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Old October 9th, 2019, 03:36 PM   #1
vtrider
ninjette.org member
 
Name: Ethan
Location: Vermont
Join Date: Oct 2019

Motorcycle(s): '09 Ninja 250R, '04 KLR 650, '74 CB350F

Posts: 17
Misfiring, bogging at specific RPM (7.5K-8.5K) !

Hello,

I have a 2009 ninja I just got that runs well *except* for between 7.5K and 8.5K rpm, in all gears except for 1st, going on flat, up or downhill. If I keep it at wide open throttle, it can eventually just barely make it through the dead zone and runs great at 9K and above...

It *sounds* to me like it's getting too much fuel in this rpm range, or the spark is missing, because it sounds gurgly, sputtery, loses power, and if I blip the throttle or let go it backfires in the exhaust. It runs really poorly in this range, almost total loss of acceleration.

I'm a little mystified because like I said the problem is just in this specific rpm range, and happens while going down and up hill at the same rpm consistently, so it's not very closely connected with engine load, apparently.

I've done a bit of homework on this, have read these threads, as well as one about a Gummy Bear (?) stuck in the snorkel:

https://www.ninjette.org/forums/showthread.php?t=10208
https://www.ninjette.org/forums/showthread.php?t=186165
https://www.ninjette.org/forums/showthread.php?t=335914

I just bought it. 2009 250r with 11,000 miles that had been sitting for 4 years with gas in the carbs. Wasn't running when I bought it, so I took apart the carb and there was ethanol residue buildup. Thoroughly cleaned the carbs, jets were clogged. New fuel and oil+filter.

I think everything is stock except for Yoshimura exhaust and carb setup:

Clip-type main jet needle, 3 spots down
Idle screws 2 1/4 turns out

I'm going to change the plugs, inspect the snorkel, double-check the vacuum lines on the carb, spray carb cleaner at vaccuum and intake manifolds to check for air leaks, maybe try removing filter and snorkel, check the fuel filters, check the coil lines. If the bike was mechanially advanced, the points would be the first thing I'd be checking -- but has anyone ever heard of the ECM doing something like this?

One note that might help is that I'm starting it without the choke -- it basically dies if I put the choke on when it's idling.

I'll see if I can strap a camera to myself to get some video/audio on the condition.

Anyway, thanks for reading this, would be very grateful for any thoughts or additional things to check, thanks.


Ethan
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