Better intake springs 3hp B&S flathead?

[Budget DIY]

Hi all. Just for fun and giggles, I came up with a plan to make the most rawdy 127cc, loud, fire spitting and obnoxious 3hp Briggs and Stratton flathead on the internet. I've got some secret sauce that I won't go into. But amongst other things, I plan on adding a RHB31 turbo from AliExpress. Stand alone E-oil supply and whatnot. AI told me that these tiny engines won't be able to produce enough CFM, but on paper, I fixed that issue. But now...

I can't seem to find parts, and I'm very much new to engine modding. Although I do know the theory well enough. And if I'm going to run close to 15 psi of pressure @ around 4200 rpm, I especially need better intake springs. Otherwise the turbo with the high RPM's, will just be causing valve float. So...

Does anyone know what part number I should be looking out for? What would be a better intake valve for this ancient flathead engine? I'd prefer to go the AliExpress route, but that site seems to be filled with Honda clone parts. I'm located in the EU (Netherlands), so ordering a (cheap) part from an USA website will probably cripple me with shipping costs.

 

[Budget DIY]

Oh, the engine is currently mounted to an unfinished/kinda abandoned motorised bicycle project. Lost motivation, got some different projects. And this turbo might make me interested again.

Frame has been notched to fit the engine, and reinforced again. Replaced both the front and rear hubs/kept the stock rims. Also notched the fuel tank, but it needs to g0 if I'll slap on a turbo. It's intended to be a friction drive, with a 1-to-1 ratio towards the roller. Roller can be pulled away from the wheel to go into "neutral". Theoretical top speed has been calculated to be about 45 km/h @ 3600 rpm, which will make me fear for my life. Adding all the boost and over revving the engine to about 4200 rpm will be a stationary party trick. While driving, the RPM limiter will be set to 3600 rpm. (spark cut electronics) Rear wheel brake lever will also cut the engine. Managed to keep the pedals, but had to widen that crankshaft by something like 15 cm? Also had to replace the rods to the pedals to some from a kids bicycle so that they are shorter and won't hit the pavement while cornering. On and the crankshaft pedal sprocket had been moved back in big time, by adding a thicc tube as a spacer.

And as with all friction drive setups: yes, I'll pedal up to some speed, before I engage the drivetrain.

PS: here is a vid of the white engine (and spare orange) running.

 

[landuse]

I look forward to seeing how this projects progresses. Have you tried Arc Racing for parts? They might have springs that will fit and that are stiffer that stock.

Ugh....I just saw that you are in the Netherlands. I am not too sure where you might get any parts there. Shipping is always going to kill you. It is the same here in South Africa. Buying anything from the US or UK is just prohibitive with shipping