1 Cylinder not running below 3000 rpm

[Offspring]

Having dismantled and re-assembled my TRX for cleaning/repair and addition of lots of shiny bolts, It now starts and runs on the RH cylinder only below 3000rpm. Above this it runs fine and pulls well on the road all the way to the redline. Below 3000 rpm the LH cylinder cuts in now and then, but only for a few seconds. During the strip and rebuild the engine and carbs were not touched as it ran perfectly before the work. The carbs were balanced a couple of weeks before the strip so should be the same now.

I have checked all the fuel and vacuum lines and found no problems. A plug chop shows both plugs are healthy (nice light tan colour).

I have checked for air leaks around the intakes and exhaust and found no problems.

I am now thinking that their is a possible intermittent fault on the LH ignition coil.

Any ideas would be appreciated.

[Omegaman]

i had the same problem as such around xmas i ditched the fuel as it had been sat a while

if you want a second bike to quickly borrow parts from to test yours im happy to help

ie LH ignition coil

[Offspring]

Cheers Omegaman, thats appreciated,

Ive just bought a couple of coils of ebay, should be with me by mid week.

I emptied the fuel tank and refilled with new fuel. I havn't cleaned the fuel taps of fuel pump. Think i will give this a go too.

[HansJ]

coil, or the secondary wire not connecting properly, or plugcap orlead, or even the plug itself would be my prime suspects as well. Swap sides piece by piece until the cut-out has moved to the RH side?

[Offspring]

Thanks for the replies.

Fitted a new coil, HT lead and plug cap. Hey presto !! job done she runs like a dream.

Further investigation revealed the HT lead to be the culprit. The left hand HT leads bends through approx 160 degrees quite sharply from the coil to the plug cap. Even though there was no sign of damage externally, I stripped away the insulation and found that the centre core was crumbling in the area around this sharp bend.

Strange thing was when I tested the spark by placing a spark tester on the plug cap it produced what looked like a reasonable spark. However when compared to the RH spark it appeared weaker, but not by much. Clearly however it was sufficiently weak to stop the cylinder running below 3000rpm.

Thanks again.

The summer bekons and the TRX is ready for the fun ahead !!

[youngy]

well done!