So it wasnt the plugs

tattoo · Post by **tattoo** » Thu Sep 22, 2011 11:34 pm

between the plug cap and the head and also the joint where the HT leads screws into the cap....

Miztaziggy · Post by **Miztaziggy** » Thu Sep 22, 2011 11:38 pm

Ok thank you

Will look tomorrow :-)

tattoo · Post by **tattoo** » Thu Sep 22, 2011 11:51 pm

tbh my problem was alittle more pronounced...it would run ok upto 55mph then misfire until it hit 65mph...not the best thing to happen at 1am on the a1...i found the coil was breaking down...i might have a coil laying around somewhere,you'll have to change the bracket and lead tho as it's a rear coil.

tinysmall · Post by **tinysmall** » Fri Sep 23, 2011 4:55 am

Also check for air leaks between the end cans and link pipes. If they are leaking, use RTV sealant.

stormingjoe · Post by **stormingjoe** » Fri Sep 23, 2011 7:39 am

Mine misfired when hot, after about 20 mins of thrashing, just changed coils, seems to have resolved it, replaced with stick coils, a renown mod. Will find out if sorted next week with 2 days of thrashing at snetterton

Fatty on a motorbike ;0D

Miztaziggy · Post by **Miztaziggy** » Fri Sep 23, 2011 10:20 am

What are stick coils and are they better than standard ones?

Just been thinking about this - and how likely is the problem due to be something to do with crap fuel or water in the fuel or something like that? Im sure I have read on here somewhere about water in fuel or low quality fuel causing misfiring...

Hmm...also just read this

http://www.aa1car.com/library/2004/ic100474.htm
"If a spark plug is wet when you remove it, it probably is not getting any spark."

When I removed by rear plug when I changed them, the rear was wet. I thought it was oil as it was brown, but now I bet the plug was brown and it was just wet with fuel, so, according to this, my rear cylinder isnt firing properly.

Strange, because it doesnt feel like it is running on one cylinder, but, I guess I should start with inspecting the rear HT lead and coil? Sound plausible?

vtryorks · Post by **vtryorks** » Fri Sep 23, 2011 12:52 pm

Ziggy, this hesitation, is like it a strange mechanical clunk/click/cough, you feel loss of forward momentum for like half a second, then it carries on normally?

Stratman · Post by **Stratman** » Fri Sep 23, 2011 3:35 pm

Check that the plug caps don't have a split in the rubber which could cause any trapped water to short the spark. Also I'd unscrew them both, thrim off 1/4 inch from the lead and screw them back in securely. I had a similar thing a few years ago when she would misfire when warmed up and it was the split rubber plug boot.

Miztaziggy · Post by **Miztaziggy** » Fri Sep 23, 2011 8:05 pm

vtryorks wrote:Ziggy, this hesitation, is like it a strange mechanical clunk/click/cough, you feel loss of forward momentum for like half a second, then it carries on normally?

No mate, no clunk or click...just a burble type of feeling as it misfires and doesnt accelerate smoothly

Been for a long drive and an update
I checked both plugs again, the back was a little brown with crap already, not sure what this is suggesting? Bike running rich maybe?

Checked in the dark for any arc and couldnt see one anywhere. I took off the rear plug cap while it was running so the bike was running on 1 cylinder only. I could then see blue sparks on the outside of the rubber plug cap going to the frame and earthing there.

Went for a long motorway drive (25 miles). Problem was there when cold and hot. Drove through town in first gear to get it hot enough for the fan to kick in and problem still there.
It starts to misfire at 6k rpm and seems to be worst between 6k and 7k. After 8k it doesnt really feel to be misfiring much.
There is no problem at all below about 5k rpm and bike pulls nice and runs smooth.
Over 7k rpm, bike feels 'lumpy' when holding constant speed. Say trying to hold 40 in first or 60 in 2nd.

- The interesting bit is that the problem feels much worse with full open throttle. If you wind on gently in 1st gear up to 1/2 or 3/4 throttle, it accelerates almost flat out all the way without much problem. If you whack open full throttle at low revs, the revs climb and then stutter after 6k.

On the motorway - same problem in 3rd gear for example, accelerates ok with minimal or no misfire with winding power on gently - even though still accelerating almost flat out. Wind power on flat out at 6k or higher and it stutters and misfires.

Winding power on gently up to about 3/4 throttle doesnt solve the problem, as it still did misfire a couple of times doing that, but no where near every time, whereas it does misfire every time when full throttle.

So im thinking that maybe it is fuel related now?

Carbs?
Throttle position sensor? How do I check this?
Exhaust blockage? Makes sense as higher RPM will require more gas flow and any restriction will cause too much back pressure wont it?

Lastly - would water in the fuel cause these problems or would the symptoms be different?
If there is water in the fuel, do you have to drain the tank? If there is no water in there - maybe it is just crap tesco fuel and filling with 99oct will cure it?

stormingjoe · Post by **stormingjoe** » Fri Sep 23, 2011 8:27 pm

Sounds like fuelling problem

, check diaphragm in tank valve for holes, possibly drain fuel out to check for contaminates, could be closing reducing fuel flow, then check diagphragms in the carb tops and vacuum hoses, if you want lift the carbs to check for contaminates in the float bowl and the rubber mount, also check for correct choke operation. Just to get you started.

Miztaziggy · Post by **Miztaziggy** » Fri Sep 23, 2011 8:31 pm

stormingjoe wrote:Sounds like fuelling problem , check diaphragm in tank valve for holes, possibly drain fuel out to check for contaminates, Ok I think worth doing, will try tomorrow
could be closing reducing fuel flow, then check diagphragms in the carb tops no idea where diaphragms are in carbs to be honest
and vacuum hoses checked these and they all seem fine,
if you want lift the carbs to check for contaminates in the float bowl Will give it a go - is it just a case of unbolting them and lifting off? No chance ill mess up something that will need setting back up properly?
and the rubber mount, also check for correct choke operation choke seems to be working fine to be honest..
Just to get you started. thank you for your input

stormingjoe · Post by **stormingjoe** » Fri Sep 23, 2011 8:38 pm

Could still be the rear coil on its way out though as thats the one that don't appear right:crazy:miss fire would mean excess fuel in cylinder

tattoo · Post by **tattoo** » Fri Sep 23, 2011 9:35 pm

+1 on the coil.....you could always change the coils round and see if it jumps cylinders

MJONESY · Post by **MJONESY** » Fri Sep 23, 2011 10:12 pm

Phreaps i am being a little bit simple here but brown plugs tend to suggest rich running,i would be inclined to check the air filter is in good nick because if it is blocked that will reduce the air getting into the carbs and make it run rich, so the stutter at 6 to 7k could be the point where the filter is seriously hindering the air/fuel ratio.

But then i could be completely wrong i'm tired and half way through moving house and the brain just is not working properly.

Miztaziggy · Post by **Miztaziggy** » Fri Sep 23, 2011 10:22 pm

MJONESY wrote:Phreaps i am being a little bit simple here but brown plugs tend to suggest rich running,i would be inclined to check the air filter is in good nick because if it is blocked that will reduce the air getting into the carbs and make it run rich, so the stutter at 6 to 7k could be the point where the filter is seriously hindering the air/fuel ratio.

But then i could be completely wrong i'm tired and half way through moving house and the brain just is not working properly.

Agreed, other than the bike was fine one day, then not fine the next.

Makes me think it is electrical or fuel based as air filter would get worse over time????

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