Hi all.

This weekend I played around with smoothing out and flowing the intake between the carb and head. All went well, but I have a potential problem.

The rubber between the intake and carb seals fine and provides an acceptable seal/match between the carb and intake opening. You can match the port openings to the rubber perfectly, but it is all in vain. As soon as you tighten the clamps, the rubber inner moves away from the intake and carb and causes a big gap on either side of the rubber ridge. This gap can be as much as 2 to 3 mm on either side and must be causing some sort of turbulence.

Has anyone come up with a fix for this? I would like to get the carb, intake port and rubber ridge to line up perfectly even if they are clamped down.

On both sides of the rubber it has a ridge/rib inside the openings. This ridge lines up with the slots on the carb and intake and helps to hold the rubber in place. I was thinking of grinding the rubber ridge down a little to give the rubber some room to expand and it might help to keep the rubber from moving away from the carb and intake.

The last idea I have is to grind the inside of the rubber ridge completely down and inserting a metal ring to make up the gap between the carb and intake.

Any other suggestions?

 

Ron Wood racing fits the front of their Mikuni TM's with an aluminum collar that bridges the gap from the carb to the intake, the inside diameter of the collar matches the inside of the carb throat and the aluminum intake manifold, and it buts right up flush against the intake manifold. a rubber boot holds it all together with clamps as usual, but the air itself never sees rubber and flows through what is essentially a seemless aluminum tract. This is along the lines of your last idea you mention, sounds like a good plan.

 

If you are using the stock carb the rubber will be a perfect match for that but once yo u have ported the intake you will indeed have a step, i just put clamped the rubber to the intake then used a pencil grinder and a stone to taper the rubber down to suit the intake.
Giving a seemless flow path.

Took a little time but was not to tricky

 

Hi Blue.

Even if you match the port to the rubber ridge perfectly, once you tighten the clamps, the rubber pulls away from the carb and intakes. It creates a 2 to 3mm gap on either side of the rubber ridge.

You can only see gaps once it is clamped down.

 

Freez- I had the same prob. The thing that got it near perfect "for me" was by applying a good amount of pressure against the carb towards the intake and tightening at the same time your applying a good deal of pressure holding the boot and carb together. It took a few times to get it tightened straight but finally worked.

 

I tried pressing them together and it helped, but the more you clamp it, the worse it gets. I think I will put it in a clamp and tighten it only till it holds.

Hopefully this will sort the gap out.

 

If I recall correctly, I held WOT and looked through the carb w/ a light while I was tightening and applying pressure while I worked it up and down slightly and tightened at the same time tightening the clamp closest to the head first . If that doesnt work you may need to find a thicker rubber boot?

 

Yes, I was thinking about using a very hard plastic, or rubber as a boot. The stock rubber is soft and deforms under pressure, causing this gap. I will play around to see if I can find a better solution.

I am making it my mission to solve this problem...lol

 

Talk about getting down to the nitty-gritty!!! I replaced my stock rubber boot with fuel filler hose and it's quite abit firmer than the stock compound and cheaper to. Might try that. You can cut it to a length that will allow you to butt the carb to the intake...worth a shot.

 

It is all these little things that add a HP here or there and makes the difference between winning and loosing.

Air going thru that carb and intake can approach the speed of sound. At that speed any little bump, crack or imperfection can cause a loss in power. Having 2 x 3mm gaps in the flow path can be a big problem.