starting issues

[dgunthor]

Hi all,

NC35 starts happily but then cuts out after a minute or two at which point it won't restart.
If I then bump start it will sometimes start or if it fails then it will then start on the next try - seems to clear something.
It will happily ride the 45 mile commute then no bother until I start it to ride home.
(Tried turning the fuel tap off last night but no different this morning)

Any ideas - could the spark be weak - coils? (new plugs 3000 miles ago)
it's a 1999 - could breather/fuel pipes be perished?
could valve clearances affect this?
what about if the carbs need to be balanced?

It's not been used much the last few years (3000 miles).

Many thanks in advance,
Dave

[magg]

Fuel flows well when engine is cranking? Vacuum tap or hoses perhaps faulty causing fuel starvation. Enough fuel in float bowls to get started but too little flow to refill immediately. Bump starting may allow sufficient fuel flow to refill float bowls and then running engine vacuum keeps fuel flowing. Does the engine run poorly when run at high rpm for an extended period.

[dgunthor]

Thanks, I think fuel starvation sounds plausible. I'll check the vacuum and fuel hoses, see if there's anything obvious.

It runs at 6000 to 9000 revs for 30 or 40 mins no problem in the morning once it's going.

When it's dying first thing if you rev it it won't rev and slowly the revs reduce until it cuts out - sounds plausible for fuel starvation?
If it was coils/spark then it would be misfiring/intermittent I'd have thought

[dgunthor]

Checked last night, vacuum pipe looked ok but the scottoiler joins onto it with a T piece and noticed part of the scottoiler pipe was cracked - replaced it.



Bike started ok this morning (though working from home so not ridden it anywhere). Will keep an eye on it but hopefully that was the issue :-D

[dgunthor]

update: that wasn't it - it's still stalling after start, then bump then start.

noticing some white/blue smoke too - will check the oil later to rule out head gasket.

think the valve clearances are overdue (44,000 kms) - could this be related?

[dgunthor]

oil level is over max and smells a bit like petrol - suspect dodgy fuel tap and fuel going through vacuum line.

will check fuel tap tonight...

edit: think that explains the smoke - suspect oil is getting into the airbox due to it being over max