Bob's 920 Special 666
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I'm on the steve maney site now. I contacted my server and they got it up for me. Just had to unplug my modem, reboot and plug back in. It took all night to re connect to the net but this morning all is well.
The only thing I can figure is my banker had it blocked. My visa card won't work on the site but at least I can look at the pictures.
The only thing I can figure is my banker had it blocked. My visa card won't work on the site but at least I can look at the pictures.
Looks like the lightweight crank question has been covered. I'll just have to wait until it's on the road before I can find out - in my head I can remember what my old Commando pulled like; but memories......... you know! I'm just keeping my fingers crossed that all the changes I am making won't un-Commando my Commando too much.
Splatt did make a good call on the honing. When I had a close look, I could see no evidence of cross-hatching, so I took the barrels off to Pete Lovell who did the work originally. He reckoned the bores had been honed, but he was more than happy to do them again - mmmmmm, I don't have the knowledge to argue, what do you think? Anyway, they are done, so will be picking them up tommorrow and can then check out the followers and valve clearance.
This is the head as it stands - a bit embarrassing compared to the perfection of Chucks Combat, but my aims were a little different when I set out on the project. First, the bigger valves and machining to match the 920 pistons. The combustion chambers have just been cleaned up.
The picture above and those below show just how awful the castings are (and the limitations of my little digital camera) and how they spoil the nice work done on the inlet and exhaust ports.
The exhaust port shot shows the worst of the defects.
So now my questions. Firstly, I was considering cleaning up the rockers. I don't really have the equipment to polish them, but I would be able to clean off casting marks and such like and be able to produce a fairly smooth finish. Does anyone have a view? Is it worth the effort, or may I do more harm than good?
Secondly, can anyone offer guidance on permissible wear on rockers/shafts(spindles). There is clear wear on my shafts - not much, but can be detected with a fingernail - and, with rockers in position, a small amount of play can be felt. Some figures may help - I have a micrometer to check O.D., but nothing to accurately check the I.D. of the rocker bores.
Cheers, Bob
Splatt did make a good call on the honing. When I had a close look, I could see no evidence of cross-hatching, so I took the barrels off to Pete Lovell who did the work originally. He reckoned the bores had been honed, but he was more than happy to do them again - mmmmmm, I don't have the knowledge to argue, what do you think? Anyway, they are done, so will be picking them up tommorrow and can then check out the followers and valve clearance.
This is the head as it stands - a bit embarrassing compared to the perfection of Chucks Combat, but my aims were a little different when I set out on the project. First, the bigger valves and machining to match the 920 pistons. The combustion chambers have just been cleaned up.
The picture above and those below show just how awful the castings are (and the limitations of my little digital camera) and how they spoil the nice work done on the inlet and exhaust ports.
The exhaust port shot shows the worst of the defects.
So now my questions. Firstly, I was considering cleaning up the rockers. I don't really have the equipment to polish them, but I would be able to clean off casting marks and such like and be able to produce a fairly smooth finish. Does anyone have a view? Is it worth the effort, or may I do more harm than good?
Secondly, can anyone offer guidance on permissible wear on rockers/shafts(spindles). There is clear wear on my shafts - not much, but can be detected with a fingernail - and, with rockers in position, a small amount of play can be felt. Some figures may help - I have a micrometer to check O.D., but nothing to accurately check the I.D. of the rocker bores.
Cheers, Bob
ntst8
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splatt said:
I'm not an expert (as some of my recent queries show) but i would have thought that the weight of the crank won't affect how much torque the engine produces - that would only be related to combustion chamber design and the bore/stroke.
What it does is reduce the rotational inertia so that the engine can spin up more easily for a given torque/power output, but also will then have less rotational momentum at speed so will slow down more easily when off the throttle or hit a wind gust or start to run up hill. The latter may or may not be so good on a road bike but i would sure love to have the spare $ to give Mr Maney and find out.
