the most suspicious to me.  

Pilot jets are so small, that even drilling them out with the correct size bit will most times result in a larger than normal hole. All it takes is a sleight wobble in the bit, and there you go, a couple of 0.0x mm's will do a hell of a lot.

 

 

Thanks for the response, I appreciate any feedback. I should have been more clear: the old pilot jet was seized and I drilled it and used a file to remove it. Then I put a new stock one in and it snuggled up nicely in place.

 

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Well, that narrows things down a bit more. Have you checked the float height? Sometimes the o-ring were the float attaches to the carb body swells up and causes havoc.

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Well, that narrows things down a bit more. Have you checked the float height? Sometimes the o-ring were the float attaches to the carb body swells up and causes havoc.

IMG_5398.JPG

That did cross my mind soon after I started the post, so I tried checking the level with a line on the bowl drain. Seems to be alright.

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I never trust checking it with a hose. I'm a bit anal like that.

 

But I'm still pretty sure that this a something or another in the carb type of problem. I'd disassemble everything again, clean everything meticulously - for instance, the brass plug where the seat seals is usually filled with junk that carb cleaner won't knock off (last time I had to polish it out with some abrasive and a q-tip on a drill).

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Your fuel level is way too high !  You need to check the needle valve and the o-ring the seat sits in.  and your float probably.

 

 

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