bike not running good

[SAMURAI47]

Hi, my dad just put a 15:1 yellow jacket copy head kit on his bike with the full circle crank and 14/14 carby plus fatboy exhaust and it seems to be be alot slower than my bike which only has a 13:1 head kit with one boost port in it and running stock pipe and stock carby.but he does hav alittle more top end than me but his takes a while to get to it.could it be the jets hes running in his carby or wat? hes running a .78 at the moment and we both hav stock 7/68 gearing and we weigh about the same. we thought that there would be a massive difference with the 15:1 kit but there isnt. also could it be cause his squish is set at .65 at the moment? or does a couple of extra boost ports and higher compression to mine only give him more top end?

just alittle confused here since his headkit cost 4times the amount mine did

thanks

[RD RACING]

if you bought a pbu yellow jacket copy, the cylinder will have as by pbu 2 x boost ports and no exhaust porting. this copy pbu may have raised exhaust port duration which is great for total rpms but low end will suffer, also squish head clearance should be set to 0.05mm. 0.065 is still ok but very close to max of 0.07mm. try a 75 jet also.

[SAMURAI47]

alright thanks alot mate will try a .75 jet

[akim21]

tell me how it goes.. im getting that head kit for my cag!

[R1pocket]

i got a head kit of RD and my bike goes i noticed huge gains in low and high end speeds. pm him.

[mac90]

go as low as 65++ may be a bit lean 70 was ok in my bike with the 15:1 kit but was not a yellow jacket one
try running your carby on his engine
and i rekon your dad would be alot heavyer than you so u have to compare bikes with same carbys same jets same rider etc to get a better idea
some people say the 13:1 with 10 mm pin has more go than a 15:1 with the 12 mm pin but the 15:1 with 12 mm pin should have better torque and top end but suffers @ take off

[SAMURAI47]

hahaha for starters my dad weighs proly 5kg more than me cause im alot taller than him and secondly my bike has the 12mm pin with the 13:1 and his has the 15:1 with a 10mm pin but with the f-c crank. so u think that i should try my stock carby on my dads bike?? alright i will try it today i'll c how it goes

[akim21]

so how did the bike go?? does it run well now?? i remember someone telling me that u had to get the crank balanced, but im not sure

[SAMURAI47]

it ran the same. now it has the worst fkn overheating problems u would eva see. after 1 and a half laps at the track it cooks the plug and melts the lead cap

need advice badly

[RD RACING]

you may need some exhaust wrap around the header pipe area so heat from the header doesnt transfere across to the head.