ginger Posted July 27, 2011 Report Share Posted July 27, 2011 So last time riding i blew my headgasket, so i started pulling the top end appart to replace it, come to find out the head looks like someone hit it a billion times with a center punch, and the cylinder has a big scar in it. Apparently the thing to do when you blow up a motor is to half ass hone it, and put new pistons in and go. anyway, i got a ADA coolhead with 21cc domes. and a set of cylinders bored to 65mm with some dune porting done to them. to fix the whole deal Question is, do i need to adjust my jetting, needles, or premix ratio for this? Also they told me to run the first 5 hours at under 1/2 throttle, and at 24:1 ratio. all i see this doing is fouling out plugs and putting carbon on the new pistons. should i run my normal 32:1 and just take it easy for maybe the first hour, and then let it eat? on my CR250 motors, we would put a piston in and no worry about breaking it in at all. cliffs, Previous owner screwed me, bought new ported cylinders and cool head does jetting need to be changed what are proper break in instructions Quote Link to comment Share on other sites More sharing options...
BrockMoto Posted July 27, 2011 Report Share Posted July 27, 2011 Yes on changing jetting... And there are detailed instructions on this site as well as your manual about proper break in Quote Link to comment Share on other sites More sharing options...
n2otoofast4u Posted July 27, 2011 Report Share Posted July 27, 2011 DID YOU SPLIT CASES TO BE SURE THERE IS NOTHING ELSE IN IT? Quote Link to comment Share on other sites More sharing options...
BUILDER Posted July 27, 2011 Report Share Posted July 27, 2011 Sounds like you have lost a needle bearing on either a wrist pin or the crank I dont think I would be putting that motor back together without checking into things much better Quote Link to comment Share on other sites More sharing options...
Jereme6655 Posted July 28, 2011 Report Share Posted July 28, 2011 if it is small little dings then it could have been detonation from lack of quality fuel or lack of octane because of high compression. or if it looks like big dings it could be cause a bearing let loose and did the cha-cha-im-gonna-eat-your-shit-up dance..... Quote Link to comment Share on other sites More sharing options...
ginger Posted July 28, 2011 Author Report Share Posted July 28, 2011 previous owner blew it up, and i know he split the cases cuz they are siliconed together, he just blew it up bad. i rode it for prolly 5 hours before the headgasket blew, only reason why i pulled it appart. i know the bottom end is clean, and i know everything i replaced is good. Quote Link to comment Share on other sites More sharing options...
BrockMoto Posted July 28, 2011 Report Share Posted July 28, 2011 know? or think? cuz if your wrong its $$$$ that you didn't have to spend... just saying.. in either two of those scenarios (bearing or deto) theres a pretty good chance something went wrong elsewhere to quote cam again.... if all you did was replace broken parts... did you really fix anything?? Quote Link to comment Share on other sites More sharing options...
BrockMoto Posted July 28, 2011 Report Share Posted July 28, 2011 any chance you did a leak down? Quote Link to comment Share on other sites More sharing options...
ginger Posted July 28, 2011 Author Report Share Posted July 28, 2011 i dont think your understanding what im typing i bought the quad from a guy, who said he had it bored to 64.5. on the stock head. i had to repair the kickstart gear because a bushing wore out and was able to tell then that the motor was complete appart for the rebuild while riding it, the headgasket blew, i could tell due to antifreeze leaking into the cylinder and outside the head. I pulled the head to replace the headgasket, and found that the reason why the previous owner bored it to 64.5 was due to him blowing it up to the point that stuff hit the head, chipping it all up. He just cleaned the head up and reused it. Well looking closer, i was able to see a big scar in the cylinder, which had to of occured when he blew it up, because i could tell it was honed, and the pistons were in great shape, just some carbon buildup. knowing the scar would kill my compression due to blow by, i got a set of freshly bored cylinders that are 65mm, and 2 brand new pistons for it. i also got a cool head to fix the chipped up head issue, i know that everything that i did is top notch, not my first rodeo building 2 stokes, i just wanted to know if it was going to knock me way out of wack for jetting. Quote Link to comment Share on other sites More sharing options...
Jereme6655 Posted July 28, 2011 Report Share Posted July 28, 2011 as long as the port job is the same and your not changing anything else then you should be realatively close on your jetting. I think what is concerning most of us here is when you said you "know" the previous owner had the cases apart because its "siliconed" back together.....umm....yamaha uses grey colored yamahbond which is like a silicone to seal the cases. there are no gaskets for the cases. Quote Link to comment Share on other sites More sharing options...
Larry's Shee Posted July 28, 2011 Report Share Posted July 28, 2011 If your first cylinders weren't ported and these are, you will have to tune all over again. Quote Link to comment Share on other sites More sharing options...
ginger Posted July 28, 2011 Author Report Share Posted July 28, 2011 If your first cylinders weren't ported and these are, you will have to tune all over again. thank you larry. i guess i get the fun of tuning it. Quote Link to comment Share on other sites More sharing options...
Larry's Shee Posted July 28, 2011 Report Share Posted July 28, 2011 if it was running good before, I would say 2-3 up on main, pilot should be ok, minor tweeking from there Quote Link to comment Share on other sites More sharing options...
ginger Posted July 29, 2011 Author Report Share Posted July 29, 2011 perfect. thank you. Quote Link to comment Share on other sites More sharing options...
camatv Posted July 29, 2011 Report Share Posted July 29, 2011 (edited) sounds like the previous owner may have rushed the job i'd split it completely and see what was wrong with the crank. if it has small roller bearing marks in the old head your new head will suffer the same fate if not have the rod break and blow out your cases. if i t was me personally i'd bite the bullet and split it and do a complete inspection of the crank and bearings.. anything even questionable i'd replace it. if you dont. then you will get the pleasure of doing it all over again and getting another set of cyls and head and etc.. if your more than confident with 2 strokes you should know all this already and also be confident in your tuning skillz? Edited July 29, 2011 by camatv Quote Link to comment Share on other sites More sharing options...
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