bi-turbo question

What is the rpm for peak performance with a bi-turbo exhaust on a 50 cc Puch Maxi?

Re: bi-turbo question

Hahaha. That is a new one! Anyone? Anyone?

Re: bi-turbo question

I don't know,Ken,but my 60 cc kit on Franco-Morini says 4.2 HP at I think 5500 rpm or so.It is rated for 8000,but I'd never rev a standard engine that high.Gives me 45mph pulling 275 lbs. cargo or so.Don't over-rev an old engine.It ain't worth the rebuild or replacement.You also got a stock clutch to worry about.(:^)

Re: bi-turbo question

Emailed Moped Warehouse with this querstion. The response was 6000 RPM. I am trying to find the best combination of sprockets for my situation. That is, top speed for level roads and starting pickup is not important. There are absolutely no hills where I live (Hilton Head, SC). I have gone through all the combinations I can make with 14 and 18 tooth front sprockets and 40 and 45 tooth rear sprockets. I find that 18 front and 45 rear gives the best performance for my needs. I can always get 34 mph and have top of a 37.2 mph. I have a digital speedometer. My next improvement try will be on the carburetor. I bored the 12 mm out to 12.5mm using a round rasp. Who knows what I will do next?

Re: bi-turbo question

Matt Wilson /

If you are interested in measuring the RPMs you can get a tinytach ( Lots of people use these on scooters.

I would think that peak revs is higher than 6000.


Standard Model, used on engines with one spark firing on each revolution of the crankshaft.

1 cylinder 2 stroke(reads 1x/revolution) Honda engines

4 stroke with electronic ignition and nopoints

2C can also be used with a 2 cylinder engine

Go-Karts generally use 2C

Note: Engines frequently referred to as a "4 stroke" may not be a true 4-stroke because they fire on the exhaust stroke as well---requiring a 2C.



Re: bi-turbo question

I got a 15mm carb for my Maxi, and it gave me a huge power increase. Ike, who is a moped army, honorary member, and frequents this site, has them for sale. You will need a bigger manifold too, but you probably know that already. I wasn't making fun, with the Hahaha in my first post...that was just a super techincal question that we don't get a lot. Swarm and Destroy! Peace.


Re: bi-turbo question

I feel a tach is unnecessary. A simple calculation converts MPH to RPM. The clutch is not slipping when you are rolling along. The crankshaft turns 5 times for one drive sprocket rotation. Using the ratio of the drive sprocket (18 teeth) to the wheel sprocket (45 teeth) and a wheel roll out circumference of 69", the RPM at 31.4 MPH is 6000. I can get up to 37.2 with a bi-turbo, a 14 mm manifold and a 12.5 mm carburetor. The biturbo is tuned for a peak power at 6000 RPM, but works well over a wider range.

Re: bi-turbo question

Does the biturbo help for acceleration?

Re: bi-turbo question

It seems to help with acceleration (power) when you get around the tuned frequency from 5500 to 6500 RPM. That would be around 24 MPH for a Puch Maxi with standard (14 front and 45 rear) sprockets.

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