DR250 throttle lag/exhaust problems?

[Livingstone]

Hiya guys,

I recently purchased a 1997 Suzuki DR250XC, for a while it's been going well but I started noticing a bit of a hesitation when opening the throttle quickly, doing medium revs. It feels a bit coughy/ spluttery/lumpy before slowly picking up speed; it does the same thing no matter what speed/gear. I can't say for sure if it was always there, or if I just started noticing it more as I got used to the bike.

The first thing I did was to clean the air filter; however, if anything, this seems to have made the problem more pronounced (or it's getting worse with time). I have drained the bowl, the fuel seemed OK, and it flows freely out the drain when opening the fuel tap with the bung open, so I guess it's not a gummy filter. The spark plug looks OK (think I will replace it anyway, though).

Perhaps part of the same problem, or perhaps not; I have noticed very little noise comes from the exhaust; and when cruising, most of the sound seems to come from somewhere near the front of the engine, and it is more of a sharp slapping sound than a healthy exhaust sound... Furthermore, there isn't much air being pushed out when you hold your hand a few inches from the exhaust, it's more like a gentle wheeze.

Riding my friends 1997 DR250R (pretty much identical bike) yesterday; it does not have the hesitation problem at all; all the happy sound comes from the exhaust (which sounds sweet); and holding your hand a few inches from the exhaust you can really feel the pulses of air.

The slappy sound from the front of the engine is making me think it might be something along the lines of a leaking gasket where the exhaust leaves the engine, but I can't feel anything when holding my hand near while the engine is running.

Any help would be greatly appreciated, hopefully I won't have to resort to taking it into the shop!

Cheers

[Henk]

If you plug up the exhaust with something (e.g. a rag) when it's running does the presure build up and the engine eventually die? If not there is a good chance you have a leak somewhere, if you can't find it with the muffler bungedup the gasket between the header and the pipe is probably a good place to start. Not enough back pressure may make it run a bit off although singles aren't usually that fussy.

[F5 Dave]

If you can't feel any leaking then there probably isn't but some soapy water when it is cold may answer the question.

Sounds like it is lean, four stroke singles are a bit sensitive & likely why the airfilter made it worse (but obviously a good thing to do anyway). Do the plug as well of course.

take the carb apart again & take out the pilot jet & check it is clear (don't poke wire). that would be enough to do it. Also a Dejebl, is that a bit road orientated? Does it have a CV or the normal dirtbike type of carb? Singles can often have accelerator pumps that squirt a bit of gas when erm, accelerating. kind of a plunger that the throttle will push.

Can adjust the idle mix screw. On a fourstroke carb will be downstream of slide & probably experiment turning it out a smidge & trial that. (if the screw is nearer airbox one would screw it in for richer).

[Livingstone]

Hi guys,

Cheers for the quick replies! Oh, wasn't sure if the pictures would work, but they seem ok; click on them to view a larger one...

Henk, when plugging the exhaust, the bike does not die, actually seems to run OK. There are two drain holes which a lot of air comes out of when plugged, shown in this pic:


There are also some little cracks around the end of the muffler which a bit of air is leaking around:


And there is a bit of a sucking noise coming from where the header meets the pipe, but I still can't feel much (if anything) leaking out of there.

Dave, I might have to wait until the weekend to get back to you on the carb. I didn't have to take it apart before to drain it, there is a little bung screw on the bottom. The Djebel version just has a larger fuel tank and a larger headlight than the standard DR250. When putting soapy water on, it boils away as soon as the engine starts, so I can't see much; or was I supposed to crank the engine over with no fuel and the exhaust plugged to test this?

Thanks again!

[F5 Dave]

Hi

Yeah I've only tried the soapy water on a cold engine with leakdown tester. Thought it might stick around long enough on a cold engine but clearly not.

I think it's a bit of a read herring. I'm assuming your mate's DR has an aftermarket muffler so more straight through. I mean if you can really hear it from the front it wouldn't hurt to pull the header, flick out the old one & fit a new gasket to be sure.

Take the carb apart & check for jet obstructions. This is all pretty simple if you are not slap dash about it & clearly don't do this over grass in case you drop something. It's not difficult once you've done it.

[Livingstone]

Cool, thanks Dave! Will get onto those tomorrow.

Friends DR has an original exhaust. Although, the end of mine has been modified at some stage; looks like it was cut and a new end added.

Cheers

[F5 Dave]

Yeah you're right that looks pretty ugly. I suspect that they just added a straight section thinking it would 'add noise power'.

Hmm, worth having a looksee with a torch to see that it hasn't cracked internally & blocked off proceedings.

[CeeBee]

Sounds as if muffler is almost blocked or major leak at cyl head / exh gasket. I would address those first as its easier than pullin carbs to bits at this stage.

[warewolf]

The Djebel version just has a larger fuel tank and a larger headlight than the standard DR250.

There's a lot more differences than that. Suspension is down-rated for one, pretty sure having a CV carb rather than a flat slide is another.

These later DR250R/DR-Z250 with flat slide carbs are reknowned for a lean stumble when rapidly opening the throttle. (So not sure if it applies to the DR250XC.) Mine had a sticky accelerator pump plunger, so did one magazine's long-term test bike in Aussie, but this is not the only cause. No known cure that I found.

In my experience, they are really particular about having a clean air filter. Very noticeable power loss when they are dirty (even if they look clean).

[F5 Dave]

Sounds as if muffler is almost blocked or major leak at cyl head / exh gasket. I would address those first as its easier than pullin carbs to bits at this stage.

What the heck does everyone have a phobia about stripping carbs? Almost as difficult as having lunch.

Good post Ww.

[Livingstone]

Cheers guys.

warewolf - cheers for this; I had done a bit of searching and hadn't been able to find jack about what made the Djebel different, so I just based that on what we could see of the two side-by-side. Air filter was the first thing I did (see first post), but it seemed to make the lag more noticeable!

Will take a look with a torch tonight. Will take a look at the carb on the weekend when I have a bit more time...

Thanks again

[Livingstone]

erm... A picture is a thousand words (click to make bigger):



and a close up:



I guess that's packing (almost hanging out the back); and I guess that it's not supposed to be there... Any suggestions (how it got there, or what I can do about it)?

Otherwise, I think I will take it in to an exhaust specialist on my way to work tomorrow, price up a repair or a new can.

Cheers!

[F5 Dave]

Yup it's been stuffed with steelo as it was probably super loud after a bodge debaffle.

Funny what you find isn't it?

There will be some place in Chch that could fix it for sure. Cycleworks in Wellington if you get stuck.

[Livingstone]

Hey,

went in to Sportzone (Suzuki Shop), they just said rip the steel-o out with a coat hanger... Done.

That fixed the air flow and noise problems. Now to take it for a ride and see if the throttle lag is any better (or worse!).

Other than that, isn't being too high-flowing also likely to cause some issues?

Cheers

[warewolf]

Air filter was the first thing I did (see first post), but it seemed to make the lag more noticeable!

It will, because the problem is a lean condition, and a dirty filter causes restricted air flow = richness. In other words, cleaning the filter will make the bike run leaner and thus lean-stumble worse.

Re: the steel-o, unfortunately you don't know how the bike is set up. It could take a bit of inspecting to find out exactly how it is set up and/or modified. eg exhaust cored for more flow & noise? carb rejetted to suit? airbox opened to suit? OEM exhaust unmodified but rusted out, allowing OEM steel-o to escape? (doubtful but possible)