Back firing when changing down a gear?

Squiffythewombat · Post by **Squiffythewombat** » Mon May 16, 2005 3:53 pm

Hi All,

My bike seems to be backfiring more than usal, it doesnt happen all the time, but at least two or three times when im out (100miles ish rides). It tends to happen when i shift down from 3rd to 2nd or 3nd to 1st and it BANGS...

Is this normal? im assuming its not? dont get me wrong i actually kinda like it, shotguning passes by, lol. Please dont tell me this is something serious, ive only just got my bike back.......

Any inputs good.....
Thanks for reading my drivel!
Toby

trebs · Post by **trebs** » Mon May 16, 2005 4:05 pm

stupid question..

You didn't fill it with 95 octane did you? Mine farts like a trooper if I don't use 98 octane.

Rob.

Spacemonkey · Post by **Spacemonkey** » Mon May 16, 2005 5:18 pm

Are the pipes leaking in air anywhere on the manifold bits? This will cause it to "bang like a shithouse door when the plague's in town..."

Squiffythewombat · Post by **Squiffythewombat** » Mon May 16, 2005 9:55 pm

petrol wise, ermmmm yeah normal the 95, i will fill her with 98 tommorow and see if that makes a difference, i will also check for air leaks when its light? (stoopid question but im asuming i will feel air blowing out?)

Spacemonkey · Post by **Spacemonkey** » Tue May 17, 2005 7:24 pm

Not always, but check for signs of carbon deposits. My Duke has a clamp that is a bit like a glorified jubilee clip (although, as it's blessed by the Pope, and okayed by the Mafia it will cost 10x more) and this was clamping the pipe where it was split leading up to the rear cylinder. This was leaking on mine, but a few mins with a hacksaw to widen the split, and some rigorous clamping produced an effective seal. Which I then clubbed over the head and flogged to Naomi Campbell.

Squiffythewombat · Post by **Squiffythewombat** » Wed May 18, 2005 11:48 am

hiya all, i cant seem to find any leaks, although this really doesnt mean there arnt any, lol! is this something serious to worry about do you think or can i just enjoy my shotgun shells

Post by **kevg** » Wed May 18, 2005 1:32 pm

I had my bike on a dyno last week and after about 25 runs it started to backfire like hell, then a nut fell off the exhaust header, once that was tightened the backfiring dissapeared completely.

i also have a K&N fitted that blocks off the air pipes to the emissions controll, that basically injects air into the exhaust to help get rid of unburnt gases probably causing the bangs by detonating the unburnt fuel.

there is also a joint in the rear pipe, that is inside the swing arm, very hard to see and also very prone to leaking, might need a new gasket.

cupasoop · Post by **cupasoop** » Wed May 18, 2005 2:46 pm

Was that the secret dyno man you were trying out kev? Was he as good as you were told?

Post by **kevg** » Wed May 18, 2005 3:56 pm

yup, he was good.

works in MCS in renfrew for the past couple of years, used to be Ian Duffus spannerman.
been racing and got fed up not being able to set the bikes up properly so him and another guy halved in for a dyno.

They are set up in a barn at an quadbike and outdoor persuits facility called Hyperside just outside Strathaven.

Â£120 for set up and as many runs as it takes to get the bike right.

ended up with 108 Hp and the fuelling set spot on after having the tank,air box and carbs appart about 6 or 7 times and a dyno run of five or six runs up and down after every time.

They also removed the plastic bits that fill in the frame at the front of the air box, this gave 2Hp straight away, helped to get air into the box.

i left at midnight and they were putting one of thier R6's onto the dyno next to check it after doing some work to it. the storm produced more Hp than the R6..

it only had 106

Pipstorm · Post by **Pipstorm** » Thu May 19, 2005 9:48 am

Popping and backfiring is usually down to a lean mixture, have you got aftermarket can on the bike?, After fitting ART race cans mine ran really lean and backfired like mad, a day on the dyno and a jet kit sorted it out and the bike now runs sooooo fine.

Before going to that expense check the exhaust joins, I ended up putting a thin film of exhaust paste round the inside of the joint to get an air (exhaust!) tight seal, as any leaks can give a similar backfiring /popping.

It's not a problem as long as the bikes not running lean, keep an eye on your temp gauge, does it rise quickly? does it get hot in traffic? mine did both after putting on the cans, The engine was running lean due to freeer flowing cans, potenially this is a big problem, melted pistons /valves -not good.

If your on original cans (get rid of them

) it's probably down to exhaust leaks.

hope this helps

Phil

Squiffythewombat · Post by **Squiffythewombat** » Sun May 22, 2005 1:47 pm

brill, thanks for all the help,

ive checked the pipes and still cant find an obvious leak, however i ran the bike on 98unleaded and it seemed to backfire alot less? put 95 in it from this other garage and BANG BANG BANG....i think it might be something to do with my regular garages fuel? or is this just stupid?

either way i will have kaz's ART cans soon (cant wait) and when they are put on, i will get them to check over all the pipes and nuts.

rockape34 · Post by **rockape34** » Sun May 22, 2005 7:00 pm

I've just put ART Race cans on and Dyno'd, The bike now runs much smoother, but, how loud??? saying that, the bike plod followed me the other day and did'nt pull me over., why not Iam not sure cos the cans are loud.........and release the thunder----GREAT I now have a smile on my face the wife fails to achieve...

Bike safe

robin1000 · Post by **robin1000** » Mon May 23, 2005 12:19 pm

Fuel makes a big difference to the running of the bike. The quality varies dramatically from garage to garage.

When I raced on the IOM I filled up with 98 octane from the local garage and my gixer ran like a bag of spanners.

98 from the pump at the paddock and it was a different bike.

Everything else mentioned is valid, and there's no better remedy than a good set-up.

Robin

Squiffythewombat · Post by **Squiffythewombat** » Wed May 25, 2005 11:14 pm

yipeeeee i cant wait!

although....i filled up from several stations over the past few days and its still back firing so maybe it is the leaks etc....ill wait for the cans to go on and if it still does it then ill investigate further i think???

bad plan? or this ok you think?

logan7 · Post by **logan7** » Thu May 26, 2005 8:25 am

Squiffy mine has a very small crack in a weld on the headers just at the back near where it goes into the cans. i can just feel the air coming out . but on the overrun my bike pops great, i love it

if its just air getting in then enjoy it.

i do