Inlet manifold issue.

stevo as b4 · World Chat Champion Joined: 17 Jul 2003 Karma :

Hi, Basically this is a question for any engine tuners out there or 2stroke experts.

My TMX30 Carb and V-force reedblock have arrived for my KMX125. I also have a new rubber inlet manifold as the old one had some hairline cracks in it.

The opening in the V-force reedblock is bigger than the hole at the flange of the inlet manifold where it bolts to the reedblock. Does this present a problem or a flow restriction, and if so should I open up the inlet manifold to the same size as the air guide/stuffer plate in the reed valve.

I'm no 2stroke expert, but I would imagine some of the benefit of having a larger carb will be lost if there is a step or restriction in the inlet manifold, but I might be totally wrong here?

The original reed block matches up with the manifold exactly, so do I need to port match the manifold to the V-force one?

can supply pics if required?

Cheers.

Vincent · Banned Joined: 16 Oct 2006 Karma :

Have you any pics of the setup? 'Just makes it a lot easier to visualise.
You deffo can't have any steps from the reed block to the cylinder, it'll mess things up...ja.
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Robby · Dirty Old Man Joined: 16 May 2002 Karma :

Is the size of the carb outlet the same as the size of the reed block input, with the inlet manifold stepping down the size between them?

If so, I would be inclined to open up the inlet manifold.

I would be less inclined if the inlet manifold fits the carb outlet, but the reed block inlet is wider. You would need to open up the inlet manifold at one end only, like a trumpet. This is going to slow down the air speed, and could let the petroil drop out of the air.

bugeye_bob · World Chat Champion Joined: 05 Sep 2013 Karma :

daft question but have you asked the sellers of the parts ?

stevo as b4 · World Chat Champion Joined: 17 Jul 2003 Karma :

I hope the pic is clear enough to see?
https://i1070.photobucket.com/albums/u482/stevo1994/reedblock/DSCF0759_zps6374db3a.jpg

The outline in gold highlighter pen, is where the hole in the reedblock comes to against the opening in the manifold.

It's not a lot of material I need to remove from the rubber, I was just wondering if performance/airflow would be adversely effected if I didn't?

stevo as b4 · World Chat Champion Joined: 17 Jul 2003 Karma :

Robby, The 30mm carb fits the stub end of the manifold as the OD is very similar to that of the std 26mm carb.

Part of the issue I think is that the V-force reedblock while having the right dimensions to fit the cylinder and the correct bolt spacing, is actually made for the KDX200/220 which run a 33/35mm Carb instead, so their inlet manifold will be bigger internally than the KMX's, and would probably match the reed block exactly.

As for the taper well the flange end of the manifold is sort of oval and id say is a bigger area than that of the hole where the carb fits. So if anything the taper would get bigger as the inlet gets closer to the cylinder if that makes any sense?

Vincent · Banned Joined: 16 Oct 2006 Karma :

If possible, I'd just shave away the step with a sharp blade.
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stevo as b4 · World Chat Champion Joined: 17 Jul 2003 Karma :

I'll have a go at trimming it away then with a sharp scalpel and smooth it out with emery paper etc.

I've got to grind out about 2-3mm on the opposite side on the actual reedblock stuffer plate, but there is plenty of meat in the plastic to do this.

cheers for the advice anyway!