Carbs/fueling advice required

[Mr_Fen]

hi,
since purchasing my NC30 I have experienced the many joys of owning an older motorcycle. I have replaced the fairing after the original crumpled beyond repair against a wall, practically rewired the bike to resolve troublesome electrical faults (it was the R/R) replaced the dial faces as the speedo stickers didn't work at night, and fitted a blue flame exhaust as the previous can seemed to have been attached with super glue.

As the bike has presented each challenge I have been grateful for the advice and suggestions presented on this forum.

As I have zero mechanical knowledge I have read most of the posts regarding fuelling and carburettors as a kind of alchemy, speaking of float bowls, needles and flat spots.

Unfortunately the little viffer has decided I must venture into this area of maintenance, given its shoddy performance last weekend.

The bike started fine with full choke, warmed up while I got kitted up and purred quite happily until about 2 miles from the house, at which point it spluttered and died. I ran through the usual things, flooded/no fuel/too much choke/not enough choke/idle speed to low/idle speed to high/battery dead to no avail.

Once I had fiddled about, drained the battery and bumped it down (and up) 2 hills I decided to call the RAC.

The mechanic checked the battery (ok) checked the spark plugs (strong blue spark) checked starter motor (spinning up so ok) checked the fuel tap (off-ok, res & on-ok)
tested suction from the engine on fuel line (ok)

He sprayed an aerosol into the top radiator as the motor turned over without success. His diagnosis was the carburettors need a service.

I have read the haynes manual and through the many posts on here about fiddling with carburettors and it sounds like hell. I am happy to stick it in a garage to get the work done but have a few queries about what I should be charged and what they will actually do.

As I have put a blue flame exhaust on the bike, should I have changed the 'trumpets' or intake spacers to compensate for something?

I have found since sorting out the electrics that if the idle is set to 1500rpm when warm it won't start the next day, if the idle is set to 2500rpm it will start the next day but idles at 3000rpm when warm (and is noisy) Is this because of the new exhaust or a sign the carburettors need adjusting anyway.

Would it be easier/cost effective to get a stage one kit?

[CMSMJ1]

for starters - all the guff about getting dyno jet kits etc and stage one this and that...is horseshit. The application of basic knowlegde is what you want!

Sounds like your plugs could be fecked to me. If not, they should have fired on the easystart aerosol he was spraying into the bike. Dumb mechanics - if it was running fine then stopped...it is not normally a fundamental failure in the carbs. More like a lack of fuel or sparks!

Check the basics - clean airfilter, good fuel ,flow from the taps, no blocked tank breathers (the one on top can cause the bike to stop like you described)

does it start now?

[Neosophist]

It just up and died eh.

Any signs of life when trying to start it?

You can compensate for an end-can by richening up the pilot screws (turn all 4 of them out 1/4 to 1/2 a turn)

I'm with CM's theory on this.

Unless it got progressivly worse over time somethings broken, thats not usually carburettors need a service as thats a gradual thing, they dont' usually just die.

You need Fuel / Air / Spark.

You need to make sure fuels actually getting down into the cylinders.. after trying to start it have a look at one of the plugs and see if the ends are 'wet'

They can die easy so new plugs might be in order.

If there dry you might not be getting fuel to the bike.

Check the usual vaccumn line, blocked breathers etc.

Or.. you might not be getting 'air', check the air filters not blocked up.

[Mr_Fen]

thanks for the pointers, the garage i usually use hasn't got a slot for a week so I think I'll have a look myself using the guide on here and the haynes manual.

Its always been a bitch to start so I think adjusting the pilot screws should help, I'll be going to B&Q/Halfords for screwdrivers, lubricant and cleaner stuff this afternoon.

Is there anything else I should do once I have the tank off?

the list so far is:
blow canned air down the hoses to clear any blockage, make sure nothing is squished.
ensure fuel is coming from the fuel tap
ensure fuel is getting to the spark plugs
check spark plugs are clean/wet sooty?
clean out air filter
write down the numbers on each bit and ensure its in the right place
don't fuck it up
be patient putting it back together

[CMSMJ1]

I'd try and start it. If no joy, get the rear plugs out and see if they have fuel on them.

This will give you a clue whether you are getting fuel or whether you have poorly plugs.

You could always give the plugs a once over through the cleansing flame on your hob to burn off any crap on the tips.

If you are getting motivated to whip the carbs off then good luck - it is not as daunting as you might imagine...just like your first lady

[Drunkn Munky]

and warm you carb rubbers up in boiling water before refitting the carbs, it'll save you a headache

[MexicanGringo]

You may as well clean the carbs out while the tanks off, buy some carb cleaner and blow through all passageways that air and fuel can travel. Its a good idea to then blow through with compressed air to ensure all solvent/crud is gone, do all this with the diaphragms/slides out.

[Mr_Fen]

ok, its been sat on the drive under its cover with the opitmate on it since its disgrace on sunday, I put the key in and after checking fuel tap was on, it started on 3/4 choke and is quite happily burbling away at 2500rpm.

Needless to say I'm pleasantly surprised, but also puzzled as to why its running now but wouldn't do anything a few days ago.

I think its still worth adjusting the pilot screws as it doesn't like idling at 1500rpm so i'll look to adjust these to 2.25 turns. To do this is it still necessary to remove the carburettors from the bike? or should I just complete the whole process as documented by DataRacer and be done with it?

[Mr_Fen]

I picked up the tools required and started working. It looks like someone has been here before though and made a mess of it. The liquid in the photo is a oily petrol mix that was thick and sludgy, I cleaned it off before re-assembling the bike. It still starts and runs fine but the idle is around 2500rpm as it splutters and dies at a lower setting. What's the easiest way to get this screw out?

[superlite]

That's oil from the crank case breather which is probably a sign that your oil level is too high. The screw looks pretty knackered! Maybe try an impact driver?