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#338922 - 10/19/10 7:19 am Norton crank in Triumph cases  
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dennisharris Offline
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Danmark
I am building a sprinter for the street. I have a T140 engine with a Norton crank, carillo rods. I will be using 34 mm Mikunis and T140 head. STD T140 pistons.

I am looking for input on cams. I am not too familiar with Norton cranks, but from what I can read around the net, they seem to be in risk of exploding above 7000? Can anyone confirm that? Any ways - if that's the case I will put a limiter on at 6900 or so. I am looking for cams that will give as much power as possible below that. I have considered two T140 inlets, but am unsure wether they deliver power at too high revs? If anyone has experience with cams that give a lot of power below 6800 and start to taper off around 7000, I would be very interested in info. Thanks in advance!

#339117 - 10/20/10 2:25 pm Re: Norton crank in Triumph cases [Re: dennisharris]  
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Mark Parker Offline
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With more displacement power like Ben says will move down the rpm range, I think the T140 inlet is BSA Spitfire profile? If so should be good. I doubt the Norton crank is that fragile, but 7,000 is probably a good limit because of the stroke, piston speed and side load, if you want other stuff to last. I've run mine to 7500 quite a bit but it's probably not good for it, plus it's twisted to 90 deg so would have different crank loading, and in 18 years the crank has never given a problem.


mark
#339211 - 10/21/10 3:30 am Re: Norton crank in Triumph cases [Re: Mark Parker]  
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09graeme Offline
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The best cams to use for the Norton crank with Triumph T140 top end is Megacycle 510-75 which will give max HP at 6800RPM. You could use a Steve Maney forged flywheel if you want to improve the crank.

#339229 - 10/21/10 8:11 am Re: Norton crank in Triumph cases [Re: 09graeme]  
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Hi guys, thanks for the comments. What cams do I have experience with? Well, I have used two T140 inlets previously in 750s, and apparently, according to http://www.postdiluvian.org/~mason/moto/cam-timing.html
is similar to the Nourish 'Z' cam or the Johnson X-75. I found this to make a 750 quite quick, with standard pipes, no air filters and Megaton "silencers". But I also remember them as best over 4.000 revs, and a little rough in the low end. The only reason I don't go for these straight away, is that I do not want cams that are effective above 7.000, because that would be wasted on an engine that does not go beyond that.

My current engine also has a Norton crank, Morgo cylinder, 32mm concentrics with stacks, straight through pipes. The cams are 1969 Bonneville cams, from which I have had removed 1mm from the base, giving app. 0.039" more lift, with the same profile. I was unsure how to time these, so I set them at 100 degrees LC. This engine is very torquey, but runs out of steam over 5.000, It will rev probably to 7.000, but there is no addition of power at high revs. Could this be due to the timing I have used? I would like to time these with just the standard 650 timing marks, but I am unsure whether the Norton crank has the mark on the timing gear sprocket in the same place as a Triumph crank would. Does anyone know?

I will look into the Megacycle 510-75 cam, as it seems to have exactly what I am looking for. Thanks again for your help.

all the best,
Harris

#339380 - 10/22/10 7:20 am Re: Norton crank in Triumph cases [Re: ]  
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09graeme Offline
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Harris please follow BenG's advice and use a degree wheel off the end of the crank and dial gauge to set up cams and ignition timing otherwise you are wasting your time and may actually decrease performance.

#339607 - 10/24/10 10:15 am Re: Norton crank in Triumph cases [Re: dennisharris]  
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76degree-triumph Offline
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Dennis, I run T140 inlet cams in my 650 pre unit race engine.
Im using 3" thruxton followers so I think you can take off around 6deg for total duration @ .020, if using 'R' followers.
My timing events @.020
IO 52BTDC
IC 78ABDC
EO 79BBDC
EC 49ATDC
Inlet lift at TDC .176"
Exh lift at TDC .168"
Power from around 3800 using open pipes. Very strong from 4600 to 7200.
What rods are you using in your stroker morgo engine?
Cheers, Chris.


