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what size of domes do i need?


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hey guys, i need to know what size of domes i need to put in my bike in order to run premium gas. Here is a list of mods i know that are done on the motor

 

-JD racing ported motor (not a 4mil)

-33mm pwk's with outerwear filters

-billet intakes

-Jd cool head.

-maybe a timing plate

 

 

that is what i can remember for now. My elevation is at 3500ft . If i can remember something else, then ill post up

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What domes are in it now and what is the compression?

 

the domes in it right now, i was told their 19cc domes, making it run on race fuel, which is very expensive here. The motor was build by JD, it even says JD on the cylinders, so its gotta be ported, cause its got tons more power over my blue one, but it doesnt matter, cause im putting a 421cub in it, when it blows up

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I don't know why everyone is saying 20cc domes. At higher elevations you can run smaller domes. I had no problem at all running 20cc domes on 93 octane and I live at sea level. I know a lot of guys who live at about 1500' run 19cc domes on premium. So at 3500' you should have no problem at all running 19cc domes on 92-93 octane

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I don't know why everyone is saying 20cc domes. At higher elevations you can run smaller domes. I had no problem at all running 20cc domes on 93 octane and I live at sea level. I know a lot of guys who live at about 1500' run 19cc domes on premium. So at 3500' you should have no problem at all running 19cc domes on 92-93 octane

oh ok, well, i will give it a try, right now i have race gas in it, and its running a bit more rich then in Oregon, and the idle is a bit higher too. So you think, that i should be able to run premium gas in it, the way it sits right now with 19cc domes?

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Do you have a compression tester? If so do a compression test. If not pop the head off real quick and check the dome size to make sure its a 19cc dome. If it is, yeah, throw some 93 in it and run it.

i dont have a compression tester, and i have no way to get one, except for buying one. Taking the head off, i can do that, but i cant put it back on, since i dont have a torque wrench either

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so, how did you verify it is stock stroke? if you have 19cc stroker domes. that will be really pushing pump limits at 3500' if it's sock stroke for sure, then 19's are fine, no problem. just sayin- assume makes an ASS of U and ME. and, remember, you will need at least 50/50 if you go below 1500-2k, depending on timing. definately check the jetting, though. after you make the switch to pump. generally, you would end up rich, but the fuel up there may make you on the lean side, since they run differnt s.g. pump at higher elevetions.

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