2 into 1 Exhaust (2015)

74ok · Apr 10, 2018

Dances with Shrapnel said:
Yep, it's a piece of high performance art. Steve's endeavors sent me down that slippery slope around 2003. Have a nice picture of Rob McClennon on my Seeley beating out Jay Springsteen on an XR750 about 10 years ago. Unreal how trackable these 75mm motors are. I built it with a five speed, switched to a six speed but realized it was unnecessary and somehwhat counter productive so switching back to a five speed. The initial motor workwas by Herb Becker.

sure, sure, i believe you

Hobot · Apr 10, 2018

84th, you may not know it but you are tugging on Superman's cape spoofing Dances reports in public. At least he confirms factory oil pumps ain't a limiting factor. There are very few engines that ever survive 8500 routinely like TC did, even less that routinely used 9000 redlines and Dances is one of em.

acotrel · Apr 10, 2018

If you want to learn about torque - ride a two stroke :

74ok · Apr 12, 2018

hobot said:
84th, you may not know it but you are tugging on Superman's cape spoofing Dances reports in public. At least he confirms factory oil pumps ain't a limiting factor. There are very few engines that ever survive 8500 routinely like TC did, even less that routinely used 9000 redlines and Dances is one of em.

wasn't intended to spoof

in short, pix or it didn't happen, or

pls post the pix, i'd love to see it

Have a nice picture of Rob McClennon on my Seeley beating out Jay Springsteen on an XR750 about 10 years ago.

Dances with Shrapnel · Apr 13, 2018

Been on a project site for last three weeks away from home base. Glad to see this thread is still alive!
A little healthy skepticism is a good thing now and then. It did happen and it was real for Rob McClennon (might have been Tim Joyce), Jay Springsteen, Herb Becker, myself and a whole slew of the thousands of people attending AHRMA Mid Ohio Vintage Days.
When I get home I may dig up the picture, then again I may not and it will remain "unreal" for 84ok.. sad.

Seeing how you are apparently from Ontario and apparently interested in Nortons, you should know Herb Becker and you could ask him.
This same Norton Seeley is as best we can tell, the second ever to win at Daytona in Formula 750; definitely with Rob McLennon as rider and definitely an epic battle with a Triumph/BSA triple. Have the trophy in my office, also have a post win celebration picture for that.

Both instances the Norton was an ultra short stroke 750 with gobs of torque throughout the rev range.

acotrel · Apr 13, 2018

Would you please put a number on 'ultra short stroke' and what size was the inlet tract ? A 82mm stroke Triumph 650 has plenty of torque, was your 750 Commando shorter stroke than that ?

Dances with Shrapnel · Apr 13, 2018

75mm stroke. From recollection: 34-36mm ports. 40mm carbs and intake valves of 43mm, may have managed 44mm or talked about tryin 44mm: can’t recall exactly. Bike is elsewhere right now but if you need the exact details I will chase them down. We ran a MegCycle N480 and a MegaCycle +D. There were several variations of this build. Started with a bathtub combustion chamber and last version we reverted back to a hemi. Jury is still out on that one.

acotrel · Apr 14, 2018

I have often thought a 75mm stroke would be good in a Commando. Triumph used that stroke in one model of Thunderbird in the late 70s. But I don't know how anyone could buy a crank out of one at a reasonable price. Do any heroes still use standard 89mm stroke Commando cranks in their bikes at Daytona ? I would not even take my own 850 to Phillip Island. At the ends of the straights, you still need some drive to get you around the next sweeping bend. I think it would run out of puff too soon unless it had extremely high gearing.
What sort of exhaust system did you use ? - separate pipes with megaphones might have given you a fright with that motor.

Dances with Shrapnel · Apr 14, 2018

Doug McCrae, Stan Keys, The Goodpasters, myself and a hand full of others ran Daytona with stock cranks. You are probably more likely to granade a crank shifting second to third on a tight technical track than at Daytona; just my opinion here. Don’t get me wrong, Daytona is hard on the vintage equipment for a variety of obvious reasons. You really need to get your jetting right there, where it can make you or badly break you.

