vm intake manifolds

[jefft]

I have a set of aluminum intake manifolds I bought on ebay. You have probably seen them before. They are quite a bit longer front to back then the stock XS rubberish intake manifolds. The length won't be a problem as I don't run the stock airbox. I think they run about $60 on ebay. I was going to use these intakes with some VM 34mm Mikuni carbs. Has anyone drilled and tapped these type aluminum manifolds for nipples so that the carbs can be sync'd? If so, at what point on the manifold did you drill?
jefft

 

[jefft]

What? No one ever done this or used this type of manifolds?
jefft

 

[XSLeo]

The alloy carb holders get used, just not many add ports. They sync with other methods. Try www.amckayltd.com/vm34-36.pdf
Leo

 

[grizld1]

Nonresponse to a question does not necessarily indicate that no one knows the answer. It often indicates lack of interest in the question and the assumption that the party asking ought to do his own homework.

Plenty of folks have used that type of mount (it's a mystery why so many who know better insist on referring to single-tract mounts as "manifolds"). Usual practice with VM's is to tap the carb body for sync. barbs. Refer to pics at 650 Central. Use a drill press and take care clamping and leveling the carb bodies. And of course you can drill and tap the flange on the mount, if there's enough meat on it and you can run the hole straight.

 

[irristeve]

I made my own alloy manifols,40mm alloy tube is the same OD as VM34's,some alloy plate cut to shape using gasket's as template,hole saw to cut holes etc.tube was cut on slight angle,then rotated to archive right angle(alinment)then got mate to weld them up,a bit of radiator hose & some hose clamps hold them on,has worked well for the last 4 years & have never had one blow off,also got carb's in closer to frame which ment I only had to trim side covers slightly

 

[Tim of DO THE TON]

Honestly I'm not sure you need vacuum gauges to sync 2 carbs. I run VM34's on my XS650 and have never used gauges. I use a drill bit to get the slide height the same at 'idle' (throttle released) and eyeball/feel them to make sure they lift at the same moment.

You can actually get your fingers on both slides at the same time on VM carbs with the filters off.

This along with checking spark plug color I have found is plenty to keep the bike running nicely.

Using a vacuum gauge might help identify a leaking intake gasket or loose hose clamp but aside from that on a twin cylinder bike I think it's overkill. Used them a lot on my Honda SOHC4 engines however.

 

[jefft]

Honestly I'm not sure you need vacuum gauges to sync 2 carbs. I run VM34's on my XS650 and have never used gauges. I use a drill bit to get the slide height the same at 'idle' (throttle released) and eyeball/feel them to make sure they lift at the same moment.

You can actually get your fingers on both slides at the same time on VM carbs with the filters off.

This along with checking spark plug color I have found is plenty to keep the bike running nicely.

Using a vacuum gauge might help identify a leaking intake gasket or loose hose clamp but aside from that on a twin cylinder bike I think it's overkill. Used them a lot on my Honda SOHC4 engines however.

Thanks for the responses. I drilled and tapped them at the flanges. Seems it all came out well. I think the vacum ports could be more accurate then the drill under slide method. When I was using my homemade yardstick sync guage I noticed that even the slightest movement to the screws made quite a large movement to the fluid in the guage. jefft