VM29mm smoothbores question about vacuum/overflow lines.

[Gregory]

Thanks for the help. I know it is not how high the bars are... but if they are range is at the bottom of only 2 or 3 ticks high, I wonder how well i am getting the bars fine tuned with one another. I will go out and work on it again tomorrow, so i will pay better attention and try everything again.

[Gregory]

I found this info this morning and may just try hanging them upside down. My gauges arent mercury they look more like silver bars.

http://www.carbtune.com/inst.html

Description

The Carbtune Pro is a mechanical manometer. It is an upgraded model of the previous Carbtune II(In the instructions the four column model is described. The 2-column model has half the contents of the 4-column.)
It gives four simultaneous readings so you can balance the throttle valves on carburettor or fuel injection bodies. (In the instructions the term “carb” refers to both fuel injection throttle bodies and carburettors.) Stainless steel rods indicate the vacuum on the scale. The clear tubes are made from high impact plastic. Damping is by a small airflow restricter in the rubber connecting tubes.
The manometer must be used vertically for a scale starting at 8cmHg (centimetres of mercury. 1 inch=2.5cm 1cm=0.4inches) and going to 42cmHg. Most bikes have readings higher than 8cmHg, but some bikes such as R-series BMWs and two strokes can have readings lower than this.
To get a reading below 8cmHg remove the plastic cable clip from the slot at top of gauge and insert it into the slot at the bottom. Push cable clip into slot from front of gauge. Hang the Carbtune Pro upside-down.
Ignore the scale figures. Zero will now be around 16cmHg on the scale but the full width scale graduations will still be 2cmHg. Absolute values are not important. Comparisons are important.

[chuck hahn]

Never knew they were reversable...cool.

[Gregory]

it started of with popping this time and kind of went away at one point after it warmed up.

no matter what i do I cant get it to idle evenly..it seems i am back to the situation we discussed where the screws are bottoming out. It is so whacked I will have to take them off again and re bench sync them.

I wish someone on here that knows how to do this **** lived nearby. so frustrated.

[chuck hahn]

well if i had then gas money I would come down and crash a night...but I just cant swing it right now. And yeah its so much easier to be there than try to explain it over the phone.

[Agemax]

it started of with popping this time and kind of went away at one point after it warmed up.

no matter what i do I cant get it to idle evenly..it seems i am back to the situation we discussed where the screws are bottoming out. It is so whacked I will have to take them off again and re bench sync them.

I wish someone on here that knows how to do this **** lived nearby. so frustrated.

pay for my flights and accomodation and i will gladly come over there and sort it out for you

[chuck hahn]

On my VM 26 carbs cold start popping was due to them being tad lean. I turned the side mixture screws in at 1/8 turn intervals till it seemed to resolve itself. You may want to turn the screws in till they seat and start at 1 1/2 out from bottom. they are flat ended so there arent any tips to break, but that doesnt mean go crazy cranking them down either. Seat them and turn them back

Thing is ( being the carbs be 26s, 29s, 28s, or CV carbs ) they are gonna perform per the engines condition. Its gonna take some fiddling but they WILL be ok.

[Gregory]

Ok I just took them off to re bench sync them...came inside to get paper clip. If you were serious I would certainly pay your gas.

Too bad the cooley isnt ready to sell, i could even swap you my other 78 gs1000 for the cooley if it was ready.

[chuck hahn]

Yeah I am serious..If I could get there I would. I got a VA appointment Monday but after that I dont have anything on the plate.

[Gregory]

I know you are bud....but for me it looks like it is going to have to be a weekend project at the moment.

I am going to be jammed up the next couple of weeks with work...if your tendon wasnt snapped I could even pay you good money to help with that as well.

I went out and started from scratch. Bench sync'ed, set the mixture screws to 1.5 turns out. It started on choke fine and sounded good when revved. As it was warming up I tried to get off of choke and turn the idle advance to get it to idle at 3500. New problem... the idle advance is bottomed out and is not high enough. to idle on it's own.

I suspect it may have something to do with the screw pictured here... (i turned it both directions and cant figure it out) .

[chuck hahn]

That screw is the slide stop. its used to prevent the slides from opening too far at full throttle. If the slides go too far up, the cut away looses effect and spoils the vacuum in the venturi. At full throttle the gap between the top of the carb throat and the bottom rim of the slide is about 1 MM.

[Agemax]

the screw you are pointing at is a stop for WOT. stops the slides opening too far. wont have any effect on idle

[Gregory]

I am mystified then about the idle. Not sure how to re set the WOT stop now either.

[Gregory]

Ok I am done for the day before I have a nervous breakdown. I ended up NOT taking them off to bench sync again, I just started backing them out the same amount all the way across, and that allowed me to increase the idle knob and get it up around 3500 rpm. I got all of them pretty even.

When I turned the idle down, it really didnt want to idle at less than 1500rpm and......

.... I noticed burp every once in a while and noticed on the gauges it was the number 3 carb.

(I dont know if it is related, but I had pulled the plugs and cleaned them earlier today and noticed number three was oilier looking than the rest.)

[chuck hahn]

May be an ignition related blurp. Guess you can trim the wire and screw the cap into frdesh wire and maybe throw in a cleaner plug to see what it does then.