Stuffers

[scooble]

I was round the workship of the guy thats tunning my engine. He showed me his modified stuffers he uses for his banshee powered drag bike and the entire stuffer had been opened out.

Looking at the KR stuffers, it appears as though the outer petals top and bottom are quite obscured by the plastic.
I am about to fill the voids in my stuffers to accomodate the 35mm carbs.
Is there any merit in opening this right out so that it exposes more of the petal area?

[mj43]

There was a debate on stuffers and splitters on RGV forum recently in the Challenge thread.

The consensus of ill informed opinion was that a slow widening from the throat of the carb was best.

If it opens too fast you will cause turbulence and stall airflow.

In the RGV reed blocks I have modified I believe they open up too fast and I have introduced a splitter to fill some of the volume and try and keep flow velocity up. Will find out if it works if I ever get the RGV back together again.

[KR-1R]

on a drag bike its only run at one throttle opening so would do no harm.

on a race bike throttle response is everything
Is the pressure difference acting on the carb side (inside) or crankcase side (outside) to lift the reed petal - or both or is it air mass flow as well? The reed stops have holes in surely not for weight. Pressure can be assumed to act on the centroid of area.

in the extreme... I cant see running without any stuffers being an improvement - which is also what extreme stuffer modifications would head towards?

I think it could be better to maintain a nozzle with same or a slightly reducing cross sectional area at each mm down the tract - the splitter could help achieve that and spread flow round to rectangle.

On the Vforce reeds I was able to close up the inherent petal gaps (and remove the one corner imperfection all together) with even sanding/planing down with #1200 paper on the cage surface.
There is also some filing and rounding off that can be done to the petal seating faces on the inside of the cage. Doesnt solve your problem because the KDX ones need mods like the 28's do

MJ you run the Vforce? - the race bike is hungry on carbon reeds? - could the tiny backwards flex on the petal when it is forced to seal contribute to faster fatigue or delamination ? is your reed damage just to the very edges or is the whole petal surface breaking up?? reed stops to limit flex??

[TwoStroke Institute]

I was round the workship of the guy thats tunning my engine. He showed me his modified stuffers he uses for his banshee powered drag bike and the entire stuffer had been opened out.

Looking at the KR stuffers, it appears as though the outer petals top and bottom are quite obscured by the plastic.
I am about to fill the voids in my stuffers to accomodate the 35mm carbs.
Is there any merit in opening this right out so that it exposes more of the petal area?

Not a good idea, those sorts of ideas have falled well out of favour. A V-Force proves that tip area and velocity is king.Just try to maintain the same cross sectional area as the carb bore.
Stuffers and splitters aim intake flow at the petal tip, where they are easiest to bend , that means less inertia lost from opening the petal.
The design above is a good one to copy

[mj43]

MJ you run the Vforce? - the race bike is hungry on carbon reeds?

I moved to V-Force as stock reeds were getting smashed every couple of meetings.
V-Force have now been in for 2 or 3 seasons. They definitely look tired and will be changed this year but that is a significant improvement on stock.

I have never done a back to back test with stock reed blocks to see what if any change they made...