Some General Questions

[alexfleury]

Questions posted to all those who know more than I. (most everybody) lol

I have my stock Elite 2001 and a 98 I just bought that looks like * but already has a BBK motor that runs great.

So after years of motorcycle riding and wrenching I am new to both scooters and 2 strokes.

I see most of the BBK have similar bore specifications. For the majority of the kits, assuming it's not a stroker, how many cc's is the motor after you install a BBK? I realize it's dependent on bore size but it seems most of the kits have similar bore sizes.

How much horsepower does the stock SR make and what do most people get with a carb BBK and pipe? I am asking about a "bolt on" kit with no porting. I know once you get beyond that there are many factors that come into play.

I haven't installed taller gearing in the BBK bike yet, it is already much faster that my stock bike. What kind of top speed am I likely to get with the BBK carb pipe and gears? I was told by the guy who built the bike that it was a Taiwanese BBK, with no port matching required and it has an OKO carb and a V8 pipe. So it is nothing special, but it is WAY stronger than my 50cc bike.

I live in the VERY hilly area of East Tennessee. Should I install 9:1 gears on my stock bike? It has a Keli variator, 6 gram weights, and a Technigas pipe. Stock carb, 91 main jet. (main jet drilled by me that's why the odd size)

Any other good advice you feel like passing along will be appreciated!

Thanks
Alex

[Wheelman-111]

Greetings:

Taiwanese bores come in several sizes from 44 through 51mm or more. The bigger bores leave little "meat" on the cylinder walls, perhaps the reason for their early demise in my hands. A 50 should hold up fairly well, provided the builder addressed the lack of chamfer on the ports. Sharp edges apparently scrape ALL the oil off the piston, leading to dry spots and seizure. 8.44 gears are a good all-around choice for a 75-82cc kit.

Honda's Factory Service Manuals specify the at-the-crank HP ratings - around 4 or 4.5 from memory. Daywot once sold a Nicasil 49mm that was incredibly durable, if a bit underachieving, and ran despite bad jetting choices including occasioinal coast-down temps above 500 without a scratch. It was affordable, durable, but not terribly fast. Still, it would handily crush a stock bore with only a modest pipe and gears.

I ran 9:1s on an otherwise totally stock piston/pipe/carb setup and it hit 49 MPH - downwind of course. The variator makes performance almost indistinguishable from stock 12:1 gearing EXCEPT FOR the 0-5mph take-off. That can hurt a little in traffic if you're trying to jump through a line of cars turning, but if you need better than the stock 40-ish speed, you should do it.

Displacement of a cylinder:
Volume = 1/2 x Bore size in CM squared x 3.1416 (estimate of Pi) x stroke in CM.
50mm x 1/2 = 25mm = 2.5 cm. Squared = 6.25. Multiplied by 3.1416 = 19.635. Multiplied by 4.14cm stroke = 81.3 cc.

You can plug in bore size 44, 47, 48, 49 or 50 and work it out the same way.

The big-block should receive 8.44 gears and so equipped will get over 55 MPH if all goes as it should. Going taller than those gears usually means the engine runs out of oomph before the variator maximum is reached, and may actually be slower because of transmission slip.

[alexfleury]

Thanks Wheelman My cus and I took both the bikes out yesterday. I weigh about 180 he is about 240 (he says lol)

On a long steep hill where I was down to about 30 mph on the 50cc bike the 75cc BBK was able to blow by me and keep accelerating all the way to the top of the hill. Both bikes still have stock gearing.

I'm pretty happy with the (mostly) stock bike. It looks good and runs good and I guess I'll leave it alone for now.

The BBK bike needs tires, paint electrical work one body panel, I already have 9:1 gears for it just not installed yet. I'm sure I'll need some other stuff once I get into it. So it will be the one I'll play with. I plan to do a complete custom job on it. I'll start a build thread when I get going on it.

Thanks to the info and advice on this board, I have two fun scooters to play with now. One pretty one and one fast one.
Purchase price for both bikes $1050

[Wheelman-111]

Greetings:

Quoth AlexFleury:

I have two fun scooters to play with now. One pretty one and one fast one.

You could swap engines in about an hour...
Then part out the ugly slow one?
9:1 gears will accelerate well, but often not tall enough to take full advantage of a big-block's power.

[alexfleury]

You are exactly right. I have already thought about putting the fast motor in the pretty bike. But I have plans to build a "nekkid" custom scooter. Even have the colors picked out. I saw a pic of one here with the frame visible and I just gotta try to build something similar. I thought it was cool! And the one I've got is pretty rough. It's a good place to start for a build like that!