Cold rear

[TROUBLED OTTER]

Noticed today that when my nc35 was running the two front down pipes where red hot but the two back pipes were cold. Does this have anything to do with balancing the carbs? I've just stripped and cleaned the carbs so was just wondering if it needs to be balanced.

[veefer400]

Stone cold pipes would indicate those cylinders aren't firing, hence no heat? I would imagine this to be fuel related due to the recent carb activity... was it hard to start/lumpy sounding?

[CMSMJ1]

Something not right with whatever you did to the carbs..

Nothing to do with balancing..the pipes should all be too hot to hold...even after 10s they will be bloody hot.

If not, they are not firing..you should be able to hear that it is a triple or a twin and it won't idle.

Did you flood it before sorting the carbs? Have you killed the plugs? Swap known working ones with the others and see what's what.

[TROUBLED OTTER]

She starts and runs with no problems. Checked spark on the two back cylinders. The plugs are brand new. I will try putting the front plugs in the rear cylinders and see what happens. Thanks guys!

[arsey30]

Was it allright before touching the carbs.

Are the pipes cold/not firing at tickover only, or do they chime in when the motor is running fast.

If hot at fast revs, then suspect pilot jets or airways, [ or air leak , carbs not seated ] if it does not run on those cylinders at all, then coil is common to those 2 cylinders.

[TROUBLED OTTER]

Was it allright before touching the carbs.

Are the pipes cold/not firing at tickover only, or do they chime in when the motor is running fast.

If hot at fast revs, then suspect pilot jets or airways, [ or air leak , carbs not seated ] if it does not run on those cylinders at all, then coil is common to those 2 cylinders.

The bike had been standing for 6 years before I bought it and I couldnt start it.So stripped the hole bike down,Cleaned everything.Bought new plugs and cleaned the jets and carbs out.
Put the carbs back on and she fired up no problem.Thats when I noticed the rear pipes being cold.It starts first time on the button but it seems to rev up very slow on the throttle.
I checked for spark on the rear plugs and they seem fine.
Is there anything else I can try other than the spark plugs?
I was told to spray WD40 on the carb gaskets and if the revs go up then I have a air leak,So I will try that as well.

[Cammo]

If it was an air leak it will generally be revving quite high when idling.

Do you know what the pilot screws are set at?

If you did the carbs then I would imagine you've set them correctly (1 & 5/8 turns out), but worth checking again perhaps, you should be able to get to them without taking the carbs off, just take the fairing off and use a long screwdriver & torch.

If the plugs are known to be good then it will usually be a fuelling issue causing this. At idle the pilot screws are responsible for the amount of fuel delivered - too rich or too lean and the plugs won't ignite the fuel mixture.

[TROUBLED OTTER]

mixture screws are set as 1 5/8 out.The idle screw is at its min,It just touches the throttle turn and it idles at 2000rpm with no choke.
Ive just had a thought.I mixed the old fuel, About a litre with new fuel,About 3 litres.Do you think this may have something to do with it?

[Drunkn Munky]

Did you mess with the screws that adjust the butterflies when you had the carbs off? You done the rubber up nice and tight?

[Cammo]

The idle screw is at its min,It just touches the throttle turn and it idles at 2000rpm with no choke.

This is a telltale sign that the carbs are out of balance. You'll probably find that the front and rear are out of balance, i.e. the front butterflies are open enough to let air in to ignite the idle mixture, the rear are not. This is what I'd be looking at. You can tell if this is the culprit by winding the idle up (which will open the rear carb butterflies more), if all cylinders start firing carbs out of balance is your issue.

Old fuel will not usually be a problem (if it ignites on the front cylinders it also will on the rear).