1950 Speed Twin outfit
1951 Thunderbird outfit (76 degree racebike, or is it 90 deg now?)
1955 BSA D3 minibike outfit
Triumph solo's
#339608 - 10/24/10 10:18 am Re: Norton crank in Triumph cases [Re: dennisharris]  
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76degree-triumph Offline
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Sorry I forgot to mention lift @TDC measured at the cam follower.


1950 Speed Twin outfit
1951 Thunderbird outfit (76 degree racebike, or is it 90 deg now?)
1955 BSA D3 minibike outfit
Triumph solo's
#339817 - 10/25/10 5:58 pm Re: Norton crank in Triumph cases [Re: dennisharris]  
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dennisharris Offline
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Hi Chris,

Thanks a bunch for the details. I will make a note of them. In the engine that I am currently running - the one with the raised t120 cams - I am using Norton steel rods of some sort. Not really sure what they are. My other engine has carillo rods.

You say you are using open pipes - do you mean no mega, just 'headers''?
Rgds
Dennis

Have a look at my blog, there are some pictures in there of my bike.
Harrisbobber@blogspot.com

#339818 - 10/25/10 6:04 pm Re: Norton crank in Triumph cases [Re: dennisharris]  
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Danmark
Chris,

7200 is probably a bit much for the old Norton crank - do you think it would be wiser to look for a cam that comes on around 3 perhaps, and tapers off at say, 6500 perhaps? I have been thinking (!) It is not just a matter of when max power is developed - it is also important what is available at the revs the engine hits in the next gear that is engaged... Correct me if you disagree.
Cheers,
Dennis

#339953 - 10/26/10 11:45 am Re: Norton crank in Triumph cases [Re: dennisharris]  
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Mark Parker Offline
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Dennis, it's not just the cam that determins the power spread, the exhaust has a large bearing on it. And other stuff to various degrees. If it were me I'd use the T140 cams. Esp if they are like the BSA spitfire cam. This is a data logged graph of my A65 with Norton crank and T140 pistons, it has the benefit of big headers and pipes, 38mm flatslides and big valves, all of which push the power up the rev range, smaller std pipes would have moved it down, and have it stronger in the midrange, smaller carbs would have done similar.



mark
#340034 - 10/26/10 10:41 pm Re: Norton crank in Triumph cases [Re: dennisharris]  
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76degree-triumph Offline
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Dennis, I have seen norton flywheels explode on racebikes. I have not seen a broken crank though, I think norton cranks are stronger than a triumph. The 1 3/4" bigend helps a lot.

I think 2 inlet cams would work well if used with a 5 speed and appropriate gearing.

The problem you will have is driving the ignition off the end of the inlet cam when fitted to the exhaust. This may lead you different cams eg megacycle.

Mark, how do the timing events I posted above compare to the spitfire cam?

Chris.


1950 Speed Twin outfit
1951 Thunderbird outfit (76 degree racebike, or is it 90 deg now?)
1955 BSA D3 minibike outfit
Triumph solo's
#340048 - 10/27/10 12:05 am Re: Norton crank in Triumph cases [Re: dennisharris]  
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Yes the Norton flywheels do explode on racebikes. I have also seen a couple. Causes a huge amount of damage and is very dangerous. Actually seen a few broken cranks too but usually with bad radiusing of big end regrinds. Plus there was an issue with the sump filter ? or oil feed drilling as well. Dont remember the details. Beltdriveman used to go on about it.

Sorry cant help on cam advice but I wouldnt run a Norton 750 crank above 7000 rpm.

John

PS thats a damn nice power curve on that BSA

Last edited by johnm; 10/27/10 12:07 am.
#340105 - 10/27/10 1:04 pm Re: Norton crank in Triumph cases [Re: johnm]  
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Chris, Mark, John.
Thanks for the replies. That powercurve on the BSA looks good, without a lot of holes. But what do you do for quick take-offs? It looks like power for launching is available around 5000 - but does that not give a lot of wheel spin? Maybe take-offs are not that important in the kind of racing you take part in (RR I assume?)

