2 replies to this topic
  • etuke

Posted April 29, 2013 - 07:59 AM


I have always run 91 pump in my bikes but there is a run we do that has a gas station that only serves 87 octane and was wondering if it would be OK to run 87 if that's all is available.It will be mixed with 91 but maybe like 70% 87 30% 91.During this winter I also plan to change the timing chain and install a new piston and was looking at the wiseco 12.5-1 compression,will this affect what octane gas I run?I don't mind paying for the 91 but there may be a time I will have to run 87.

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  • grayracer513

Posted April 29, 2013 - 08:33 AM


I don't recommend using even that much 87 octane (AKI), but if you are at a higher altitude (say 3500+) or lower temperatures, you may get by with it. Try to avoid lugging the engine hard. You might also consider adding toluene at 10-15% to the 87.

12.5:1 is stock compression, so it won't effect anything. If you are going to stay at that level, the best piston choice is the OEM Yamaha piston. Cheaper, fits better, runs quieter, and is overall more reliable. Even if raising the compression ratio, I'm not a fan of Wiseco's. Unless they've change in the last couple of years, they rattle excessively, and IMO, there's no excuse for that anymore. I lean toward CP's, and unless it's a race bike only, I'd pass on any piston that doesn't have two compression rings.

  • etuke

Posted April 29, 2013 - 10:23 AM


I'm at sea level but its not as hot here as the states,probably gets to 80-85 in the summer not very often does it go higher.The wiseco I was going to buy was in a kit with a hotrods crank,cylinder works cylinder and all the bearings and gaskets.It was cheaper to buy like this then source out all the parts separately,plus I would have a crank on hand when needed.Maybe I can find some other deal and buy the piston from the dealer.I'm not a racer,more trail rider with some sand pits thrown in,doubt if the bike will ever see the rev limiter or 5th gear for that matter.

Edited by etuke, April 29, 2013 - 10:24 AM.

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