Engine build prep (2014)

worntorn said:

Fullauto said:

What about under three grand? What shape is the curve?

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Power curve under three grand? Doesn't much matter on a Commando as long as it runs from idle to 3 k. Three thousand and up is the isolastic zone, below that is the paint shaker zone best avoided whenever possible.

The Rider's manual tells you to shift down when forced to go slow so that revs are back in the smooth zone above 3 k.

Glen

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Accepted wisdom. Mine doesn't shake . It's fairly smootn through the rev range. o to three thousand RPM is where my bike is generally used in traffic. Its important where the power starts.

Yours must be quite different from most other Commandos if it is smooth at low rpm. Have you switched to light weight pistons perchance?

The isolastics are designed to start to work above 3 grand, not below. When designing the bike way back when, the designers tried for smooth from idle up only to discover that much vibration came back again at high rpm.
So harder rubber went in and the compromise was made, with the idea being that no-one spends much time below 3 k rpm. We get to put up with shakes below 3 so that it goes smooth from 3 to the redline. And my MK3 is smooth as glass in that range.

I do get stuck riding below 3 grand briefly in traffic now and then, but when that happens Honda 90 power would suffice.

For me, and i suspect a lot of other riders, 3 grand is low end, 4500-5500 is mid range and 6500 is shift time. Nigel's reworked engine would do nicely! :mrgreen:

But we all have different riding styles.

Glen

Fullauto said:

What about under three grand? What shape is the curve?

Click to expand...

Ken, under 3k the power is basically as before, with a slight rise as it gets close to 3k, but basically, as before. Sadly, I don't have the torque curve info, but I think that it is better than before, at least if my seat of the pants results are anything to go by.

Ultimately though, for me, on a street bike, the most important characteristic of the sub 3k engine performance is good manners, smooth running and fuss free 'ride through traffic' ability, so actually power output doesn't really come into it.

Being an old bloke, I tend not to use the rev range like I used to. Mine is extremely strong right off idle. I can shortshift a couple of times and then open it up and it pulls, hard. Personally, I like it that way. I was discussing this with Ben at British Imports and he agreed that mine was the best mannered, lightest steering, best handling Commando with the best engine characteristics he'd ever come across. A big call. But, I'll stand by it. So will he, I hope!

You obviously are young enough, and with the fire in the belly, to use the performance available, and enjoy it. As I get older I just don't need it. The steering is sweet and light. A Lansdowne conversion for the front forks, Ikon shocks on the back, and Avon Roadriders on the correct size rims and I defy anybody to ride it and disagree. I revved it to 6000 a couple of times but I just don't need to. I prefer the low end and mid range grunt available and let it whisk me along without any drama. I intend to do a lot of miles on this bike and treating it right is important to achieving this goal. I've done almost 6000 miles in about five months and I just can't get enough of it.

Unlike any modern bike, the Commando can be all things to all people. Depends how you build it and what bits you use.

worntorn said:

Yours must be quite different from most other Commandos if it is smooth at low rpm. Have you switched to light weight pistons perchance?

The isolastics are designed to start to work above 3 grand, not below. When designing the bike way back when, the designers tried for smooth from idle up only to discover that much vibration came back again at high rpm.
So harder rubber went in and the compromise was made, with the idea being that no-one spends much time below 3 k rpm. We get to put up with shakes below 3 so that it goes smooth from 3 to the redline. And my MK3 is smooth as glass in that range.

I do get stuck riding below 3 grand briefly in traffic now and then, but when that happens Honda 90 power would suffice.

For me, and i suspect a lot of other riders, 3 grand is low end, 4500-5500 is mid range and 6500 is shift time. Nigel's reworked engine would do nicely! :mrgreen:

But we all have different riding styles.

Glen

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I've had a couple of sets of isos now and they start out harsh (the Atlas Conversion as I call it) but then settle down after a few thousand miles. The only time I get noticeable vibes is a short band at about 2500 to 2800 through the footpegs. Everywhere else is nice and smooth. I don't know whether they use different compounds or what these days but that's the way it is. The 850 (MKII) I had in the 70s was very much like a light switch, Vibes to 3000 and then smoothness. I don't have lightweight pistons or a crank balance or anything else. Just attention to detail when it comes to setting it up. Really, it's taken me six months to get it how I like it mainly because when it comes to change something I do it to gain advantage in performance rather than looks. Function over form. Every time.
Mind you, I've never ridden two Commandos the same! They are all different animals.

Still, it looks pretty good. If anybody over my way wants to ride it, you are quite welcome to do so and put your findings up here.

worntorn said:

Yours must be quite different from most other Commandos if it is smooth at low rpm. Have you switched to light weight pistons perchance?

