ISO Seeley ??

JIm, I tend to take a more minimalist approach. From my experience with old Triumphs, I know you don't have to do much if you concentrate on torque and gearing and steering geometry. My friend's 650 Triton has never been revved over 6,300 RPM. When it is in the hands of our A grade policeman friend, it is almost unbeatable in Period 3 Unlimited historics. There are 1000cc featherbed Vincents there in the hands of superbike riders.
When I built the Seeley 850, I made a decision to definitetly not go top end with it. If I wanted to do that I would have bought the Nourish Weslake motor and raced in Period 5 against the Z900s and Katanas. All have to contend with in Period 4 are 1000cc CB 750 Hondas which handle like bags of shit however dominate the class - I will get them next time.

acotrel said:

My 850 only runs standard petrol compression with methanol fuel. Rohan has taken me to task over the low comp ratio saying you need high comp. to get methanol working properly. High comp is an option with methanol, however not absolutely necessary. My friend's 50s 500 manx on 14 to one comp. ran two degrees ignition retard behind standard timing for petrol, my 850 runs 4 degrees more advance ahead of standard timing for petrol - if you think about burn times it is logical. And it dramatically affects the way power is delivered around TDC. We also run a speedway Vincent with flat top pistons on low comp. with methanol, it is as quick as the 12 to 1 comp motors. Any vibes I have with the Seeley are low frequency, however the bike is smooth and fast at 7,000 RPM. Crank is balanced at 72%.

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As once explained to me once by an F1 engineer... The WHOLE purpose of an internal combustion engine is to compress that gas. More compression = more efficiency = more power. Even small passenger petrol cars these days are over 11:1 !
The primary advantage to methanol is to allow higher CR.
You are happy and clearly enjoying your racing, i take my hat off to you that long may it continue.
However, you are kidding yourself about a few basic facts here.

Your story about the 650 Triumph beating all comers reminds me of a time I was preparing my racer in Dresda's race shop. A customer came up to talk to me (as they often did). He had an old, period 650 PU Triton and had spent tons of cash on shiny goodies. I quizzed him as to his plans for the motor. "Leaving it alone" he said. I looked at it to see small carbs, old 8 stud head, etc, etc. clearly nothing 'special' in it.
"It absolutely flies, NOTHING can stay with it" he says.
My racer was a 906cc 8 valve with nearly half inch valve lift, 38mm smooth bore carbs, lightweight valve gear, billet NRE 180 degree crank, 11.5:1 CR, belt drive, interspan ignition, safe to 9,000 but but normal rev ceiling of 8,000
I asked him "what do you rev it to?"
"Never been above 4000" says he.
"Oh..." says I.
End of conversation.

comnoz said:

The perimeter framed bike I built in the 90's used a suspended engine and four isloastic mounts with the swingarm attached to the trans. It was somooth as an electric motor and had none of the soggy handling attributed to isolastic mounts. Jim

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Very nice Jim. Very nice perpetration too. I've seen pics of this before but not realised it was ISO. Sadly though, a frame of that nature wouldn't be any good to me as it wouldn't qualify for CRMC or BHR events. However, it proves the concept of a lightweight ISO frame.

Your "loops" that hold the front ISO could also be added to a Seeley sans down tubes. However, on balance, it would probably be easier to use a version with a full frame loop.

Good food for thought there though sir!

comnoz said:

Al-otment said:

Neat! Think I've spotted 3 of the mounts - 2 at the rear on the vertical tubing and 1 in front of the barrels. I assume No.4 is in the standard head steady position? If this is the case, Jim, I wonder if you tested with the front of barrel iso removed?

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Yes, the fourth iso is on the head. I first built it without the front iso and hanger. It was good as long as the isos were adjusted very tight but that brought out some vibration.
After I installed the front hanger and mount it was like a riding a solid mount frame but without the vibs. Jim

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That makes sense. Without the front iso the plane formed by the other three mounting points is 'shallow' (i.e it provides a relatively small lever) in relation to the rear wheel radius and would not provide as much resistance to torsional forces in comparison to the plane formed with all four mounting points. I think you could have done away with the bottom rear mounting point because the plane formed by the remaining three would still have 'depth' to it and provide similar resistance (i.e a large lever) to the four mounting points.

Hi

I can only speak about the Mk2 frame. I did the 960 engine at Donington this year & had to fit the 750 engine for Snetterton. Chalk & cheese. The smaller engine that I had used before, the vibes were crisper. Little bit taughter, more noticeable. The exhaust note was a lot louder as well. The 960 is very comfortable, pretty much all the way to 6,800 which was probably the problem.
Vibes you get used to, bad ones you don't forget. So far all the Seeleys have been more than acceptable. strangely the worst for feel (not vibes) was my Norvil with Corillo rods. It felt much harsher.

