Leaky / sticky valve

[BigVeeGrin]

for a long while i have suffered an intermittent misfire/backfire and the storm would stall on idle. No compression issues or anything.

Just had a long overdue major service, bike is transformed and the mechanic reckons it's a sticky/leaky valve. i've had to save for the service and wonder if this is something i can live with for a while as i'm broke and still just in a job? The mechanic wasn't too worried, saying no harm can really come from it, even if it's a bent one as they're hard as hard can be.

or - is it something i could have a go at with a manual, some perseverance and enthusiasm? or is shimming,grinding and all kinds of complex stuff involved?

I'm not a mechanic, but also not a complete nob (debatable some will say) - so bit of advice really chaps

[cupasoop]

If it sounds more like a cough / sneeze coming from under the tank then they all do it to some extent. Turn your idle speed up to about 12/1300 and keep your carbs balanced which should minimise it.

[BigVeeGrin]

ok cheers - meant to say it sometimes sounds like very mechanical and a heavy, deep clonk! Rear cylinder.

[oldbikeman]

Check your CCTs

[sirch345]

BVG,
Compression would not be good if you had a bent valve.

I would be more inclined to think the same as Rich (Cupasoop) as a cough back through the air box as the engine stalls is a common thing for the Firestorm and it happens very intermittently as you mention. But having said that a lot of owners do not experience this at all. That can sound quite concerning if you're not used to it happening, and yes I would say it does sound slightly mechanical as it stop the engine in it's tracks.

My bike used to do it, but since fitting after market cans and altering the mixture it doesn't now. As Rich says, keeping the tick-over on the high side will help as will keeping the carbs regularly balanced.

Chris.

[benny hedges]

new plugs as well.
if you idle it a lot and lug round at low rpm they're probably well coked up.

[BigVeeGrin]

cheers all - it's got new plugs, balanced carbs and manual ccts (done 4 months ago).

It's got Viper cans on - might that cause some problems? Supposedly they were a straight replacement for the standard (it came with the Vipers so I might pop the stock ones back on and see if any difference).

Intermittent is actually a euphemism for most of the time i realise, and slightly mechanical is one for half expecting the rear piston to make my acquaintance through the seat - when the revs rise i guess it's not got a chance to cough back. It did when being serviced with the airfilter and box off and the carbs caught fire!

I'll swap the cans over and raise the idle and see where we get.

[benny hedges]

ah. check there are no air leaks where the link pipes join the collector pipe under the swing arm.
slight air leak there will make it pop & fart on over-run.
also check the chain isn't hitting the left link pipe - it would do that when you throttle off and get a bit of slack... then go again under power as it pulls the chain tight on the top run.

just a thought...

might just want a proper good thrashing that'll sort your sticky valves

[oldbikeman]

If it sounds bad then check it out properly,guess work ain't good enough .Can be expensive or dangerous. Loud cans are no cure.No Honda motor started out making bad noises.There are lots of little chains , cage bearings etc on this engine.

[tony.mon]

It's normal, they all do it.
Don't strip the motor or anything expensive, advice given so far is accurate.

[BigVeeGrin]

thanks for all the advice.

took the vipers off, put the stock cans back on and on the basis of a mental hour out this afternoon it seems transformed. lost the groundshaking character but things seem a lot less violent and it ticks over beautifully. i guess the vipers were not straight swaps. see how we go to and from work this week