Honda Spree and Elite 50 Forums

Just picked up ruima 51mm bbk. Got it free
44mm 2ab mini stroke
Af16 unported
7.1 gearing

I would like to max out the rpm cause old owner gave it to me cause he said doesnt rev as much
I want to learn about port timings and give the best performance
I am still learning and please let me know whats needed to learn first

I love seeing this kind of post. I love to experiment with stuff that someone else said didn't work properly when it should have worked properly. I wish I knew more about port timing and such. There is a lot to it. I would check out some of the 2 stroke tuning books, like the Jennings book. Look at the fundamentals of the 2stroke. The other tuning variables like pipe and jetting can also affect the revs quite dramatically. You will have a lot of fun learning and experimenting

Greetings:

It's exciting! That bore and ministroker crank add up to a gin-you-whine 90ccs. Keep in mind that this an 80% increase in the intended capacity of the engine design, including its forced-air cooling system. Honda usually means high quality and the block and tackle of the AF16 is robust, but the "wiggle-room" is approaching its limits when 90cc or bigger stroker cylinders are bolted to the cases.
I would hesitate to Max out the 90, and you might consider settling for the "standard" Ruima performance for the sake of longevity.

For the cases, if you lay the Ruima gasket over the AF 16 you'll note how undersized its boost port appears to be compared to the Ruima's throaty inlet. Most people advise marking the crankcase and opening up the boost to match the gasket. On the cylinder, clean up any casting ridges and smooth away what you will, but radical port timing and very high RPM is riskier for the stated reasons. I cannot stress enough how important it is to chamfer the sharp edges of the ports' exit to the cylinders; otherwise they act as efficient oil "scrapers" and the piston goes hot and dry very quickly. I've blown up two of those 51mm bores possibly for this omission. The other possibility is that the cylinder wall is wafer-thin. This makes it extremely intolerant of jetting errors and hot spots that result. Avoid the temptation to over-oil. Ditch the pump, install a pump plug and pre-mix at 32:1 with your choice of synthetic Pre-Mix (only) oil. I'd choose a 26 or a 28mm Polini carb to feed this beast, and a pipe that's designed for 90ccs. 7:1 gears may be too tall.

Update. I started to port the boost area to match the ruima. I did my homework and looked where to stop cutting on the block.
I know i shouldnt take his word and maybe just install the bbk and try and tune it but i also notice that the exhaust port are real small for a 51mm
I have bought a ton of jets and weights since i had the corsa in it .
Also i bought a light purple center spring from a shop here that told me that center is good for mini stroke/strokers

So i grabbed a little flat head and lightlyl0 the exhaust ports. My god the carbon was so bad. The inner ports was almost 3mm thick carbon and the outside of exhaust port was 1-2mm thick all around. Started wondering no wonder he didnt want it lol