Chris

Chris said:

Hi..........Vibes you get used to, bad ones you don't forget. So far all the Seeleys have been more than acceptable. strangely the worst for feel (not vibes) was my Norvil with Corillo rods. It felt much harsher.

Chris

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With the iso mounting bracket holes square to the frame C/L the iso thrust faces should be very close to parallel. Therefore you should be able to set clearance at max. 0.006" and have very good handling and very little vibration apart from the 2,000 - 3,000 rpm range. No harsh vibes and certainly not enough to cause discomfort.

Uncomfortable vibration on a road bike turn most journeys into an ordeal. Not what you want when covering hundreds of miles per day.

Chris said:

Hi

I can only speak about the Mk2 frame. I did the 960 engine at Donington this year & had to fit the 750 engine for Snetterton. Chalk & cheese. The smaller engine that I had used before, the vibes were crisper. Little bit taughter, more noticeable. The exhaust note was a lot louder as well. The 960 is very comfortable, pretty much all the way to 6,800 which was probably the problem.
Vibes you get used to, bad ones you don't forget. So far all the Seeleys have been more than acceptable. strangely the worst for feel (not vibes) was my Norvil with Corillo rods. It felt much harsher.

Chris

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That's good info Chris. How did you achieve 960cc BTW? And what do you mean by "was probably the problem" re the 960?

Hi, from the "GUS KHUN WEB SITE"
Like the other Mark 3 Seeley frames (the ones with no front downtube) employed by the Kuhn team over the years, chassis No MK3CS149N was fitted by them with a bolt-on ladder-type subframe connecting the front engine mount to the headstock to provide added stiffness and to support the rigidly- mounted engine better. During its in Scotland, this was removed and the engine mounted flexibly using Isolastic mounts, presumably to reduce vibration. When Richard Peckett of P&M Motorcycles, to whom Pete entrusted the task of rebuilding the bike, stripped it out, the first thing he did was to replace the Isolastic rubbers with solid blocks to mount the engine rigidly again, to stop it shaking about all over the place when running.

http://www.guskuhn.net/GKMLtd/Racing/GKMRacing.htm

Better like that , more polite towards them........!

Hi Eddie

Spec below
Norton Commando 960cc Engine

Bore 81mm stroke 93mm
Camshaft 7S
Factory settings 0.225 thou lift on inlet valve at T.D.C with 16 thou tappet clearance.
We ran 15 degrees advance on timing gears to give 200 thou lift on inlet valve at T.D.C now inlet opens 61deg. B.T.D.C closes 78deg. A.B.D.C exhaust opens 88deg.B.B.D.C closes 60deg. A.T.D.C all checked with 16 thou Tappet clearance
Running Tappet clearance 16 thou all round

Ignition- Boyer Brandsden Mk 2
Ignition timing 28 deg B.T.D.C

Crankshaft- 93mm Maney Lightweight
Connecting Rods- Carrilo
Crankcases- Maney
Pistons- JE modified, Weight 396grams each
Cylinder Barrels- STD Norton 850cc relined and bored 81mm

I was flat out at Donington far to early & to often.
Actually had to have sprockets made!!!!!!

Chris

Chris said:

Hi Eddie

Spec below
Norton Commando 960cc Engine

Bore 81mm stroke 93mm
Camshaft 7S
Factory settings 0.225 thou lift on inlet valve at T.D.C with 16 thou tappet clearance.
We ran 15 degrees advance on timing gears to give 200 thou lift on inlet valve at T.D.C now inlet opens 61deg. B.T.D.C closes 78deg. A.B.D.C exhaust opens 88deg.B.B.D.C closes 60deg. A.T.D.C all checked with 16 thou Tappet clearance
Running Tappet clearance 16 thou all round

Ignition- Boyer Brandsden Mk 2
Ignition timing 28 deg B.T.D.C


Crankshaft- 93mm Maney Lightweight
Connecting Rods- Carrilo
Crankcases- Maney
Pistons- JE modified, Weight 396grams each
Cylinder Barrels- STD Norton 850cc relined and bored 81mm

I was flat out at Donington far to early & to often.
Actually had to have sprockets made!!!!!!

Chris

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Chris, that's sounds like a beautiful spec you've got there mate!
How do we start a conversation about me asking you if I can have a go out one day...?
Oh, I just have...