I always ran the Steve Maney 2-1 exhaust. Herb Becker tried two single pipes and they apparently did not have merit with the engine as configured ........ or maybe we missed something.

acotrel · Apr 14, 2018

I have always found it easier to race with a 2 into 1 pipe than two separate pipes, but the separate pipes usually give more top end. The trouble is that most race circuits have at least a few slow corners. So the choice depends on where you want to stick your neck out the most. Personally if I am going to crash, I prefer to crash where I am going slower. So I concentrate more on improving my performance in the corners rather than on high speed sweeping bends or very long straights. What I really dislike is running out of power on high speed sweeping bends. My bike oversteers when I accelerate and tends to understeer and run wide when I back off. It is set up for short tight circuits. Somewhere such as Phillip Island or Daytona is a different game.

Kvinnhering · Apr 15, 2018

I have a question for you, gentlemen. Does low-mounted 2-1 exhaust system exist in the market with the same effect increase as Booking 850 has? I use the bike for rally and therefore need saddlebags and there is no room for high-mounted exhaust systems.
One combination can be pipes from Viking exhaust and muffler from Bokking? Or can Bokking 850 provide low-mounted system?

Fast Eddie · Apr 15, 2018

Viking makes the Dunstal 2:1 downpipes, and offers mufflers. I would have thought that was the best you’ll find.

Perhaps ask for feedback on here from Dunstal 2:1 users past and present regarding performance characteristics ?

Dances with Shrapnel · Apr 15, 2018

At one time BUB made a neat two into one that was slung low.

JimC · Apr 15, 2018

Question for racers: Disregarding rider input, which discipline is most difficult to build and prep a bike for? Drag race, road race or Bonneville?

Fast Eddie · Apr 16, 2018

I would have thought Bonneville, I’ve never done it, but the sustained WOT and the harsh environment must create pretty unique challenges.

acotrel · Apr 16, 2018

I would have thought you would need to be very careful with the motor in a land speed bike. If the gearing is right, the motor ends up spinning at high revs at very high speed for a longer time than in the other two competitions. Although setting up for Daytona might be similar in many ways - failures can be much more catastrophic for the rider than with drag racing. In the land speed situation, a get-off doesn't seem to have the same dire consequences as one at Daytona - also you are on your own - not with other competitors. With drag racing, a blow-up can happen anywhere, so you have a two-thirds chance of being slower if it happens. I think drag racing is much safer.
Also in road racing, you are much more heavily reliant on brakes - the cause of most of my crashes. In road racing, you can only go as fast as you can stop. To be successful, you need to be compulsive obsessive, which I am not.

Danno · Apr 16, 2018

Fast Eddie said:
Viking makes the Dunstal 2:1 downpipes, and offers mufflers. I would have thought that was the best you’ll find.

Perhaps ask for feedback on here from Dunstal 2:1 users past and present regarding performance characteristics ?

The SS clone had a Blair exhaust back when it was a Fastback with a BMW fairing. Loved the sound and the uprated performance, but I never liked that huge underpipe hanging down. When I converted back to Roadster spec, I got a Winning 2-into-one pipe from Leo Goff
and subsequently converted the outlet to a Supertrapp setup with baffles one could add or subtract to vary performance (noise!). Never really liked the sound, so I traded it to a guy from Belgium for the SS pipes it currently wears.

The Dunstall exhaust was excellent for quality, sound and performance enhancement. I had it on there long enough to blue the plating and get it re-plated in black chrome before I traded it off.

oldmikew · Apr 16, 2018

Had a Dunstall 2into 1 into 2... Yes it gave superior midrange I think as much as 5bhp was claimed. but nothing on top end. Maybe the stuff Dunstall exported to the States was of superior quality, but mine build wise was an abomination. The system was designed by Dr Blair.. have always been curious as to whether the much vaunted 'Decibal' silencers were also his , or whether it was built round them as a given.

What I do not know is how it would work with bigger ports valves and a more radical cam. Mine had a standard RH1 with 30mm Concentrics. What I do know is that I dustbinned it , totally fed up with its inferior build quality.

2 into 1 Exhaust (2015)

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