kevincurtis Posted August 28, 2013 Report Share Posted August 28, 2013 I just recently got my 421 together, I'm running it with pump 91 octane with pro design cool head and 24 cc domes at sea level. i did a compression test today and my compression raised to 160 psi after break-in, i know its quite high for 91 octane, and my timing is still at 0" I want to advance it 4 degrees.. i'm thinking I'll have to get some custom domes to run pump fuel, but if i was to run a higher octane what would you's recommend i run ? just curious because this is my first time playing with my bike with the compression bumped up, Any info would be great thanks ! Quote Link to comment Share on other sites More sharing options...
trickedcarbine Posted August 28, 2013 Report Share Posted August 28, 2013 Decision time, you can probably get domes from a builder and be riding next weekend on pump if you wanna pinch pennies. Or, you could start messing with some race fuel and put that little kitty cub near it's potential. When running race fuel you basically decide which octane you need, and whether or not you wanna have to occasionally purge your bike like an alky bike or not, which is the only down fall to the oxygenated stuff. Basically you are gonna spend more money on a new dome set up, or you just spend that extra loot on fuel for your current set up and not have to wrench on it. Not to mention the better fuel would let you give it some timing. For a consistent performing fuel I would check out VP C12. If you are thinking o oxygenated stuff, check out the VP 113. It is stellar! Been running it since The shop ran out of C12 last winter. I will probably not switch back. I can keep the compression up and run more timing on the straights of a 1/2 mile oval then I could on the C12. Quote Link to comment Share on other sites More sharing options...
Methfireroad Posted August 28, 2013 Report Share Posted August 28, 2013 I just recently got my 421 together, I'm running it with pump 91 octane with pro design cool head and 24 cc domes at sea level. i did a compression test today and my compression raised to 160 psi after break-in, i know its quite high for 91 octane, and my timing is still at 0" I want to advance it 4 degrees.. i'm thinking I'll have to get some custom domes to run pump fuel, but if i was to run a higher octane what would you's recommend i run ? just curious because this is my first time playing with my bike with the compression bumped up, Any info would be great thanks ! It all depends on what u really want to do. I'm running my cub on 93 pump and +7 timing and 19cc domes. U just have your domes cut right. And I almost made 90 hp on the dyno........ I picked pump fuel because it beats paying 70$ to 100$ for 5gal of vp.. There is pluses and minuses for both... Quote Link to comment Share on other sites More sharing options...
Deadbeat Posted August 28, 2013 Report Share Posted August 28, 2013 It all depends on what u really want to do. I'm running my cub on 93 pump and +7 timing and 19cc domes. U just have your domes cut right. And I almost made 90 hp on the dyno........ I picked pump fuel because it beats paying 70$ to 100$ for 5gal of vp.. There is pluses and minuses for both... decent pump numbers, who cut the domes on your motor? Quote Link to comment Share on other sites More sharing options...
kevincurtis Posted August 28, 2013 Author Report Share Posted August 28, 2013 It all depends on what u really want to do. I'm running my cub on 93 pump and +7 timing and 19cc domes. U just have your domes cut right. And I almost made 90 hp on the dyno........ I picked pump fuel because it beats paying 70$ to 100$ for 5gal of vp.. There is pluses and minuses for both... No actually I'm running the Vito's big bore 13 degree angle domes and pistons, if I decide on pump fuel looks like I'll need some custom domes.. Like you said pluses and minuses for both Quote Link to comment Share on other sites More sharing options...
Methfireroad Posted August 28, 2013 Report Share Posted August 28, 2013 decent pump numbers, who cut the domes on your motor? I'm running a K&T 421 4mil drag ported cub. Thing runs like a top and starts in the first kick every time.. Quote Link to comment Share on other sites More sharing options...
MarineNYC Posted August 28, 2013 Report Share Posted August 28, 2013 It all depends on what u really want to do. I'm running my cub on 93 pump and +7 timing and 19cc domes. U just have your domes cut right. And I almost made 90 hp on the dyno........ I picked pump fuel because it beats paying 70$ to 100$ for 5gal of vp.. There is pluses and minuses for both... That's what I was thinkin Quote Link to comment Share on other sites More sharing options...
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