new motor

[blue 48]

hi got a new 48cc kit today done what the sticky in this forum said to do all good and ready to go , it seems slower than my other one it runs well im very happy with it. i wont take it too quickly, when its run in i hope it will be a bit quicker. is this the case? its exactly the same as the other one carb and all. all this for $130 with everything +10 for all new bolts/studs/locknuts ect. ill send in some photos soon of both of them

 

[HeadSmess]

mmmmm, run in makes a difference even though in my opinion its more "getting all the nasty china grease out of the bearings" and not really a break in as such...

things that i dont think are in the sticky but make differences.

first, i take off inlet manifold. turn engine to TDC, scribe skirt of piston. pull it all apart and file out the scribed section... use new circlips on reassembly!

while its apart, swish out the crankcase with some petrol then diesel or petroil mix.that china grease is nasty stuff!

clean any burrs out of ports and manifolds.

clean everything and put it back together...

 

[motorpsycho]

wow, my 49 c.c is just as fast as my 66 c.c.
what size wheel do you have and what size rear sprocket is on it?
gear ratio and wheel size can make a HUGE difference in how fast (or slow) the bike is.

 

[blue 48]

hi guys its running like a dream now. it goes alot faster since the first post and is on par with my other one now (old one 36 tooth on a 26 rim 60kmh without revving too hard) ( new one 44 tooth on 26 inch rim 50kmh im happy with that ) saying that im putting a 36 tooth on the new one soon no rush though.

@ headSmess what does the filing of the skirt of the piston acheive im interested please reply thanks

 

[FelipeCobu]

hi guys its running like a dream now. it goes alot faster since the first post and is on par with my other one now (old one 36 tooth on a 26 rim 60kmh without revving too hard) ( new one 44 tooth on 26 inch rim 50kmh im happy with that ) saying that im putting a 36 tooth on the new one soon no rush though.

@ headSmess what does the filing of the skirt of the piston acheive im interested please reply thanks

The HT engine is a "piston ported" engine, (do not uses a reed valve) so by changing the piston skirt you are actually increasing the timing off the intake port.

 

[HeadSmess]

yup. and theres the fact that the piston in a ht never completely exposes the port... theres about 5mm that interferes.

its killing two birds with one stone. uncovering the port more will allow a larger volume of air through.

uncovering the port for longer will also increase the volume of air able to pass.

add the two together and you have lots more air...with fuel...that goes bang...


take too much off though and it starts spitting back out through the carb at low speeds... so only do whats necessary!

 

[blue 48]

so like u said file it flush with the port yes?