Front Right Cylinder Failure - Help/Advice Needed

[alexwitham]

Hi Guys.

Having a few head scratching moments on the latest addition. The front right cylinder doesn't want to play ball at the moment so currently I own a 300cc V3 nc30.

I have a strong spark, the plug isn't fouled, I can smell petrol on the electrode so I assume the carbs are not blocked, the exhaust from that cylinder is hot (which confuses me) and it starts up OK.
If I remove the HT lead from the cylinder is question, the revs do not drop. Any other cylinder will cause the bikes RPM to drop enough to almost stall the bike.

My next steps will be to check the over the carbs, before removing the rocker cover to check the internals (which I had to do anyway to replace the gasket as I have a leaky front cover).

Before going into the engine and looking at valve train, can anyone suggest anything else?

Thanks, Alex

[VFRkieran]

Compression test would be my next port of call before going any further.

[The Novice]

From my limited experience I would say Kieran is spot on, it's getting fuel and firing as the exhaust is getting warm, that points to a lack of compression as your getting little or no power from that cylinder. Good luck.

[Cammo]

I'd start with a compression test, then carbs if it checks out ok.

Can you get it to fire at any rev point or won't fire whatsoever? Try holding it for a couple of minutes at 5000 revs and see if it clears up.

[porndoguk]

I'd start with a compression test, then carbs if it checks out ok.

Can you get it to fire at any rev point or won't fire whatsoever? Try holding it for a couple of minutes at 5000 revs and see if it clears up.

Mine runs on 3 when i start, ive checked the carbs hundreds of times and its just something i live with now,

Its C3 for mine when i hold the revs or when bike is warm its fine.

[GF Racing]

You can have a spark in free air and not under compression --- try a fresh plug 1st.

Cheers

Graeme

[alexwitham]

So which kind gent would like to loan me a compression tester?

Graeme - I've already tried a fresh plug, no joys unfortunately.

Cam - No I havent been able to hear it fart into life at all.

Alex

[arsey30]

Alex,
From what you say, it sounds like it fires at higher revs [pipes get hot] but not at tick over.
Check valve clearances, but perhaps it's carb balance [number 4 throttle stop set low] or pilot screw setting, or just a dirty pilot circuit.

[alexwitham]

Thanks for the input Dave. I'll be sure to give the carbs another comprehensive look over if the compression test reports no issues.

Can anyone help with the correct PSI for the cylinder compression?

Thanks

[CMSMJ1]

Less than 140 is poor. You will be wanted 180 or so..maybe 200 or so if all is well.

Sounds like a pain in the arse mate, hope you find something easy to sort.