Posts
25
Joined
8/28/2019
Location
Methuen, MA
US
Hey guys,
I recently got my freshly built CR running, it is a 2005 with the following motor specs:
- New OEM crank / bottom end
- new OEM cylinder
- Wiseco piston
- Phathead cylinder head (H31 dome which is their lowest compression ratio)
- Lectron carb
- V force reeds
The motor sounds beautiful, however I was getting some noticeable detonation during heat cycles on pump gas (93 octane). I mixed in 50/50 with pump 93 and Cam 2 race fuel (pump 110 octane). I am still noticing some detonation despite some improvement.
So, I measured the compression with a snap on gauge and hit a pretty lofty 250 PSI.
I assume it is due to the head, and the owner of Phatheads is doing some research for me to help sort it out.
I really just wanted to raise the question and see if anyone is running 250psi in their CR's or comparable 250 two strokes?
I'd like to toss some 110 octane, or even 116 and send it for the rest of the season, but I'd love some feedback from the gurus on here! Put a lot of time and money into the engine so naturally do not want to do anything careless.
Thanks
I recently got my freshly built CR running, it is a 2005 with the following motor specs:
- New OEM crank / bottom end
- new OEM cylinder
- Wiseco piston
- Phathead cylinder head (H31 dome which is their lowest compression ratio)
- Lectron carb
- V force reeds
The motor sounds beautiful, however I was getting some noticeable detonation during heat cycles on pump gas (93 octane). I mixed in 50/50 with pump 93 and Cam 2 race fuel (pump 110 octane). I am still noticing some detonation despite some improvement.
So, I measured the compression with a snap on gauge and hit a pretty lofty 250 PSI.
I assume it is due to the head, and the owner of Phatheads is doing some research for me to help sort it out.
I really just wanted to raise the question and see if anyone is running 250psi in their CR's or comparable 250 two strokes?
I'd like to toss some 110 octane, or even 116 and send it for the rest of the season, but I'd love some feedback from the gurus on here! Put a lot of time and money into the engine so naturally do not want to do anything careless.
Thanks
It's a high compression motor by design. (It's actually tough for me to kick it over when the ring is fresh!)
The Shop
Hopefully that will fix it up as well! Will report back
C12 is one of the best, if not the best, option for 2 strokes. It's all I run in my 2 strokes. VP110 is another good option for a little less money and both with take away any detonation.
I used to run it years ago in my TRX250R, never had an issue
Also, looks like that piston is domed (I couldn’t recall which series was domed and which was flat...looks like flat on 02-04 and domed 05-7)?
If so, and if the head was for 02-04 (flat piston), there’s your answer.
The builder confirmed that the head was intended for an '05 with domed piston - he is being very helpful and actually cutting two spare domes for me with lower compression / less aggressive squish.
Going to see how the bike performs next week on straight race fuel and pending that I may be testing out another dome.
Appreciate all of the feedback guys
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