Dies with choke, runs without, idle increases as heats up.

[MikeBb]

this is an nc35 right, turning the screw in will richen the bike

Are you sure about this?.. I have the screws set out from what they were before, and the problem is now worse, It still dies with choke, and now it intermittently burps fire when it is idling. I went to have a go at balancing the carbs tonight but there was no point with it running this poorly.
The problem remains with the airbox and filter removed

[vfrman]

A lower float height will allow more fuel into the bowl...so yes, richer.

[MikeBb]

Well this issue continues to drive me insane.

Some experiments tonight,
wound out pilot screws 1/8th to 1 6/8ths per advise on here that doing so will lean it out. It ran worse. fire from exhaust on idle + dies with choke.
From here wound them in one half turn, to 1 2/8ths.. Bike seemed to run a bit better, as in idle adjustment screw seems to need to be wound on less to keep it running, still dies with choke.
Tried in another half turn, no change, still dies with choke burping a little fire at idle.
From here went overboard. 2 1/4 out. creating theoretical very lean. No difference. Dies with choke immediately and with only a small amount.
went out 1/2, 2 3/4, no change
went out again, 3 1/4 (!!!!). no change.
All experiments were tried with and without the airbox/filter, with no difference to any result. No result is notice if i hold my hands over the trumpets and no vacuum is felt, so the idle air must be fine.

After experiments i pulled one of the plugs, and predictably it was wet and looked like shit.

As it came out: http://imgur.com/SlbK47T Wiped down: http://imgur.com/igHQYjM

carbon on them seems to come off with my fingernail. next step is to pull em all and clean em. Plugs are only 400kms old so buying new ones would piss me off, especially if they didnt fix the issue.

So, from the fact that wildly fucking with the pilot screw didnt affect how the bike idled very much, it would suggest that the pilot screws are missing parts or are blocked. Which they are not, and which cant be the case, as only a week ago i had them apart and cleaned out with degreaser and an air compressor.

Which leaves float heights... which is a completely subjective measurement, leaning against the knob on the valve, slightly slightly compressing it, making sure the float is seated, gives roughly the same result as simply having the carbs upside down, this measurement with a steel rule and vernier calipers is correct at 12~13mm.. if the knob on the needle is not at all touched the measurment could be ~14... which would make it leaner?!?!!

Just removed the carbs and pulled out all the pilot screws to confirm that no parts are missing or the needles broken off. Will take in to work with the air compressor again tomorrow, focusing on the pilot circuit. To clarify, going in reverse, this circuit goes from a hole in the carb near the butterfly, up through the pilot screws needle valve to one of the 3 brass fittings in top of the carb, with no fuel added along the way? (i just want to know where i should be focussing on unblocking)
Thinking about this seems like such a stretch, as it is so odd that it would be blocked equally on all 4, but if the shit running was caused by the plugs and the pilot circuit had no fault, and if the pilot screw setting is as sensitive as i am led to believe.. then wouldnt it have eventually died when i wound it to the extreme values above?..

[Neil22]

Well this issue continues to drive me insane.

Some experiments tonight,
wound out pilot screws 1/8th to 1 6/8ths per advise on here that doing so will lean it out. It ran worse. fire from exhaust on idle + dies with choke.
From here wound them in one half turn, to 1 2/8ths.. Bike seemed to run a bit better, as in idle adjustment screw seems to need to be wound on less to keep it running, still dies with choke.
Tried in another half turn, no change, still dies with choke burping a little fire at idle.
From here went overboard. 2 1/4 out. creating theoretical very lean. No difference. Dies with choke immediately and with only a small amount.
went out 1/2, 2 3/4, no change
went out again, 3 1/4 (!!!!). no change.
All experiments were tried with and without the airbox/filter, with no difference to any result. No result is notice if i hold my hands over the trumpets and no vacuum is felt, so the idle air must be fine.

After experiments i pulled one of the plugs, and predictably it was wet and looked like shit.

As it came out: http://imgur.com/SlbK47T Wiped down: http://imgur.com/igHQYjM

carbon on them seems to come off with my fingernail. next step is to pull em all and clean em. Plugs are only 400kms old so buying new ones would piss me off, especially if they didnt fix the issue.

So, from the fact that wildly fucking with the pilot screw didnt affect how the bike idled very much, it would suggest that the pilot screws are missing parts or are blocked. Which they are not, and which cant be the case, as only a week ago i had them apart and cleaned out with degreaser and an air compressor.

Which leaves float heights... which is a completely subjective measurement, leaning against the knob on the valve, slightly slightly compressing it, making sure the float is seated, gives roughly the same result as simply having the carbs upside down, this measurement with a steel rule and vernier calipers is correct at 12~13mm.. if the knob on the needle is not at all touched the measurment could be ~14... which would make it leaner?!?!!

Just removed the carbs and pulled out all the pilot screws to confirm that no parts are missing or the needles broken off. Will take in to work with the air compressor again tomorrow, focusing on the pilot circuit. To clarify, going in reverse, this circuit goes from a hole in the carb near the butterfly, up through the pilot screws needle valve to one of the 3 brass fittings in top of the carb, with no fuel added along the way? (i just want to know where i should be focussing on unblocking)
Thinking about this seems like such a stretch, as it is so odd that it would be blocked equally on all 4, but if the shit running was caused by the plugs and the pilot circuit had no fault, and if the pilot screw setting is as sensitive as i am led to believe.. then wouldnt it have eventually died when i wound it to the extreme values above?..

