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

[MikeBb]

Hi all, so I have been running my nc35 garage-rescue for the past week and its quirks are as follows:

When cold, choke + throttle blip helps it start but must be removed as soon as the bike fires up as it runs very roughly or not at all with choke on. Also when cold the idle screw has to be increased quite a bit to get it to run, then it seems to idle fine at 1500rpm/what i set it at. Later on when the bike has heated up the idle speed sits at 2500-3700 rpm due to the increased setting, and can be wound back significantly to get it back to ~1500.

I did some tests this afternoon and with the bike in an idling condition, if i remove the two smaller tubes from the rear of the airbox (i think these are the idle air supply?****) and block these i can feel no vacuum, and the bike doesnt respond. (suggesting blocked) If i sprayed carb cleaner the bike reacts all over the place (suggesting not blocked)

Im suspecting the idle circuit is blocked and by having an increased idle setting i am just having the idle fed through the main butterflies, and that pulling on choke forces the idle circuit to be used, which is blocked which kills it. (?) i am unfamiliar with these carbs. Although i did pull out the jets and clean the float chambers/float valves.

Another suspect maybe the reg/rec wiring. I replaced my regrec and harness recently and my battery does not go flat, but the voltage measured at battery is not a whole lot higher at idle than off. and with revs, the voltage at the battery increases after rolling off (to 14.5) I will do the reg/rec wiring mod but could someone confirm that after running wires directly from the reg/rec green/red to the battery + and -, that the green and red wires from the reg rec to the harness are cut, or left, with the battery in paralell.

Im taking the carbs in to work tomorrow where ill have access to compressed air.


**** Carbs are out and im studying them a bit, i may have misread where i saw someone on here say the 2 tubes that go to the airbox are for the idle supply as it seems like they go to the vacuum chambers, in this case is the idle supply the 3 small tubes that are next to each funnel on the airbox side?

[Neosophist]

I did some tests this afternoon and with the bike in an idling condition, if i remove the two smaller tubes from the rear of the airbox (i think these are the idle air supply?****) and block these i can feel no vacuum, and the bike doesnt respond. (suggesting blocked) If i sprayed carb cleaner the bike reacts all over the place (suggesting not blocked)

those two little tubes run from airbox to the subairfilter, do not spray carb cleanr around this area, all it does is provide clean filtered air for the sliders.

they are not idle air supply. i dont know where you have this idea of an idle air supply? the idle circuit is fed from the main airbox like the rest of the carbs.

If it dies with the choke on from cold then the bike is probably running too rich, using the carb guide on here you can set the carbs up to standard, float height, pilot screws and jets.

if your pilot jets were blocked it wouldnt idle.

it could also be caused by a leaky float valve flooding one or more carbs. id start with a good service and make sure jets are in correct and float heigths are right and pilot screws are set

pulling the choke one will not "force the idle circuit to be used" the choke is a spearate circuit.

[MikeBb]

OK, pulled the carbs apart and cleaned with carb cleaner / compressed air in the 3 holes on top of the carbs next to each trumpet, and removed the pilot screws and cleaned in there, cleaned the screw-needles themselves and put back in ~1.6 turns out as in the carb write up on here. Also did the Reg/rec mod by wiring directly from the regrec outputs to the battery.
Unfortunately still having the same issue, starts up and idles ok but dies with choke. I even tried without the airbox (theoretically causing a lean situation) and the same thing happens. dies with choke. The note changes significantly when choke is added, I might upload a video tomorrow to demonstrate. I was going to put back together the bike this afternoon but I noticed that hte fuel tap is leaking so it will stay in bits for now

NC35,
Stock airbox, filter, flap is in place.
Yammomoto specA full exhaust,
112 main jets
recently cleaned out float bowls, valve seat, emulsion tubes, and jets, and checked float height, and bench synced the carbs.
recently replaced spark plugs
Recently checked valve clearences, all within range.
fuel tap flows fine
Last tank got me 6L/100km / ~39MPG which seems to be about what to expect from this bike which doesnt suggest its running overly rich.

thanks

[MikeBb]

Any help with this? Or diagrams i could look at? Still cant figure this one out.

[vfrman]

What did the plugs look like that you replaced? My money, based on what you are describing, is rich mixture.

[MikeBb]

thanks, they looked like crap, but the bike had been sitting for 5 years so I wouldnt know what to expect.

what other things cause rich running? im also leaning towards that being the case but I just cant figure it out.

blocked exhaust - not the case
blocked intake - not the case, air filter is new and symptoms were the same with no air filter
too big jets- have 112 all round, bigger than standard but not unreasonably so
incorrect float heights - I checked these a while ago.. but I guess I will again
incorrect pilot screw- all are 1 5/8 turns out.. maybe try winding them in?

is it possible that the idle jets are completely blocked and that its idling off the main jets?.. I didnt clean the parts that looked non- removable last time but I might try again.
the bike doesnt feel particularily down on power, and Im getting 130kms before hitting reserve.

[vfrman]

It's really hard to tell without having the carbs in front of me. Pull one of the new plugs and see what it looks like.

[Neosophist]

what do you have the floats set at? its 12.5mm on the 35 not 6.8mm like on the vfrs... this is an nc35 right, turning the screw in will richen the bike

[MikeBb]

Thanks guys, Ive got a vacuum carb balancer in the mail, when it arrives this week Ill gut the thing and report back on more precise float heights and spark plug conditions, Yes its a 35.

[MikeBb]

Ripped the carbs out and apart today, carb cleaner + air compressor.

A few notes on this:
float heights are all correct, If the measured float height is lower (meaning the float sits higher when upright) then it will run richer, correct?
pilot screws are all correct at 1 5/8ths of a turn out from In.. they may have been 1 9/16ths out, or maybe they are now 11/16ths, they are a tinier bit out now than they were before.
I discovered this from my front two carbs: http://imgur.com/c3hhM31
thats a rear emulsion tube and a front emulsion tube, both out of the front carbs, I cleaned and corrected this.. but it was an odd discovery. Both wide spaced emulsion tubes are now in the front carbs, as per the threads on here.

Fingers crossed!