[tylerw2239]

Hey everyone,

I looked in the search but I cant quite find what im looking for.

My cylinder has been bored out and ported and the head has been modified for high compression. I maybe have about 40-50min on the motor and after the first 3 heat cycles I had about 140 psi.

I was told to have it run race gas, but what is the difference between leaded and unleaded? There is a racetrack I work at that sells 110 I think, but its all leaded. Will this hurt the bike?

1998 cr125

 

[ThatTwoStrokeGuy]

nah, originally, lead was introduced into fuel to prevent valve seat recession (i think)

some people run AV gas 100LL which is low lead but it still contains lead

i'd just try to get some ERC, VP, or Sunoco.

and if you ask me, 140 psi sounds a bit low...

 

[MX86]

140 is way low if you had the head milled should be 175ish would be my guess.

 

[flotek]

these are things you should ask your builder about



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[tughill283]

my stock yz 125 had 180lbs compression,it ran fine on 93.

 

[tylerw2239]

alright, maybe it will increase as it breaks in and seats the rings more properly? I'll do another test sometime soon.

As for now 93 is my juice until i can see if that race gas has lead in it at my track.

Thanks everyone.

 

[ThatTwoStrokeGuy]

ha ha ha! your rings are seated buddy! somthing is really wrong with the top end, check the bore for out of round! you don't wanna find out the hard way