BannedCR500Riders.com

Ok I have been here a while and I dont want to sound stupid, But can someone explain "squish band" I know you check it with a piece of solder but what is the purpose and what is the optimum squish? Also what happens if it is bad? I have done lots of top ends on different bikes and never really checked. I thought you can keep milling it down as long as the piston dont touch the dome .

this isnt my head but i showed in red what the squishband is





purpose: a short version in lamens terms, it squishes the fuel mixture into the dome where it is concentrated very close to the spark plug, where its more likely to burn without detonating

optimun squish: .040-.050 is a good number, .030 would probly be even better. if you ask any 2stroke guy that knows what hes talking about, he will say that the tighter you can get the squish the better. problem is when you go too tight, you run a chance of things colliding if bearings aint tight, plus the rod may stretch slightly at high rpm also, so you need to be careful and take very accurate measurements when you get super tight

width and angle of the squishband are a topic on their own also. if you want to get a 20 page understanding of how the head works, i would get some books from the library or online

makes total sense i tottally understand now. most of the heads i deal with(not cr500) dont have that deep dome in the middle they are usually a more even cup shape. exept i think my old yz 490 had a similar head shape as the cr500.

Hey thats my old head

mine read like .090+ i better get a thinner gasket! this motor hasnt been fired yet and isnt in the bike yet so nows a good time to fix it. thanks bud you saved me a lot of headache and time.

dewayne likes them at .060 to resist detonation, they will detonate if there isn't enough squish. the width of the squishband effects the powerband. a narrower squish makign a wider combustion chamber and a flatter combustion chamber will make a higher reving motor, a motor made to make down low torque like our motors will have a wide squish band, narrow combustion chamber and a deep combustion chamber. when heads are modified for a higher reving bike they will stage the combustion chamber so it appears to have 2 squish bands, the primary one, then one that looks like a transition. I believe 100hp, or brit have pics of a head that looks like what I am describing.

that does make sense, because i have one that has a narrow band and a shallow chamber but another has a wide band with a deep chamber and the plug hole is angled different. the latter i bought from a guy that said it had been milled down. and he was sayin stuff about the squish but i didnt understand.

dannygraves wrote:dewayne likes them at .060 to resist detonation

serious ? more or less heres what gordon jennings says: clearance should be kept at a minimum only barely enough to avoid contact between piston and head, .045 maximun on big engines. the trapped mixture under the squish band never gets completely burned, there for never contributes to helping make power. i think i can safely assume the stock cr500 head would have a huge amount of unburned fuel that never contributes to anything other than getting blown out the exhaust

The squish on my old head was past zero on one side and about 10 thou on the other, I can state for a fact that when I slapped a stock head back on the bike lost a little bark down low but revs out better now.

It now idles a little longer too

britincali wrote:The squish on my old head was past zero on one side and about 10 thou on the other, I can state for a fact that when I slapped a stock head back on the bike lost a little bark down low but revs out better now.

It now idles a little longer too

sounds like it was a work of art for sure . you got it all squared away now ?

No.......

where did all the coolant go ?

??????????????????

you dont know where a qaurt of antifreeze went ????

Probably out the exhaust.....

you signing up for hillclimbs next year ? i probly will if it aint a ungodly amount of coin. plus if gas stays $1.50 gal then it will be cheap to get there

Im gonna try not to make too big of a fool of myself at glenhelen.

britincali wrote:Im gonna try not to make too big of a fool of myself at glenhelen.

it ok brit, just accept that its unavoidable, unless of coarse I go and make an even bigger fool of myself!

dahondaboy wrote:Ok I have been here a while and I dont want to sound stupid, But can someone explain "squish band" I know you check it with a piece of solder but what is the purpose and what is the optimum squish? Also what happens if it is bad? I have done lots of top ends on different bikes and never really checked. I thought you can keep milling it down as long as the piston dont touch the dome .

heres 4 different configurations, each different than the other