Carb adjustment problems

[zillaguy89]

OK well, I (we) had the ole DT running pretty decent. It ran OK but had a little surging problem,I though actually riding it would clear it up, but no. Kinda felt like it was loading up, it'd run a little boggy feeling, then all the sudden it seemed like it would run "right" for a split second and about jerk me off the back of it. it would do that every so often. So I felt saucy and blasted it up and down the road a couple times. (its an enduro, so its got a speedo, even running crappy 65 mph was no problem hehe) I took a couple trips to the corner and back, about a mile altogether, and I pull back into the driveway, and it starts misfiring and smokin worse than it was. SO I kick it a couple times...no go. Pulled the plug out...black. I clean er up and stick it back in...starts on 1 kick, no choke, just like it had been doing. It was running as well as it was before, so off I go across the field, and I get all the way to the back of my property and it loads up and dies again. I pull the plug again...black. I clean it again and check the spark...it looks a little weak, but still blue. So I pulled the carb off, took it as far apart as it'll come, and I boiled all the metal parts, all the extra little air inlets and passages were kinda cruddy, but I got it all cleaned up, I reset the float level, it was a little high, about .1 inches or so. I put it all back together and set the mixture and idle needles to the specs in my manual. Starts on 1 kick, no choke, runs like a bat out of hell for about 5 seconds and its all downhill from there. Again. Boggin, missing, and eventually loading up and dying after about 45 seconds. Fouled plug every time. Somebody please tell me what I'm missing! Am I too heavy with the oil mixing? thats my next guess. I believe I've got it at 32:1 right now. should I mess around with the idle and mixture screws?

[Bandit]

did you flush out the tank before putting fresh fuel in it? could have debis in the tank an it run fine untill it gets to the carb.. it being an enduro it may not call for 32:1 and may be like 40:1 or even 50:1, i dont know much about the older bikes but i'd check those things, hope it helps

[Bandit]

oh yea, an try a ngk plug or even a next number hotter plug

[370banshee]

ok mike that fuel is mixed at like 36:1 if i remember right. it sound to me like the carb is jetted to rich. pull out the main jet and go get a jet bout 2 sizes smaller. thats a mikuni carn so loomis should have the jets for it. take out the old jet to take with you so you can make sure you get the same style jet just 2 sizes smaller tery that and i bet you'll be in good shape

[atcsteve]

maybe try a smaller main jet.or possible air leak?get a few smaller jets,try 1 size smaller.get some new plugs.start and ride it hard to 3rd or 4th and shut off while throttle is open,THEN check plug right there.continue to jet and check plug is correct color.If that dont work proably another problem.anyway hope it works out.

[zillaguy89]

OK, I'll go smaller on the mainjet, and I'll buy the "correct" plug and go one hotter, just to be safe. Having a suspended drivers license makes it tough to get places to buy toy parts. =) One number higher is one hotter, correct? so I'll get a B8ES and a B9ES?

[zillaguy89]

Oh yeah, and I did flush the tank out. it was nasty, the gas was so old that I had to take the petcock out and dig the crud out of the passages with a screwdriver. THe previuos owner said it developed a rust hole in the tank, and he lined the tank with that white sealer crap...maybe thats part of my problem too.

[go-blow-or roll]

Originally Posted by DT250rider

OK, I'll go smaller on the mainjet, and I'll buy the "correct" plug and go one hotter, just to be safe. Having a suspended drivers license makes it tough to get places to buy toy parts. =) One number higher is one hotter, correct? so I'll get a B8ES and a B9ES?

with NGK it is backwards, higher the number lower the temp, champion is higher the number higher the temp. something else to check is your needel, make sure that it isn't bent and hanging up in the carb.

[zillaguy89]

OK this afternoon I put in a 2 step smaller mainjet, and a new plug, same heat range. Fired right up first kick, idle's smooth, and runs great up till about 1/2 throttle, and then it falls on its face and bogs and misses and catches like it was before. plug is still a little black, but not like it was before. I gotta get to work now, I'll mess with it more later

[Banshee]

If it is falling on its face at 1/2 throttle that usually means I believe you need a smaller needle. If I remember correctly this is how your carb works correct me if I am wrong

0 - 1/4 throttle is your pilot jet
1/4 - 1/2 throttle is your needle
1/2 - 3/4 throttle is your main jet and needle
3/4 - full throttle is your main jet.

I would try bringing the needle clip down one notch

I have a document that exlpains this let me see if I can dig it up some where.