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View Full Version : M900 excessive backfire on over-run

SteveG
30-10-2016, 06:09 PM
Hi folks.. Last 2 ride outs have had impressive/ excessive backfire on over-run. Turned a lot more heads than usual with the booming Termi's today - descending down the long hill into Hurstbourne Tarrant especially noisy. Put 2 tanks fuel through and not any better, so I am looking where to start for a fix. I am sure I have heard or read that air leaking into exhaust is a frequent culprit.. any other likely suspects on th M900 or recommended checks to carry out? Any advice welcome. Cheers.
Darren69
31-10-2016, 08:05 AM
IIRC there are only 3 places where the exhaust could leak: where it joins the head and where it joins the collector and where it joins the silencers. You need to check all are gas tight also check carb rubbers are not perished or split.

The other culprit could be snapped head studs which the M900 and 900SS were well known for. So check all the head studs are not broken, that there is no movement and you can't waggle them about by hand.

Hopefully it will be your exhaust leaking not the studs.
Dirty
31-10-2016, 09:34 PM
When you find out what is causing it can you let me know so I can do it to mine :mand:
SteveG
31-10-2016, 09:47 PM
When you find out what is causing it can you let me know so I can do it to mine :mand:

Haha.... if it's broken studs you can have them in exchange for your good ones ;)
SteveG
10-11-2016, 06:34 PM
Update.. while looking over the bike at the recent chilly Hants/Wilts brekky meet me and Darkness spotted the culprit. Missing nut from the exhaust header clamp ... easy mod if you fancy the lovely crackles and bangs on over-run Dirty ;)
Pedro
10-11-2016, 06:48 PM
Update.. while looking over the bike at the recent chilly Hants/Wilts brekky meet me and Darkness spotted the culprit. Missing nut from the exhaust header clamp ... easy mod if you fancy the lovely crackles and bangs on over-run Dirty ;)

Since when is my name Darkness?

:nash:
SteveG
10-11-2016, 07:04 PM
Since when is my name Darkness?

:nash:

Ha... sorry Pedro...!! You are right... brain-freeze!!!! :dunce:
Dirty
10-11-2016, 08:10 PM
Update.. while looking over the bike at the recent chilly Hants/Wilts brekky meet me and Darkness spotted the culprit. Missing nut from the exhaust header clamp ... easy mod if you fancy the lovely crackles and bangs on over-run Dirty ;)

Excellent, I'll get on it :mand: