chopper build up

[dan]

hey all, ive recently been doing up a 200cc briggs flat head as some of you may know. then i thought to my self hang on a minute i dont have any thing to put the engine in so i thought to my self "id like a sleak chopper to cruise around on". so i set off building my little chopper.

this is what i have in mind for gearing straight driven 15t front sprocket and 52t rear. its running a 13" wheel with a small car tyre. let me know what you think.

here are the pics

cheers, Dan

 

[robbie]

According to the speed calculator on this site your bike should be able to go 77 mph. I read the numbers on your tire and looked up the outside diameter online, and I assumed 3600 rpm on the engine, although I'll bet yours will be faster. You may want to gear it slower for better acceleration. I'd want some shock absorbers for such a fast bike.

Other than the lack of suspension, I like your frame. It looks pretty cool.

 

[Imbo]

if robbie is rght about that 77...i would not trust it....i would go for gearing near 13ft 55rear...the speed like that is insane....also your acceleration would be horrible with a possibility of burning out your engine. if you could get a TC that would probably help alot with acceration and speed

 

[HellSpawn]

Also, a wider front tire will save your life.

Steering with that dinky tire will be horrible.

 

[dan]

front tyre is plenty wide enough, i have a lot of trust in my welds and fab skills as this is what i do for a living. as for the speed factor i dont know.

 

[robbie]

http://www.diygokarts.com/speed-calculator.html

That is from the link on the bottom of this page, where it says DIY go kart and mini bike home page. According to the info I found on the web, your rear tire is 24.9 inches in diameter. Put your numbers in the calculator and adjust your tooth count until you get a speed you think is practical. If you gear for too high of a speed, you'll fry your clutch. With a non shock absorber frame you may want to keep the speed under 40. Otherwise you could hit a bump in the road and go flying.

 

[dan]

http://www.diygokarts.com/speed-calculator.html

That is from the link on the bottom of this page, where it says DIY go kart and mini bike home page. According to the info I found on the web, your rear tire is 24.9 inches in diameter. Put your numbers in the calculator and adjust your tooth count until you get a speed you think is practical. If you gear for too high of a speed, you'll fry your clutch. With a non shock absorber frame you may want to keep the speed under 40. Otherwise you could hit a bump in the road and go flying.

there is no clutch. may be building a 2 speed box for it tho

 

[r97]

no clutch? direct drive? that ratio is a bit high, may be able to manage with a 2 speed, but usually torque = more fun than speed

nice shop!

 

[robbie]

Were you thinking of having a direct drive from the engine to the wheel with no clutch? Or do you have some other plan in mind? A 2 speed gear box would be cool, but in that case you would need some kind of clutch.

 

[dan]

well as i have a cracked fly wheel i have no engine. does any one have a 200cc 6 hp briggs flywheel?

 

[brendonv]

Car tyre on the back! Man turning will be ****. You will have hardly any grip. Also because you got such a wide tyre on the back and a small one on the front, when you turn you will be turning a smaller distance on the front and a greater distance on the rear. A wider front tyre will make it go a lot better. It will turn like poo the way you have it. Also because a car tyre is flat, you will be rolling the front tyre and sort of have like 1cm of bite on the rear.

 

[dan]

ah its all fun and games lol might opt for a moto tyre on the front aye

 

[sideways]

With direct drive and that super high gearing you will have to get it rolling about 20-30kms before the engine will start. You need to gear it down.

Thanks

Hayden

 

[dan]

yep called a jack shaft my good friend

 

[dan]

and its a roller very happy all looks to be well little bit more machining tomorrow and my axle will be sweet as. goin to have to run the sprocket and chain on the out side of the frame :/. should be all well tho. heres some pics.

cheers, Dan

 

[sideways]

Going to mill any fins into that head?

Interesting placement of the spark plug, to say the least.......

Post some pictures of the head please, I'd like to see the combustion camber.

Any lawnmower flywheel from an engine of that block size should fit, as long as they were fitted to a mower with the same type of pull starter and one without points.

Thanks

Hayden

 

[dan]

sorry heads strictly top secret...... nar jokes. why do you think the plug placement is strange? and no fin to be milled in to the head, tho i was thinking of running water ports in it to water cool it.

 

[devino246]

and no fin to be milled in to the head, tho i was thinking of running water ports in it to water cool it.

Remember that you can over-cool the engine. Water cooling it would be overkill.

 

[dan]

yep yep i havent touched it yet it shouldn't get to hot any ways.

 

[dan]

heres what the bike looks like now,

this is what im goin to make it look like tell me if you think this looks better,