Intro to Mantini MBK 1 video

[sparkwizard]

This is a nice video. I never heard of these people.

 

[sparkwizard]

I thought it looked like a V twin would fit in the frame @zefer is building. I really want one of these even more, now.

 

[Mark Brooks]

Wow, just watched the video, very impressive!

Big Block in it and hang Sloopy! Lol

 

[zefer]

There is a ton of room for a big block and a V twin...the design of the frame suggests a lot of possibilities. I have given some thought to a small displacement vintage motorcycle engine for my bike.

 

[sparkwizard]

With the proper jackshaft gearing, that would be a fun ride!

 

[zefer]

I've never run a jack shaft mini before so I will need guidance with this and im thinking about running a torque converter as well. I am old school...clutch chain and tensioner is where I have been most successful
There will be questions

 

[sparkwizard]

To use a motorcycle engine, look at the relationship between the motorcycle tire and the sprocket on the motorcycle. The sprocket is usually about 1/3 the tire diameter. It would be tough to find a sprocket that is 1/3 the diameter of a mini bike tire, so a jackshaft could be used between the motorcycle transmission countershaft sprocket and the mini bike wheel to gain some speed with the smaller tire.

Ask away, Sir!

 

[zefer]

Just me thinking too much.
I have a pretty stout tillotson 212
Electric start thats built to an honest 15 hp. I am going to run with a torque converter.The bike is set up with a jack shaft final drive ( not sure how many teeth on the counter shaft gears )..the sprocket is a 62 tooth # 40 chain
I have no idea what the final gear ratio will be ? I will be fitting up the tilly on a riser to gain some clearance for the converter backing plate.

 

[sparkwizard]

That will be PLENTY of power.

 

[Nunzio]

I'm sure there are others but I use this one to choose my gearing and calculate final ratio. Given the size of the wheels we are using, I think 6:1 is an ideal target. https://www.burrisracing.net/calc/

 

[sparkwizard]

I generally divide the tire height, or diameter, in inches , by 2. Then I try to get a gear ratio close to that.
12 inch tire, divided by 2...6to1
20 inch tire, 10to1. It usually works pretty well.

 

[Minimichael]

I generally divide the tire height, or diameter, in inches , by 2. Then I try to get a gear ratio close to that.
12 inch tire, divided by 2...6to1
20 inch tire, 10to1. It usually works pretty well.

Thanks for this rule of thumb. Never thought of it that way. Makes sense then that the lower ratio set ups would require greater torque but high ratios like 10:1 might get away with less torque.

 

[sparkwizard]

Taller tires need more leverage, so a larger numerical ratio is needed.
Half the tire diameter has always gotten me in the ballpark.

And if you are using a jackshaft, figure the ratio between engine and jackshaft, then figure the ratio between the jackshaft and the rear wheel.
MULTIPLY them to figure your overall gear ratio. Do NOT add them.