Squish band

[JerryAssburger]

Hi Jaguar! I enjoyed reading the technical posts on this forum and saw this discussion on Squish Bands... Meanwhile, I found a head for the China Dolls on E-bay that are 13-fin and look like they're devoid of any Squish-Bandery.....
Does this help?
http://www.ebay.com/itm/131407518169

 

[Deleted member 12676]

I think those angled plug heads have a higher compression ratio.
Anyone correct me if I'm wrong.

 

[Street Ryderz]

I think those angled plug heads have a higher compression ratio.
Anyone correct me if I'm wrong.

No your right there are 6cc and if you look closely it's not cut all that well but there is a squish on that head!

 

[JerryAssburger]

Okay I'm back. That head in the Ebay ad I posted above definitely is DOME type head, no squish band except for a gentle curve to transition from the gasket surface. I took both heads and filled them both with water as accurately as I could, and with the spark-plug in place, they're identical in volume. The motor came with the head with the machined squish-band. Unfortunately it was leaking pretty good around the gasket area, even when torqued down with a new gasket. (Rough gasket surface.) So I took a chance and bolted the domed one- instant success, and I have now logged about 15 minutes on my new engine.
I'm thinking that for normal use, these motors are expected to pull cleanly from 2500-6000 rpm, which tells me it should be tuned for low/midrange grunt. They definitely don't like to be revved past 6000, that's for sure. I'll try to post pix of both heads side-by-side, but in the meantime, I drew up my best approximation of the chamber profiles.



Hope this helps in your search for a non-squishy head.

 

[Bike_Builder]

maybe never. JNMotors has my top end and torque pipe but is whining now because some of the chrome is flaked off. If we can trust each other we can have an on-line video match. When I get back to the States I will make another 60cc to race and we both can video our rides going from a stop to 1/4 mile. Shortest time wins.

My money is on you and your pipe. These guys know nothing about scavenging either.

 

[Bike_Builder]

Sure, I've done a lot of research Jaguar. What do you take me for? I manufacture cylinder heads and other kinds of performance enhancing parts for these engines. I certainly don't do this stuff blindly.

I have spent countless hours building and testing these designs, compared with other designs, etc. When I first started out running these kind of engines, I ran into terrible problems with detonation and overheating.

If you are putting around at 30 MPH it's probably OK to run stock equipment.

I started making these cylinder heads because they were necessary in order to do what I wanted to do, which is to travel 40-50+ MPH.

I have read that book from Jennings. It's very good. If you too have read that book, and understood it, certainly you would have seen then the importance of the squish band.
You know, it probably does create more mixing of air/fuel mixture, well, the more the better!

I have made and tested a lot of prototypes. I don't think you have. You shouldn't talk like you are an expert about something unless you really are.

Large manufacturers guided by proven racing results, who have tried everything under the sun make squish band combustion chamber cylinder heads for small engines.
This is for a very good reason, because they allow you to run higher compression without the damaging effects of detonation. My god, this is basic stuff here!

They would never support what you are saying about combustion chambers. You tests were just weak or flawed, or you don't have the capabilities to test different designs.
You know, you would have to make different cylinder heads to do this. Have you done that? I get the feeling that you don't have the capability to do this.

I have done this type of research, and you are quite wrong here. I saw some You tube video a while back promoting your Jag ignition box, and it was pathetic!

That pretty model was revving that sad little engine with a scared look on her face, like, "who is this guy that put me up to this."

All stock, revving so lamely. Gosh, it was sad. There was no punch there.

Make an engine and race against a competent racing team and see what happens. If you would like me to continue, I can talk about why using a ignition retard module is a compromise solution to the quest of better performance.
-Fred

Your over-heating problem is due to incorrect ignition timing. You should have corrected that before trying to test how a 2-stroke behaves with a squish-band or any other tests you have made. Also, those heads you make wouldn't have to be so damn heavy to sink out the heat those "stock" C.D.I.s' create for you. You may find also that the plug you are using is too small to create real power. Spark fuel and pressure. I say pressure not compression because we are dealing with two-strokes. Initial compression is irrelevant in creating power with a smoker, higher is not better most of the time. 6.5:1 ish is about the norm and the best if you are scavenging well. You still have my pipe Fred? Try it and a proper C.D.I. and then you can start to learn about scavenging a smoker.
A squish-band is only any good at 9000 rpm and up. It's there to rob heat from the situation on super high revving race bikes. They don't care about the power-loss due to it at low rpm because they never idle her down. It's a fancy name is all. People hear racers talk about it and figure it'll make them go faster. You're worried about sales, we want all-around performance and reliability out of an engine that truly behaves like a KDX or the old PE. Look at how the big boys built those bikes. No "squish-band" there I bet.