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hi bob v regarding rockers get as much weight off the ends as you can then polish them,regarding wear on the shafts if you can detect it with a finger nail you,ve got at least half to one thou wear,as was said earlier it wont affect function but will affect pressure,and too much oil in the head means less where its needed most (crank) regarding cam followers are they new,if not they will ruin the maney cam,ask steve to grind them,what push rods are you using and what valve springs are you using , looking at the pics the top collars are,nt std , get maney valve spring and titanium top collars and push rods,going back to rocker oiling i prefer the scrolled shafts and the feed off the return side of the pump but thats my preference,having spent a lot of money on the bottom end its not worth scrimping on the top is it, its obvious to me that this bike is not being built for thousands of miles of cruising,its being built to get from A to B as quick as poss good luck and keep us informed
According to my 72 -750 manual the 750
rocker bore is .4998/.5003in. or 12.694/12.708mm.
rocker shaft is .4988/.4985in. or 12.694/12.669mm.
I'm not sure if it is the same on the 850 but I'd think so.
Polishing the rockers won't do anything like Ludwig pointed out but lightening them will help. A lightened valve train aids response of the valve springs. Although Norton rockers have fairly centrally located spindles mass moment inertia is another effect created by reciprocating masses which can be lessened with lightening. Here is a quote out of an old hot rod mag.:
Mass Moment Of Inertia
"Mass moment of inertia is the relationship between the center of gravity of an object with irregular geometry and the rotational axis. The Mass Moment of Inertia of a solid measures the solid’s ability to resist changes in rotational speed about a specific axis. The larger the Mass Moment of Inertia, the smaller the angular acceleration about that axis for a given torque. The further the center of gravity is from axis of rotation, the higher the mass moment of inertia. The higher the mass moment of inertia, the more spring pressure needed to control the rocker arm instead of the valves. For example, every gram that is removed from the nose of a rocker arm (lower mass moment of inertia) operation RPM goes up significantly."
I've enlightened several sets of rockers but until now have never had the benifit to compare notes (thanks to the internet). Hence I always played it safe and just took off the obvious. The weak spot is where the arm meets the end so I just polished that area and then filed off high spots toward the spindle area from that reference. Even though they are already the smallest area the ends are where lightening or removing meat will be most effective. I've always played it fairly safe and never gone too radical so it would be nice to compare photos with anyone who has. I've never had one break on me either though. All work was done with files and emery cloth by hand.
Any little blemishes you see are the original surface as I wanted to stay safe and only removed the obvious. Taking out material to below that level would allow much more metal to be taken off all over. Maybe the next set I do I'll push the envelope a bit more.
I also lightened the lifters but I don't have a set that's easy to photograph. It is generally understood that enlightening the valve train adds RPMs. I'm a bit of a chicken though and always try to shift at 7000. There have been times when I was caught up with other things though and shifted around 7200-7300 and she was still pulling strong. And there have been many times I've looked down at the tach after a shift and saw it counting down from around 7500. I've never had my bike on a dyno but that would be the way to test for sure.
Did you radius your lifters? Most high performance cams require a slight radius on the lifters.[/b]
rocker bore is .4998/.5003in. or 12.694/12.708mm.
rocker shaft is .4988/.4985in. or 12.694/12.669mm.
I'm not sure if it is the same on the 850 but I'd think so.
Polishing the rockers won't do anything like Ludwig pointed out but lightening them will help. A lightened valve train aids response of the valve springs. Although Norton rockers have fairly centrally located spindles mass moment inertia is another effect created by reciprocating masses which can be lessened with lightening. Here is a quote out of an old hot rod mag.:
Mass Moment Of Inertia
"Mass moment of inertia is the relationship between the center of gravity of an object with irregular geometry and the rotational axis. The Mass Moment of Inertia of a solid measures the solid’s ability to resist changes in rotational speed about a specific axis. The larger the Mass Moment of Inertia, the smaller the angular acceleration about that axis for a given torque. The further the center of gravity is from axis of rotation, the higher the mass moment of inertia. The higher the mass moment of inertia, the more spring pressure needed to control the rocker arm instead of the valves. For example, every gram that is removed from the nose of a rocker arm (lower mass moment of inertia) operation RPM goes up significantly."
I've enlightened several sets of rockers but until now have never had the benifit to compare notes (thanks to the internet). Hence I always played it safe and just took off the obvious. The weak spot is where the arm meets the end so I just polished that area and then filed off high spots toward the spindle area from that reference. Even though they are already the smallest area the ends are where lightening or removing meat will be most effective. I've always played it fairly safe and never gone too radical so it would be nice to compare photos with anyone who has. I've never had one break on me either though. All work was done with files and emery cloth by hand.
