Misfire - 3,500-4,000 RPM

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cliveyandrews
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Misfire - 3,500-4,000 RPM

Post by cliveyandrews »

I've been riding Pauline's 'Storm for the last few days - and I've noticed a misfire/splutter around 3,500-4,000 RPM, usually after using more throttle/revs, backing off, then rolling on the throttle. It clears its throat with more Revs and throttle - and is fine at high revs or large throttle openings.

The bike had manual CCTs about a 1000 miles ago - and had to have the head off as the mechanic had the chain jump some teeth and bend valves (he is a qualified mechanic honest!)

It's had new plugs (iridium), at that 1,000 mile point, a very recent new battery and reg/rec. the bike has a K&N - but when I looked at the old plugs they weren't obviously weak.

Soooo - any thoughts? Anything obvious/known failure points that I need to check? (Do coils fail, any diaphragms fail?)

I can ride through it, but its Pauline's bike - and I need it to run right and be smooth for her to gain experience safely....

Cheers guys!
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Wicky
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Re: Misfire - 3,500-4,000 RPM

Post by Wicky »

Try a normal filter if it hasn't been rejetted for the K&N.

When were carbs last balanced? Check for any air leaks in the intake/exhaust system. Is the vacuum hose intact and correctly placed.
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cliveyandrews
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Re: Misfire - 3,500-4,000 RPM

Post by cliveyandrews »

Wicky wrote:Try a normal filter if it hasn't been rejetted for the K&N.

When were carbs last balanced? Check for any air leaks in the intake/exhaust system. Is the vacuum hose intact and correctly placed.
I'll double check the vacuum hose. It was faultless until the CCT replacement - the workshop know Storms well and have done loads, so I'm not inclined to think something's been replaced wrong. I wonder if a coil could be going? I'm sure fuel is getting through. I'm gonna try another few tanks of fuel in case it's dirty - the bike doesn't do many miles - and stands around a lot....
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cliveyandrews
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Re: Misfire - 3,500-4,000 RPM

Post by cliveyandrews »

It's been suggested I pull the Iridium plugs for OEM spec...? (Mine runs fine on Iridium mind you)
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cliveyandrews
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Re: Misfire - 3,500-4,000 RPM

Post by cliveyandrews »

It's been suggested I pull the Iridium plugs for OEM spec...? (Mine runs fine on Iridium mind you)
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darkember
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Re: Misfire - 3,500-4,000 RPM

Post by darkember »

cliveyandrews wrote:
Wicky wrote:Try a normal filter if it hasn't been rejetted for the K&N.

When were carbs last balanced? Check for any air leaks in the intake/exhaust system. Is the vacuum hose intact and correctly placed.
I'll double check the vacuum hose. It was faultless until the CCT replacement - the workshop know Storms well and have done loads, so I'm not inclined to think something's been replaced wrong. I wonder if a coil could be going? I'm sure fuel is getting through. I'm gonna try another few tanks of fuel in case it's dirty - the bike doesn't do many miles - and stands around a lot....
Humm, they know their storms well even after bending your valves or was that another mechanic??? :?
tony.mon
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Re: Misfire - 3,500-4,000 RPM

Post by tony.mon »

Sounds like a carb strip is in order, and check the vac hoses when you have the airbox off beforehand.

And make sure the plug caps are properly pushed on....
It's not falling off, it's an upgrade opportunity.
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Re: Misfire - 3,500-4,000 RPM

Post by cliveyandrews »

Same mechanic. I do trust him. sh1t happens - and he rectified it all. I'll even go back to him if I can't find an answer....
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cliveyandrews
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Re: Misfire - 3,500-4,000 RPM

Post by cliveyandrews »

tony.mon wrote:Sounds like a carb strip is in order, and check the vac hoses when you have the airbox off beforehand.

And make sure the plug caps are properly pushed on....
I'm thinking crap in the carbs. It's the erratic nature of it. Like a block in a pilot jet?
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Duffy1964
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Re: Misfire - 3,500-4,000 RPM

Post by Duffy1964 »

[I'm thinking crap in the carbs. It's the erratic nature of it. Like a block in a pilot jet?[/quote]

I would try carb cleaner first :lol: :lol: :lol:
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cliveyandrews
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Re: Misfire - 3,500-4,000 RPM

Post by cliveyandrews »

Well - I pulled the carbs off and apart last weekend. Some gunk in the rear main, but that's it. Cleaned the bowls etc, but by then my back was fooked, so no test run. If I can drag my lazy butt out of bed I might stick some miles on it this morning.

Make sure it's ok for RTTW next week....
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Gavla9980
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Re: Misfire - 3,500-4,000 RPM

Post by Gavla9980 »

So was that the outcome to the problem ? Crap in the carbs.
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Kev L
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Re: Misfire - 3,500-4,000 RPM

Post by Kev L »

Clive was last on here in 2016 mate, so you may not get a response.
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Re: Misfire - 3,500-4,000 RPM

Post by Gavla9980 »

Hi kev, Thanks for you're reply. I did notice it was a while back the thread was on here but thought I would chance my arm to see if I got a response. Im assuming that was the outcome as he didn't return to ask anymore questions. Its a shame he didn't post the outcome for others to see. Cheers m8
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Re: Misfire - 3,500-4,000 RPM

Post by fabiostar »

my yellow one had the same problem. new plugs and all. but when i changed the few hundred miles old plugs for another set it cured mine. dont trust new plugs :thumbup:
the older i get,the faster i was :lol:
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