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

[vfrman]

You could try getting the carbs sonic cleaned...

[Neosophist]

In Sydney in the parramatta area. Definitely NC35 carbs.

Have not done the test with O-rings in choke pistons as i have had thoughts that it will not work. If they were not seated properly, and letting fuel through, then indeed it would cause a rich idle, but it wouldnt change the designed maximum and mid settings for choke flow. So if my problem was that the choke pistons werent seating, it would not cause the thing to die with choke, Just idle rich.

So again i am stumped, my next thought is to carb clean+air blast (for the 3rd/4th time) all the jet air sources, only this time with the pilot screws, emulsion tubes/jets, float bowls, and choke valves all removed, as previous times when i did this most of them were mounted. My theory is that previous attempts at cleaning them might not have been thorough as having the jets mounted when cleaning might have just made any gunk settle at the emulsion holes. and that removing those parts whilst doing a clean will increase airflow from the air compressor.

This is the last straw (in a 'clutching at straws' way) that i have left. failing this i will go back to trying wild pilot screw settings.

you cant clean the carbs without removing the jets and pilot screws etc.

make sure your air bypasses aret blocked either as that can cause it to be rich

[MikeBb]

gave the stripped carbs a blast today with avgas, and by cleaner, and the air compressor, stick it in one hole and feeling for airflow out the other side.

The air lines that feed the emulsion tubes for the idle and main jets are clear and flow very well.

The pilot screw hole was a curious one though, as sticking the air compressor in there, i couldnt really find where its air ended up, but it seems to feed from the idle jet.

all other holes i went over and found 'the other end' just fine.

make sure your air bypasses arent blocked either as that can cause it to be rich

Which one is this?

[Neosophist]

top of the carbs by the trimpets

[MikeBb]

http://i.imgur.com/h6oulwi.jpg

Of the 3 brass tubes, pumping compressed air in to 2 of them leads to a clean stream of air from where each of the jets seat. pumping air into the 3rd one seems to give air from the pilot screw hole, but it seems the air is distributed to more direct lines / the flow is not very high. dripping liquid into the pilot screw hole causes that liquid to readily drip out the brass tube. I dont know how much airflow should make it through here so I'm not fit to judge whether this line is partially blocked or not.
For what its worth my last attempt at measuring milage with this thing got me 5.5L/100km (42mpg).

[Neosophist]

http://i.imgur.com/h6oulwi.jpg

Of the 3 brass tubes, pumping compressed air in to 2 of them leads to a clean stream of air from where each of the jets seat. pumping air into the 3rd one seems to give air from the pilot screw hole, but it seems the air is distributed to more direct lines / the flow is not very high. dripping liquid into the pilot screw hole causes that liquid to readily drip out the brass tube. I dont know how much airflow should make it through here so I'm not fit to judge whether this line is partially blocked or not.
For what its worth my last attempt at measuring milage with this thing got me 5.5L/100km (42mpg).

cant remember off hand but if all 4 carbs are hten same then its probably ok :D

[MikeBb]

Fiddled around with pilot screws the other day, just at idle, no airbox.
Fully closed, doesnt seem to make much difference.
Fully open, "runs" extremely rich, wet sound from top of carbs.

Couldnt get em sonic cleaned.. nobody has a big enough bath ..

So stuck bluetack over the brass tubes on top of the carbs.. inverted them and filled the pilot circuit up weith methylethylketone, let it soak for a while blasted the fuck out of it with compressed air, from both directions, a few times.. it damn well auta be as clear as it could be.. all the pilot circuits seem to have the same resistance seen in the ammount that drips out of the brass tube when pouring liquid into the pilot screw hole. also when i put my mouth (I DID WHAT) on the pilot screw hole and blow through it with a thumb and finger over the pilot hole in the intake and the idle jet hole, there seems to be the same ammount of resistance in each one. I should note that there is quite a bit of resistance there.

put it all back together and fiddled with the float heights (brought 2 of them down) so that holding the carbs at a 45* angle and passed over a vernier caliper depth guage set to 12.5mm.

ripped out the plugs and predictably they looked like shit. http://i.imgur.com/ONHbxjZ.jpg http://i.imgur.com/8mv2ise.jpg

Black. That is after soaking in MEK for a bit and having a scrub down with a toothbrush, the black isnt coming off. But notice the centres are brown. on this page: http://ngksparkplugs.com/tech_support/s ... aqread.asp they describe a healthy plug as having a brown centre, and their picture of a healthy plug has a black edge like mine. Dont get me wrong, im not cheaping out here. If i thought buying a new set of plugs would fix this issue i'd do it in a heartbeat. My problem with blaming the plugs is that these plugs are only ~700kms old, and i had this issue even when they were brand new. So whilst the bad plugs might explain why it idles like shit now, it doesnt explain how they got bad.

