Honda TRX250R Forums banner
1 - 8 of 8 Posts

·
Registered
Joined
·
4 Posts
Discussion Starter · #1 ·
Hey guys. I'm almost ready to start my R for the first time in 5 years. Just finished having it bored and installing all new seals and bearings. 66.75 piston, 72mm stroke. I'm now just trying to figure out what I need for octane. I performed a UCCR on it and it came out to 16.25 / 1 with the squish at .045 I believe, (its written down at home and don't remember off hand.)
I have been searching all morning on what octane I will need but I'm getting conflicted answers. TRX250R Compression / Compression Ratio Chart If I'm reading this correctly, it says I can run 110 but when I look at race fuel manufacturers specs, they are saying 110 is only good to roughly 14 to 1 compression ratio. I have not done a compression test on it yet as the bike is still up on the stand until its all put together.
If anyone can shed some light on this it'd be greatly appreciated.

Brad
 

·
Registered
Joined
·
691 Posts
110 octane race fuel comes out to actually being around 105-107 and that is usually the reason why they say its only good for up to 14:1. VP C12 race fuel is close or actually 110 and is suitable for 15:1 or higher (possibly).
 

·
Registered
Joined
·
4,254 Posts
that's some serious compression.are you sure you did that right?it has to be one small head,shaved cylinder...I think the have a c23 or something like that.i have seen vp c116.
 

·
Registered
Joined
·
4 Posts
Discussion Starter · #5 ·
Thanks for the help. It was my first UCCR but I'm pretty sure I did it right... Last time this engine was dynoed, it made 56HP peak and 52 consecutively. That was YEARS ago tho and I don't remember what fuel it was on. I know there was about an 8hp difference between fuel brands. This bike won the 94 GNCC Nationals.
 

·
Registered
Joined
·
13,278 Posts
Check the BDT section in theis forum, under UCCR....full step by step instructions.

As an FYI; VP110 is rated up to a max CR of 13/1...C12 is 15/1. You can find verifcation on the VP racing Fuel Web site. On small bore engines, like OEM 66-67 MM bores, you can get away with 16/1 with C12; this is also validated by VP Racing Fuel Technical Department.

Carlos
 
1 - 8 of 8 Posts
Top