Le Mans CX100 Vacuum / Barb Adapter Fittings

[lomax]

I need help from the amazing and knowledgeable Guru's that reside on this forum. 

I have a 1980 moto Guzzi Le Mans CX100 and am trying to do a carb setup on it. It runs great but I want perfect. I do have a harmonizer to do the balancing but cannot seem to find Vacuum / Barb Adapter Fittings that will fit the intake. I have tried Motion Pro 5 and 6mm fittings and they are too small, I tried 8mm fittings and they are a bit too big. For the life of me I cannot find 7mm fittings. Or could they be 1/4 " SAE (which I also cannot find) . I highly doubt that as it is Italian. They are NOT pipe thread. Can anyone point me in the right direction to find adapters or give me any advice on how to proceed.

This is what I am lookin for





And this is where they need to fit. The small silver screw in the black rubber boot.

[pehayes]

Several indicators in that carb pic tell that things are not stock original.  Pull the allen head screw and verify if it is SAE or metric and what pitch.  Find some hobbyist with a lathe and he could reproduce those fittings in a flash.  I've made my own several times.  Otherwise, pull the manifolds and re-drill and re-tap to whatever dimension you prefer.  If it were stock I'd send you to Motion Pro as their fittings are relatively simple and cheap.

Patrick Hayes
Fremont A

[Antietam Classic Cycle]

Since those Delrin manifolds are made in Europe, the thread is going to be metric. I have a pair here and can measure the thread size tomorrow when I'm back in the shop. 

[John A]

Tips for a mig welder can be found in the correct size and thread if you want high quality hose nipples . 6x1 mm by memory.

[Antietam Classic Cycle]

I just checked - the vacuum port thread size on those Delrin manifolds is M6-1.0. There is a Heli-Coil type insert in the plastic that could possibly come out, so make sure that's still in place.

[guzziart]

I just checked - the vacuum port thread size on those Delrin manifolds is M6-1.0. There is a Heli-Coil type insert in the plastic that could possibly come out, so make sure that's still in place.

Yep, the helicoil does come out.....usually with the screw in it .
FWIW, I got sick of fiddling with them so the last time they came out, I cut a small length of brake pipe, installed a couple threads (same O.D. as the helicoil O.D.), added a dab of JB Weld and screwed them into the manifolds, capped them off with common vacuum port caps, aint been a problem since....that was 11 years ago.
Art

[lomax]

Tips for a mig welder can be found in the correct size and thread if you want high quality hose nipples . 6x1 mm by memory.

Brilliant Idea, I will give that a try . Thanks

[lomax]

Since those Delrin manifolds are made in Europe, the thread is going to be metric. I have a pair here and can measure the thread size tomorrow when I'm back in the shop.

That would be greatly appreciated. I am thinking tapping and JB weld might be the ticket if the welding tips don't work.   Thanks.

[Kiwi_Roy]

I believe the usual thread in Guzzi's is 6mm
I have used a pair of 6mm grease zests with the ball removed.
plastic tubing will get soft and fall off, you really need a short length of rubber hose in the adapter, rubber can take the heat.

[Antietam Classic Cycle]

That would be greatly appreciated. I am thinking tapping and JB weld might be the ticket if the welding tips don't work.   Thanks.

I already responded a few days ago.

I just checked - the vacuum port thread size on those Delrin manifolds is M6-1.0. There is a Heli-Coil type insert in the plastic that could possibly come out, so make sure that's still in place.

[John Croucher]

I use brake bleeder nipples.  Cut the blanked taper end off or drill a hole through.  Works great. 

[lomax]

Mystery solved. While at the shop today for other issues  We found that YES they are M6-1.0 nipples just like Antietam Classic Cycle said. The ones I got from Motion pro were evidently marked wrong and thus did not fit.

I can only hope this helps some one else out that may have the same question.

Thank you all for the great advice.

Marc