Building a Daily Driver 48mm BBK

[bakaracer]

Thanks Wheelman, for being HELPFUL...

For $80 plus shipping that looks like a sweet deal, and it should be a straight forward install. Do you know if anyone has actually used this carb? Or what size pilot & main jets would be used? If worst comes to worst, the jets are a couple bucks a piece, I could order a handfull and go the trial-and-error route.

So I've read threads on here that make it sound like people have been able to get the 48mm kits running properly, was I wrong in reading this? Were these false claims? I will not accept that this kit CANNOT be made to run properly.

the problem is the head. the stock head design is not made for the 48mm bore even if the head is cut to the size of the bore.you need to recut the squish band and angle it towards the combustion chamber at a 12 to 14deg angle.

[Trafficjamz]

I could bolt up a 48mm head for an af16 and see if it runs better.

I think the stock exhaust is the biggest restriction right now.

[juniorsdad]

Bakaracer:

This is at least the second thread now where the squish band has been mentioned. Do you know of a machine shop who knows what needs to be done to the head to accomplish this? If not, which would be the preffered angle, smaller or larger, or is that untested, and the angle purely theoretical?

Taz offers a suggestion for a machine shop on the sheet that comes with his kit, does anyone know if THEY know how to properly cut the squish band?

[Trafficjamz]

Bakaracer:

This is at least the second thread now where the squish band has been mentioned. Do you know of a machine shop who knows what needs to be done to the head to accomplish this? If not, which would be the preffered angle, smaller or larger, or is that untested, and the angle purely theoretical?

Taz offers a suggestion for a machine shop on the sheet that comes with his kit, does anyone know if THEY know how to properly cut the squish band?

who toboggan from Michigan?

He does not cut the proper squish

[Trafficjamz]

I don't even know if you can cut the squish band properly from a 86 and up head.
These are pics of mine.

[juniorsdad]

I could bolt up a 48mm head for an af16 and see if it runs better.

I think the stock exhaust is the biggest restriction right now.

Would that be a stock af16 head??? Thats still a 50cc motor right? Does it have a larger bore? Does it actually bolt up to the NQ50 cylinder?

[Wheelman-111]

Greetings:

That's a tidy squish band, but I would think that some extra combustion chamber volume would need to be hogged out to make up for the 30% displacement increase. In other words, reshape the whole chamber a bit deeper. Otherwise a stack of head gaskets could be used, but the squish band alone won't provide sufficient volume. What was your Compression Ratio?

[Trafficjamz]

around 150 psi

[juniorsdad]

I've discovered this week that I have no free time except for on weekends, so I still haven't put it together. It will be assembled this weekend though, at least getting the jug in place. I think I'm going to hold off on the head for now. I want to see what the differing opinions are on the use of stock/modified/alternate heads.

On the other hand, I could assemble it to check compression. I guess it just depends on how motivated I get.

[Petrock's 1984 Spree]

Dont you have to cut the head if your going to use a big bore kit?

Im having a local CNC shop do mine, $35 bucks and itll be finished. They said its really easy to do, even to cut the 14 degree squish band

[bakaracer]

the combustion chamber is to small on the stock head and the angle of the squish band can not be more than 15deg. most 48mm kits range from 12 to 14deg. these 48 and 44mm kits for the spree has only been out maybe a year and thse were made for taz.so im sure no r&d has been done like alot of race companies with established names do before they sell kits to the mass market.if you look at aftermarket heads for these types of engines,they look nothing like a stock head looks and depending on what the rpm they run at will determain the head design.head design plays a big roll in how the cylinder will run.here is an example of 2 different 50mm head designs.the one on the right revs higher than the one on the left due to the lower cylinder compression and larger combustion chamber.this is how most aftermarket heads look like for any scooter

[Trafficjamz]

Dont you have to cut the head if your going to use a big bore kit?

Im having a local CNC shop do mine, $35 bucks and itll be finished. They said its really easy to do, even to cut the 14 degree squish band

I would like to see pics after it is done.

[Trafficjamz]

I could bolt up a 48mm head for an af16 and see if it runs better.

Would that be a stock af16 head??? Thats still a 50cc motor right? Does it have a larger bore? Does it actually bolt up to the NQ50 cylinder?

No not stock. The stock af16 head is only has clearance for a 39mm bore.

Yes the bolts hole are the same.......but i don't think the plastic covers will clear.

[bakaracer]

If they are the same size,buy a aftermarket head for the af16e motor 72cc kit.

[Petrock's 1984 Spree]

I would like to see pics after it is done.

Yeah no problem. I cant wait to get it all back together, so i can bring that AF16E down into the storage room to work on