'06 slight surging under steady speed

[CaliGrrl]

My '06 surges, ever so slightly, under steady speed and about 6,000 rpm. Feels more normal under acceleration, but not so much holding a speed. It doesn't sound like she surges, I just feel it. It's a pretty quick normal-slow-normal-slow-normal-slow type thing.

Checked the brakes, s'ok. Just did the valves. Carb has never been touched, full stock, 16,000 miles on the bike. Have been running a bit of Sea Foam in the gas every few tanks lately.

So where do I start looking? Bike runs pretty nicely but if there's something I can look at that will make her stop the surging I'd like to know about it.

[Triple Jim]

They all do that, Kerry. They come very lean right in the cruise throttle range, and the feeling is that you're about to have to switch to reserve. The fix is putting shims under the carb needle clips to raise the needles a little. I did it to mine, using 1/2 mm thick washers, and it was enough to get rid of about 98% of the surge. I've heard of some guys needed thicker shims, or two washers, but I really wanted to retain the very high gas mileage, and would rather have a tiny bit of surge very rarely, than loose the nearly 70 mpg it gets.

[csmith12]

I bet you have already done some of these, but for completeness...

Airbox/filter
Get the bike in the air then spin the wheels to ensure brakes are not draggin
Check for vac leaks
Ensure petcock is good shape
Fuel filter
Gas cap and seal ok?
Gas tank vent tube clear?
Valves = done....

Ok... if all those check out
Carbs - time for a good cleaning and maintenance/sync

Wish you the best and hope it something simple.

EDIT: You are in CA, you may have other fuel line options that I have no experience in. Charcoal canister and such, those need to be checked as well.

[jkv45]

Some good suggestions already. My first thought was a lean mixture in the 1/2 throttle range, so shimming the needles would correct that.

Another thing that may contribute to a surging feeling is a loose cush-drive. There is a ton of slop in the stock system that makes on/off throttle choppy also.

We have done it on all of our Ninjas, and it does help. I like remove almost all of the slack so it just barely goes back together.

Here's some info on how to shim to cush-drive - https://faq.ninja250.org/wiki/How_to...the_cush_drive

Making an adjustment to the idle mixture screws may help as well, but the carbs need to have the caps removed. They are adjusted lean from the factory, and going to a setting of 2.5 turns out sets the mixture close to optimum.

Syncing the carbs is also a good idea - https://faq.ninja250.org/wiki/How_do...carburetors%3F

Cap removal - https://faq.ninja250.org/wiki/Removi...re_screw_plugs

Setting the idle mixture screws - https://faq.ninja250.org/wiki/How_do...dle_mixture%3F

When you are trying to diagnose a carb-related issue, think in terns of the throttle position (1/8, 1/4, 1/2, etc) instead of the RPMs. That helps to determine the fuel circuit and jets that are controlling fuel flow at the point where the issue occurs.

[CaliGrrl]

Thanks a lot, that gives me something to look at and think about.

[Ram Jet]

Originally Posted by CaliGrrl

My '06 surges, ever so slightly, under steady speed and about 6,000 rpm. Feels more normal under acceleration, but not so much holding a speed. It doesn't sound like she surges, I just feel it. It's a pretty quick normal-slow-normal-slow-normal-slow type thing.

Checked the brakes, s'ok. Just did the valves. Carb has never been touched, full stock, 16,000 miles on the bike. Have been running a bit of Sea Foam in the gas every few tanks lately.

So where do I start looking? Bike runs pretty nicely but if there's something I can look at that will make her stop the surging I'd like to know about it.

I agree with the guys suggesting shimming the jet needle. It's pretty easy to do and here's a source for the shims;


https://www.jetsrus.com/individual_p...09_396_su.html

Surging is usually a sign of a lean condition.

I just bought some myself.

Bill

[Triple Jim]

I went to my #4 washer drawer and measured a couple to get the desired 1/2 mm, but if you don't have a washer collection, you'll have to wait for the order to arrive.

[ducatiman]

OP...did the bike surge from new? Or is this a fairly recent phenomena?

[CaliGrrl]

I got the bike used a year and a bit ago, at 7,000 miles. She's above 16,000 now, and has done the "surge" thing the whole time. It's gotten slightly more noticeable since I've been holding a steadier speed with a friend who has a scooter. Previous riding has been canyoning, with more acceleration/deceleration than cruising.

[ducatiman]

very possible....decel valve vac hose leak? Either the upper side at the valve....or the lowers (between the carbs)

I've encountered a few, some extremely loose recently.

Within my carb service, I'm strongly suggesting renewal while the carbs are split and hoses accessible....a matter of convenience and reliability.

An '06...11 year old hoses (if original) you may want to carefully examine them.

[CaliGrrl]

Thank you for your suggestions!