Something very worrying has happened

[Slinn84]

Ok coming home from uni today on the thundercat and i was going down a straight road so i thought i'd strech her legs a bit, doing 90mph at 9000rpm and i closed the throttle to slow down a bit and after a second or so heard a loud crack coming from the rear of the bike.

thinking i'd just gone over a loose man hole cover i carried on

the same thing happened again going up another road tho soon after, high revs, close the throttle and another loud crack (getting worried now)

when i got home i had a look round the back at the exhaust and could smell something burning coming from the silencer, not the normal exhaust fume smell either, something more sinister. there was also a strong smell of petrol in the garage after i parked her up for a bit

there's no petrol leak from the pump, hoses or tank so i'm assuming something engine wise has occured

any ideas? is this just my bike backfireing? if so whats the cause

i'm really at a loss of to what is cuasing this cos the bike has been behaving perfectly lately

cheers

[Bezzer]

Coming off the throttle is when you get carb icing if your bike suffered from it as the idle circuit is affected. Would have been ultra cold at 90 I'd guess it's on the edge of icing as you've slowed down but not fully affected, got a bit of excess fuel and you ended up with a bit of a backfire....that is just a guess, see if it happens again
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I used to be indecisive but now I'm not quite so sure.

[Kickstart]

Chain adjustment?

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[ThunderSteve]

Same thing happened to me yesterday morning on the way to work.
Was doing about 70 though, checked the cat over at work, did not see anything obvious. So the sugestion of carb icing makes most sense to me.

I bought some lead replacement fuel additive this morning when I filled up, added some and no icing to or back from work at all. Not even the dreaded slow down and get iced.

All the best.
Steve

[Slinn84]

ok

[Bezzer]

[Slinn84]

nice one beezzer i'll give it a try

can anyone else vouchfor this stuff?

i've heard of all kinds of additivies for petrol but always been warry of them, after all engines are designed for petrol, so i assume that nothing else should get in them but i'll try it out

cheers guys

[Bezzer]

It's THE cure dude, anyone who has used it swears by it, causes no problems and it WORKS. .
https://www.socweb.co.uk/forum/forum_posts.asp?TID=30891&PN=1
[url][/url]
____________________
I used to be indecisive but now I'm not quite so sure.

[Kickstart]

[Slinn84]

an air leak in the exhaust? sounds likely now, there's a small rusted hole in the downpipe where the 4-2-1 goes from 2 to the link pipe. could this be the cause?

it happened again today, does'nt happen all the time tho, and only at high revs, simply solution i suppose is not to rev her too hard.

cheers

[Kickstart]

Hi

Air leaks tend to cause backfires in the exhaust.

Get some GumGum and plug the hole up and see if that fixes it. Might not last long but will at least let you know if that is the problem.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[NSR Mick]

might be worth checking the cush drive rubbers

[colin1]

I had this today or something similar when riding through thick fog on my 600. Not very loud but for a sec I was scared cos I thought the tyre had popped
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colin1 is officially faster than god