pablopab50 Posted September 7, 2015 Report Share Posted September 7, 2015 I am going to trail ride and casual roll race on dirt and asphalt. It has Small bore Shearers big porting 35 PWKs 21cc domes +4 timing pump gas set up. I currently have 20" ITP mud lites but I'll probably get some 22" holeshots or 22" mud lites again. Do I NEED a longer swing arm? I currently have stock length. Quote Link to comment Share on other sites More sharing options...
sleeper06 Posted September 7, 2015 Report Share Posted September 7, 2015 21cc domes are not safe for pump fuel you will burn it down , add timing and heat dangerous mixture . Your static compression might be throwing u off with the porting but you uccr is still to high for pump . Who told those are pump domes Quote Link to comment Share on other sites More sharing options...
J-Madd Posted September 7, 2015 Report Share Posted September 7, 2015 Dome issue aside, yea you need a longer swing arm. I rode mine with a stock swinger and it would wheelie on gravel roads (while blowing the tires off) at will while sitting on the tank. 2 Quote Link to comment Share on other sites More sharing options...
BANSHEERSA Posted September 7, 2015 Report Share Posted September 7, 2015 Ok i have a question then i hav3 a 421 Cheetah Cub with 20 domes im fixn my top end now and wondering what should i set my timing at? And why i dnt teally understand the timing plz explain Sent from my SM-G900P using Tapatalk Quote Link to comment Share on other sites More sharing options...
BANSHEERSA Posted September 7, 2015 Report Share Posted September 7, 2015 And im on pumped gas Sent from my SM-G900P using Tapatalk Quote Link to comment Share on other sites More sharing options...
trickedcarbine Posted September 7, 2015 Report Share Posted September 7, 2015 You know the cause of the last top end failure? I'm betting it was detonation. To much compression and not enough octane means that the fuel mixture is igniting on pressure/heat before the piston shoves the mixture in to the dome completely where the spark plug should light it. You add timing to that and it becomes a time bomb. Timing just creates way more heat and more detonation.(pre detonation/pre ignition, whatever your school of terminology is) That 21cc dome would may be fine on a stock cylinder, but a dome that same size and stuffed with 3-4mm more piston and a little stroke and you're just slamming way more volume in to the same sized combustion chamber. Quote Link to comment Share on other sites More sharing options...
pablopab50 Posted September 7, 2015 Author Report Share Posted September 7, 2015 I'm on ground sea level. That's what Stephen Carroll at BP Racing ATV told and sold me. Should I keep stock timing then? Or could I add more octane with boosters? Quote Link to comment Share on other sites More sharing options...
pablopab50 Posted September 7, 2015 Author Report Share Posted September 7, 2015 (edited) Also, I don't want the bike to become a duner/drag set-up like with long ass swing arms... I want to keep it trailable and still drift the corners Would +1 or +2 length fix the wheelie issue? Forgot to mention I have 15/40. Edited September 7, 2015 by pablopab50 Quote Link to comment Share on other sites More sharing options...
sleeper06 Posted September 7, 2015 Report Share Posted September 7, 2015 My friend runs a 421 cub on a +2 and its trail friendly, I built this about 7 yrs ago . I decked the bottom of the cylinder , ported it and run 22 cc domes on race fuel with 8* of timing . Motor flat out halls the mail . A plus two will work if you can ride if you can't ride you will hurt yourself. Don't dance around the dome issue look into it, I'm not saying it to be a know it all, I've built many Cubs and use 21cc domes in asphault bikes all the time , but we're not running pump fuel Quote Link to comment Share on other sites More sharing options...
BANSHEEBEEFM2M Posted September 7, 2015 Report Share Posted September 7, 2015 24 cc domes. +4 swingarm Sent from my LG-H343 using Tapatalk Quote Link to comment Share on other sites More sharing options...
pablopab50 Posted September 7, 2015 Author Report Share Posted September 7, 2015 My friend runs a 421 cub on a +2 and its trail friendly, I built this about 7 yrs ago . I decked the bottom of the cylinder , ported it and run 22 cc domes on race fuel with 8* of timing . Motor flat out halls the mail . A plus two will work if you can ride if you can't ride you will hurt yourself. Don't dance around the dome issue look into it, I'm not saying it to be a know it all, I've built many Cubs and use 21cc domes in asphault bikes all the time , but we're not running pump fuel What do you mean by if I can ride.. I know banshees are hella strong and I shouldn't pop the clutch on asphalt but like my question was more like since having longer swingarm it kind of transfer the whole bike weight more to the side when taking a curve. So, this is why stock length is good for trails. The bike mostly keep its 4 wheels grounded. I don't really want to buy +2 a-arms and Axle. I'm 150 pounds and when I take corners I fully transfer my weight to the right (correct) side. So balance is not an issue. Quote Link to comment Share on other sites More sharing options...
lil Doobie420 Posted September 7, 2015 Report Share Posted September 7, 2015 ffs 1 Quote Link to comment Share on other sites More sharing options...
Dunatic619 Posted September 8, 2015 Report Share Posted September 8, 2015 I'm pretty sure sleeper means if your capable of handling a strong engine with stock banshe length swinger. It'll be prone to popping up and breaking the wheels loose, easily. So if your not expecting that wheelie, and like most new riders, get scared and keep on the throttle instead of letting off, or hitting the back brake, you'll end up on your ass. Quote Link to comment Share on other sites More sharing options...
pablopab50 Posted September 8, 2015 Author Report Share Posted September 8, 2015 I'm pretty sure sleeper means if your capable of handling a strong engine with stock banshe length swinger. It'll be prone to popping up and breaking the wheels loose, easily. So if your not expecting that wheelie, and like most new riders, get scared and keep on the throttle instead of letting off, or hitting the back brake, you'll end up on your ass. Oh right on. I must agree with you and him. Whenever I surprise wheelied I just let the gas. But obviously 421 is way stronger than my previous modded stocker set up. When it's too fast I clutch in and let the throttle. Then brake. I'm no pro but I got used to the bike. Quote Link to comment Share on other sites More sharing options...
mike0chek Posted September 8, 2015 Report Share Posted September 8, 2015 chek my mods below, ive been riding on pump gas all summer with 24cc domes and stock swinger drag ported and +3 timing with no issues so far, also i am right at sea level. 1 Quote Link to comment Share on other sites More sharing options...
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