Performance issues

[kooolkidd21]

hello posters i need some help i have a ht 80cc engine kit that doesnt perform it max's out at around 35kmph and i have tried everything to increse speed i have cut down the baffle i have matchported all my gaskets i have hotter plug ive adjusted my carby i was running a 16 : 1 mx have now cut it to 40 : 1 was too rich im really stumped i was wondering if anyone knows why my engine doesnt perform thanks.

 

[motorpsycho]

how many miles do you have on it?
what size wheels are you using, and what size rear sprocket?
you should be getting at least 40 kph out of it. (35 kmph is 21.749 mph. 40 kmph is 24.856 mph.) most of these motors (66 c.c. or 49 c.c.) will only see 22-28 mph(35.4 kmph - 45.05 kmph) max when they are stock from what i have seen.
cutting the baffle isn't REALLY a performance mod...i mean it does add a little, but not as much as if you put on an expansion chamber. port matching gaskets is usually only good for a tiny gain on the top end.
have you checked your head gasket? checked for air leaks at the intake manifold and carb?
are you running the stock air filter? a high flow air filter is good for a little extra power as well. don't expect these engines to run 40-45 mph (72.4 kmph) out of the box, you have to tinker and experiment with a lot of different things. each engine will perform and respond different.
i have a 49 c.c. slant head, with an exp. chamber, high flow air filter, ngk spark plug, running it at 32:1, with a 44 tooth rear sprocket on 20" wheels. i am getting 25-27 mph top speeds (approx 43.5 kmph)

 

[give me vtec]

Could just be your engine... what brand is it... where was it manufactured???

It makes a big difference, I have ran a zoombikes slant head, grubee skyhawk, and flying hoarse. The zoombikes was hands down the fastest, the slowest hands down was the flying hoarse (by about 10 mph).

If you want more power mill your head. I assume your head is a dome shape when you take it off??? Go down to harbor freight or home depot and get a set of files and about 5 different grits of sandpaper from really rough to really fine.

Start with the rough file and work your way down to the fine grit paper. File the little lip off so that the whole underside of the head is flush. Be sure to file the lip off VERY evenly. When you get down to the end, you should be on your fine file. Then secure a piece of the roughest sandpaper down to a VERY flat table and work it around in circles "wax on, wax off". Insert your spark plug, but dont connect it. Manually turn the engine around a couple of times and check to make sure your plug clears when you are finished. It was good for a noticeable boost in power for me when I did it to my grubee head.


I wouldn't run 40:1... I wanted to see what would happen if I ran a rich mixture so I put a bunch of 50:1 chainsaw mix I had in my dela cruiser. It was a death blow for my poor old zoombikes motor.

 

[cabinfever1977]

Well its either you weigh more, your bike has small wheels or you have a lower quality engine, take your pic.