E: Engine Squish

[Bradley Burt]

I spoke to John Trease about it in his shed. 58hp. I know Geoff's ES4.

Most classic racing I've seen the quick P3 500 bikes with top riders are quicker than the unlimiteds........The misconception that a bigger supposedly more powerful bike will be way faster in lap times simply isn't true.

Exactly my point! Big HP means nothing if you can't go around a corner. Lakeside's a tight track (unlike the Island) so the smaller, more rideable bikes should be quicker.

2017 Nationals at Goulburn: David Woolsey Qualifying 1:13.8 on the triton with 73hp and 25-30 years of development. I (wood duck) 1:13.1 on the learners approved 250cc proddy with half the hp. It took one week of "development" for the track and I was 11th in my class. Corner speed beats big hp.

 

[eglijim]

Amen and the BTH guy won’t alter the ignition range . Using the short stroke Manx squish combustion chamber as Ian Hamilton did on stock 84mm or 86mm bores and 11-1 CR with a pop up piston and dual plug fixed advance 18 degrees full advance gave maximum power as shown on a rolling road Dyno on my Grey Flash racing engine Using a John Renwick cam.

Having just seen this post and been heavily involved with Ian during all of our riding and racing lives , the 86x90 engine with Manx style pistons and 12.5: 1 CR was always our "old reliable" backstop race engine ( as well as the one we used at Daytona in 1988) , it almost always produced 86 bhp with 39.5 mm Amal mk2 smoothbore carbs . later developments used 90 then 94mm squish pistons to our design by JE but need the cylinder heads machined to accept the part of the piston which was proud of the liner at tdc which produced the flat squish area and also concentrated the combustion chamber area.

 

[vibrac]

Ben Kingham and Josh Brookes are a great example. From what I understand there was nothing particularly special with the engine. Smoothness and consistency resulted in quick lap times. I don't think they were the fastest in a straight line either.

128 MPH at 5500