Here is the work done by RichT (aka top geezer)
When thinking about a low cost replacement for the GT kits I considered casting a reed manifold for use on standard barrels. The plan was to boost the performance and fuel economy with the use of a PM runner reed valve. I would cast the inlet manifold and modify barrels with a boost port on a CNC jig (long reach tool). To test the idea I built the above kit which was back to back tested with a 200cc engine.
This kit was 210cc, iron barrel modified with a large boost port, used a 68mm 350 LC piston and a PHBL carb. The production version would have a solid mount so it was a little shorter.
It was tested against a lightly tuned Indian stage 4 200cc with PHBH 30mm carb.
Both tests utilised the same, engine, ignition and exhaust so it was as close a comparison as you can get.
The kit did return exceptional MPG, nearly double that of the standard. However, the peak power was slightly down, even with 360 degree timing, a large boost port and cleaned up transfers. It was very tractable and pulled well but lacked the rev band that standard had. I had hoped for a comparable power delivery with wider low end, this coupled with smaller carb and massive MPG increase would make it worth it (and a very cheap option) but sadly the performance facts did not stand up.
The conclusions I came to were:
1. No question reed valves in almost any form are good for economy
2. Economy alone does not warrant producing such a kit
3. Asymmetric inlet port geometry is not good for boost port gas transfer
4. Any benefits in transfer port area are negated by peak flow restriction by the petals
5. For a reed valve to work well in this location it has to be bigger
6. Why do they work on the runners so well? I reckon it is because they are case mounted so the rate of flow is more consistent than an asymmetric barrel mounted inlet.
I had discussed it with Scooter Center also and they said they had trialled a similar item (probably LTH) and come to the same conclusion.
About 12 months later LTH released theirs and after separating all the spin and reading the posts I have seen no similar back to back test that proves a significant performance increase and certainly none that warrants the price. People are now modifying Rapido’s to take the LTH! If there isn’t a significant difference with a standard barrel then there will be less with a Rapido, plus you are easily in TS1 territory.
I was going to sell the manifolds for £25 and make a manual for building the rest for maximum low cost but, at the end of the day if I don’t believe it offers a significant benefit then I don’t believe in producing it. If there was just 2 BHP increase I would have done it but there just wasn’t and people are really fixated on peak power which isn’t always right but in this case it was such a large negative that could not be ignored.
Best regards
Rich T
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