First timers might find a 47mm BBK a better option

[humanshield]

I've installed all sizes of BBK's

Right now, several people are installing 50mm BBK's on their scoots...and many are having issues.

I'm of the "opinion", after seeing a lot going on, that people who have little or no experience with engine building and tuning might want to go with the 47mm BBK as their first shot.

The reason being is that it is not as demanding in terms of the compression, heat, tuning and break in as the 50mm BBK is.

The 47mm BBK will also likely last longer if you tend to ride hard.
The step up from 49cc to 72cc is still  a big jump and only about 11cc's less than the 50mm piston kit.

If you've never done a engine build or rebuild, please view as many of Brent's videos as you can (several times).
And consider starting with a 47mm BBK....then maybe moving up to a 50mm BBK later if you choose.

Might be the difference between success and failure.

[larrball]

I take it you are talking about the 139 clone (china) engines?
The Honda's would take a beating much better then the china ones given the fact that some came out with the 60cc's that did just fine.
Your right if you'r new to the game then a 47mm would be great.. you doin't have to change anything to benefit But you might want to turn up that A/F mix all the way on an 18mm carb.
My 09 jonway vip had a 60cc in it and it did a bit better then the ATM 50 of the same year, but i sold it and moved on to a 2T.
Am i happy with the 2T?
HA! you tell me...

NOTE:: This is the fastest way known to man to remove tattoos,feet,arms and a savings account.

[gsx600racer]

Nov 18, 2016 23:27:34 GMT -5 larrball said:

I take it you are talking about the 139 clone (china) engines?
The Honda's would take a beating much better then the china ones given the fact that some came out with the 60cc's that did just fine.
Your right if you'r new to the game then a 47mm would be great.. you doin't have to change anything to benefit But you might want to turn up that A/F mix all the way on an 18mm carb.
My 09 jonway vip had a 60cc in it and it did a bit better then the ATM 50 of the same year, but i sold it and moved on to a 2T.
Am i happy with the 2T?
HA! you tell me...

NOTE:: This is the fastest way known to man to remove tattoos,feet,arms and a savings account.

That has to be one of my favorite YouTube vids beside these two. 

[Deleted]

My original build was the Glixal 80cc bbk with their 20mm carburetor, which by the factory specs has a #90 main/#30 idle. I then dumped almost twice as much into the 100cc bbk, 23mm valve head, A9 cam and the same 20mm carburetor, and got in reality, very little performance gains over the 80cc kit, seemed more like a shifting of the power band upward.

Considering the likely reduction in engine life I'll see even if treated correctly, and the money spent, I would not go the 100cc route again and focus on squeezing a bit more out of the 80cc through fine tuning.

[gsx600racer]

When I ventured into the scooter scene several years ago, I started out with a 4t machine. I like everyone else, I wanted to go faster, lol. I did a lot of reading and it seem to be the general consensus that an 80cc kit was the way to go if you were using the stock crank and looking for longevity. 100cc were for those that were willing to split the case and install a new crankshaft and possibility have the case halves machined to get the new cylinder to fit.

Either way 80cc or 100cc, it going to take certain level of skills to build either one. I do agree with humanshield with regards to starting of with an 80cc for the best chances of success for the first time builders.

I ended up selling my 4t scooter before doing any engine mods to fund my 2t projects.

[humanshield]

Nov 19, 2016 13:56:31 GMT -5 peascreek said:

My original build was the Glixal 80cc bbk with their 20mm carburetor, which by the factory specs has a #90 main/#30 idle. I then dumped almost twice as much into the 100cc bbk, 23mm valve head, A9 cam and the same 20mm carburetor, and got in reality, very little performance gains over the 80cc kit, seemed more like a shifting of the power band upward.

Considering the likely reduction in engine life I'll see even if treated correctly, and the money spent, I would not go the 100cc route again and focus on squeezing a bit more out of the 80cc through fine tuning.

There is a very simple explanation for what you experienced and I 100% agree.

When you go to a 100cc kit, you're reaching the maximum amount of air the engine can flow.  However, get a big valve head, match the ports and a bigger carburetor and then you will realize the full potential of larger displacement.

Think of it like this.....imagine even a 400 cubic inch motor with racing heads and cam(s) ...with one 30mm carburetor on it.

If it can't flow....it won't GO

[humanshield]

Nov 19, 2016 17:18:03 GMT -5 gsx600racer said:

When I ventured into the scooter scene several years ago, I started out with a 4t machine. I like everyone else, I wanted to go faster, lol. I did a lot of reading and it seem to be the general consensus that an 80cc kit was the way to go if you were using the stock crank and looking for longevity. 100cc were for those that were willing to split the case and install a new crankshaft and possibility have the case halves machined to get the new cylinder to fit.

Either way 80cc or 100cc, it going to take certain level of skills to build either one. I do agree with humanshield with regards to starting of with an 80cc for the best chances of success for the first time builders.

I ended up selling my 4t scooter before doing any engine mods to fund my 2t projects.

I love riding my 2 strokes around.   My smallest is 125cc's and largest is 400cc's
If I didn't have so many two stroke motorcycles I would have bought a 2 stroke scooter by now.

The 400cc 2 stroke is....pretty quick.   Like Z06 Corvette quick 

[Deleted]

Nov 19, 2016 18:54:52 GMT -5 humanshield said:

Nov 19, 2016 13:56:31 GMT -5 peascreek said:

My original build was the Glixal 80cc bbk with their 20mm carburetor, which by the factory specs has a #90 main/#30 idle. I then dumped almost twice as much into the 100cc bbk, 23mm valve head, A9 cam and the same 20mm carburetor, and got in reality, very little performance gains over the 80cc kit, seemed more like a shifting of the power band upward.

Considering the likely reduction in engine life I'll see even if treated correctly, and the money spent, I would not go the 100cc route again and focus on squeezing a bit more out of the 80cc through fine tuning.

There is a very simple explanation for what you experienced and I 100% agree.

When you go to a 100cc kit, you're reaching the maximum amount of air the engine can flow.  However, get a big valve head, match the ports and a bigger carburetor and then you will realize the full potential of larger displacement.

Think of it like this.....imagine even a 400 cubic inch motor with racing heads and cam(s) ...with one 30mm carburetor on it.

If it can't flow....it won't GO

Or I could just stop fooling around and buy a 150 or 250 ")

[Deleted]

Just out of curiosity humanshield, how much do you think the stock 50cc exhaust is holding things back if at all?

[eclark5483]

Think I'll stick with the 69 ci, 100 HP, V-twin engine on my Scout. Life is more fun in cubic inches, not cubic centimeters.

[Deleted]

Fun is relative, and I can't pull a clutch because of an injury.

On the other hand, you can't take an Indian Scout on logging roads and pavement gets boring as hell so my Jeep takes care of that.