[vfrman]

Those plugs look fine.

I can't remember, but did you balance the carbs?

[magg]

Agree with vfrman, plugs look ok to me given they respresent idle speed fueling and random adjustment of idle mixture screws.

"Fiddled around with pilot screws the other day, just at idle, no airbox.
Fully closed, doesnt seem to make much difference.
Fully open, "runs" extremely rich, wet sound from top of carbs."

Idle is the only time you should be adjusting the pilot screws, with air filter fitted. Best way to set them is with vacuum gauages unless factory recommended setting give acceptable idle. Again, if cold starting is the only problem, a "choke" (fuel enrichment) issue would appear to be the most likely problem. Why do you insist on playing with the pilot screw and throttle idle settings if the engine runs satisfactorily once warmed up?

[MikeBb]

Carbs are ballanced.

I was fiddleing with the pilot screws because thats all i have left. everything else is to spec and i have even bought many new parts for this thing and still not seen any results.

Every time i replaced a part or did some clean+blast session i returned the pilot screws to standard settings

I cant see how this could be a choke mechanism issue as its my understanding that the choke squirts fuel in addition to the fueling that the idle sources, rather than cutting off the idle source. A faulty choke mechanism would surely just make no difference to the way it runs??. This and the choke is such a simple system, the bar/lever mechanism DOES work, the plungers DO come out and go back in, and the feed is NOT blocked.
The only way i can think of it being a choke issue is if hypothetically my float levels are so wrong and low enough that when the choke is activated it just sucks air from the float chambers instead of fuel. Although to the best of my findings in stuffing around with an air compressor, the choke gets its fuel from the main jet. Unfortunately I just have no conclusive data on this as it seems nobody has ever taken an rvf400 carb and a dremel and cut it apart to see just what line goes where.
This and the fact that my plugs come out black as shit, and i can hear wetness sort of sound coming from the top of the carbs which has been mentioned before on this forum to indicate rich running.

Most recently, as i posted above, i soaked the carbs, concentrating on the pilot screw circuit, in mek and blasted with an air compressor. I did the same with the plugs as well as hitting them with a wire brush. When i put the carbs on the day before yesterday and ran the bike without and airbox (and admittedly with the carbs only clicked into their rubbers rather than tightened up) I had the choke successfully working, to the point i could rev the bike up and down by moving the choke lever. When i got the airbox and all that back together it worked to a lesser extent (a little choke increased idle a little and more killd it ) Which i thought to be because the bike had warmed up by then. So i waited untill the next day. When i tried the next day after work it did not work at all. Which i thought to be maybe because it was 20 degrees. So i tried again this morning before work, at 3 degrees C. And it did not work at all. This afternoon i took the plugs out and gave them a very good clean, but still no results. Im resigning myself to the fact that this is an unresolvable issue, Im not enjoying the problem solving aspect of this issue one bit and i am beginning to hate the bike because of it.

To confirm, the following actions did not help:

Replacing idle jets
Replacing main jets
Carb clean + air blast all ports
MEK + air blast all ports
float heights checked 12.5mm
Pilot screws checked 1 5/8 turns.
Cleaning plugs

The following configurations had no effect or did not help:
No airbox
Pilot screws all the way in
Pilot screws all the way out (kills engine/fuel mist when carbs removed.. as in super rich?)

An experiment based on the idea that i am actually running lean and that the choke is sucking air instead of fuel, and lean-killing it when activated; would be to put fuel in a spray/mist bottle and spray extra fuel into the intakes with the thing idling, i should theoretically see an increase in rpm at idle while cold?

Evidence against this being the issue is that when cold the bike sometimes NEEDS full choke ON to start, it just has to be put away as soon as the bike ticks over.