Those stupid accelerator pumps are a Beyotch@!!! I hate them! Running an 8 vs. a 9 will burn more of the fuel in the chamber hence the hotter temps. Found out recently that unless you have the head decked at least .030 you can run 100 or 101 octane just fine.

 

I like the accelerator pump, It works just fine for me, to each is own...If you have a true 12:5 compression ratio I would strongly recomend nothing less than 104 octane...call VP, and or any other Fuel distributor and ask them what that specific comp ratio it calls for...its usually NOT 100 octane for 12:5...Why in the world take the chance of too low of octane? By the way ThePunish wont admit it but I told him how to set his carb up, I just told him to put it back the way it came and the bike came alive for him..LOL And im by far no mechanic or an Expert...I do know this though, knocking comming from a motor is not a nice thing to hear, ive heard it a few times[ not too great on motor]. is punisher just caught up in a cloud of denial about the raw power of my 720 lately? soon, he will come across my new creation [he will need a full face helmet so he wont get sand blasted].LOL n/k

Hillbillyds go from 105 octane and then go down from there if you want to test it, and I think leaded fuel that is designed for 4-strokes is better on motor..And if its oxygenated you might lean out just enough for where you need to be..I think VP has some really good fuel, and I actually have had better luck with the higher octane unleaded, it seems to burn better..This is just my experiances..Let me know the results... Oh, I think the higher octane fuel burns cooler, jet a bit leaner to compinsate.

 

Another thing to consider when choosing or switching fuels is the specific gravity of the ones you are using. A lighter SG will flow more fuel through the same size jet as compared to a higher SG.

Here is some good tech info only plugs. NGK plug tech Lots of pictures of correct and incorrect jetted plugs. It also explains the heat ranges of the plugs and reasons for them.


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Perhaps my good friend Annihlater didn't see my post talking about the piston in our 720's isn't actually a 12:5:1 piston. It is actually more like a 11:1 piston. Cope Racing just got finished with a 720 and they said that to get 12:5:1 you have to cut the head at least .030. They CC'ed the cylinder and head for a friend and they told him this. Now those of you who don't know about Cope Racing they are like Vance & Hines, So they know their SH@T![img]i/expressions/face-icon-small-happy.gif[/img]

 

Like I said "105 octane if it is at 12:5, depending on compression".. My heads have been decked on my bikes so the compression of piston doesnt even really matter, didnt you know that TonI..you can get 14:1 off of a stock piston cant you, by shaving??? correct me if I am wrong Punisher.
By the way, does samcoe performance still have part of your motor Toni...?? Are you still bringing sam to Dumont for halloween

 

I wasn't refering to your Motor Mario. I know all about it.[img]i/expressions/face-icon-small-smile.gif[/img] I am explaining it to everyone else.

 

I was just bustin your chops ticket taker..Are you flying into St. George?

 

sorry i got in on this thread so late, i also have been working on running rich. i'm down to a 142 and still rather rich. that was one of the first things azsand told me when i got my quad running at sand mt. i'm going to jet down again next time i go out. it seems odd that woods would send out a 150 for a stock 650 and a 720 would run a smaller size. but since that guy here in the northwest has a set of 39's i'll be starting over again maybe i'll be lucky like azsand and just be able to take the jets out, azsand i think you might want to admit when you can take out the main jets your ds might have a drinking problem.[img]i/expressions/face-icon-small-smile.gif[/img] for those of you that where not there we were all jetting azsand tried a couple and then comes up and tells us he just took his out all together.

 

Spark plug heat range can effictively effect power output and jetting. How? As we know, spark plug heat range will alter the temp your engine is running at. An engine running too hot or too cool will make less power and will ultimately need different jetting.

 

Many thanks for all the input, fellas. I am not decked, just have the JE claimed 12.5:1 piston that came with the Sam Coe 720 kit, so ya'll think the compression really is less than claimed? If so, sounds like the 100 octane might just work! I also didn't realize that the bigger bore would want leaner jetting, I assumed the opposite with the whole vacum thing?[img]i/expressions/face-icon-small-blush.gif[/img][img]i/expressions/face-icon-small-disgusted.gif[/img][img]i/expressions/face-icon-small-happy.gif[/img][img]i/expressions/face-icon-small-mad.gif[/img][img]i/expressions/face-icon-small-shocked.gif[/img][img]i/expressions/face-icon-small-tongue.gif[/img][img]i/expressions/face-icon-small-shocked.gif[/img][img]i/expressions/face-icon-small-mad.gif[/img][img]i/expressions/face-icon-small-happy.gif[/img][img]i/expressions/face-icon-small-disgusted.gif[/img][img]i/expressions/face-icon-small-blush.gif[/img][img]i/expressions/face-icon-small-sad.gif[/img][img]i/expressions/face-icon-small-blush.gif[/img]