DT200R - Idle Issues

[Paper Mache Man]

Ok, so I have a DT200R '88. It's an old dirt bike but it's scrubbing up nicely.

I've been rooting around with the jets and finally got it working properly (it now starts 1st or 2nd kick and runs with the choke off). This is a big step up from a bike that was a complete bitch to start and stalled 500m down the road.

Anyway, MY IDLE! I can't seem to get a nice smooth idle in the low revs. I can keep it so it will idle a bit too high than what I'd like and then if it goes a bit lower it goes a LOT lower and needs prodding to keep it ticking over.

I'm not sure what choices I'm left with. The idle screw is very far in to keep it running, way more than I'd like but as soon as I turn it out it sputters and dies. I'd say that where it idles before it dies (normally about 5-10 seconds) is where I want the idle at.

So what can I do? I've had to increase the pilot jet from 25 to 35 to now 45 in order to get the bike running ok-ish. 25 it just wouldn't start, or run without major issues. 35 it would start but with some difficulty and required the choke to run properly (choke off would cause a massive flat spot coming out of idle sometimes killing the motor). 45 it starts ok every time but I still can't nab the idle.

So, I was thinking maybe a 40 would lean it out a bit and maybe raise the revs as a consequence? I don't know it's just what I've been told - I'm not sure it would do anything except make it blow a bit less smoke.

What say you?

[rr390]

Have you checked ur crankcase seals? My 98dt would run but not idle-had nothing down low-would also get hot very quick. Ended up being seals. I noticed a small airleak noise when kicking the bike over-couldnt work out where it was coming from! then i noticed oil dripping from flywheel side cover-screw at bottom with seal on it.wiped oil-it was dark-didnt make sense? smelt oil-uh huh-2stroke-found my problem.It may not b but worth checking! If ur flywheel side seal is as chopped out as mine was-when u remove sidecover and start bike u get uncontrollable revs.you will also get alot of engine noise.

[Cynic]

The idle screw is very far in to keep it running, way more than I'd like but as soon as I turn it out it sputters and dies. I'd say that where it idles before it dies (normally about 5-10 seconds) is where I want the idle at.

So, are you turning the idle speed up and down with the mixture screw or the idle speed screw. Confusing, one corrects the mixture, one controls the resting height of the slide.

You should be able to blend these together to get the idle, set rpm, run air screw in and out stopping at peak rpm and winding the revs down to what you are after.

If not then probably there is a small air leak. I wouldn't jump at crank seals as they generally make it run hot and a complete bast4rd to start, i know my DT was when they went.

[Paper Mache Man]

Thanks for the interest guys. The crank seals appear ok but only externally - basically it's not spewing crap out the side of my bike.

I will have to pull it apart eventually, I've just been putting it off until I source parts and save some cash. I'm planning to take it out next weekend so I'll need to decide if I can get it done before then. I've really been told enough times to check my seals though so I'll just have to do it lol...

My carbi doesn't have a mixture screw unfortunately, the jets are set and don't allow adjustment, there is only the air screw after that.

The slide doesn't seem too bad either but I've never seen a new slide so maybe it's worse than I think.

Really just wanted to check it's not an issue with my jetting before I move onto the bigger items.

Working on a bike this old 2nd hand can be interesting. I emptied a cup of rust (I kid you not) from my fuel tank the other day.

How it was running without a fuel filter before is beyond me.

Thanks guys.

[2 Wheels]

What make carb is it ?

I think with you running it on a 45 pilot jet that this is to big. It is probably (kinda) acting as the choke being on. With the pilot this big it probably wont allow the revs to come down any more than they can.

Me thinks you should come back down to 35 and start again trying to balance it out.

Have you done all the checks--- starting at the fuel tank and working your way to the carb.

I think you are drawin air in somewhere along the way to carb.

What is your air filter like?

What condition is the pipe in?

[Paper Mache Man]

Well I might try a 40 at some point but I can't go back to 35, it just doesn't start and I can't get out of 1st unless I'm running down hill (with choke off).

I'm seriously considering the 40 as most dt200s running premix seem to do ok on it. I've seen a few people mention fowling etc on a 45 and bitchy problems on a 35 (although many people find it works fine - which is why I bought that size in the first place).

Yeah all the checks are done, no leaks to speak of. The air filter could be a problem, it's not on at the moment. I've experimented with different (makeshift) air filters to check what effect the resistance has but it doesn't seem to affect the underlying problem. I'm talking basic stuff here, stockings and filter materials etc. Eventually I'll fix the original or get a pod filter.

I know this will affect the idle, but I don't think it's related to the problem itself.

Ok so to me it sounds like the pilot could do with a jump down to 40. Less fuel should mean less revs, just so long as the engine doesn't stall every time I touch the accelerator.