Dear Friends,

Please kindly advise me at least the direction to dig ( After rebuilding carburetors with the new kit (I was as much careful as possible) bike still has problems with idle speed - it jumps, I cant get it stable to 2k RPM, works more or less fine on 3k. Exhaust stinks, it eats fuel quicker then it should (imho). Pilot crews are at 3 turns out. New spark plugs. Compression is perfect! Carbs were NOT synchronized yet.

What could it be?
- some mistakes were made during carburetors assembly;
- fuel leakage (but I didn't notice any);
- Petcock? Is it possible smth wrong is with petcock? Could I avoid of using it just for tests?

anything else?

Thank you guys )

choke stuck? or leaking/missing pilot needle o-rings.

Why three turns out? You are describing running very rich at idle and you have the pilot needles maxed rich.

choke stuck?

- looks like not, but probably need to double check. At the moment the choke cable is disconnected.

leaking/missing pilot needle o-rings

- You mean the longest, jet needle? actually I replaced almost everything incuding o-rings, but not this jet needle.

three turns out?

- Tried 2 1/4, 2.5 - the same...


Also, I didn't synchronize them yet. Could be the root cause?

Also, when running idle on 3k RPM, sometime it pours fuel through the air vent hose...

Quote from: Masterflies on February 05, 2020, 12:53:56 PM
choke stuck?

- no, works fine...

leaking/missing pilot needle o-rings

- You mean the longest, jet needle? actually I replaced almost everything incuding o-rings, but not this jet needle.

three turns out?

- Tried 2 1/4, 2.5 - the same...


Also, I didn't synchronize them yet. Could be the root cause?

Also, when running idle on 3k RPM, sometime it pours fuel through the air vent hose...

Float level too high or stuck float -
Synch is needed only is someone "unsynched" it at some point. Good to do, and easy to do with looking at light under the butterflies.
Cool.
Buddha.

Quote from: Masterflies on February 05, 2020, 12:53:56 PM

- You mean the longest, jet needle? actually I replaced almost everything incuding o-rings, but not this jet needle.

"jet needle", I think you mean the main needle here?

I am talking about the pilot needle, which is what you might think of as the "screw" you turned three turns out... That thing has a spring, a teeny washer, and an o-ring on it, in that order. If the o-ring is gone/leaking, then it will run super rich at idle no matter how you adjust it, which is what it might be doing now.

Quote
three turns out?

- Tried 2 1/4, 2.5 - the same...

Did you try 1 turn out? 1.5 turns out? Because if it's already too rich then adjusting it richer and it still acts too rich is what you would expect.

Quote
Also, when running idle on 3k RPM, sometime it pours fuel through the air vent hose...

Yeah, that's stuck float needle(s) or float level too high or both. Which may also be causing your problem, in addition to pilot needle leaking or set too rich.

Quote from: The Buddha on February 05, 2020, 12:58:04 PM
Float level too high or stuck float -

Well yesterday I double checked floats - all in places, nothing stuck... really don't know what to do else at that point... maybe will try to return back the old needle valve and its seat.

Quote from: mr72 on February 05, 2020, 01:10:41 PM
I am talking about the pilot needle, which is what you might think of as the "screw" you turned three turns out... That thing has a spring, a teeny washer, and an o-ring on it, in that order. If the o-ring is gone/leaking, then it will run super rich at idle no matter how you adjust it, which is what it might be doing now.

I've put new pilot needle and washer and o-ring... But yes, will double check if everything is on place and maybe return back old ones to test.

Quote from: mr72 on February 05, 2020, 01:10:41 PM
Did you try 1 turn out? 1.5 turns out? Because if it's already too rich then adjusting it richer and it still acts too rich is what you would expect.

Will do, thanx )

Quote from: mr72 on February 05, 2020, 01:10:41 PM
Yeah, that's stuck float needle(s) or float level too high or both

As mentioned above, I really don't know what to do else with floats and their needles, only to return back old ones.

But also will check if everything is ok with choke. Choke linkage bar slides freely, but maybe smth wrong is with choke plungers.

It is better to check the floats with the hose method shown on a post here, I think in FAQ. Carbs installed on bike and wet, the hose goes on the blow and loops up beside the carb, you see how high the level is, should be top of the bowl. One at a time.

Quote from: Masterflies on February 05, 2020, 01:46:48 PM

Quote from: The Buddha on February 05, 2020, 12:58:04 PM
Float level too high or stuck float -

Well yesterday I double checked floats - all in places, nothing stuck... really don't know what to do else at that point... maybe will try to return back the old needle valve and its seat.

You also may have a leaking O ring at the seat of 1 float.
You do U tube method ? You have to put it in prime for that to be accurate and have a working petcock.
Cool.
Buddha.

Guys can you please poke me on that topic which describes the clear tube method, and maybe some good howto on float height adjustment? thanx

FOUND IT ) http://www.bbburma.net/FloatHeight.htm

Guys I found some nice way howto test needle valve and its seat with compressed air: https://www.youtube.com/watch?v=nAe_5YwWoV0

Which is probably not a secret for you, but definitely for me ) Have you ever tried that? Any feedback? )

That required you to take the carbs apart. I use lung power to test it sometimes.
Just use a new tygon hose, and don't suck it back by accident.
Cool.
Srinath.

Quote from: The Buddha on February 05, 2020, 12:58:04 PM
Float level too high or stuck float -

Quote from: mr72 on February 05, 2020, 01:10:41 PM
Yeah, that's stuck float needle(s) or float level too high or both.