The isolastics are designed to start to work above 3 grand, not below. When designing the bike way back when, the designers tried for smooth from idle up only to discover that much vibration came back again at high rpm.
So harder rubber went in and the compromise was made, with the idea being that no-one spends much time below 3 k rpm. We get to put up with shakes below 3 so that it goes smooth from 3 to the redline. And my MK3 is smooth as glass in that range.

I do get stuck riding below 3 grand briefly in traffic now and then, but when that happens Honda 90 power would suffice.

For me, and i suspect a lot of other riders, 3 grand is low end, 4500-5500 is mid range and 6500 is shift time. Nigel's reworked engine would do nicely! :mrgreen:

But we all have different riding styles.

Glen

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Mines really quite quick, and a joy to ride now between 3,000 and 5,000. Which, as you say, is definitely 'mid range' to me.

But for absolute maximum speed, I need to change up at over 7,000, that way its still in peak power in the next gear, and so on. It has a more-or-less flat power output around 63-64bhp from 6300 to 7500. That's nice, and it makes it very easy to ride very quickly, and really, there'd be no real advantage in fitting a 5 speed box me thinks.

Obviously, one starts thinking about that stock crank flexing around in those stock cases when riding in this 'spirited' fashion... hence recent conversations with Mr Maney... and plans for the next iteration....!

Yep. A disintegrating crank doesn't bear thinking about. I'm sure your power delivery is addictive too. I'd better not!

Fast Eddie said:

Obviously, one starts thinking about that stock crank flexing around in those stock cases when riding in this 'spirited' fashion... hence recent conversations with Mr Maney... and plans for the next iteration....!

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Then there's the marginal gearbox with all that new found power coursing thru.....

worntorn said:

Fast Eddie said:

Obviously, one starts thinking about that stock crank flexing around in those stock cases when riding in this 'spirited' fashion... hence recent conversations with Mr Maney... and plans for the next iteration....!

Click to expand...

Then there's the marginal gearbox with all that new found power coursing thru.....

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Got that covered with the much lighter clutch and Maney outrigger (albeit the outrigger is currently sat on the shelf)!

Anyway, when are you sending that RH10 head sat on your shelf to sir Comnoz....?!?

Rather than mess with a nice running oil tight bike I might look for a project bike which would utilise a Jim modified rh10 and perhaps some other enhancements. I'm not sure that the head on it's own with an otherwise stock engine would be so effective.
I would also like to borrow some of Ludwig's ideas as spelled out in the 300 pound Commando thread. Too bad the photos have all been removed from that thread.

Glen

worntorn said:

Rather than mess with a nice running oil tight bike I might look for a project bike which would utilise a Jim modified rh10 and perhaps some other enhancements. I'm not sure that the head on it's own with an otherwise stock engine would be so effective.
I would also like to borrow some of Ludwig's ideas as spelled out in the 300 pound Commando thread. Too bad the photos have all been removed from that thread.

Glen

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You'd be surprised. Just the Fullauto head on mine made it a much more effective tool. I'm thinking of going back to a 23 tooth sprocket (from 22). With Jim's modified head I think you'd find the same. I was really impressed with Ludwig's bike too. A pity he doesn't post anymore.

worntorn said:

Rather than mess with a nice running oil tight bike I might look for a project bike which would utilise a Jim modified rh10 and perhaps some other enhancements. I'm not sure that the head on it's own with an otherwise stock engine would be so effective.
I would also like to borrow some of Ludwig's ideas as spelled out in the 300 pound Commando thread. Too bad the photos have all been removed from that thread.

Glen

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There are many wise folk on here who say all that's needed in a fast Commando engine is a stock Commando cam. So I'd guess it is capable of feeding a hotter motor. The porting work alone may only give a limited boost, but boosting the CR, plus perhaps getting the squish working, would come together as a noticeable improvement package I suspect.

A few folks on here also said that a PW3 was a waste of time when used with a single VM34 Mikuni too. And, that the cam wouldn't work without a healthy increase in compression. All I can say to that is........Ha!!!!

Fullauto said:

A few folks on here also said that a PW3 was a waste of time when used with a single VM34 Mikuni too. And, that the cam wouldn't work without a healthy increase in compression. All I can say to that is........Ha!!!!

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Hmm, but you didn't try a stock cam, with the same head / carb como. Might have been even better?!?

The argument about a big cam with stock CR is that the big cam loses some CR in use, so the 'effective CR suffers even If the 'measured CR' is good. This loss is due to the increased duration.

