2S Cam into an 850

I bought a 2S cam, but have not used it. My 850 motor is very strong between 5,500 RPM and 7000 RPM. If the 2S cam moved the power band up by 1000 RPM, I would lose half of my usable rev range. The most I ever see is 7,300 RPM. With the changed balance factor 8,000 RPM might be OK, but I never go there to find out.
I was watching a video this morning about Commando development in which a guy was revving his motor regularly to 8000 RPM. It split the drive side case through the bearing. The only thing which saved it was a steel ring which had been fitted around the outside of the bearing, and that was distorted.

I have to make that on-board video.

acotrel said:

I have to make that on-board video.

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Bucket list

You have no idea how the 2S cam works Al, yes it will run more freely above 7,000RPM but it also improver the torque and get up and go from 4,500RPM to 6,500RPMs the midrange is where the 2S cam works the best a lot better than a stock cam and the power delivery is so much smoother and quicker, why I like it so much, it just improves the whole power delivery through every gear, but then I just don't have a 2S cam working in my motor, its built to breath and come alive when I open that throttle up, it has no restrictions at all for a road going bike, running stock gearing.
If I was building my Norton for the track at the time I would have installed a 3S cam and different port and valve work on the advice of my high performance section in my workshop manual, remember I built this motor in 1980 and there weren't the cams around that are now available on the market these days.
The 2S cam was made for on the road performance gain.

Ashley

The 2s does not appear to be a profile for increasing the midrange.
From my reading, the performance cams all gain some top end at the expense of the middle, as compared to the stock SS type profile.
It's a trade off.
You could boost the CR to get some of that below 4500 rpm back. You can also do this with the stock cam and get an even stronger midrange. I'm running a stock cam at 9.8 to one static cr on the 920, no pinking.

Here are Jim Comstock's thoughts on the 2s in an 880.

"The 2S cam will be a little peaky. It will trade a bit of below 4500 rpm power for more power above 5000. Not a bad street cam if you ride in a sporting manner. The fact that the engine is larger does not mean the cam "comes on" earlier but the

fact that the engine is larger does make up for some of the lower RPM loss. It would likely be better on the street with some advance- maybe even up to about 10 degrees.

What I like to do when using the 2S or 4S on the street is grind a 4 inch radius on the lifters. That will give you the advantage of the extra lift without the losses you get with the long duration. That makes for a nice torquey street motor. Then install it with about 5 degrees advance. Jim"

The amount of advance needed on the cam can be affected by the exhaust system. I run my cam 12 degrees advanced to suit the 2 into 1 exhaust. The exhaust valve opens at about 92 degrees BBDC, The thing about this is, all the bits need to work together, but we usually only change one thing at a time. When you advance the cam to suit the exhaust system, it affects the jetting. The jetting, ignition advance and compression ratio are in balance to give the best combustion conditions. If the jetting is even only slightly too rich, the motor develops less power. When you run a 2 into 1 exhaust system, it affects the heat build-up in the motor. The whole thing becomes a juggling act.
Many years ago, I spent a lot of time modifying a 2 into 1 exhaust system to get it to work properly. It is easy to make a mistake if you have pre-conceived ideas.
Generally speaking, if you replace a standard cam with a race cam, and change nothing else, you will usually get better performance. But the increase in performance can come from the leaning-off effect from the change in the relationship of the cam with the exhaust system. - Especially when you use petrol as fuel.
With Triumph 650s, the first Bonnevilles had an E3134 race cam on the inlet and an E3275 Tiger 110 cam on the exhaust. When the E3134 is used for both, you got the distinct power band. One of my mates had a 1963 Bonneville - we imported the E3134 profile cam for the exhaust and the bike became much faster. The cam had a different number because of the points extension. But the exhaust cam made a significant difference. A standard Commando cam is close in timings to a Triumph E3134 race cam. The whole thing is about resonance - with a race cam, you can usually feel the difference when it comes on song. It is a matter of sensing where the power band is and gearing and jetting to suit it.

I suggest the main thing is, whatever cam you use, for best performance everything needs to be optimised. I have changed cams in lots of bikes, but did not think much about what the interactions might be. There is nothing more frustrating than being in a road race and some person with a standard looking and sounding bike blows you to the weeds.

Well I do know my own Norton and the 2S cam did liven my motor up between 4,500 to 7,000 RPMs in a big ways, it will run freely after 7,000RPMs but why, no need too on a street bike, but as I say it's not only the cam that works in my motor and each motor is different in how it performs, what works well in my motor might not work for others, but I have always said my Norton is a freak, for the first few years from new I had a lot of problems with ignition and carbs and nearly sold it from these problems but once I built it for the Featherbed frame and did the work on the motor for the Featherbed as well performance upgrade it woke the Norton up and it became a very reliable bike since the conversion from 1980 till today, it surprises a lot of modern bikes and get me up in the ranges and tight twisties, no one gets the better of my Norton.
I have clocked up more miles than all my mates in the time it was an everyday rider, and now with the Joe Hunt maggie and rebuilt old Amals it has made it even better, that big spark has liven it up even more.
I love my 1200 Thruxton which has taken over most of my full time riding but my Norton is still my favorite fun bike, it gets a lot of attention when out whether parked up it always gets lookers and even riding always get the thumbs up, its no show pony and is showing its age but its aged well and only minor things have let me down, but the motor and GB I have never had a problem and its always has from new been oil tight, I think the oil and STP mix has helped my motor live a long happy life.