I am quite sure that T140 inlets with "R" followers will give Spitfire profile. I will be using only 32mm carbs and 1 3/4 pipes probably with megacycle silencers, and slightly longer intake manifolds, to try out the advice given by Dwain Taylor in "Tuning the 650 B-range Triumph".

Norman Hyde in England offers machined T140 inlet cams that have the ignition timing threads.

Thanks for the input regarding the explosive Norton crank. I will put a limiter on my "slow" engine with the modded T120 cams on 6900 revs. I think I will use a Pazon ignition system - I seem to recall that this system has an adjustable rev limiter.

Someone mentioned Steve Maney making solid flywheels, but I was only able to find complete cranks on his page, which is over my budget limit.

I found these specs for T140 cams:

"specs for Stock Triumph 750 short rod:"
Intake: 26.5* - 69.5* 111.5* lobe center
Exhaust: 61.5* - 35.5* 103.0* lobe center
measured @ .020" tappet lift
running clearance .010" intake and exhaust
valve lift: .350" 278* duration


Johnson Cams state:

Triumph T-75 Cam
Stock 750 twin intake. Use in exhaust also, for hot street motors and racing, where endurance means more than the last HP. Good to 7000rpm with stock springs. Similiar to Nourish Z.
Intake .345 105 .010 S 294 40 74 .020
Intake .345 105 .010 S 270 29 61 .040
Exhaust .345 105 .010 S 294 71 44 .020
Exhaust .345 105 .010 S 270 59 32 .040

They are not in complete agreement.

I have just decided to put one of the engines in a T140 frame, and have started looking around for spares.

rgds
Dennis

Last edited by dennisharris; 10/27/10 1:05 pm.
#341811 - 11/07/10 3:57 am Re: Norton crank in Triumph cases [Re: dennisharris]  
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Jack Adams Offline
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DH,It took me a while to find this dyno chart from my Hot Rod Triumph,This is about 6 or 7 years old,but it is a 76mm x 88.5mm (Nourish crank)T-140.Mega-cycle 1060 cams,36mm mikuni flatsides. As you can see it makes for a strong yet very reliable combo.Since building this motor in 2002, I haven't even taken the head off since. I think you will find good mid-range torque will make for a bike that is more fun on the street than just hi-rpm hp.Jack

#341820 - 11/07/10 5:15 am Re: Norton crank in Triumph cases [Re: dennisharris]  
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Mark Parker Offline
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The cam in my BSA is Spitfire profile but with offset buttons giving .410" lift, the buttons also effect timing slightly which I measured at inlet 53*-68* exh 80*-43* with .020 lash.
The dyno graph of the BSA is from the data logger when it was 818cc. The bigger bore cyl I've been using the last few years really helps it breath, and it has around 20HP more these days. I would like to put it on a Dynojet one day but none are around here.
I agree with you Jack, midrange is really nice on the street, hills, headwind, loaded up, makes little difference.


mark
#342526 - 11/10/10 5:14 pm Re: Norton crank in Triumph cases [Re: Mark Parker]  
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I have taken the top off one of my Norton cranked unit engines last weekend. The one with the standard t120 cams that had some material removed from the base. Measured inlet cam opening from app 38 to app 75 or so. Lift only .323. No wonder it was only marginally quicker than a T140 with a slightly hotter exhaust cam, and that was after we passed 100mph.

Also examined the head. Seats are located almost 5 mm deeper in their pockets than what they should be. Can anyone recommend a good head shop in UK or Germany? I was tThat will definitely have to be fixed before I put it back together.

Due to the disappointing measurements of those cams I am taking the cases apart and will be fitting two T140 cams. My friend is looking into whether he shall be able to machine a standard inlet cam to take the Boyer rotor.

And since that is apart I will have the crank balanced with the T140 pistons as well.

Damn it. Not really what I wanted to do. I really wanted to focus money and effort on the second engine. Well, that's life ;-) It's easy on a Triumph ;-)

#343152 - 11/14/10 6:59 am Re: Norton crank in Triumph cases [Re: Jack Adams]  
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Jack, nice looking power curve there. I am surprised that you are using such big carbs - 36 mm - are you able to get good response at lower revs?

