Author Topic: Bike stumbles between 2-3000rpm (Read 5289 times)

Robbieukb12 · « **on:** April 14, 2005, 01:45:21 PM »

Hi at the end of last year i fitted Ivans jet kit with no problems
it rode pretty well but a little on the rich side.
This year i serviced the bike oil/air filters plugs and after riding it i found it wasn't running to well when riding around town when the rev's are around 2-3000 it seems to stumble or surge for want of a better word it isn't smooth low down. ride it hard and it pulls like a train.
like i said it was running a bit rich so i turned the a/f screws in a bit they were 3 1/4 out i have now set them at 2 1/2 this made a bit of a difference but not completely cured it, has anyone got any ideas.
The needles are set at the 3rd groove like Ivan recommends.
I roughly know that at idle and low speeds it's the pilot jet thats working and then the main kicks in (correct me if im wrong) but i was thinking could the pilot jet be gummed up a little?

Oh its a 2002 1200s sorry for not saying earlier.

Cheers

Robbie

Red01 · « **Reply #1 on:** April 14, 2005, 10:00:32 PM »

A. Did the bike sit over the winter?
B. If so, was the fuel stabilzed?

If A. is "yes" and B. is "no," your carbs need to be cleaned.

Robbieukb12 · « **Reply #2 on:** April 15, 2005, 09:59:57 AM »

yes it did sit over winter but it got fired up every few weeks or so.
it has crossed my mind if the pilot jets are gummed up a little, i'll put some cleaner in the fuel or somthing like that see if that helps.

Cheers
Robbie

WEINERDOGBONE · « **Reply #3 on:** April 18, 2005, 01:14:16 AM »

Robbie, I had the same problem with my B12 after it sat all winter. I used fuel stabilyzer but it didn't completly work. I used this stuff called Sea Foam. My mechanic swears by this stuff. It is some kind of snake oil that claims to clean fuel systems as well as about anything else. It worked like a charm. I just dumped about 2 ounces in the tank and it took care of my stumble. I don't know if you can buy this stuff in your area or not. I bought it at Autozone here in the USA.

Robbieukb12 · « **Reply #4 on:** April 19, 2005, 01:52:24 PM »

thanks i checked out there web site looks pretty good. Can't say i have heard of it here but i'll look sure look into it

Robbie

99er · « **Reply #5 on:** April 19, 2005, 06:49:51 PM »

Yeah,
I would completely drain the tank as that gas is shot and run some cleaner in fresh gas. Drain some of it through your bowls for a while to get rid of any sediment. I remember that Dale recommends STP in the clear plastic bottle (gold liquid). I don't know of any UK cleaners. They're mostly all based on acetone anyway.
Marc/Atlanta Georgia USA

Robbieukb12 · « **Reply #6 on:** April 20, 2005, 01:43:33 PM »

I put some Redex carb cleaner in the tank see if that helps. That Sea Foam stuff is not available in the U.K.
i have already got rid of the old fuel some time ago must have had 2 or 3 full tanks of new fuel gone through so far.

Thanks for all the help guys

Robbie

Robbieukb12 · « **Reply #7 on:** May 21, 2005, 06:24:23 AM »

Well after a few tanks of redex i decided to take it to a dyno centre and the guy said it was running on the lean side according to the gas machine i thought it was too rich (shows what i know).
Anyway i had the needles on the third clip as recommended and the mixture screws out about 3.5 turns, the mech' has now put the needles on the 4th clip and mixture screws out to 5 turns this i thought was too much but it definatly got rid of the stumble i had at 2000-2.500rpm.He also replaced the trumpet in the airbox sayint this was important due to air turbulance or somthing like that.
It has also increased Bhp and torque but it now pops and banks big time on decel, not just after you have nailed it you can be cruising at 30-40 shut the throttle and you get loud popping, has any one got any thoughts on this?
Hopefully you will see the dyno results below

Robbie

Boosted-Bandit · « **Reply #8 on:** May 22, 2005, 03:11:40 PM »

Popping on deceleration is most definately a lean condition on the idle circuit.
I would go 2 up on the idle jets and readjust the screws accordingly.

Robbieukb12 · « **Reply #9 on:** May 23, 2005, 05:24:23 PM »

Problem sorted a friend of mine listened to the bike while idling and said there is somthing not quite right there so he told me to take the tank off as i did he spotted a small diameter pipe that goes from No 4 carb to the tank and also splits and joins on the pair system had come off.
because these pipes are different diameters it looks like the mechanic had mixed the tank pipe with the pair pipe which had then become disconnected and was sucking air hence the bad popping from decel.
Once this was all connected back to how it should be there was no longer any popping at all and the idle is now like a purring kitten.

Robbie