Your head has incredible velocity, more than my re-worked RH10. Maybe that exta high velocity prevents some of the effective compression loss of the big cam due to the force of the incoming charge?

I rode a mk3 once that had a single Mik, stock CR and PW3... and stock RH4 (one of the worst heads for velocity I believe)... it wouldn't pull the skin off a rice pudding !!

I took the bike for some more 'arse Dyno' testing yesterday.

On my usual 'test circuit' the Maney system felt worse than the peashooters, despite it showing a little more mid range power on the Dyno.

I know its rich, and it felt like it was not carburating correctly. So further experiments with that system will wit until I try mating it to the next iteration engine and dial in the carbs accordingly.

Until then, the peashooters and 1 3/8" pipes perform remarkably well, as Jim Comstock predicted they would.

Fast Eddie said:

Fullauto said:

A few folks on here also said that a PW3 was a waste of time when used with a single VM34 Mikuni too. And, that the cam wouldn't work without a healthy increase in compression. All I can say to that is........Ha!!!!

Click to expand...

Hmm, but you didn't try a stock cam, with the same head / carb como. Might have been even better?!?

The argument about a big cam with stock CR is that the big cam loses some CR in use, so the 'effective CR suffers even If the 'measured CR' is good. This loss is due to the increased duration.

Your head has incredible velocity, more than my re-worked RH10. Maybe that exta high velocity prevents some of the effective compression loss of the big cam due to the force of the incoming charge?

I rode a mk3 once that had a single Mik, stock CR and PW3... and stock RH4 (one of the worst heads for velocity I believe)... it wouldn't pull the skin off a rice pudding !!

Click to expand...

Nope, Apart from things like conical valve springs and coatings, the only thing changed was the cam.

I miss understood Ken, I assumed you had rebuilt the engine with cam etc and head at the same time.

Now I understand that you ran it with the head and stock cam etc... Then stripped it to replace the cam. Is this correct?

If so, can you give us a brief explanation of the before nd after experience?

Fast Eddie said:

Fullauto said:

A few folks on here also said that a PW3 was a waste of time when used with a single VM34 Mikuni too. And, that the cam wouldn't work without a healthy increase in compression. All I can say to that is........Ha!!!!

Click to expand...

Hmm, but you didn't try a stock cam, with the same head / carb como. Might have been even better?!?

The argument about a big cam with stock CR is that the big cam loses some CR in use, so the 'effective CR suffers even If the 'measured CR' is good. This loss is due to the increased duration.

Your head has incredible velocity, more than my re-worked RH10. Maybe that exta high velocity prevents some of the effective compression loss of the big cam due to the force of the incoming charge?

I rode a mk3 once that had a single Mik, stock CR and PW3... and stock RH4 (one of the worst heads for velocity I believe)... it wouldn't pull the skin off a rice pudding !!

Click to expand...

The main reason that I would rather build a complete Hooligan Commando than alter this almost stock MK3 is geographical.
I live in Vancouver and pretty much every big tour from here means mountain passes. This MK3 pulls really hard and makes no fuss on those. One of the big passes to the east is the Salmo Creston climb, 23 kms long in total with much of it at 8%. This is a grade where you will see modern cars pulled over with hood up, worried owner peering into the steam filled engine compartment. The RV people avoid it like the plague, it tends to incinerate their automatic transmissions.

My loaded MK 3 will pull up that entire grade holding 80 MPH at half throttle in top gear, no pinging, no fuss.
I have done it full throttle at 90 +. It left a somewhat modified Vincent 1000 behind on that pull. At first the Vincent just slowly dropped back, then it started to get some preignition and disappeared from mirror view.

I wonder if 10.5 to one CR and big cam that works great in the UK would be problematic on a hot day climbing one of these big grades?
I also wonder how much more I could or should get from the old bike . 80 MPH at half throttle climbing in the heat with full luggage on board seems pretty good. There isn't anybody going by.

There are no grades anything like this in the UK (not even Scotland) I think very little of this stuff in most of OZ.

Jim Comstock has the same sort of grades to deal with, in fact we ride some of the same US stuff ( Beartooth) I note that he has heat sensors on his modified engine to monitor the situation.

So the hooligan bike will be fun, but for those big Mountain passes I'll leave this MK3 alone, it just works so well now.



Glen

Fast Eddie said:

I miss understood Ken, I assumed you had rebuilt the engine with cam etc and head at the same time.

Now I understand that you ran it with the head and stock cam etc... Then stripped it to replace the cam. Is this correct?

If so, can you give us a brief explanation of the before nd after experience?

Click to expand...

