1990 DR250 carb setting

Been looking around on the forum here, and it looks like a gold mine. I've just picked up a New To Me 1990 DR250 from someone, I pulled the carb out and cleaned everything. P.O. said that he already had it out to clean it up, but that he could only get it to run run on half choke, AND the fuel literally ran right through the carb. After I cleaned it it will now run, but I think that the pilot screw is not set right, if I let it run, the exhaust ends up glowing red hot by the engine. I've turned it back a bit and it seems to have helped. What is the standard starting point for this? And is there any other jets or anything that are adjustable?

Looking through the Service Manual I'm not seeing anything on the number of turns to put on the pilot screw. It just says to count the number of turns on it to begin with, and having bought the bike off of someone that was messing with the carb to get it running, I'm not sure exactly where the setting should be...

Well, been to hot out to be bouncing on the kickstarter, going to re look at it tomorrow. I hope to get someplace with this. If nobody knows the answer here, I'll post it up once I figure it out.

After I cleaned it it will now run, but I think that the pilot screw is not set right, if I let it run, the exhaust ends up glowing red hot by the engine.

A glowing header after a few minutes of idling is actually very common. It's even addressed in the owners manual.

Suzuki says the cure is not to let the engine idle for extended periods if possible.

You can play with the fuel screw to try to get it to run a little richer without loading up but there is no "standard setting" for the fuel screw.

If it's an S model the fuel screw comes pre-set and capped off from the factory.

Yeah, the header was SOLID RED though. Maybe that would be common, but I hope not. So from reading my manual, I haven't seen any standard setting for the carb screw, and sounds like you are telling me the same thing. I have read that if I get a jet kit for the carb, not only will it run better, but it will give me the number of turns and stuff to get it right. Is that true? I'm going to see what I can do again tonight I hope, I've got a day full of shoveling in front of me again, but it isn't going to be so hot so I hope to have some energy left. :eek:

I wouldn't bother with a jet kit unless you plan to make major modifications -- cut airbox, free-flowing pipe, big bore, etc.

Start with 1.5 turns out on the pilot, and adjust from there.

Check out the DR350 Wiki for a good page on CV carb. tuning, esp. pilot mixture. Your 250 will not be significantly different, other than the actual size of the carb. & the sizes of the jets.

Take notes of what your current settings are, and note what you change & what effect it has on running. You'll have her purring in no time!

Yeah, the header was SOLID RED though.

Yup, that's the kind of red I'm talking about. :eek: If the bike idles ok and runs good right off closed throttle then you're worrying over nothing.

Is this bike an S model or a Dirt model?

I agree with Judas, a jet kit is a waste of money.

All you need is an adjustable needle and a couple jets from Kientech.

If you have the dirt model then you already have the adjustable needle.

I'm no expert and my 90 DR250 M always ran "hot" (you could smell it) but never anything close to "glowing red"....I would have the carb checked out possibly by a mechanic before you let the exhaust and oil/or plastic parts get anywhere near that hot again...Just my two cents worth...On a side note, the owners manual only explains the adjustment of the idle screw so I have no detailed info to provide on the pilot screw..

This is the dirt model bike. I'll be needing to pick up a few things as I go with it too. As far as the engine work goes... Let's just say that I would not put it past me to rebuild it, but first things first. Spent the day on a Jack Hammer today, tomorrow should be better so I'll get back on it then. I think I'll try turning the pilot screw in and maybe starting over at 1.5 turns, or even a scooch less...

Another thing I noticed come to think of it. There is a "ribbed barrel" shaped piston riding on a spring in the lower bowl casting. That piston does not seem to rise and fall very smoothly and seems to get stuck down there rather easily. Is there a lube I can use on it that will remain effective in that environment? The manual doesn't say anything about lube either though. I'm using the CLYMER Suzuki DR 250-350 1990-1994 Service, Repair, Maintenance Manual too by the way.

As far as the engine work goes... Let's just say that I would not put it past me to rebuild it,

Another thing I noticed come to think of it. There is a "ribbed barrel" shaped piston riding on a spring in the lower bowl casting.

Rebuild the engine for what reason???????

The DR's can and do run over 1,000 degrees at the header. It's not a big deal.

That "barrel" shaped piston" is part of the accelerator pump and has nothing to do with the idle circuit.

What I'd be worried about is the problem you are eventually going to run into with the carburetor wearing out. All Mikuni TM31 (The DR250 Dirt model came with the TM31) and TM33 pumpers have a design flaw where the channel in which the slide rides up and down in wears out from constant operation. Since it's part of the casting it can not be repaired or replaced and then the carb is junk.

I'm actually surprised that a 1990 TM31 has not warn out by now.

You'll know it's shot when it will no longer maintain a steady idle because of too much slop in the slide channel effecting proper air/fuel flow.

The TM33, which was stock on the DR350 dirt model is still available and a very popular performance mod but the TM31 is no longer available as far as I know.

The tm33 is a bolt on option? I'm new to bikes, but not to mechanical work. I'm currently building an SBC and restoring a car. So that takes priority. The price on the bike was too good to pass up, and I've always wanted a dirt bike. But I won't be rebuilding the engine til the camaro is done, and if I were to it would be for performance reasons, if I felt it was lacking.

The tm33 is a bolt on option?
The TM33 fits the DR350. The DR250 takes the TM31.

Ok, so it isn't a bolt on option for the DR250. I'll be messing with the bike at some point today so I'll have more information on it.

I just had my carb off and the pilot screw was set at 13.5 turns....Hope that helps...

^^^from where, start if threading til stop? I think the method is generally all the way in, then count back on a carb.

From where it starts to grab the threads....I removed mine to clean the orifice and pulled out on it as I removed it and it cleared at 13.5 turns...Never thought to screw it in and back it out....My bad....

The tm33 is a bolt on option?

I used a TM33 with my DR250S. My mechanic had it installed for me, but it shouldn't be that complicated.

So I figured I would update this as the problem is solved. I ended up giving the bike to my BIL's friend who is a wiz at working on these things to rebuild the carb and get it running right. He got it running, but only with the choke on halfway. So it ended up sitting in my garage for, wow, almost a year. I was almost going to trade it for a 1977 Craftsman 10/6 tractor with a plow, but the more I thought about it, the more I thought I was getting the short end of the stick.

All this time, I've known that if the bike is running fine on half choke, then the reasoning is that it is not getting enough fuel, but I've just never gone out and looked into it. Well, yesterday was the day, I went out, put the bike up on my motorcycle jack and started checking things out. Pulled the fuel line off and it looked like it was replaced, it looked new. Pulled the petcock out of the tank to see if there was a filter on there, and there was, one of those screen jobs, actually two, one level for the regular, and another for the reserve level. They looked fine. Pulled the petcock apart, all good in there. Then I looked at the connectors the fuel line go on, sure looked bigger than 1/4", looked at the line I was using, it was 1/4" ID, I had some 3/8" from my Camaro Project car, it was a bit loose, so I put some of that on. I really could use some 5/16", but for a test of theory this was just what I wanted.

Bike runs great! So, I'm keeping it, I need to see what is all in getting a lost title for a motorcycle in the great state of Illinois, and proceed to make this thing street legal so I can ride it around.

I'll be looking around at what I can do to get it up to speed, how to add turn signals and a brake light and license plate mount, electric start would be so nice, speedometer and tach, passenger footpegs and then once the car is done, I'm going to make this my project and pull it all apart, powdercoat the frame and rebuild the motor, basically make it like new. I would also love to make all of the plastics black.

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