Failure of Happy Time style 2-stroke Big End Connecting Rod Bearing

[Fabian]

Hi iron monkey

If you have read my previous posts, you'll know that i don't exceed 3,500 rpm.
Any more rpm and the engine is starting to vibrate itsef to bits - this is the main problem that needs to be solved - apart from the atrocious crankshaft balance factor, the factory assembly process could be a significant cause of excessive vibration with these engines.

Anyway, the thread isn't a debate about why you should not be making these engines reliable just because they are cheap.
The thread is about listing the methods of reengineering the product to make it a useful piece of machinery for daily transport with dual functionality as a recreational bicycle.

Feel free to comment on the modifications you've made in design and finished product, ideally with detailed photos and instructions for the other members who may have a need to replicate the process.

Fabian

 

[iron_monkey]

Anyway, the thread isn't a debate about why you should not be making these engines reliable just because they are cheap.

No, on the contrary they are sufficiently reliable for some people, including me. Maybe you are getting your engines from a bad batch/supplier?

If you simply want more reliability, you may as well get the 4 stroke(unless you have a thing for these 2 strokes) for the fraction of the cost.

One can easily deal with the red cover (if that makes the engine too visible) by repainting it or taking it off.

 

[Fabian]

I had the option of purchasing either a 4-stroke or a 2-stroke kit.

The advantages of the 4-stroke engine were numerous.
Unfortunately the 4-stroke engine was 3 times the size and double the weight of the 2-stroke kit.

It couldn't be used as a centre mounted engine, but only above the rear wheel.
They had an example in the shop - it looked ridiculous
Just this unsightly, ungainly and almost unsafe looking engine perched lopsided on the bike.

The 4-stroke conversion screamed out - pull me over, throw the book at me and confiscate the bicycle.

The 4-stroke kit was not even worth considering, if you are trying for a stealthy look.

Fabian

 

[iron_monkey]

There are plenty of center mounted 4 stroke kits, and the bike doesn't have to be large or have high seating either (from the pictures I've seen).

Anyway, if you really like 2 strokes, then so be it; just making you aware of cheaper options.

 

[Fabian]

I have seen 4-stroke centre mount kits but once again from a police perspective, they look like a "big" engine.

Naturally a "big" engine must be more powerful than a "little" engine - that stands to reason if you are a police officer with no knowledge of engine design.

The 4-stroke kits just stand out too much, attract too much attention because of their large size.
If you live in an area where motorised bicycle kits are legal, the 4-stroke system is a far better option but it is not a stealthy option if you "need" to be discrete about your engine setup.

Fabian

 

[iron_monkey]

Those 4 strokes aren't that much larger, they only significantly wider. They will still fit an average old style mountain bike.

If the police are in a bad mood and want to fine you, they will; imho the size of the engine isnt going to change that. The particular noise and pollution of 2 strokes doesn't help either.
Your reasoning is only going to work if your jurisdiction have a 50cc rule, and even so the 4 strokes will fall under that with an appropriate 49cc plate/label.

If you want to avoid the law then an electric motor hub kit is your only option if you still want a 'motorised bicycle'.

 

[Fabian]

Regardless of how good a 4-stroke kit may be, it's too big to be used as a discrete engine; portraying big size = big power.

This thread is about listing the methods of reengineering a 2-stroke Happy Time style Chinese bicycle engine to make it a useful piece of machinery for daily transport with dual functionality as a recreational bicycle.

Feel free to comment on the modifications you've made in design and finished product, ideally with detailed photos and instructions for the other members who may have a need to replicate the process.

Fabian

 

[Mountainman]

good luck finding one of those

a police officer with no knowledge of engine design.

good luck finding one of those
because facts being what they are
most pooolice are just not that lame regarding this size issue

and if and when a motor cycle cop pulls one over on a MB
be ready for the real thing fast !!

ride that MB thing

note -- an official looking heavy duty stamped cc plate may be important ??

 

[arceeguy]

Seems that 200 watts is the maximum power output that Australia allows to be "legal". A 50cc happytime engine is at least 1,500 watts. (around 2HP) So really, no matter what he does, he is illegal. (unless he wants to pull the motor from his kids Mattell Power Wheels and put it on his bike)

Fabian and the other good folks from Australia really have to have that ridiculous 200 watt restriction stricken from the law books instead of thinking of creative ways to make an engine more stealthy.

In any case - Fabian has indicated that his creation is a "one off" project just because he wants to do it - much in the way a mountain climber climbs a mountain. Why? Because its there.

 

[Fabian]

I agree arceeguy

If the plain studid, ridiculous and draconian 200 watt law was abolished, i would try and find a way of installing a 4-stroke engine kit.

Having said that, the law is the law and when you don't have a car licence you need to be even more careful at how you go about things.

I am using a standard exhaust pipe with a large R/C silicon deflector tip to dampen down the already quiet muffler.
The bike is surprising quiet from the exhaust side but i'll have to do the mods suggested in other posts at quietening down the primary drive gear whine.

Australia is not far off a Stalinist, communist Russia with it government regulators.

Fabian