E: Engine Squish

[Bradley Burt]

Greg Brillus's Twin racer also won Philips Island with Phil canning aboard.

Phil raced the bike at Philip Island in 2018. He won the class due to a DNF by David Woolsey in Race 4. His fastest lap was a 1:58.005. That's over 10.5 seconds slower than the lap record, and 8 seconds slower than the 39hp production machine mentioned above. No disrespect to Phil at all, but this is what happened. The competition was not there.
To put things in perspective, my 2nd ever outing on any motorsport circuit was at Philip Island in 2016. I did a 2:01 with a top speed of 183kph on a learner's approved cbr250r proddy. I was about 95kg plus leathers, helmet etc at the time. The Vincent twin achieved 212kph in 2018. 29kph (18mph) faster than me, a tonne more hp and only 3 seconds quicker??? And I'm only a wood duck on a good day. The only way of knowing what a motorcycle is capable of is with a good rider onboard.

I've been fortunate enough to ride both of Luis Gallur's 500 Eglis in 2018. One which Cam raced at the IOM and the other which Maria Costello was racing here in Australia. Luis told me Cam's bike had 53hp and Maria's had 48hp. Luis wanted more. 2 weeks earlier Cam did 1:49s at Eastern Creek and had the pace to win the class if he didn't have 2 DNFs. So why bother chasing more hp? Are you better off with a time bomb or a reliable race bike?

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.

 

[greg brillus]

Why the negative approach to getting more power from these bikes........Might as well tell Ken Horner, Patrick Godet, John Renwick, Alp, Steve, Mal, David T........anyone in the Vincent racing world..........Your all WASTING YOUR TIME..........by the way, that 810 Triton that "Duf".......(David Woolsey) was racing belonged to Fraser McMillan.........Fraser spent at least 25 to 30 years devoloping it and it put out 73 Rear wheel HP........how many trick Triumph's do you know of that put out that much power.........wasted all that time for nothing.

 

[Bradley Burt]

G'day Greg,
There is no negativity intended at all. I was sticking to the facts. The stopwatch doesn't lie.

The Horner's machinery and Godet bikes have/had quality riders onboard proving success. I don't know David T or anything about him so can't comment. No idea why you dragged those other names into this. When did Alp, Steve and Mal compete in circuit racing???

I don't know Fraser McMillan but the Triton sounds like a weapon. No time wasted at all, after all it beat the Vincent in every race it finished that weekend.

I remember Peter Campbell (PC) talking about gearing motorcycles for the track. Always gear the bikes for the fast corners. Even if you have to back off a bit down the end of the straight. Everyone goes through the slow corners at the same speed. The fast corners is where the time is found. What PC doesn't know about circuit racing isn't worth knowing. I remember him talking about how he detuned a superbike (for Shawn Giles I think it was) years ago to make it more rideable, and the lap times came down. The bike handled better.

Enjoy,
Brad.

 

[flashvin]

Tim, Hate to sound negative, but the twin spark BTH will probably cause you more grief than you might know........The issue is that the advance curve is the same as per the single spark version, only the output wires are simply doubled up to drive 2 output coils. What this means is that if you run say 26 to 28 degrees full advance, the fully retarded possition will fire way after TDC. If your engine has electric start you might get away with it, but on the kickstart it will be difficult to start......Good luck with it all.

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.

 

[greg brillus]

Yes I think it depends also on what fuel you intend to use.........Because i'm running methanol the higher the compression the better (to a point).......i remember watching Cam Donald starting John Trease Harley race bike at Phillip Island when i raced there in 2015........John's electric rollers used 2 9" disc grinder 240 volt motors, and it took at least 2 guys pushing hard down on the seat to fire it up........The sound was amazing.......This is the bike that Brad mensioned was 10 seconds faster than anything else in the P3 Unlimited class........although Cam told me some time later that the bike was a monster to ride, it also has about 130 odd HP.......Down the straight it had a massive advantage in speed........At some point of speed measurement, my Vincent was about 208 Kph and the Harley was 245.......I know that bike was always "On the limit" of reliability, but it sure was fun to watch........I wish to keep some reliabilty with mine, so wont be pushing things to rediculous limits, but with some effort you can make these engines go much better.......Hopefully by the new year we will have a "Useable" proto type roller follower and a cam profile to match........If we close those valves that bit earlier on the inlet, and get some more dynamic comp into it, it should really come to life.

