dr 650 surge

Has anyone else experienced a bad surging while at sustained speeds using 1/4 throttle? Currently have stock carb with procycle jet kit, slide drilled, largest main jet clip on 4th groove, airbox mod, and about to install a new exhaust. I've tried adjusting the fuel mixture multiple times, but cant get the surge to go away.

If anyone has experienced this and knows what's causing it, or how to fix it, please let me know.

I've never worked on a DR so with out feeling the surge my self I don't have much to guess on. does it go away with a little more throttle, or if you let off a little? have you tried moving the needle up or down a notch?

That surging is usually a lean issue. You probably need to go up a size on the main jet.

Yep, I get it. I'm pretty sure it is because I opened the top of the airbox too much. I notice the surging more when there is a crosswind. I think the wind causes an airlfow change in the airbox. Don't know if it is creating a low pressure from the air moving across the top or a high pressure surge. So i'm going to experiment with trying to alter the flow to prevent the cross winds from affecting it.

as stated above i've got the largest jet in it. procycle's equivalent of a dyno 170 jet.

Switchblade315 • Today 07:47 AM
I've never worked on a DR so with out feeling the surge my self I don't have much to guess on. does it go away with a little more throttle, or if you let off a little? have you tried moving the needle up or down a notch?

Once you let off the throttle or increase throttle it does go away, but as soon as you hold steady it comes back. So, to get rid of the surge you have to constantly accelerate or decelerate.

Woodbutcher, where do you have the smaller filter that comes from the top right side (throttle side) of the carb located? mine currently sits on top of the airbox opening and i've heard that this may be an issue as well, I'm going to try relocating it later to see if that makes a difference. Has anyone tried taking the hose off/shortening and sticking a filter on the side of the carb? Is this possible?

0-1/4 throttle = pilot jet

1/4-3/4 throttle = needle jet

3/4 - WFO = main jet.

I get it at 80mph indicated. If it's that bad, move the clip down another notch and give it a whirl. I left mine on the 4th notch, just because my MPG is doing great at 50mpg. Throughout my range of speed and gears, I only get that surge at 80 and everything else purrs perfectly. I think if I move the clip one more notch, it would run too rich and I might lose the surge, but also lose my mpg's.

Go over to the DR650 thread and see what those guys think.

http://advrider.com/forums/showthread.php?t=135295

Ok, I'm currently on the 4th main jet groove, Not sure how changing this would affect the pilot jet but i'm gong to
1. install new exhaust
2. relocate 2nd smaller air filter
3. move from 4th groove to 5th

Saw on Thumper talk something about adding a .25" washer on the preload spacer on the slide return spring?? Anybody know anything about this?

Cut a drink bottle in half and use it as a capsule for the little secondary filter. Made a big difference with my bike, even more so after I swapped back to the factory filter from the little Uni.

Sarah

Thats the main reason I've left my DR stock. Go to the DR 650 forum plenty of info there.

It sounds to me like you're going too rich with the carb (at least until you get the exhust installed)

Try droping to the third clip on the needle and go back to stock or only slightly richer main.

Clean the pilot jet (or replace it with stock size).

If all that doesn't help-it seems that most of the DR riders complaining of surging have drilled their slides & I've often wondered if just plugging the hole can help (JB weld) ?

Good luck and report back if you find a "fix"

I think sometimes it's just the bike, my husband's '05 surged like the dickens bone stock.

n2deep--- Be sure to check out www.drriders.com


Sarah

Yeah 1/4 throttle is where its starting to come on the needle. You need to rase the needle so go down a notch with the clip. My XL500R didn't surge but it knocked. I went to the needle out of a 98XR 400 it tapers twice. It made it richer off the bottom but leans it out just above then rich again.

good idea

I wouldn't touch a thing until the pipe is installed.

Mine is stock except for a shimmed stock needle, fuel screw adjusted accordingly and snorkel out. Runs ok for what it is, a big heavy white pig

My DRZ400 does the same thing. Crosswind hits, bike slows a bit. Gust stops, it perks back up.

I compensate by not riding in a straight line for any length of time.

My beemer had a surge, I spent a couple of hours reading advrider, then fixed it with a piece of wire.



seriously though, on the carbed bikes ive messed with, you have to be ready to spend some time with a full jet kit, and understand what you are doing when you modify the air intake, or exhaust, otherwise, it will not run as well as it did stock.

thats been my experience at least

That's the reason I never cut a hole in my air box. Too finicky acting with the pressure differences. Hows the mileage on the 400 with the JD kit?

Mileage is around 50mpg. No noticeable change from stock really.

The 3x3 mod and jetting IS noticeable when it comes to throttle response. I've got a stock pipe, so there is more to be had, but I like to keep it stealthy...

ok, the new exhaust arrived, it looks good. Went to take the stock exhaust off and decided to go ahead and take the whole exhaust off. Grinded the inside of the header some and it's currently sitting at 2Combs shop waiting on him to ceramic coat all of it. Hopefully i'll have it back by midweek. Get it installed and see if that makes a difference. Talked to a suzuki dealer and his mechanics they're recomending I change the slots on the needle.

Is this in top gear? I'll assume so, because in the lower gears, the engine should easily rev out at 1/4 throttle opening. In fact, at 1/4 throttle opening, it should even rev out, or almost rev out, in top gear. The alternatives are that you are going pretty fast when the surging happens, that the surging does not happen at 1/4 opening (but at some smaller opening instead), or that the engine runs so poorly at 1/4 opening that it will not rev out as far as it should. Which of these would you say applies?

Regards,

Derek