Vanguard 23 Carburators

[slonomo]

Originally Posted by Shepard

Have you ported the intake manifold and removed the center web between the 2 manifold holes? It should have a semi sharp edge to it so the intake flow isn't restricted and is guided into its port front or rear.

I haven't done anything to the intake. That's a good point. Maybe there is something on the intake causing an imbalance in the air flow.

[Shepard]

The flow is slamming into the flat spot in the middle. Which cylinder is fouling the short leg or long leg of the manifold? Look at the picture and you'll understand what I'm saying.

[BIKERMIKEYBLACK]

SLO that manifold I got from you has a plenum instead of two holes does yours have two holes ?

[slonomo]

I think you guys are right. The adapter was just an open plenum, no holes. It's the plug in the right cylinder if you're facing the crank, by your pic it's the long one.

So Shepard, you're saying I need to radius the flat spots, basically do a port smoothing job. That's a lot of material in that location. I'm going to need a better porting tool. What type of bit do I need to remove a high amount of aluminum? I have the fine stuff for blending and polishing.

[NCPW]

A carbide tip burr should do fine with the soft aluminum.

[slonomo]

Update:

The adapter I used (for HF670) has an open plenum design, and the 23 Vanguard has a dual intake plenum. So it was pointed out that the air/fuel mixture is flowing through the open plenum then hitting the flat spot on the vanguard intake where it splits into two intake runners.

To remedy, I simply removed the plastic spacer and shaped it. I used a dremel tool with a sanding drum. Worked really well, didn't melt the plastic. I just removed small amounts, then checked it often.

I think this will eliminate any turbulence created by the flat spot, it's not shaped with a sharp angle.

[slonomo]

This mod to the intake did not cure the flooding issue. It runs well for 5-10 minutes then floods the right side cylinder (when facing the crank). Many of you have commented and helped be figure this out, thank you. It's obvious that this carb is too big for this type of engine.

The next step is to go smaller. Blackwater Performance and Performance Vtwins both sell the same carb for their Vanguard builds. The 34mm Mikuni VM.

[slonomo]

Blackwater Performance sells an intake made to adapt this carb, it's much different than the one I have. Might give that a try. They do have a complete kit, but it's for a mud boat. They will sell just the carb, or any other parts you might want. They are NOT a sponsor, but I feel this is an option that is not available from a sponsor. Mods, if this is against the rules please let me know.

https://backwaterperformance.com/col...rd-21-to-23-hp

https://www.youtube.com/watch?v=YZfampE1Blc

[raydhd]

Performance 670 also recommends the 34 mm mikuni on their engines with about the same displacement as the vanguard.

[slonomo]

Originally Posted by raydhd

Performance 670 also recommends the 34 mm mikuni on their engines with about the same displacement as the vanguard.

Well, that's 3 performance shops that use the VM34. Guess what I ordered?