80cc 50mm

[magoconnor]

Hello.

I plan to purchase a 80cc 50mm. 

Will it be ok compression wise, to run it with a 47mm bvh? 

The kit I will be buying: Airsal 81,33 ccm 50mm gy6  

Has anybody any experience with this kit or this brand? 

[KSR Moto]

Well I use 50cc head on a 47mm kit it will work but you wont get its full potential

[magoconnor]

Uhmm..

The setup: 50mm cylinder with a 47mm BVH.
My question is, will this produce too much compression?

[3strokeengine]

Mar 19, 2018 20:09:00 GMT -5 magoconnor said:

Uhmm..

The setup: 50mm cylinder with a 47mm BVH.
My question is, will this produce too much compression?

Run 93 octane fuel and check the plug for aluminum and make sure its not detonating.

Worst comes to worse and its pinging you can install 2 headgaskets like i did with a 52mm piston and 47mm BVH and that motor runs well in the mid to upper rpms goes around 55 mph, more compression helps torque in the lower RPMs and hp remains around the same.

[KSR Moto]

Mar 19, 2018 20:09:00 GMT -5 magoconnor said:

Uhmm..

The setup: 50mm cylinder with a 47mm BVH.
My question is, will this produce too much compression?

I dont think so

[GrumpyUnk]

What is "too much compression"? It will increase, causing the starter motor to have to work harder to kick it over. It may cause detonation, which you can combat with increased octane and possibly moving the trigger pickup CW a bit to retard the spark timing a slight bit.
Will it damage anything? Well, putting an 50mm bore onto a connecting rod, and rod big end bearing designed for something a bit smaller will likely lead to failure a lot quicker than adding a bit of compression will do. IOW, the size of the bore adds a lot of rod pressure, as does the increased mass being accelerated downward and then forced upward. The compression pressure won't kill anything, and will produce more power and torque, but does add more load to other components. Will the piston rings seal? Likely yes, with no problem. Will you have detonation, pinging, knock, pre-ignition, valve rattle or whatever other name you want to use? Maybe so, maybe no. It depends on fuel supplied, fuel:air ratio, temperature, spark timing, and whether you have carbon deposits that can glow and cause the mix to fire off too soon. Do you have any of those conditions? YYwillV.
Honestly, it is hard to say. The failure rate for 50mm or 52mm(?) is higher than for other sizes. Given that someone who WANTS one, WILL use the power more, and more often, which may tend to make the results more anecdotal than statistical. I suspect if you are judicious in your use, and don't beat it too much, it will do fine. But. You have to pay attention more to something you have personally modified than something put together by the designers, who, hopefully, were edjumukated in this stuff. A 50cc will last a good long while with decent maintenance. Double the displacement(almost) and the mass being whipped back and forth 8,000, no wait, 16000 times per minute(up AND down...) increased by a good factor, and you ARE putting a good load on the rod, crankpin and bearings. In short, 'future cloudy, check back later'

tom