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Dirt Bike Mods & Maintenance
03CRF450 Hotcam+HeadMod by Eric & Rich - Jetting question...
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[QUOTE="Rich Rohrich, post: 800481, member: 16241"] The Wiseco piston and pin combo is about .5 grams lighter than the OEM parts so weight differnces have no real effect. Depending on the fuel you run it's pretty common to have to lean out the pilot jet needle and main , but until you can do a proper WOT plug chop I would use the ride and feel method and not pay too much attention to the way the plug looks. When you are riding it easy it's tough to get enough heat in the plug to keep it clean regardless of the jetting so you'll see more carbon buildup than you would normally. Yep, that's normal. There are a couple of things going on here that you have to take into account. The Hot Cam closes the intake valve later than the OEM cam which will lower the final pressure you are reading. The Honda manual numbers are based on the earlier intake closing pressures. As an example, if you close the intake valve 10 degrees later on the CRF it will lower the final cranking pressure by about 40 psi. Some of that is made up with the increase in compression ratio, where a one point increase in compression ratio will raise cranking pressure about 20 PSI (BTW all these numbers assume no compression relase active) you can see it will balance somewhat. I don't remember the exact degree differences between the Hot Cam and OEM off the top of my head, but hopefully this will make it clearer. You'll also find that as it breaks in that the reading will be higher as well . Single ring piston designs need a good seal to keep from leaking becuase they don't have a second compression ring as a helper. As the ring seats leakage will be reduced and cranking pressure will tend to go up. Last but not least your atmospheric conditions and gauge can influence the numbers some as well. All in all I'd say you are good to go. :cool: If you have any other questions I'll be happy to answer them. [/QUOTE]
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03CRF450 Hotcam+HeadMod by Eric & Rich - Jetting question...
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