squishy topic

dahondaboy · Post by **dahondaboy** » December 7th, 2008, 7:26 am

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 .

100hp honda · Post by **100hp honda** » December 7th, 2008, 5:05 pm

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

dahondaboy · Post by **dahondaboy** » December 7th, 2008, 6:47 pm

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.

britincali · Post by **britincali** » December 8th, 2008, 8:23 am

Hey thats my old head

dahondaboy · Post by **dahondaboy** » December 8th, 2008, 8:38 am

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.

dannygraves · Post by **dannygraves** » December 8th, 2008, 9:47 am

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.

dahondaboy · Post by **dahondaboy** » December 8th, 2008, 9:57 am

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.

100hp honda · Post by **100hp honda** » December 8th, 2008, 5:37 pm

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

britincali · Post by **britincali** » December 8th, 2008, 5:51 pm

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

100hp honda · Post by **100hp honda** » December 8th, 2008, 5:56 pm

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 ?

britincali · Post by **britincali** » December 8th, 2008, 6:02 pm

No.......

britincali · Post by **britincali** » December 8th, 2008, 6:02 pm

http://www.bannedcr500riders.com/board/ ... php?t=4795

100hp honda · Post by **100hp honda** » December 8th, 2008, 6:11 pm

where did all the coolant go ?

britincali · Post by **britincali** » December 8th, 2008, 6:13 pm

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

100hp honda · Post by **100hp honda** » December 9th, 2008, 12:13 pm

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

britincali · Post by **britincali** » December 9th, 2008, 12:19 pm

Probably out the exhaust.....

100hp honda · Post by **100hp honda** » December 9th, 2008, 12:27 pm

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

britincali · Post by **britincali** » December 9th, 2008, 12:41 pm

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

dannygraves · Post by **dannygraves** » December 9th, 2008, 12:43 pm

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!

100hp honda · Post by **100hp honda** » December 10th, 2008, 8:41 pm

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

BannedCR500Riders.com

squishy topic

squishy topic

Re: squishy topic