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what compression should I run?


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With my current mods I have about 184 on each cylinder compression. Am I loosing a lot of top with this. I have good low end but everyone I see seems to have less then me. I hear that lower comp pulls harder on top and high comp is for bottom end. I have a ton of bottom with this bike pulls instantly but wondering if it would be faster in a race with lower comp.

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with that higher compression you are losing some revs on top. id say drop down to about 170 lbs and youll notice a pretty big difference in revs. i run all my bikes at about 170 or 175. 180+ are stump pulling bikes that will pull huge gearing off the bottom but will suffer on top due to increased compression. what size domes are you running right now? whats your setup?

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4 mill dune port, 35 Pwk, noss head 20+2 domes, +5 timing, vF2, cpI's, Noss clamp on K&N no lid, jettin, is 45, 158, plugs look good, I had 15-41 gearing but couldnt stay in the power band when I launched in 2nd kinda bogged, on clay, went to 14 41 now it leaves hard, wheelies pretty good when it leavs, power is now. I think I need to try like 14-40. I loved the 15 for the long pulls but it was a litte slow getting to the power band. Now its instant but doesnt feel that fast. This thing feels like it has a lot more power then it did before the build, wheelies on its own through 3rd and I can pull 5th easy but doesnt really pull my buddies piped yfz that much more then it used to on the road. I dont get it. hits hard at first, I dont under stand.

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stock, 20 in razors, 215, extended axle, extended a- arms. Leaves really hard now in sec, spins and wants to come up fast. more worried about the fact that I dont really pull that hard on him in the road like I thought I would. It feels way faster, but not seeing it, he is however a jocky 140 soak and wet, but that was the same when I just had, pipe, reeds, head, timing and flywheel, I was always a little faster but Im still just a little faster. doesnt make much sence. I cant think of anything I can do to get more power and still be trail able. I feel I should have enough done alread to put some good lengths down.

I really dont expect to be faster in the dirt this thing is never going to hook enough to win there but I should own the road.

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Our quads are almost identical power levels I believe. I have boss intake and pods and t5 not cpi's, other than that. I have a +4 swinger to help keep the front down. I'm 230 pounds and have 15-41 gearing. IF you can handle taking off in first the 15 tooth front gear will help you pick up a lot on the road. To me it is a night and day difference when racing. Its a pain in the ass sometimes when you hit neutral shifting but the gains are big. We are in that in between power level of taking off in second gear with 15-41 on roads or dunes with 22 paddles and still needing first gear for our weight and gearing. If we had cubbys it would make up that difference and launch all day in second with out a problem. I don't want a light switch bike and I'm never going to see 180 pounds again, so I launch in first with a 15 or 2 with 14 tooth.

 

As far as compression, I run 165 and it pulls hard, bottom to top, revs out quickly, having cpi's or shears would help it pull longer on top, but it revs out quick.

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If you are running a single, than ya, thats great for trail but not wide open runs on roads and dragging. The size of your main and pilot tells me its not a single though. I run a 168 main and 58 pilot in mine with cel needle differrent jetting for pipes and porting and elevation. If you are running dual 35's they are plenty for that motor. I know of a lot of drag and screaming engines that run 34pj and 35pwk's.

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