How to improve 4 stroke engine

[LewieBike]

Thanks. I understand everything you said except the quote above: what do you mean "buy one or two steps 'leaner' which would be 'jetting down'"?
Why should I jet down? Can't I just leave the engine as it is but just go easy on him in and after the break-in period?

The leaner main jets are only going to be possibly needed if and when you cross the Rockies, or other big mountains.

Worse case scenario: anything over 5000' average will cause your engine to lose some power and make your engine run rich, you'll get a little black smoke from the exhaust without the choke on, possibly fouling your spark plug with carbon, fuel mileage will worsen. It may not get that bad, and you may be able to cross the Continental Divide without re-jetting and just suffer some power loss and slightly worse fuel mileage.


I'd leave the stock main jets installed while doing break-in and while in CA, but having the leaner jet as a back-up if the higher altitude air conditions are making your bike run much worse than expected. You should get familiar with taking the carb apart to change the main jet. I believe there's some HS149 threads in this sub-forum detailing how to take your carburetor apart.

 

[Chris Kennedy]

This is a great kit! Just wish it looked more like a motorcycle engine then a lawnmower engine!

Hi,
I bought this kit:
https://www.bicycle-engines.com/49cc-4g-t-belt-drive-complete-gas-powered-engine-kit/

How can I improve the motorized bicycle? Obviously, there are s**tty parts in any engine kit. Which parts I should replace for better ones?

Most of improvments I read in this forum are on 2 stroke motorized bikes. I don't see much of elaboration on 4 stroke bikes though.

 

[Charles Laypool]

I had that same kit stock would go 27mph with a 48t sprocket. What mods I did was new exhaust pipe (stock 2 stroke pipe) and new carb and intake (2 stroke stock nt carb and intake) got me up to 31 mph. Kingmotorbikes sells a hand full of mods links are below

Carb and intake. https://www.kingsmotorbikes.com/collections/4-stroke-parts/products/4-stroke-nt-carburetor

Exhaust pipe. https://www.kingsmotorbikes.com/collections/mufflers/products/chrome-exhaust-muffler-1

Also I would stay far away from the freewheel drive drain iv had 3 fail on me and with the freewheel u cant use the engine to help u slow down witch saves ur brakes.

 

[dmopedMA]

high air flow intake filter

Any recommendation on this?

 

[Theone]

Nt carb and air filter bro like charles laypool said

 

[bakaneko]

Any recommendation on this?

Nope, but AGK sells some that you can take a look at. Double check everything.

https://affordablegokarts.com/colle...rts/products/uni-high-flow-air-filter-adapter

 

[KCvale]

Lifetime NGK 7544 (CR7HIX) Iridium spark plug is a must.
You can get them from SikeBikesParts or NGK direct.
Loose the can exhaust, a cheap 2-stroke pipe works well, no catalyst in the cheap pipes.

I do not recommend using an NT Carb as a performance enhancer.
Just a nice air cleaner works great.