I am looking into getting MisterHP big bore 730 kit but am debatting on compression. Can someone explain what fuel I would need for different compression ratios? 12:1, 12.5:1, 13:1, & 14:1 compression.

 

without looking it up, I would say with 12:1 also 12.5:1 run half premium (98 octane) and half race gas (110) above that, you'll need to run 100% 110 octane gas.

 

If you are truely considering the 730 kit from Mister HP, I would call him up and discuss it with him. It appears that he will not be offering a true 14:1 piston in his big bore. He went with a light weight casting which sacrificed some compression. The piston I will be getting should be around 13:1 maybe a little higher. Youshould be able to adjust the deck height using different thickness gaskets. For the ~13:1 I will be running leaded 111 race fuel.

 

Sandaholic,
I have a Christmas present in my shop for you.[img]i/expressions/face-icon-small-wink.gif[/img]

 

I wish I had a christmas present[img]i/expressions/face-icon-small-sad.gif[/img] maybe tax return time will bring a whole new package for the ds.

 

Why would somebody run the 13:1 instead of a 14:1? You've got use 110 either way. Is it an alcohol/nitrous thing?


OregonDunePatrol has given excellant recommendations. Last week Eric reccomended 100 octane for 12:1. I'm not so sure I could buy a 730 at 12:1. In the back of your mind the 14:1 would be there......

I'm mainly a trail rider, so I'm having really bad inner turmoil over this same question.

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Well I would for one - I'll be eventually moving down from the 14:1 to a 12.5:1 because the horsepower gain is eclipsed by the rev up speed of the lighter piston. The more you put on top of the piston, the more mass you aquire; that robs quickness. I have a 13:1 on my EX and lightened the flywheel to compensate. It works good.

 

Yeah, what OregonDunePatrol said! According to Mister HP, the weight savings was more benifitial then the added compression.

 

Thanks. I thought the 14:1 would rev faster. But then I also assumed the pistons would be equal in weight.

Sandaholic, you getting serial #1 for Christmas?

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Hey Eric, I assume this will also apply to the 800 kit? If so, no problem. I'll be seeing you in the very near future to drop off my DS for the 800 installation, I'm sure Randall told you about our plan. Merry Christmas!