Ashley

If your featherbed Commando handles, you must have the motor in the right place. With many featherbed hybrids, the motor is often about an inch back from the front frame mounts, because it looks better. When you are in a corner, if there is not as much weight on the front, a featherbed bike can help you lose confidence, because of the way it feels. A Manx Norton has about as much trail as you can get with the featherbed frame, and the weight is very well forward. When you are in a corner with it, if you get off line, you just give it more gas, and the Manx does the right thing - it steers in the direction you want to go. If the weight is further back, the bike can feel light and airey, and understeer.
There was a theory that the best motor in the best frame should give you the best bike - it is not correct. Most bikes do not do what a Manx Norton does. Japanese bikes do not usually self-steer in corners when you gas them - they either stay neutral or understeer.
Most guys do not grab a handful of throttle mid-corner, while on a lean. They probably do not identify the transition point in the corner. What you see when you watch racing, is not what you get.

Al my Commando motor is as forward as it can get in the Featherbed frame with the motor tilted, my mate who got me into Nortons and Featherbed frames, his 750 Commando motor in his Featherbed frame was mounted upright like the Dommies were, my mate Don made a lot of mistakes when he built his Commando/Featherbed his crank was lighten and polished, in fact a bit too much which didn't do any good performance wise and the balance factor was a bit wrong and effected the handling, after he sold me one of his Featherbed frames he proceed to build Tritons instead, so he gave up using Norton motors.
You can't just jump on a Commando/Featherbed and push it, you got to learn how to ride it and how it handles, it took me about 2 months to really start to push mine, you don't steer the Featherbed if the motor and frame are set up right it will get you through the corners without effort at all from the rider, I hardly use my brakes when out, I slow the bike down before the corner then once in the corner I open the throttle and put the power down and the Featherbed does it magic and even better with a motor that will bring that power up quick as mine does, the rider is just along for the ride and sometimes I got to look back and think, did I just power through that corner, it's hard to explain but it's like I am riding on rails, with the torque of the motor, frame, good suspension, tyres and being a light weight build as well a very experienced rider who knows his bike, it amazes me every time I ride it and the cam and work done inside my motor as well built for the Featherbed frame, what I done I did everything right, everything is set up the way I built it back in 1980, why change anything when it already is right, the only thing I have done in over the 40 years I built it is to add upgrades like Lansdown internals in the front end, full front brake upgrade, make the bike even lighter and the best of all that Joe Hunt magneto, was worth the money for the best spark ever and I don't care what others think about the JH hanging off the side of my motor as it works so well there and not stuck behind a hot motor.
Al you make a lot of comments about Featherbed frames and all but really you have never owned one and how many have you ever rode or built for that matter, none I bet, well not one that has a hot 850 motor in it and build for perfect handling as well lots of torque and you just don't hop on a Featherbed and push it to it limits straight away as you got to take your time to learn to ride it, get to feel the bike, let the frame and motor do all the work and enjoy the ride as I have done for the last 40+ years of riding my hotrod 850 Featherbed, puts a smile on my dial like no other bike has, I love my modern Thruxton but my hotrod Norton is my life, built by my own hands and will be with me till the day I die, it's such a great handling bike and does everything right for me, love it.

Ashley

I like the blue. Is that a stock Norton colour?

Glen

worntorn said:

I like the blue. Is that a stock Norton colour?

Glen

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Hi Glen, no my mate owned a car panel repair shop at the time and his painter at the time was a member of the Rebels MC and a very talented painter/air brusher, my mate did the paint job for no charge and was the colour I wanted, I always loved blue, it was painted over 30 years ago now and is showing its age, has scratches, chips and a little bit of paint flaking off around the filler cap, hence the two British flag stickers on both side of the tank the one you can't see is right beside the filler cap and protects the flaking paint, when the tank was being painted I say the painter didn't prep the area around the filler cap very good.
It's an original 1957 Wideline Featherbed tank and it's been damaged long before I got the frame and tank back in 1979 the tank is full of Bog (body filler), love to replace it but I love the shape of it and they are hard to find one that is any good, so I use what I have.
Originally when I did the conversion back in 1980 another painter mate did the frame and the tank was painted Gum Metal Grey, but the great fire of 1983 melted that and I rode the Norton around after the fire with a charcoal and fire damage tank, it was a real rat bike for a few years before it was repaired and new blue paint job.
Lesson, don't run velocity stacks with no air filters and have a leaking petrol tap, back fired through the carb and up she went while I was on it, did top end damage more than anything, tank, seat, wiring and melted speedo face, I had it rewired next day but had to wait a week for the seat to get repaired and the following week 100 miles from home the Boyar black box decider to shit its self from the fire, the GMG paint job was only on the bike for 6 months,
nearly lost my Norton from that fire, but lucky the tank wasn't bolted down and able to pull it away from the bike when the fuel lines melted, to this day my tank is still not bolted down.

