Short Stroke 750 Dyno Run

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My Herb Becker built, big valve Fullauto head short stroke 750 with JS pistons and rods on the dyno.
Herb went with a more conservative cam on it to get not peak power but good torque + power, more useable hp on the track.
I will be racing at the Vintage Motorcycle Days at Mid-Ohio this weekend, I believe I will be in garage 11 if anyone comes down, drop by.

A big thank you to Ken at Fullauto for helping to make this happen, thanks to Jim at JS Motorsport as well.

I am a little late posting this, we ran the race bike on the dyno in May but I was away traveling for work and missed some race weekends in June.

Dyno run- in case you are wondering, Herb's motors always puff just a bit of smoke even when new, I think because he doesn't use oil seals on the valves-

[video]https://www.youtube.com/watch?v=jgkLhxxJMGY[/video]

My win at Mosport last year-

[video]https://www.youtube.com/watch?v=NfhurWZKm7E[/video]

My racing at Mid-Ohio last year, short as it was-

[video]https://www.youtube.com/watch?v=-vSxmZUnU5M[/video]
 
Wonderful mean angry sounds with ear splitting grins so what was the power band rpm figures?
 
Hi Doug thanks for posting and sorry to see the Maney cases in such dissarry.
What cam did you end up running in the new motor?
Regards Mike
 
Thanks for the video clips, Doug. You have inspired me to get going again. I particularly like the Mosport clip. What stroke is your short stroke commando engine ? When I first built my bike I never believed in it, I now think that the long stroke is the major asset of the commando engine. However I can see how a short stroke motor would be an advantage on a circuit like Mosport.
 
Hey Mike, cam is a Megacycle from Jim Schmitt, I believe it is a stage 2 ? running on BSA lifters.
Herb believes it may benefit from a more aggressive cam but I am going to try this one this weekend and see how I like it, driveability is important
 
Hi Doug, good stuff, I am also talking to Jim about his WebCams.
JS is also getting a cam ground up , same as his JS2 (PW3) so will be interesting to see ho that turns out.
Please give some feed back after your race days.
Regards Mike
I sent you a PM
 
Hey Doug,
It’s nice to see it’s all coming together. I talked to Herb at the Paris Rally June 20th and he showed me the graphs of the Dyno run at Dons. Really nice torque numbers and it should pull like a train. Hats off to Fullauto for all his support. Herb definitely has a lot of respect for the stuff Jim Schmidt produces and so do I as I was picking Herb’s brain for balancing my P11 crank with the Lightweight pistons and Carrillo Norton Rods. I have them now at Forest & Forest in Ayr for the balance treatment. I will send this and other bits off to get Cryogenic treated down the road. Hopefully by the time I get back from the NC Rally I will start assembling the engine finally. Don did my valve guide work fitting the Kibblewhite black diamond valves and guides. He has done work for me in the past and He is good too. I want to get my bike on his dyno one day just to get it sweet.
Good luck at the Races. 8)
Cheers,
Thomas
CNN
 
Brooking 850 said:
Hi Doug thanks for posting and sorry to see the Maney cases in such dissarry.
What cam did you end up running in the new motor?
Regards Mike

Indeed... Anyone thinking that Carrillo rods are outside the budget of their current build should fast forward and pause at 07:30 into the third video...

Been there. Done that. Not fun!
 
Nice bike - awesome sounding too. I plan on being there Saturday to enjoy some racing. Might stop by to say hello
 
My old Dommy smoked a bit at one time.....in those days of youth one must have ridiculous go faster modification was to fit the super dooper 6 start pump worm gear. Not being totally brain dead I fitted non scrolled rocker spindles and drilled out the inlet area oil return hole through the head and barrel. it smoked....A LONG time later an ex AMC race mechanic friend suggested we take a look inside the inlet rocker area with the motor running and apart from covering the rear of the bike and us in oil it was noted that evn at low revs the oil was rising above the top of the inlet valves and thus passing down them causing the smoking motor. i cured it by fitting an external oil drain from the side of the head (at a level below the top of the valve guides) back to the timing chest. Recently I was told a few race motors have a drain taken from between the inlet guides back into the rear of the crank cases.
I suspect the oil seals on the inlet guides was Nortons way of curing the problem whilst increasing guide wear!! Takes a real brain to do that not that there were any left at what ever they were calling themselves by then with Mr Hopwood and Mr Hele having left ...... As I heard it the ONLY reason for the 6 start worm was on the Domiracer to cheaply and without having to redesign the oil pump to allow for the increased oil flow required to lubricate the pressure fed supply to the cam lobes..... On road going lumps Norton having cleverly removed the cam shaft oil bath Mr Hopwood so carefully designed into his Dominator engine design to ensure the cam and followers were CORRECTLY lubricated at ALL times especially during the engine start up period when galling will take place resulting in assured cam and follower premature failure. As my old Piper tuning notes state...something like...'In our experience most cams that fail start to do so at the moment of engine start due to lack of lubrication between the cam and followers.....' . With Mr Hop-woods oil bath as the cam rotates for the first few revs the lobes dip into the RETAINED oil oil supplying the lubrication required before oil is flying about in the cases from the crank. Mind you it also flew about in triumph cases but at one time nearly 50% of 650s had the exhaust cam at the front of the motor replaced under warrenty. Mr Hopwood wrote to me ..and I quote...'The cam shaft tunnel of the Dominator engine was designed to retain as much oil as possible with the lip of the tunnel running within 1/8 -3/32 of the flywheel rim to pick up oil from it....' Funny how early Dommy engines never had premature cam failure problems till that is clever souls went and removed the oil bath as Norton owners fitted higher lift cams to enable them to 'go slower' taking a rotary file to the oil bath tunnel as shown in the Dunstall tuning book and removed the oil retaining required to lubricate the cam correctly at all times.
 
Unless you're increasing the piston speed, (and not just rpm), there's no need to increase cam duration on a short stroke engine.
The same duration cam will basically run to the same piston speed, regardless of stroke.
 
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