Hi

Eddie I don't know if you are still a member of the Vintage club? CRMC? I have a few bikes out on loan. Have a look at the calendar & choose a meeting , I can sort you out with something. (could bring out a triple for you? hehe)

Chris

Your cam timings look like what I consider to be ideal for separate pipes, are you using megaphones ? Is the 7S cam a Norton factory item ? When I first built my 850, timings like that is what I was looking for. I advanced the inlet opening on the 850 cam to open 60 degrees BTDC (nil clearance) However the exhaust timings were not really where I wanted them to be - seems to work well with the 2 into one exhaust - don't really know why but many of the old superbikes which used 4 into one pipes had a similar stagger between inlet and exhaust timings. I recently bought a 2S cam from Bwolfie and I'm going to try that later. I think I haven't yet fully optimized the timings to suit the exhaust - it is still very loud, so I think it is wasting power. The motor produces loads of torque and is deceptive to gear correctly.

acotrel said:

Your cam timings look like what I consider to be ideal for separate pipes, are you using megaphones ? Is the 7S cam a Norton factory item ? When I first built my 850, timings like that is what I was looking for. I advanced the inlet opening on the 850 cam to open 60 degrees BTDC (nil clearance) However the exhaust timings were not really where I wanted them to be - seems to work well with the 2 into one exhaust - don't really know why but many of the old superbikes which used 4 into one pipes had a similar stagger between inlet and exhaust timings. I recently bought a 2S cam from Bwolfie and I'm going to try that later. I think I haven't yet fully optimized the timings to suit the exhaust - it is still very loud, so I think it is wasting power. The motor produces loads of torque and is deceptive to gear correctly.

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That 2S can will need more than stock CR...

Hi

The 7s is I believe a John Lovell cam. I know it was always listed by Fairspares. I now it wasn't good on the 750 but it works on the big engine.
Steve Maneys 2 into 1 works well & runs at 105db which is the limit we have to adhere to. I use his silencer as I don't want to have any aggro with the noise testers.
Twin Meggas probably have end cans now days.

Chris

Chris said:

Hi

Eddie I don't know if you are still a member of the Vintage club? CRMC? I have a few bikes out on loan. Have a look at the calendar & choose a meeting , I can sort you out with something. (could bring out a triple for you? hehe)

Chris

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Chris, you are an admirable Gent! And a bad man. PM sent...

Chris said:

Hi

The 7s is I believe a John Lovell cam. I know it was always listed by Fairspares. I now it wasn't good on the 750 but it works on the big engine.
Steve Maneys 2 into 1 works well & runs at 105db which is the limit we have to adhere to. I use his silencer as I don't want to have any aggro with the noise testers.
Twin Meggas probably have end cans now days.

Chris

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I did a track day on my modified airhead, I failed the noise test at 107db with my "quiet" silencers, the limit was 101db @5500 revs.....a local workshop made up some dampers to fit in the exhausts and I squeaked in at 98db. Really cut the power

Why does comp. ratio have any effect on the way the 2S cam works ? I know the combat ran higher comp. - so what ? Is it really necessary, surely timings are about standing waves - harmonics , pipe diameters and lengths ?

Unread postby acotrel » Mon Jan 06, 2014 8:33 am
Why does comp. ratio have any effect on the way the 2S cam works ? I know the combat ran higher comp. - so what ? Is it really necessary, surely timings are about standing waves - harmonics , pipe diameters and lengths ?

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Good question to me too Al as the 2nd most powerful Norton twin I had was 750 with 2S cam and standard 28.5 port head, mis matched 32 mm manifold with intruding rough curd gasket exiting 2-1> Dunstall long megaphone, which felt so dogged down weak I got rather depressed and for some relief shot a 12 ga slug through the mega supertrap end cap - then in shear shocked joy became a sportsbike hunter to find moderns to damn wheelie limited to stand a chance up to 90 mph and had to go well beyond 130 to catch up in straights if over 1/4 long others just solo fun out ahead for me. I first discoved this in my driveway which it tight off sloped and twisted so barely off idle 15 mph 2nd gear blip to end up on tail light *** pissed Not Pleased*** I could of been so depressed stupid not to be holding on some, ... so got set as a drag racer would grip and set hard in seat back, gave it a bit more YIKES still ended up over seat hump!!! Did it once more 3rd time before end of driveway going ~25ish/2nd this time - and was able to stay in seat enough to stay in control and cracked a Shit Eatting Grin that has never left me since. Key point of making Norton Power is keeping the charge velocity up and extracting the exhaust pluses. Peel was strong enough to treat up drive train by twisting shafts, fracturing bushes, fanning 520 size teeth over and popping off 3rd gear teeth snapping throttle going too slow, d/t a 990 Monster I'd waited behind a car to give em a fair chance before some nice turns appeared again. I had no need of blower to accelerate to the ton but will need one to not get caught up with in the longer opens is all and would of torn drive train apart any way w/o TTI tranny. Still not a quick as the very light and lowered p!! though.

acotrel said:

Why does comp. ratio have any effect on the way the 2S cam works ? I know the combat ran higher comp. - so what ? Is it really necessary, surely timings are about standing waves - harmonics , pipe diameters and lengths ?

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Well, for one thing, a longer overlap cam reduces effective compression ratio, so an increase in mechanical CR is needed just to get back the same effective CR as with stock cam. Raising CR is probably the most "bang for the buck" performance mod you can do, as long as you don't get ahead of the anit-knock properties of the fuel you are using.

Ken