Author Topic: Help, surging and backfiring on start up.  (Read 2708 times)

Offline fowfam

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Help, surging and backfiring on start up.
« on: June 29, 2007, 01:14:22 AM »
Help, after rebuilding the carbs, installing a factory pro jet kit, and putting everything back together, the bike finally starts after sitting idle for over two years.  Unfortunately as soon as you hit the start switch it backfires out of the exhaust once, and revs to 2k.  After a few seconds it surges to 4k with no throttle, with lots of smoke out of the exhaust.  I am at the end of my rope here, I'v probally gone through the carbs at least 5 times, any help would be appreciated :sad: .  Thanks, Josh.

Offline Bartjan

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Help, surging and backfiring on start up.
« Reply #1 on: June 29, 2007, 04:40:23 AM »
that it backfired out of the exhaust is just because there was some mixture in it.

what color is the smoke?
- blueish means there is oil burned
- white is moisture aka water
- brown/black means the mixture is rich

also check if there isnt any false air drawn in at, that would explain why it reves go up.
chec by spraying some burnable goody (deoderant/brakecleaner/...) across the intake rubbers (between the cilinders and carbs) to listen if the motor respond, which means a leak
ofcourse don't spray in the airfilter
1991 US Bandit 400

Offline fowfam

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Help, surging and backfiring on start up.
« Reply #2 on: June 30, 2007, 12:27:25 AM »
Hi Thanks for the repiy, sprayed the boots and airbox with brake clean, nothing.  Checked the pipes while at 4k with a temp gun. #3 and #4 running close to 200 degres cooler that 1 and 2, any advice?

Offline Bartjan

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Help, surging and backfiring on start up.
« Reply #3 on: June 30, 2007, 05:38:04 AM »
do a compression test/check on all cilinders

what color is the smoke? have you tried driving the B4 yet?
1991 US Bandit 400

Offline Forde

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Help, surging and backfiring on start up.
« Reply #4 on: June 30, 2007, 03:02:25 PM »
have you set your idle speed and checked the choke cable
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Offline gsxr400 racer

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Help, surging and backfiring on start up.
« Reply #5 on: July 01, 2007, 12:54:58 PM »
sticking choke cable was my thought to
1988 gsxr 400 sp (sprint bike)
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