Ashley

Looks the same colour as mine. Mine is a Ford colour. Which is about all I can remember !

Yes it does look to be the same as your bike Nigel. I have a similar colour on my BSA . They all look great to my eye.
I once rode the BSA into a big building where it was part of the bike show. One of my clubmates, who was judging there, shouted " Oh God I hate that blue on an A10!" And he meant it! The BSA did not win anything other than a few admiring looks from people who did not hate the colour.

The judges own A10 is a drab green with a fair number of big runs in the tank paint, his own backyard spray can paintjob.
There is no accounting for taste or the lack of any functioning brain filter on us old guys!
I found the photo from that show. This fellow looks happy to see the old A10. I chatted with him a bit, he had fond memories of his A10 Road Rocket he owned when those were new. Too bad he wasn't a show judge, I might have had a chance! Back to regular 2s cam programming

ASHLEY, I learned to race on a Triton. It sounds as though you have your featherbed commando set up properly - most guys get it wrong. The problem with handling is you have to be stupid to find out when you have it good. Most guys do not recognise the transition point in corners. When it moves back, you can power through the corner, but how do you know it has moved back unless you get stupid and gas the bike really early? When you gas the bike, it rotates fore and aft around it's centre of gravity, that steers the bike, and makes the difference between understeer and oversteer. When the bike oversteers, you can really gas it hard in corners, where normally it would run wide. Neutral handling bikes usually oversteer slightly if you gas them mid corner, If you get into a corner too hot, it is normal to trail brake then pick a spot where you are going slow enough, the get back on the gas.
Most road bikes are built to be safe, so have neutral handling. PW found that out with the the first Commandos - race steering is not for road bikes. The rider adjusts to the bike.

Alan, I don't have a Featherbed Commando. Ashley does though.

Glen

worntorn said:

Alan, I don't have a Featherbed Commando. Ashley does though.

Glen

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Sorry, I have just fixed it.

acotrel said:

ASHLEY, I learned to race on a Triton. It sounds as though you have your featherbed commando set up properly - most guys get it wrong. The problem with handling is you have to be stupid to find out when you have it good. Most guys do not recognise the transition point in corners. When it moves back, you can power through the corner, but how do you know it has moved back unless you get stupid and gas the bike really early? When you gas the bike, it rotates fore and aft around it's centre of gravity, that steers the bike, and makes the difference between understeer and oversteer. When the bike oversteers, you can really gas it hard in corners, where normally it would run wide. Neutral handling bikes usually oversteer slightly if you gas them mid corner, If you get into a corner too hot, it is normal to trail brake then pick a spot where you are going slow enough, the get back on the gas.
Most road bikes are built to be safe, so have neutral handling. PW found that out with the the first Commandos - race steering is not for road bikes. The rider adjusts to the bike.

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I get embarrassed when I look at these old photos.

Al I know how to slow my Norton down as I come into a corner without using my brakes and I know when to put the power on when in the corners, been doing it on the Featherbed for over 40 years, remember I do ride it all the time, it's not a sit in the shed bike and talk about when I use to race.
As for Tritons, I am not a fan of them although my mate Don who got me into Nortons and Featherbed frames, he became a turn coat to Norton's when I built mine, he built hi compression Triumph race motors and wonder why he kept blowing them up when out on the track, his thinking was higher the compression the more power they produced, we are still mates and every time he comes around he still shakes his head in how reliable and how well mine runs and the simplify of how everything is set up.
I think he realized he should have kept with the Commando motors, it's only took him 40+ years to admit he made a lot of mistakes.

Ashley

Back to the 2S cam... At the end of this riding season my ageing right knee began to complain about starting my Atlas. It has a Commando top end and bearings. That's 9:! compression IIRC. It also has the stock Atlas cam again if I remember correctly. Making it an E-start is not an option but perhaps a longer duration cam is along with a T-160 KS lever.

The primary drive has held up well over the years ( I had it apart to fix the side-stand lug last summer and a new alt. rotor) so I'm not afraid of a few more ponies that I might never use. I'm wondering if y'all think it would be worth the effort to change cams for easier starting. I have a spare 2S cam. Maybe just the T160 lever would do the trick. I also have factory Atlas mufflers with the ends cut out of the baffles. They look a bit shabby and I look at those Goldie repops and wonder how they perform... How 'bout Commando pea-shooters? What's involved in putting those on an Atlas frame to match a 2S cam?

I have the rest of the winter to work on it so time isn't an issue except for the Honey-do lists that seem to grow.