Hi All,

I am experiencing very weird problem with my 1989 nc30. Bike starts fine on full choke, runs for about 3-4minutes on 3000rpm during warm up and dies afterwards suddenly in few sec. If I hit starter button again straight afterwards, it is reluctant to start. If I wait for a 2 minutes or so later on, bikes starts immediately and is ok.
Bike does not have any issues when warmed up afterwards and can go over 80 mph. If engine is warm, problem does not occur.

Carbs has been cleaned, vacuum hose ok and fuel flowing. New sparkplugs ER9EH.

Its a 1989 Honda NC30 with 66k on clock

Any ideas gents ?
Cheers.

how long are you leaving it on full choke for?, i dont tend to leave mine on choke for very long , just to initally get it started then drop back to half choke or less just to keep it ticking over, you could be leaving it on full choke too long and flooding it as such

Sounds like your carbs could do with a strip and clean

Hi,

Well, I have to leave it on choke for about 3 minutes, otherwise it will not tick over.
Carbs has been stripped and cleaned. A week ago.

Something isnt right, are the emulsions the right way round. Idles screws set right, etc.

Had the same problem with mine 2 years ago all done to being dirty and poorly set up.

Maybe the the fuel tap diaphragm has fault that causes intermittent flow at first start-up.

Well, I initially thought that they might be problem with fuel tap, but carb bowls are primed and there is plenty of petrol for it to run over minutes. Strangely, at the point when the bike is about to cut off, it does not give spluttering sound as it is running out of petrol. Its more like it suddenly gives up and does not provide spark. To explain it better, its running on 3k @ idle with choke, then it does not slowly dies from flooding... revs drop suddenly from 3k straight to 0 in 2-3 seconds. I would assume, if there is any fuel problem, bike would eventually sputters and go slowly from 3k revs into 0.
Whats more weird, it only does in the evening. I have no problems starting it up in the morning... Any clues please?

btw, carb jets are 2 turns out front & rear.

spyrius wrote:Well, I initially thought that they might be problem with fuel tap, but carb bowls are primed and there is plenty of petrol for it to run over minutes. Strangely, at the point when the bike is about to cut off, it does not give spluttering sound as it is running out of petrol. Its more like it suddenly gives up and does not provide spark. To explain it better, its running on 3k @ idle with choke, then it does not slowly dies from flooding... revs drop suddenly from 3k straight to 0 in 2-3 seconds. I would assume, if there is any fuel problem, bike would eventually sputters and go slowly from 3k revs into 0.
Whats more weird, it only does in the evening. I have no problems starting it up in the morning... Any clues please?

Turn your carb idle screw adjuster up quite a bit so the revs are high without the choke. (will be super high with teh choke) but it's ok

It sounds like your idle revs could be far too low (common after fiddling with the carbs)

So when the RPM drops it cuts out.

If this cures the problem.. dial it out until your about 2000rpm and vaccum balance the carbs if you have gauges then drop the 1200+/- 100rpm and it should be silkey smooth if the carbs are clean and setup properly

Just pulled carbs out from engine, gave it full cleaning, blowing and new valve seats. Replaced all crap with stainless hex bolts.
With regards my problems, it seems like vacuum hose is kinked as suggested . Its folded near the right rear cylinder vacuum take off. I tried to suck from the vacuum hose leading to that cylinder and I could feel there is a bit of flow of air, but hugely restricted. Might it be culprit of my startup problems?

So if I run on choke, does it use a bit more petrol and is starving itself ? Funny, it does not do once warmed up.
Plugs are fine, slightly brownish with no sooth or oily deposits.

Hope the nightmare would be over

Will put the fresh petrol in when this awful weather would be over.
fingers crossed....