VM29mm smoothbores question about vacuum/overflow lines.

[Gregory]

Thanks guys.

Chuck I don't mind using the sync passage for the vacuum line. When I first started it u it had some backfires and sputters, but I did get it to idle at higher revs.
AZR if I am remembering correctly, my gauge wasn't hardly moving at all (until i plugged the breather tubes). I thought had it up around 2-3k, but maybe that was after i plugged the lines.

I wonder if sucking air through the bowls would cause it to not move the gauges?

I will re-address all this again after I get my bowl gaskets in, then report back.

 

[Agemax]

dont mean to hijack the thread but as it is a relevant question, i was wondering if you HAVE to use a push/pull throttle cable assembly on the 29mm smoothies? i know they say you have to on the 33's but i have been running my 28's with a single cable with no problems and as the 29's have the same strong return spring set up, is there a real need for the push cable?
TIA

 

[Gregory]

I was told by an old timer here that you can just use one cable. Since my setup had a two positions, I just went with the two cable system.

 

[Agemax]

I was told by an old timer here that you can just use one cable. Since my setup had a two positions, I just went with the two cable system.

Thanks Gregory, i thought it would be ok but just checking.

 

[Sandy]

As far as I know you should use a return cable with any non CV type carb. There is a possibility of the slides hanging and the only way to close it is with the cable. With only one return spring and one bracket there is no redundancy built into the return mechanism other than the return cable. I guess it's there for a reason. I've also heard on big motors flowing a lot of air that the flow can be high enough to actually hold the slides up or at least delay their closing, maybe the air flow binds the slide in the bore. That might just be myth, I'm not 100% sure on that.

 

[Fjbj40]

Yes they will hang, I found that out the hard way!

So I guess the 29's do not have the vacuum port between the #3-4 carb like the 33's do?

 

[chuck hahn]

No vacuum ports on 29s. One thing i was thinking of is the small hole in the back of the jet block being blocked by spider nests or something. I was the one that rebuilt them for Greg and I am sure they were very good when i was done. They were done about 1 1/2 years ago and have been setting around since far as I know.

Theres a tiny hole in the back of the jet blocks and the gasket has a corresponding hole..which I am sure i lined up correctly. I think I would take a e wire ( paper clip or whatever fits in the jet block hole ) and poke it thru to see that the gaskets hole is clear too. Take a light and look at the back of the jet block and youll see the hole. bend a wire and stick it in the hole to be sure its not clogged and the gasket hole is there.

 

[Gregory]

Will do, I may even give you a call when I get around to them when the gaskets arrive. I had them wrapped in a large plastic bag inside a box here in my office.

 

[Gregory]

Thanks for the help on the phone today Chuck. I got the new gaskets in and re bench synced the carbs. I put them on and the first thing was the breather hose between 1 and 2 started gushing gas as soon as I hooked the gas line up. I tapped on the bowl and started it, and it seems to have cured that. I had a little popping but it seemed to smooth out some as I synced the carbs....

BUT......I had a very slight reading on the gauges so i got them where they were all about the same height across. then i revved it and noticed that the bars would not go up when revving but seemed to go up as it was settling back down.

Anyway here is a video. I am sure something is wrong because these things usually read a lot higher than this. Also I notice in the clip they are not level but they were originally before I pulled out the camera.

 

[chuck hahn]

So..does it run good and not have hammering sounds like its all out of whack or smooth??? The exercise isnt how high the gauges goes its how even tha bars are. Sometimes as the slides are moved a lot youll see the bars go higher lower..and youll,hear the RPMs follow that change.

If its steady and seems to sound right I wouldnt worry too much. I dont have speakers on this old laptop so I could actually hear it..thats why i ask.

And Yeah ive seen my gauges do the same as the RPMs come down...the bars will flex up and then settle back.

 

[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

[h=3]Description[/h]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 :smug:

 

[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) .