#343153 - 11/14/10 7:04 am Re: Norton crank in Triumph cases [Re: dennisharris]  
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Here is a pic of the Norton crank I have just pulled out of the T120 engine. I am surprised that it has been so extensively drilled, and I am wondering whether it has been weakened. Maybe I am wrong, but I just don't like the fact that it has been drilled in the "thin" part of the fly wheel?

#343276 - 11/14/10 11:10 pm Re: Norton crank in Triumph cases [Re: dennisharris]  
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76degree-triumph Offline
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Dennis, those holes were drilled to balance the steel rods.

Jim Schmit has a book that tells ta how to modify the norton crank, including thining down that thin area right down to the face where the crank 1/2's bolt up.

I have done this on my dirt bike engine (820 unit triumph) but I have not ridden it since the rebuild.


1950 Speed Twin outfit
1951 Thunderbird outfit (76 degree racebike, or is it 90 deg now?)
1955 BSA D3 minibike outfit
Triumph solo's
#343361 - 11/15/10 10:33 am Re: Norton crank in Triumph cases [Re: 76degree-triumph]  
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Ok - Maybe It's not a problem. Have a look at this other crank I have. It seems that the flywheel has been cut in the sides, maybe for the same reason.

#343371 - 11/15/10 11:57 am Re: Norton crank in Triumph cases [Re: dennisharris]  
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Dennis, the crank to the left is the way to go, conrods excluded.

Im stumped why the norton stud/nut arangement is sooooo long and heavy! In this day and age with modern material they dont need to be this long or heavy.

I see the crank on the right has had its drive side mainshaft ground to suit the triumph main bearing. It gives less grip on the taper but I have never spun a front sprocket in 9 years of racing.






In the bottom pic the crank with the rods and pistons is the 76 deg crank, with an inlet cam to suit next to it. This arrangement has been thrashed for a while now with no major faults. (Stupid ones yes.)

The tapped holes in the crank are to play with balance factors.

In the pre unit I can drop the sump and install grub screws to play with the balance. Ive not have to do this. It runs much smoother in this configeration.

MARKTT I know you is watchin grin


The crank with the blue tape is the 90 deg version, waiting for funds to complete.

Cheers, Chris.


1950 Speed Twin outfit
1951 Thunderbird outfit (76 degree racebike, or is it 90 deg now?)
1955 BSA D3 minibike outfit
Triumph solo's
#343539 - 11/16/10 3:09 am Re: Norton crank in Triumph cases [Re: dennisharris]  
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Dennis,I believe the flatslides with long intake tubes make for great response from idle to redline. the fact that they are 36mm doesn't seem to matter as far as I can tell by the seat of the pants method and the torque curve seems to confirm it. Jack

#343687 - 11/17/10 1:00 am Re: Norton crank in Triumph cases [Re: 76degree-triumph]  
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Yep Chris, that I am, just hoping you come up with that offset cam for your 90* crank...Mark

#344941 - 11/24/10 5:03 pm Re: Norton crank in Triumph cases [Re: Jack Adams]  
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Jack. That sounds interesting. How long are the manifolds you are using? I am probably going to use 32mm concentrics. I used to run with stacks only, but with the amount of money this is costing me, I don't have the stomach for running without filter after this rebuild.

#344946 - 11/24/10 5:18 pm Re: Norton crank in Triumph cases [Re: 76degree-triumph]  
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Chris. That is some impressive stuff you're showing off there ;-) those cranks sure look great - is there a big difference in the way the engine feels at 76 rather than 360? I have found a local balancing firm that will balance my crank dynamically, it sounds like they know their stuff.

Since balancing the crank includes rods and pistons, I am looking to fit new pistons, which means going to "020 T140 pistons. But I am using a Morgo cylinder, which, with standard t140 pistons already looks quite thin - I wonder if it will take a rebore to fit 020 pistons? How thin can that sleeve get and still last?

It looks like you don't approve of the rods on the crank to the left ;-) I have been told they are Norton steel rods, probably not as good as the carillos. I believe the rods on the crank to the right are made for use with a STD T140 cylinder, rather than the 650 height morgo unit.

Rgds,

Dennis

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