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The cheetah top end is what I'm asking about Sent from my iPhone using Tapatalk

Hey guys, just finished building my 4mil long rod, ported stock cylinder build on my banshee. After heat cycles and running multiple tanks through the bike, I loaded up and took the bike to Winchester bay. While there, I faced nothing but dissapointment in my new build. The bike was getting beat by my buddies stock banshee up banshee hill. This was extremely dissapointing due to the fact that prior to the build, my bike was consistently 1-2 quad lenghts ahead of him. the powerband feels extremely short and it is hard to even get the front end off the ground. It sounds like it is running very crisp and clean but the power is lacking. 3rd gear tops out almost instantly after shifting and then 4th gear is a struggle to hold rpms. I am running my stock carbs with 370 main jets and 30 pilots. I have tried 28mm flat side mikunies and got all the way up to 410 mains and it was still acting extremely lean. Spark plugs were backing out. This is when i switched back to the stock carbs and it made it run much more crisp and stopped backing the plugs out. I have 19cc stroker domes in my pro design cool head also paired with the weisco 795 pistons, hot rods 4mil crank with the 115 long rods and no spacer plate. My cylinders are an agressive dune port set up for a 4mil and they were ported by Carl. my timing is advanced +4, I am running 10 paddle haulers with a 14 tooth front and a 43 tooth rear sprocket. Anybody got any suggestions on trouble shooting this?

i have a stock cylinder 4 mil with 66 bore. no issues. its not that the walls are too thin, its the fact they dont make a piston for any bigger of a bore. if i melt mine down, i am gonna look into nic plating the cylinders to give them life again, unless there is a smoking deal on aftermarket.

Oh boy you had me scratching my head like wtf. I'll take those cylinders back if there useless to you. I will tell you this those cylinders correctly set up will outrun a serval. Brandon the duration was 195-196 with 35 blowdown, not optimal for that pipe but I've used them before also. What really got me was how he said the gear revved instantly and I know with my porting and those blowdown numbers it should feel like turbo when it gets on the pipes and over rev better than most. It just sucks you never got to see the full potential of those cylinders .

My travel season is over and I will gladly take the bike and figure it out for you. Me personally would run shearers on that set up the lrd could be heat soaking the cylinders or incorrect signal which would explain why you could throw 410s at it and it still be lean . I have done 100s of 4 mill stockers and never had anyone disappointed with port work so I would love to see what the deal is. I also have every pipe known to man on hand so I can see what works best. I feel for you .

Should the bike shut off when pulling one spark plug wire or would it just shut off the side that the wire was pulled off?

Agree with above, you need to check the squish clearance as this may indicate some of what is going on. Beyond that, it might be wise to pull the head and verify the exhaust height so the duration can be determined. It sure sounds compression related though. Wrong pistons or wrong domes. You also mention having detonation issues. That can happen with very loose squish due to the flame front pretty much exploding, rather than getting a centralized controlled burn. You should NOT be having detonation issues with that setup, and timing can easily go beyond 4*.

Reed are good, where could i have a air leak? all gasket new, i sync them by the top caps on carbs.