misfire advice needed

[timwilky]

My curvy has today developed a misfire. The engine was doing about 7000 RPM when suddenly it lost all power, tacho dropped to about 4000, coughed and spluttered and then returned to full power.

This happened twice more. I then took a 15 minute coffeee break and when I started the engine it was ticking over roughly but showing zero rpm and then went back up to 1200. I thought all was ok until about 100 yds from home when on a bend it lost power and then kicked back in. Nearly kicked me off. Once in the garage it coughed and spluttered again.

I have never had any problems before with misfiring. I topped up the oil before setting up and filled up with fuel at my local Asda. I am tending towards a fueling problem due to the intermittent nature of the misfire. The other possibility could be the Meta alarm playing up, but again I would doubt it as it is as if a single cylinder cuts out, except for the strange zero revs indicated when it was ticking over.

Has anyone got any pointers where to start looking. 16000 on the clock. I last serviced at 14700 when I changed plugs as well as the normal oil/filters etc. plus the valve check.
I have had the obligatory chaffing of the loom against the sub frame and will shortly be pulling off the plastics looking for any new wear. Is this likely to be coils, plugs anyting else?.

Before anyone suggests water on front plug, weather was very good. Bike had done about 60 miles trouble free before this occurred

Could be a loose coil connection, lift the tank and check the connectors, I had this happen when I first got my bike and the front cylinder was kicking in and out all over the place, very frustrating but an easy fix if that's the problem.

What model is it?

[Biker Biggles]

Sounds very similar to my son's bike a couple of months ago.We thought it was coils playing up(so did RAC)but it turned out to be chafing in the loom.The culprit was three wires including the one which goes from the ecu under the tail unit to the front coil.The breaks were under the rear cowling near side where the loom bends around the subframe,not the usual place under the riders seat bolt.I had to strip all the sheathing off the loom to find it but had more or less identified it by checking continuity between connections at the ecu and coils.The front one was earthing when it should'nt.Good hunting.

[timwilky]

Well, I can't see any obvious chaffing of the loom under the rear end, but I have seen just how bad the alarm is fitted. I am now in the process of remove extranious wiring and rerouting in an easier to maintain, ie straight and tiewrapped route.

Maybe water in the fuel. I have had this before. Unfortunately the only way to cure that is to drain the fuel from the tank and the carb floats (curvey).

[Viney]

Tim, worth checking the fuel. I know of 4 people that recently have had issues with asda fuel. Sally, being one fo them's car tank, was get this, 50% water. Shes still trying to get her money back from Asda.

Failing all this, try unplugging the ECU, cleaning the contacts, then plugging it back in.

[Kylie]

I had really bad misfiring recently and it was the electric contacts on the fuel pump that was at fault, some corrosion in there. After clean to contacts all is fine. But mine's a K3...

Is it possible it is the Battery?

I left mine for two weeks while on Holiday, came back and the Battery was dead.
I tried to charge it up but it didn't want to know, it wouldn't hold the charge, but still I could ride it for a while (with what ever charge I managed to ge tin their) and found that the bike was sort of coughing, and also the RPM indicator was at 0.


Replaced the battery and all is OK now.

Just a thought.

I agree, check the fuel.

[timwilky]

ok I have the tank off anyway whilst I checked the coils etc. I notice crud in the bottom of the drain so am tempted just to empty the couple of litres in there and throw it.

I did about 100 miles yesterday and had about 4 episodes of misfire each lasting about 2-3 seconds. I would have thought electrical would have been repeatable hence my inclination towards fuel. Stange though my brother filled up at Asda as well but from a regular pump whilst I used the card fill ones.