NC21 still not running right

[Viffer77]

No good.

After changing the overpriced rubbers and yet more tweaking. Still has the problem!

I agree that this is an air leak problem, but just don't know where from!

It's really pissing me off!!!

Any suggestions?

Help.

[Neosophist]

Hmm,

So what's it doing now, the revs hanging on the way down?

Any other problems?

[Viffer77]

Exhaust way too hot and flat spots once you've pinned the throttle for a few gears. If I cruise for a bit it then runs ok.

WOT seems to cause it some serious problems!

[Neosophist]

Exhaust way too hot and flat spots once you've pinned the throttle for a few gears. If I cruise for a bit it then runs ok.

WOT seems to cause it some serious problems!

Vaccumn pipe is to be suspected if WOT is killing it.

Weak ones leak / collapse in on themselves at full vaccumn which shuts off the flow of fuel until you back off. have you replaced the smaller fuel vaccumn pipe?

Hot as in glowing?

[Viffer77]

If you spit on the end can, it doesn't sizzle. It flies off.

I haven't changed the vacuum hose.

[Neosophist]

Standard end-can or aftermarket?

They do get hot.

Are your downpipes 'glowing' (this would indicate a really lean mixture)

Change the vaccumn hose and see if that solves your fuel starvation issue.

I can't remember what jets you have in the carbs.. 110 / 112's?

[Viffer77]

Hi Neo,

Standard can. Haven't noticed the downpipes glowing, but the power loss induced by fuel starvation would obviously lean up the mix quite a lot.

110's & 112's.

I will have a look at the vacuum pipe. Is there an easy test that you know of other than putting my lips round it and sucking.

Cheers.

Ben.

[Neosophist]

Take it off and stretch it, weak spots will snap the pipe, it generally dies where it connects to the engine.

[Viffer77]

Tried it, no good! The hose seems alright. I've given it some real suction and stretched it it nearly twice it's size.

I am at a loss now!

Any more suggestions (other than putting a match to it!).

[Neosophist]

Have you had a look at the fuel tap, theres a gauze filter inside the tank attached to the fuel tap.

If you remove the four screws from the tap you can inspect the diaphram too and make sure it doesn't have any holes in it.