pocket bike 50cc to 399cc

[Eric492]

hi guys in new here. i was told about this site by a friend rotore? i think is his screen name. but i got an old 25ci 11hp briggs from him w/ a rusty norman racing clutch *14 tooth*.

i need some help w/ performance for this engine because i want to throw it on my pocket bike. i read threw some articles about eliminating the head gasket so thats one mod but im not so sure about the carb or exhaust. also it is a vertical engine so i think it'll be tilted 40 degrees w/ some extra oil to create a mist should lub it, what do you guys think?

its 399cc 11hp briggs so i think a 28mm mikuni w/ a 1inch exhaust should give me some ponies and removing the govener but i wont take it past 4500-5000rpm.

here are some pictures of the bike and engine together. it'll be a tight fit i know but moving both gas tank and battery tray should do it.

 

[devino246]

To use a vertical engine, you'll have to turn the engine 90* so the output shaft is horizontal. Then rotate the carb 90* so its level. You also have to fab up an oil dipper to lube the internal parts. I dont see that engine fitting on that bike, but i may be wrong. Its also gonna add alot of weight.

 

[Eric492]

what can i use to make a dipper and the engine doesnt have to be 90 degrees just the carb right?

yes it'll add 65lbs but it'll fit if i relocate the gas tank and battery tray.

 

[devino246]

The engine has to be rotated 90* and the carb is rotated so its at the original angle. I think you can use spring steel for the dipper. Google it. I doubt you'll gain that much speed. The new engine looks like a flat head, so the valves floating will work as your new governor.

 

[Eric492]

ok cool

w/ 14t clutch and 50t sprocket i should to off a 45mph thats good enough for me.

valve float?

 

[devino246]

Thats a ratio of 3.57. Thats gonna destroy your clutch and bottom end.

Valves float when the engine is running so fast, the valves dont have time to close. With an overhead valve engine, floating valves can hit the piston and cause damage. With a flat head, theres nothing in the way and it simply slows the engine back down

 

[Eric492]

oh ok what type of gear ratio should i aim for?

 

[devino246]

6:1 should be fine. You may have to use a jackshaft to get the ratio.

 

[Kaptain Krunch]

Your original ratio would be fine, with it being a pocket bike, with fairly small tires, and a quality clutch, i wouldnt worry. 6:1 is very low, you would have a hard time keeping the front end down.

 

[devino246]

How big are the tires?

 

[Eric492]

Your original ratio would be fine, with it being a pocket bike, with fairly small tires, and a quality clutch, i wouldnt worry. 6:1 is very low, you would have a hard time keeping the front end down.

my original ratio was about 3.5:1 and i could hit 30mph easily on that 4hp 2-stroke so 11hp should pull nicely and yes 6:1 i will have a hard time keeping the front tire down.

How big are the tires?

15 inch semi racing slicks

 

[Eric492]

here are some pictures of the bike w/ out some of the body panels. it isnt the easiest engine to start so more of a reason to throw the briggs on it and the wire harness from hell is driving me crazy *headlights, horn and speedo dont work* so im going to start from scratch on that.

 

[devino246]

What kind of bike is it?

 

[Eric492]

x2 super pocket bike *chinese knock off*

 

[devino246]

I thought of getting one of those. Mabe if i get a job this summer.

 

[Eric492]

you should these things are awsome and can be made street legal

 

[devino246]

Since it doesnt look like im getting my liscense any time soon, i may have too. As long as the seat is 25" off the ground and its under 50CCs it would be a moped, but a whole lot cooler and cheaper. Any ideas what kind would be good?

 

[Eric492]

X7 would be you best but or an x2 like mine 33" seat height but there are alot of other choices

 

[devino246]

33"? The higher the better considering im 6'

 

[Eric492]

me 2 man http://www.minipocketrockets.com/x18-r-4-stroke-super-pocket-bike/