NSR 250 MC18, only one cylinder at a time....

[nickvr]

I have a MC18 NSR250. Something weird started happening a few weeks ago. The right cyclinder would stop firing intermittently. The results is complete power loss. I can hear it fire even so often but exhaust gas is cold. Took at to garage, they've cleaned the fuel lines / tank etc. It went 100% for few weeks and today the left side stopped firing. It is like 100% dead. This is driving me crazy, there is fire on the sparkplug. i guess it has something to with fuel or maybe CDI? Any ideas will be appreciated. Nick

[Paulus]

I have a MC18 NSR250. Something weird started happening a few weeks ago. The right cyclinder would stop firing intermittently. The results is complete power loss. I can hear it fire even so often but exhaust gas is cold. Took at to garage, they've cleaned the fuel lines / tank etc. It went 100% for few weeks and today the left side stopped firing. It is like 100% dead. This is driving me crazy, there is fire on the sparkplug. i guess it has something to with fuel or maybe CDI? Any ideas will be appreciated. Nick

A friend had a similar problem on his NSR (many years ago now) and it was the breather on the tank that was at fault. Did they clean/inspect that when they looked at the tank?

[jade]

Check - Sparkplugs first, make sure they are definately firing, give them a quick clean with a toothbrush and petrol,
Check coils - they both have power going to them
after that, Id check your pickup
after that your cdi.
It will be something simple, a mechanic could sort it..

[bumsex]

can you smell raw fuel?
Drain the foat bowl of the suspect carb and note whether fuel comes out or not

[imdying]

Get it fixed... I've seen people ignore that exact symptons you describe and boom!

[hurricane_r]

maybe running it low mixture on the oil, set the oil adjustment to standard

[Chrislost]

my mates one was running on one cylinder at idle, but at about 4000rpm it would pick up again, balanced the carbs and it was sweet, for about a week beore somthing else went bad.

[nickvr]

Definitively not spark related! I'll check the tank breathing. The one side in completely dead. I'll check the fuel pipes to the carb. Thanks for advise thus far, much appreciated.