What is the history on the bike? Did you have it runnng fine then it sat around or you just bought it?

If you just bought it then I would say some half wit has poked out your pilot jets with a needle or tip cleaner, that would be the first thing I would replace with those symptoms, remember the pilot screw is only adjusting a percentage of the overall flow, if the overall flow is way too high then no matter what you do with the screw it will still be super rich, float height would have to be over flowing almost to make a big difference like that.

If you have some spare pilot jets just sight through them up to a light and see if there is a size change.

Replace them and I would say that's your problem.

Cheers

[magg]

Believe NC35 and NC30 pilot screws have an O ring seal, washer and spring. Perhaps you carbies are missing one or more of the O ring seals which may cause pilot screw adjustments to be ineffective.

[MikeBb]

Thanks Neil, History is that i bought it off a guy who had it sitting for a few years. It seems odd that the inside of the pilot jets would be damaged, but its not outside the imagination (i found the wrong emulsion tube in one of them so..) A 4 pack is available here http://www.ebay.com.au/itm/JET-KEIHIN-P ... 2ede6bf641 , can anyone confirm that this is the correct part. keihin #35..
I did take out one of the pilot jets and hold it up to light and it is indeed a tiny hole, but doesnt look damaged. but if we're talking 35 microns then i wouldnt be able to detect it anyway i guess.

Magg, all the parts of all 4 needle valves are in place, and none of the needles are broken off and stuck in the bore. To confirm, i have a needle, and in order, threaded on to it is the spring, the washer, and the o-ring. one of the needles had the washer missing which someone has replaced with an equally sized second o-ring. whether this causes issues or not it is still only 1/4 of the carbs out of configuration.

Today i removed all the pilot screws and soaked and cleaned and picked at them with my fingernails to get absolutely clean, also soaked the pilot air circuit with carb cleaner and blasted with compressed air from both ends to confirm that it definitely is not blocked. I also removed and cleaned up all the spark plugs.

No dice unfortunately.

It seems that this bloke here viewtopic.php?f=24&t=40726&start=10 had the same issue which I think, unless there is info missing from that thread, he fixed by adding a missing washer to the slide needles. Would this make the slides sit slightly open-er at idle? i cant see how this would help.

[Neil22]

Thanks Neil, History is that i bought it off a guy who had it sitting for a few years. It seems odd that the inside of the pilot jets would be damaged, but its not outside the imagination (i found the wrong emulsion tube in one of them so..) A 4 pack is available here http://www.ebay.com.au/itm/JET-KEIHIN-P ... 2ede6bf641 , can anyone confirm that this is the correct part. keihin #35..
I did take out one of the pilot jets and hold it up to light and it is indeed a tiny hole, but doesnt look damaged. but if we're talking 35 microns then i wouldnt be able to detect it anyway i guess.

Magg, all the parts of all 4 needle valves are in place, and none of the needles are broken off and stuck in the bore. To confirm, i have a needle, and in order, threaded on to it is the spring, the washer, and the o-ring. one of the needles had the washer missing which someone has replaced with an equally sized second o-ring. whether this causes issues or not it is still only 1/4 of the carbs out of configuration.

Today i removed all the pilot screws and soaked and cleaned and picked at them with my fingernails to get absolutely clean, also soaked the pilot air circuit with carb cleaner and blasted with compressed air from both ends to confirm that it definitely is not blocked. I also removed and cleaned up all the spark plugs.

I would buy the pilot jets and put them in, people poke them out when they are blocked and being only brass it flogs the hole out. Even a 20 percent increase in size will ruin performance.

Adding washers to your slides will do nothing to cure your problem

Cheers

*fixed the quote. vfrman

[MikeBb]

Thanks Neil, ordered a 4 pack, theyre due on monday but fingers crossed for tomorrow, for future references i will post my results back here.

[magg]

Re-reading your posts, I have a couple of observations based on my experience with my NC30 and the info contained in the Honda General Serice Manual for by-pass type choke systems.

The usual starting proceedure would be to set choke to full and press the start button. Engine fires up and runs at high idle rpm, that can be adjusted by the setting of the choke. After 1-2 minutes I return choke to off position and engine should settle at normal idle rpm.

If when starting your engine, full choke setting does not result in an immediate start at high idle rpm then I would be investigating the choke circuit. The idle jet/needle circuit has no effect until the choke has been set to off, the amount of fuel supplied by the choke circuit should exceed that provided by the idle circuit. From your posts it reads as you are trying to overcome a choke circuit issue by forcing a high idle speed with a cold engine.

The choke system is a separate function to the idle system. The idle needle jet setting should only be set after the engine has reached operating temperature and the choke is fully off.

[Neil22]

Thanks Neil, ordered a 4 pack, theyre due on monday but fingers crossed for tomorrow, for future references i will post my results back here.

Good stuff, While you have your carbs off it would pay to just have a sight through the butterflys and just make sure they are in the ball park just to get you started. I usually do that while tidying up carbs on a new bike before syncing them on bike.

And compare the new and old jets up to the light and hopefully you see a difference.

I would say most probably not a problem with choke as if some of the plungers were stuck open then it would probably start and run well from cold. Although deff worth checking that all the linkages and your cable adjustment are letting the plungers return fully.

Cheers