Squish ?

[BlasterKX]

ok guys the guy who did my porting said my squish is off in my head. i am ready the same comp. i did before the tear down and porting. and its the same tester. i put on a shaved head thinking that would help with the comp for sure. I sent him my rings and pistons etc. he said they were still in great shape(which they were rings had alot of spring left and were nice and smooth) so he ported them and did a light honing to them. and ive been easy with it so the rings seat properly but im just clueless to whats wrong with it now???? im getting tired of this. the shaved head did have alittle bit of grinding done to the domes so maybe its all messed up. any help would be most appreciated.

Thanks

[drap660]

squish is piston to head clearence. In my experience 40 to 50 is good anyhting higher than that the bike will be slow and any less than 40 you are running a risk

[BlasterKX]

my builder said 35 no more no less is where i should be at. but whats the chances of maybe my tester beying junk? its a harbor freight special.lol plus it showd up on my buddies lt250 at 150psi so idk???

[drap660]

Compression and piston to head clearence are 2 different things. 35 is not so bad alittle tight if u ask me but w/e. How are you testing the piston to head clearence. The only way to do it is with some soder and a micrometer

[BlasterKX]

thats what he told me to do but idk if i want to put some soder down in there cuz if it breaks off or something i gotta take it apart.

[drap660]

just use thick soder that doesnt break easily and fold it like an L shape then slip it in and try to angle it to the side of the cyl. Not on the intake or exhaust, just the side and turn the motor over. That will squish the soder and then you can mic it

Edited February 18, 2009 by drap660

[BlasterKX]

thats it? so just bend it to where it will be near the crown or edge of the piston and then turn the motor over? what should it measure to be? with a shaved head 20 thousanths?

[J-Madd]

Yeah...be careful not to get it in a port/transfer. Did that once, and if fell to the bottom. Got lucky getting it out because the motor was on the bench.

[drap660]

Wow, 20 would be insane. Like I said earlier, 35 is cutting it close. I usually run them at about 40. But yea thats it.

[drap660]

To avoid getting in a port just make sure the piston is past the ports before you drop in the soder

[BlasterKX]

il try that. well my buddy went home and tested the comp. tester ive been using. he took his kdx into a shop and it did a comp test at 180 on there tester. so we know what his is. last night he came over and we did his lt250. it was reading 150psi. then i did mine and it said 110-115. so he took the tester home to try it on his kdx(the one the shop did 180 on) and it is only reading 140 psi. so i think the harbor freight special tester is about shot.lol hes bringing his new tester over tonight and were going to try it out.hope it reads better then 110

[Pincushion]

If you're going to run a tight squish (>0.40") then be very vigilant with your bottom end. If your crank or rod bearings develop play then you wont have much wiggle room between the piston and head. I run my YZ @ 0.45" as a compromise of performance and safety. Race motors that get rebuilt ofter run it much tighter cause they're not going 200hrs between bottom end rebuilds.

 

Also, dont confuse decking the head with squish clearance. Proper squish clearance is a combination of lowering the chamber to the proper height as well as machining the bowl to the proper volume and angle.

 

For measuring instructions go here:

http://www.rb-designs.com/squish-band-test.htm

 

Ron @ RB Designs is the man whom does all my motor work. He's worked on my YZ, Banshee and my boat motor. Super nice guy, honest and a helluva machinist.

[BlasterKX]

il see what his new tester says. i thaught it was weird how it read the same thing before and after posting and a shaved head. so if it reads better then the last one then f*ck it il leave it the way it is

[trex banshee]

il see what his new tester says. i thaught it was weird how it read the same thing before and after posting and a shaved head. so if it reads better then the last one then f*ck it il leave it the way it is

 

 

if your getting the same reading from before and after the porting with the same tester then i don't see the problem? Even if the tester if off and doesn't give you an accurate reading it was just as far off before you tore it apart, right?

 

So did you get them ported AND add a .020 shaved head? This would still make a little since, how far did he raise your exhuast port?

 

Also on squish, ive always shot for no tighter than .040, especially on your setup riding style i would definitly not run any tighter than .040 probably closer to .045.

[BlasterKX]

so what ur saying is that you wouldnt really worry bout it? i just asked him how far he raised it and waiting for him to text me back. i just listen to what he says about the squish ive never really gotten to far into that shit. and yes i got them ported and i installed a shaved head.