Author Topic: norris race cam  (Read 915 times)

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Offline mad mike

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norris race cam
« on: March 23, 2023, 11:14:31 am »
  Advice please gents, im building a replica of my old race bike.  [from 1976],.... 836 cc Ported  f2 head and high comp 10.25 pistons.  4/1 yoshi exhaust ,  Not sure on carbs as yet, and a Boyer ignition,  ..... I have a Norris race cam. which i propose to use in it , however i have no cam  timing  info. for it .... The numbers engraved on it are  ...... Norris RR .... or possibly RB ? ....  Can any of you learned gents advise on this cam regarding timing?   or can i just split I/o - E/c equally over TDC ?   and also any idea on power band? ... Ie .is it a high rev/ upper powerband cam,  ....or will it give a wide spread of power ?  thanks in advance.   Mike.
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Offline gschuld

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Re: norris race cam
« Reply #1 on: March 23, 2023, 11:28:19 am »
125-NR might be the one you are looking for

George

Offline PeWe

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Re: norris race cam
« Reply #2 on: March 23, 2023, 12:21:42 pm »
« Last Edit: March 23, 2023, 12:23:23 pm by PeWe »
CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Offline mad mike

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Re: norris race cam
« Reply #3 on: March 23, 2023, 12:24:18 pm »
George, thanks for the info, ..... but my cam is not listed there, It is clearly engraved Norris, followed by RR or possibly RB ? unsure which it is , .... Looks more like RR.
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Offline mad mike

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Re: norris race cam
« Reply #4 on: March 23, 2023, 12:44:53 pm »
Pe-We, Thanks for the info. ...  That RR cam seeme to be the one !  It's just what i want regarding power / torque.    Many thanks.
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Offline MRieck

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Re: norris race cam
« Reply #5 on: March 24, 2023, 01:49:59 pm »
Pe-We, Thanks for the info. ...  That RR cam seeme to be the one !  It's just what i want regarding power / torque.    Many thanks.
Similar to the Megacycle 125-60 which is a very good cam.
Owner of the "Million Dollar CB"

Offline mad mike

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Re: norris race cam
« Reply #6 on: March 25, 2023, 07:40:26 am »
  Thank you mike.
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Offline PeWe

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Re: norris race cam
« Reply #7 on: March 25, 2023, 10:08:08 am »
Important to find a good timing. That "cam card" does not have the important numbers. Only full lift and full duration.

In: open/close at 0 lash and 1mm lift (0.04").

Might be:
IN open same or near to EX close.
EX open same or near to IN close..

Only good if IN open is 2-4 degrees more than EX close.

Start to set it as a stock cam. The timing will tell how to move the adjustable sprocket.

I usually tighten the valve adjuster screw until the dial gauge needle start to move 0.02mm or so.

When 0 lash is done you can check at running lash.

I should check In/Ex at 0.10/0.15 mm. That lash work as advance of the cam.
« Last Edit: March 25, 2023, 10:24:34 am by PeWe »
CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Offline MRieck

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Re: norris race cam
« Reply #8 on: March 25, 2023, 04:05:42 pm »
Important to find a good timing. That "cam card" does not have the important numbers. Only full lift and full duration.

In: open/close at 0 lash and 1mm lift (0.04").

Might be:
IN open same or near to EX close.
EX open same or near to IN close..

Only good if IN open is 2-4 degrees more than EX close.

Start to set it as a stock cam. The timing will tell how to move the adjustable sprocket.

I usually tighten the valve adjuster screw until the dial gauge needle start to move 0.02mm or so.

When 0 lash is done you can check at running lash.

I should check In/Ex at 0.10/0.15 mm. That lash work as advance of the cam.
Per.....I just set the valve lash to what is stated. Getting that "zero" reading is really hard as you just never know how much you are preloading the the rocker arm. ;D  I recommend putting in the running lash and just subtract the # from the open and closing numbers. Take it from somebody who F'd around with brass sheets etc on shim /bucket arrangements to get "zero" lash. Use what you are running at.....that is the real number. ;D ;D ;)
Owner of the "Million Dollar CB"

Offline PeWe

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Re: norris race cam
« Reply #9 on: March 26, 2023, 06:37:25 am »
Important to find a good timing. That "cam card" does not have the important numbers. Only full lift and full duration.

In: open/close at 0 lash and 1mm lift (0.04").

Might be:
IN open same or near to EX close.
EX open same or near to IN close..

Only good if IN open is 2-4 degrees more than EX close.

Start to set it as a stock cam. The timing will tell how to move the adjustable sprocket.

I usually tighten the valve adjuster screw until the dial gauge needle start to move 0.02mm or so.

When 0 lash is done you can check at running lash.

I should check In/Ex at 0.10/0.15 mm. That lash work as advance of the cam.
Per.....I just set the valve lash to what is stated. Getting that "zero" reading is really hard as you just never know how much you are preloading the the rocker arm. ;D  I recommend putting in the running lash and just subtract the # from the open and closing numbers. Take it from somebody who F'd around with brass sheets etc on shim /bucket arrangements to get "zero" lash. Use what you are running at.....that is the real number. ;D ;D ;)
Fully agree Mike,
I'll do the 0 lash with adjuster pretightened, pass the lashes in valve train to see if it will be close to cam card numbers, lift especially.
Different cam holders and rocker arms have different lash which affect timing too.

The final running lash check to verify the balance in vs ex.

A good thing to have frame kit, possible to time cam again.
I have tried different timings on my 125-75 cam. I marked cam and sprocket with punchmarks when it was close to cam card.

A few degrees retarded or advanced relatively the best numbers reduced power rather much.
10whp less ( dull torque) as worst with cam retarded.  First run on dyno so no more runs needed at that visit.
Another dyno run with ca 3 degrees more advanced than best lost 5whp.
Last 2 dynos with +3whp. The only changes was main jets 2.5 step smaller and cleaned pods.

So the small adjustments can make a difference
« Last Edit: March 26, 2023, 07:57:32 am by PeWe »
CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Offline mad mike

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Re: norris race cam
« Reply #10 on: March 26, 2023, 12:46:33 pm »
Yet again gents.  , i thank you both, [Per and Mike] for your knowledge and kindness..   Best regards .   Mike.
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Offline bear

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Re: norris race cam
« Reply #11 on: March 31, 2023, 09:53:19 am »
Just a thought. If your using a 410 head it might be worthwhile double checking your compression numbers. You may struggle to achieve the  cylinder pressures your after with the larger combustion chambers.
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Offline mad mike

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Re: norris race cam
« Reply #12 on: April 02, 2023, 11:05:43 am »
 Thanks for the tip bear, I will check it, ....I'm not after building a GP bike , .... just a close copy of my old race bike.  but i do want it to be as good as finances [and my skills allow.]  thank you.  Mike.
BELIEVE NONE OF WHAT YOU HEAR, AND ONLY HALF OF WHAT YOU SEE.