I've actually done about 23,000 miles with my head now. My first production head (no 2). After the bad smash over four and a half years ago, the bike sat around, neglected for a couple of years while I regained interest, and cash to do the job. Basically, pre smash, it had my Fullauto head, porting untouched, along with standard size Black Diamond valves. The VM 34 Mikuni had been on since before my time with it, it had a standard cam and crank etc. It was described by a Norton mechanic as "strong" and left a long term Norton owner quite impressed. He couldn't believe it only had a single carb. He runs an 850 with a Gus Kuhn big valve head with 10 to 1 compression. Don't know what the cam is he uses. I was running a 23 tooth sprocket for some time, which was great for relaxed cruising on the highway, where it spent much of it's time in those days. It was a bit breathless when pulling back to 70mph from anything lower. Then, I went to a 22 tooth sprocket, which seemed ideal everywhere.

It was rebuilt with a reground crank, resleeved to standard bores, polished crank cheeks, rods and rocker gear etc. A Jim Comstock reed valve breather was fitted along with standard pistons, which were ceramic coated on the crowns and with teflon coated skirts. Combustion chambers, ports and valves were ceramic coated. Jim's conical valve springs were also fitted. The PW3 cam completed the engine work. The Mikuni was stripped, cleaned and refitted. I retained the 22 tooth sprocket which it pulls easily and I'm thinking of going back to a 23 tooth, which I think will be ideal. The motor is noticeably stronger now from idle on up and is a pleasure to use. No power steps, just good, meaty power to at least 5000 rpm, which is about all I use in most circumstances. Also, I get about 65MPG plus running around town. That's Imperial gallons. In it's last incarnation, 55 to 60 MPG max. I absolutely love it.

worntorn said:

Fast Eddie said:

Fullauto said:

A few folks on here also said that a PW3 was a waste of time when used with a single VM34 Mikuni too. And, that the cam wouldn't work without a healthy increase in compression. All I can say to that is........Ha!!!!

Click to expand...

Hmm, but you didn't try a stock cam, with the same head / carb como. Might have been even better?!?

The argument about a big cam with stock CR is that the big cam loses some CR in use, so the 'effective CR suffers even If the 'measured CR' is good. This loss is due to the increased duration.

Your head has incredible velocity, more than my re-worked RH10. Maybe that exta high velocity prevents some of the effective compression loss of the big cam due to the force of the incoming charge?

I rode a mk3 once that had a single Mik, stock CR and PW3... and stock RH4 (one of the worst heads for velocity I believe)... it wouldn't pull the skin off a rice pudding !!

Click to expand...

The main reason that I would rather build a complete Hooligan Commando than alter this almost stock MK3 is geographical.
I live in Vancouver and pretty much every big tour from here means mountain passes. This MK3 pulls really hard and makes no fuss on those. One of the big passes to the east is the Salmo Creston climb, 23 kms long in total with much of it at 8%. This is a grade where you will see modern cars pulled over with hood up, worried owner peering into the steam filled engine compartment. The RV people avoid it like the plague, it tends to incinerate their automatic transmissions.

My loaded MK 3 will pull up that entire grade holding 80 MPH at half throttle in top gear, no pinging, no fuss.
I have done it full throttle at 90 +. It left a somewhat modified Vincent 1000 behind on that pull. At first the Vincent just slowly dropped back, then it started to get some preignition and disappeared from mirror view.

I wonder if 10.5 to one CR and big cam that works great in the UK would be problematic on a hot day climbing one of these big grades?
I also wonder how much more I could or should get from the old bike . 80 MPH at half throttle climbing in the heat with full luggage on board seems pretty good. There isn't anybody going by.

There are no grades anything like this in the UK (not even Scotland) I think very little of this stuff in most of OZ.

Jim Comstock has the same sort of grades to deal with, in fact we ride some of the same US stuff ( Beartooth) I note that he has heat sensors on his modified engine to monitor the situation.

So the hooligan bike will be fun, but for those big Mountain passes I'll leave this MK3 alone, it just works so well now.



Glen

Click to expand...

My Norton spent nearly three years in the Pilbara region of Western Australia where a group of riders, including me and the Commando, would do a 300km round trip to Auski Roadhouse for a coke and a burger at any time of the year. In summer, this would mean leaving Tom Price mid morning with the temperature hovering around 48C. Then, as you went through East Munjina Gorge, it was like somebody had opened the oven door. This is no exaggeration. Temperatures get up over 50C. You certainly have to acclimatise and wear proper riding gear. If you wore a T shirt, the skin would be flayed off you.

The Norton never showed anything which indicated overheating, idling normally when you stopped.