 

[Bradley Burt]

That’s 10s faster than the P3 unlimited machines in 2018. The Trease Harley has done consistent 1.47s. A couple of G50 Matchlesses in the P3 500 class have done consistent 1.49s in the past. Dave Cole from NZL did a 1.49.0 on a G50. The competition nowadays is pretty limited. Only 6 in the P3 unlimited class for 2019 and only 2 of them finished all the races. Guaranteed a plastic trophy just for finishing.

Talking of John Trease, that comet-norvin he built (500cc) did a 1:51.05 at Philip Island on its first outing there. In that race it started last (25th) as it didn’t qualify and finished 2nd, lapping 4 riders in the 5 lap race. 1.53s avg including the standing start from the grid, with traffic!! No Godet machine has lapped the Island quicker… yet. Cam Donald, Alex Sinclair and Levi Day have all got within 1s. All interesting stuff.

 

[greg brillus]

You should ask Ian Boyd.......that is his bike.......( a Vinton ) is its nickname........Trease built the engine to unbelievable specs and cost........Davidd will know, but i think it had over 60 HP.......All of these classic bikes can be made to go much better than they did years ago with all the modern technology and materials available now........When i raced at PI with the Vincent, there was a huge amount of P3 unlimited bikes mixed in with others that i can't remember. The numbers after that years seemed to drop off considerably........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........it is my belief that the unlimited classic bikes are actually much harder to ride on account of their extra weight for one thing, and you cant go any bigger in brake sizes (in Aussie that is)........At the Aussie titles at Lakeside back in 2014 (my actual first solo race on the Vincent) the fastest time David Woolsey did on Frasers Triton was a 1.10 and Some other bloke from South Australia on a 500 Manx did it in 1.07........The 500 senior class is very competetive........That ES4 of Jeff's is very quick.

 

[roger v]

For once my interest is not from a racing point of view. I am building new top end on My electric start Comet (Road), and I am loath to open out a standard head to 90mm so I simply want to use the 3mm land formed by the 84mm head to 90mm bore discrepancy and the top of the piston to give me a bit of pep to my relatively low (still to be measured ) CR. I am also firing twin plugs on the BTH (I have them so why not use them) so finding a good ignition timing will be fun. Fortunately my son Ben is installing a rolling road intended for classic bike tuning so we should be able to get it right.

Hi Tim Its about a year since this , so did you do the 90 mm piston / 84 mm / 3mm squish job ? regards Roger

 

[roger v]

What do you consider is a minimum Distance/Clearance for opposing surfaces (eg piston and head) in line with the stroke? I have got .030" in my head but I have no idea were that originated.

Hi Tim From my Velo experience where a Viper head / bore of 72mm is opened out to 86mm to suit a Venom piston , a flat squish band of 7mm x 0.040 " has been established for many years using either a flat top MSS piston or an Omega forged item . I believe that AJS 7R also has a 0.040 gap . Both my Velos run a 8 : 1 compression ratio with two plugs fired electronically with 32 degrees of advance in place of the std 38 for a normal eight to one . The result is a bike that starts easily , ticks over at 1000 rpm and picks up quite a bit quicker than before . So as I am starting from scratch with my Vincent project I was hoping to use this as a basic kick off point . My concern is that 3mm is very shallow , has anyone ever filled the head between the valves to give a partial band area and using a seven to one standard piston machined to suit whilst not raising the comp ratio to much more than eight to one . regards Roger

 

[vibrac]

been assembled and running for over a year did the Columbres rally but the twin racer took up a lot of last summer so mileage has been restricted. I should take the head off and have a look and fit a second plug hole to the shadow head for a decompressor but the electric start seems not to mind and the lithium batter stays charged even with 3 months of non use. So I guess it will be later in the year