Need modification advise..VM 29s

[chuck hahn]

So I got around to firing up the mewly aquired S I went to Kentucky a few months ago to get. I primed the carbs and she fired right up..then died after a few minutes after I put the petcock in the ON position. Reprimed and fired up..repeat scenario a few times. Pulled the tank and there wasnt any vaccuum tube from carbs to petcock. I looked where the port is 'SUPPOSED" to be and there isnt a nipple. In fact the carb body is molded with the usual spot cast closed. I need to mod these so i can hook up a vaccuum to effect proper operation of the petcock. I was thinking about carefully drilling thru the body to open up the spot that would normally have the vaccuum nipple. I can scavenge a nipple off a set of 26s to put in. Question is am I on track with my thinking here? What can I do to get the situation straightened around?

[Nessism]

Chuck,

Use the sync port hole on the head - get a threaded nipple and permanently attach it to the head, then run a vacuum line to your petcock. Simple and effective mod.

[chuck hahn]

Me and Dale had talked on the phone earlier and discussed that option. He didnt know though if while rapping up the engine it would cause the diapram any problems. The regular port applies a pulse and its very low suction as well. Thats why i was wondering about opening up the regular spot.

[Steve]

The vacuum port on the carb and the sync port are going to see the same amount of vacuum at virtually the same time. There should be NO difference.

.

[chuck hahn]

ok then..anyone got a spare syncing nipple laying around they would like to donate to the cause?

[tkent02]

You can modify your petcock to make it a manual petcock.

[chuck hahn]

PM me the details....PLEASE!!!

[srsupertrap]

You can modify your petcock to make it a manual petcock.

This VM29 modification has worked fine for me; Turn your petcock to Prime when running and Off when not running

[chuck hahn]

Supertrap..yeah that works too, but knowing me i will forget to turn it off and if the carbs leak a bit i dont want to run a risk of filling the crankcase with gas..

[srsupertrap]

Chuck

Just my two cents but I believe everyone running VM29's have merely capped the vacuum port of the GS1000 petcock and used

Prime position for On
On position for Off (since we have disconnected & discarded the vacuum tube).

So you are back to a gravity feed setup and I have never had any problems in 25+. Personally I would not modify the VM29's to accept a vacuum port because that will diminish the value of the best bolt on Carb Mikuni ever made

[chuck hahn]

I have the original set of 26s that were taken off many years ago but they are all crapped up inside.. I dont really want to get into doing another set of carbs right now, so i guess i had better get used to the idea of turning it to the on position everytime i get off the bike. If I put the 26s back on I will most likely sell the 29s. They are spotless and are running very well on the bike right now.

[razooki]

For Vm29s you need to run the bike with the petcock on "Prime". I had the same problem when I got mine. Just remember to turn off the petcock when the bike is not running. My vacuum hose from the petcock is not connected to anything.