turbowrenchhead Posted May 21, 2014 Report Share Posted May 21, 2014 (edited) I did the liquid test. I can get 14cc's of oil into the chamber when the piston is at TDC. I tried this calculator but I don't know my exact deck height is. When I had the heads off it looked like a 0 deck height. With zero deck height I get a compression ratio of 14:1. My rule of thumb that the most compression you can run on pump gas is around 11.5:1. The combo is 66x54 bore/stroke with a .045 squish http://www.cbperformance.com/v/enginecalc.html Edited May 21, 2014 by turbowrenchhead Quote Link to comment Share on other sites More sharing options...
984mmshee Posted May 21, 2014 Report Share Posted May 21, 2014 Wouldnt your squish be the deck height Quote Link to comment Share on other sites More sharing options...
turbowrenchhead Posted May 21, 2014 Author Report Share Posted May 21, 2014 No, deck height is the distance the piston is away from the top of the deck. Depending on you base gasket, stroker crank, etc determines where you piston sits at TDC. Quote Link to comment Share on other sites More sharing options...
turbowrenchhead Posted May 21, 2014 Author Report Share Posted May 21, 2014 Measured my deck height, its .004. Makes sense because that is what I had shaved off the decks. Quote Link to comment Share on other sites More sharing options...
BANSHEE HP Posted May 21, 2014 Report Share Posted May 21, 2014 With a stock cylinder at 4.037, a .020-24 base gasket and standard pin height piston you should be .010 from the top of the bore at tdc. Quote Link to comment Share on other sites More sharing options...
turbowrenchhead Posted May 21, 2014 Author Report Share Posted May 21, 2014 Base gasket is a .015 thickness Quote Link to comment Share on other sites More sharing options...
registered user Posted May 21, 2014 Report Share Posted May 21, 2014 you dont have to know the deck height do you know how to find tdc with a piston stop and degree wheel ? if so then do that and put small amount of grease around the very outside of the piston so the oil cant leek down the walls. torq the head on and add oil. you have to be pretty accurate with tdc and the amount of oil otherwise it throws off your numbers 65x54= 147cc head =14cc 147cc+14cc/14cc= 11.5:1 Quote Link to comment Share on other sites More sharing options...
registered user Posted May 22, 2014 Report Share Posted May 22, 2014 (edited) fat fingered it 66x54=185 185+14/14= 14.2:1 to find the comp ratio you only need the full stroke volume and head volume with piston at tdc Edited May 22, 2014 by registered user Quote Link to comment Share on other sites More sharing options...
turbowrenchhead Posted May 22, 2014 Author Report Share Posted May 22, 2014 So the calculator was really close. Next question isn't 14.2:1 way to high for pump gas? My last combo was pretty much the same setup. The differences were the base gasket was a oem one and that measured .026 thick. The pistons were numara's. They also have a dome that looks identical to the wiseco's. I'm betting that my compression ratio was real close to this new setup. I didn't have any detonation or pinging issues with it last year. Quote Link to comment Share on other sites More sharing options...
WINDYCITYJOHN400 Posted May 22, 2014 Report Share Posted May 22, 2014 A - You can't hear detonation the way you think you can. If you do......it's REAL BAD. B - You broke pistons and cylinders. What makes you think you didn't have issues? C - Thicker base gaskets raise cylinders and lower compression. Thinner gaskets lower cylinders and raise compression. Quote Link to comment Share on other sites More sharing options...
turbowrenchhead Posted May 22, 2014 Author Report Share Posted May 22, 2014 What is uccr? Quote Link to comment Share on other sites More sharing options...
turbowrenchhead Posted May 22, 2014 Author Report Share Posted May 22, 2014 In your opinion is my compression too high? Quote Link to comment Share on other sites More sharing options...
sheerider11 Posted May 22, 2014 Report Share Posted May 22, 2014 In your opinion is my compression too high?Figure it out! Your learning a lot right now. Way more then most will ever want to do on this site. Don't start asking basic questions now. You've been doing good so far. Quote Link to comment Share on other sites More sharing options...
turbowrenchhead Posted May 22, 2014 Author Report Share Posted May 22, 2014 I would say anything over 11.5:1 is to much for 93 octane. My last setup had to be in the high 13's and I there was no physical damage to the pistons. I small chuck if metal broke off between the boost and intake but that was because I ported it too thin. The bike pulled really hard when it hit the power band. My experience last year says that a two stroke jetted properly can handle higher then 11.5:1 Quote Link to comment Share on other sites More sharing options...
WINDYCITYJOHN400 Posted May 22, 2014 Report Share Posted May 22, 2014 Figure it out! Your learning a lot right now. Way more then most will ever want to do on this site. Don't start asking basic questions now. You've been doing good so far. THIS ^^^^^ The info is being spoon fed to you. Don't rush to the desert. If you wanna go the DIY route and NOT have it bite you in the ass....then this info is the meat and potatoes of the important details. Supplement your info......do a google search of any tech terms you are not 100% familiar with. (2-stroke uncorrected compression ratio) It's one thing to ask a question you don't know the answer to. But the real learning comes when you start asking questions you never knew to ask..... Try calculating what different base gasket thickness would do to your UCCR. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.