Thank you guys a lot, and the answer is - I'm an idiot. The Carbs Kit was not the right one, so the sizes of needle valve and o-ring were not correct, so everything was constantly leaking. I temporarily put the old valves and o-ring, and ordered the right kit. Now it's much better, idle could be kept at 1500-2000 RPM, although there are still signs of the rich mixture and de-synchronized carbs:
- smoke from the pipe
- exhaust stinks
- idle is still unstable but not as much
- returns to idle very slowly or doesn't want to return without "blipping" the throttle
- getting worse as it warms up

So the plan is to
1) measure floats with U tube
2) play with pilot screws - to try 1 and 1.5 turns out
3) waiting for gauges - will synchronize them according to High Science )

Synch is easy to do by eyeball. When the carbs are off when you're swapping seat O rings, look at daylight from the air box side. Adjust the butterflies with the throttle stop screw, to have minimum daylight that looks like a crescent moon under the butterflies.
Then adjust the synch screw to make them equal. Synched - no vacuum tubed needed.
Cool.
Buddha.

Quote from: The Buddha on February 07, 2020, 07:28:09 AM
Synch is easy to do by eyeball

Good to know! Anyway I wanna have gauges in my garage so I've ordered them, will synchronize as soon as they arrive )

Quote from: Masterflies on February 07, 2020, 06:54:05 AM
idle could be kept at 1500-2000 RPM, although there are still signs of the rich mixture and de-synchronized carbs:...

- returns to idle very slowly or doesn't want to return without "blipping" the throttle

Idle speed is set way too high, that's why it won't return to idle.

Set the idle speed ONLY AFTER IT IS FULLY WARMED UP, ride on the road 15 minutes or more. Then set the idle mixture correctly WITH IT FULLY WARMED UP. Idle speed really is a function of idle mixture. There's a certain idle mixture setting where the idle speed will be maximum on a fully warmed bike. That's the right setting. Then you adjust the throttle stop so that it "idles" at 1100-1200 rpm when fully warmed.

Idle speed when hot vs cold should be within 100rpm of each other. With hot being higher.
30 seconds with choke and it should hold idle. 30 mins of riding later it should be no more than 100 rpm over that.
If that is not happening, your mixture is wrong.
If hot idle is much higher than cold idle, you're lean.
If hot idle is a lot lower than cold idle, your mix is too rich.

If it wont return to idle, you may have a leaner than ideal mixture. But really it depends on how much you are higher, if its 100 rpm or so, I'd call it as spot on.

Cool.
Buddha.

Quote from: mr72 on February 07, 2020, 08:02:02 AM

Quote from: Masterflies on February 07, 2020, 06:54:05 AM
idle could be kept at 1500-2000 RPM, although there are still signs of the rich mixture and de-synchronized carbs:...

- returns to idle very slowly or doesn't want to return without "blipping" the throttle

Idle speed is set way too high, that's why it won't return to idle.

Set the idle speed ONLY AFTER IT IS FULLY WARMED UP, ride on the road 15 minutes or more. Then set the idle mixture correctly WITH IT FULLY WARMED UP. Idle speed really is a function of idle mixture. There's a certain idle mixture setting where the idle speed will be maximum on a fully warmed bike. That's the right setting. Then you adjust the throttle stop so that it "idles" at 1100-1200 rpm when fully warmed.

That is completely wrong.
1.Setting idle mixture with it fully warmed up is a nice way to burn your fingers.
2. Idle speed isn't a function of mixture, its a function of how wide the butterflies are open, and even if mixture plays a part, you can change it by changing the idle screw aka throttle stop screw. And if you're not allowed to touch the idle screw, then idle rpm tends to get higher as it gets leaner and lower as it gets richer, to the point of stalling.
3. The "certain idle mixture setting where the idle speed will be maximum" will be lean as a crack ho. Idle rises as you lean the mixture, definitely not what you want, but the setting I prefer is slightly lean, that's why 100 rpm from cold to hot. Else you'd have trouble with warm re-starts.

The sequence is this, set idle mixture, set idle rpm when you've started it and let it run 30sec to 1 minute on choke.
Go for a ride. Observe what rpm you're at 15 min, 30 min etc.
Wait till it cools, adjust idle mix, adjust idle screw for idle rpm. Repeat.

Cool.
Buddha.

Thank you guys once again!!! Now it's much better, keeps normal idle speed. Can you plz also advise,
1) when I'm on idle and sharply rising the throttle to 4-5k RPM, sometimes poppings occur through the pipe, and immediately after that RPMs go down and engine could stall like no more fuel goes to engine, and to keep it alive i have to "blip" the throttle one more time. Is it also a matter of wrong mixture, or problems with needle jet, or something else?
2) In a 'Poor Man's Rejetting Pictorial' (http://www.angelfire.com/mt2/mikesgs500/rejetting/) there's a nice description on how to adjust the mixture. Using this approach, should I adjust both screws simultaneously, or one by one?

thank you )



This could be rich, try 1/4 turn in on air mixture screws. You're almost there. Also let it idle 30-40 seconds after fully warmed up and let it cool and pull the plugs and look, if its more black than dark grey, then you're on the richer side of ideal, and idle being a shade leaner than ideal, is far better IMHO. That's why it should idle ~100rpm higher when hot than when cold.

Cool.
Buddha.