How to get a 70cc 4speed in frame?

That's an awesome engine, but does seem a bit big.

A horizontal cylinder engine like your 70cc usually requires a bike with a stretch frame or chopper frame. There is no way the 70cc motor will fit that worksman unless stretch that frame. if this is your first build, I would go with a simple engine kit like an HT 2 stroke. if you want a four stroke on that worksman, go with a rack mount kit from Staton or Thatsdax.You could mount an HS four stroke in the frame of a more conventional beach cruiser (like a huffy Cranbrook).

That's a four stroke engine. This is the 2 stroke section.

I say this with all honesty, just buy a motorcycle. A bicycle is not meant to do 55+ mph unless you replace everything ie; wheels, tires, every bearing, etc. I dont know of an engine that will do 55+ and still have torque for hills. Maybe a 16hp morini?

If you get this http://www.morinifrancousa.com/engine5.htm with a radiator and all the goodies, you will have one of the most badass bikes I have seen.

Sounds like you need a DeNardis or MotoMorini engine. Ktm uses the morini in it's minibikes.
The DeNardis is a aftermarket replacement for the Morini. Expect to pay about 450-500$ for one of these screamers.

mrblack98 said:

GP460 isn't. What about that for the Board track racer. How would I go about mounting that inframe?

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The link in your original post is to a 4 stroke Lifan engine.

mrblack98 said:

Hmm ok thats a possibility... Now as far as China Girls go. If I were to upgrade the crap out of it, bored, new carb, expansion pipe, gaskets, intake, etc. with a SBP shift kit, what kind of top end speeds would I see?

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A), china girls cant be bored because they are aluminum with a very cheap chrome coating. B), the more mods you make, the harder they are to properly tune and therefore the more risk of a shorter engine life. C), realistically 40mph, maybe a little more with a shift kit.

pretty close to the same you'd see if you did nothing

"new carb, expansion pipe, gaskets, intake, etc. with a SBP shift kit" - none of these will in any way increase the "risk of a shorter engine life" & in fact could prolong it if installed properly - the only "risk" is that due to the increase in preformance you may be tempted to abuse the motor more.

Adding an expansion chamber is the single most significant "upgrade" available for these motors, as it is an intrinsic part of a two stroke system - a two smoker will run w/o one ofc, but poorly in comparison. A new carb isn't nearly as significant a change if the one you have functions properly w/the correct mixture. Upgrading gaskets to ones that don't leak is a commonplace "modification" (repair) & "intake etc." is best achieved through no more than gasket & port matching, another minor "repair" that is required due to the lack of quality control.

I would like to point out that "shift kits" do not give you any more speed than what could be achieved w/o one, provided only that the final gear ratios are the same - the difference being that in that instance the single speed would need assistance during initial acceleration as it'd be geared tall.

If anything shift kits marginally reduce potential maximum top speed through added friction/drag - the additional chains, bearings & sprockets each taking a small toll.

The application of a shift kit improves acceleration and gives you the option of reducing cruise RPM, both valid reasons for installing one & the latter may well increase engine life - if you're willing to deal with the additional maintenance a shift kit requires.


Actual stock speeds vary wildly due to the random quality, but unless major modifications are attempted (reeds/moped top end/etc), realistically it's very unlikely you'll see 40mph+ even with all the mods you mentioned (flat ground), but you may get close. What you'll get is a far smoother running motor that's more powerful than stock and if not abused, should be at least as if not more reliable as you've fixed the factory flaws.

You wanna cruise 30 all day, a 49CC or higher 4-stroke or a chinagirl 2-stroke can do it.

40+? Well...lol...I don't condone such a thing on a bicycle

mrblack98 said:

Challenge accepted.

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some light reading for ya then http://motorbicycling.com/showthread.php?t=11141

I think I'll stick to the chatbox and commenting on my own threads from now on.

mrblack98 said:

Aw sorry man, I appreciated all your comments.

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It's not you bro. Staff don't seem to agree with anything I have to say lately.