Any little blemishes you see are the original surface as I wanted to stay safe and only removed the obvious. Taking out material to below that level would allow much more metal to be taken off all over. Maybe the next set I do I'll push the envelope a bit more.
I also lightened the lifters but I don't have a set that's easy to photograph. It is generally understood that enlightening the valve train adds RPMs. I'm a bit of a chicken though and always try to shift at 7000. There have been times when I was caught up with other things though and shifted around 7200-7300 and she was still pulling strong. And there have been many times I've looked down at the tach after a shift and saw it counting down from around 7500. I've never had my bike on a dyno but that would be the way to test for sure.
Did you radius your lifters? Most high performance cams require a slight radius on the lifters.[/b]
Yes Bob,just polishing you rockers will do more harm than good because you remove the outer skin which imparts a certain strength, you can restore by shot peening after polishing and lighting,it recompresses the surface and removes small surface imperfections.If the man said those barrells were honed I think you should have tried someone else.You should end up with with a nice even 120 degree ,approx, cross hatch.Don't believe the crap about needing a course hone,if you run it in properly,ie dont ride it like limp wristed wus chugging around at 2500rpm in top gear,most ring manufactures post run in procedures.Post a photo when you get them back.
To everyone who answered my last couple of queries, thanks for your efforts, they are very much appreciated. Really liked your illustrated photos RennieK, thanks.
Chris and Ludwig, thanks for the insights regarding oil pressure and rocker shaft clearance. I had not considered this at all, so new shafts are a distinct possibility for the final build of the top-end. Chris - give me a little credit :wink: , those valves you see are Maney supplied racing quality, same for the springs and titanium collars. The followers, of course, are new - typically, the followers that came out of the donor bike were odd pairs. Not two different pairs, but two different followers making up a pair! I am sticking with standard pushrods for the time being. I won't be ripping its nuts off at every opportunity and it will be doing plenty of touring miles, but I also want to be able to use its full performance and not be scared about it breaking/falling apart.
Regarding the cam/followers. Consensus in the heart of Norvil land (I live only a few miles from the luscious Les Emery), is that the Maney cam is essentially a 4S and there is no need to radius the followers for this cam - something to do with lack of quietening ramp, although I don't want to open a can of worms here. Anyway, I have the barrels back, so I may as well bog off and start trial fitting the thing together; now where is that plasticine and engineers' blue?
Cheers, Bob
Chris and Ludwig, thanks for the insights regarding oil pressure and rocker shaft clearance. I had not considered this at all, so new shafts are a distinct possibility for the final build of the top-end. Chris - give me a little credit :wink: , those valves you see are Maney supplied racing quality, same for the springs and titanium collars. The followers, of course, are new - typically, the followers that came out of the donor bike were odd pairs. Not two different pairs, but two different followers making up a pair! I am sticking with standard pushrods for the time being. I won't be ripping its nuts off at every opportunity and it will be doing plenty of touring miles, but I also want to be able to use its full performance and not be scared about it breaking/falling apart.
Regarding the cam/followers. Consensus in the heart of Norvil land (I live only a few miles from the luscious Les Emery), is that the Maney cam is essentially a 4S and there is no need to radius the followers for this cam - something to do with lack of quietening ramp, although I don't want to open a can of worms here. Anyway, I have the barrels back, so I may as well bog off and start trial fitting the thing together; now where is that plasticine and engineers' blue?
Cheers, Bob
Sorry to open a can of worms but I'm just trying to be helpful. On the Maney web site it says:
Also in my little gold mine of parts recovered from 25 years ago is my brand new 4S cam. I came across the original invoice for this a while ago and although the invoice was for a Norvil 4S cam the cam I got back in 72 was a Dunstall 4S cam. Here is part of the instructions:
Check the price difference on regrinding the followers between this and the Maney site. (4LB vs 40LB) Do you think this is a typo? hehe, These instructions were printed August 71.
It could well be that the concensus amongst the folks up in Norvil land have found through experience this "premature wear" is insubstantial and grinding a radius is not necessary but these two sources indicate otherwise. I'd like to find out more before I drop the funds for this mod.
Rennie,
All "proper" norton race cams i.e. 2S, 3S and 4S as well as the PW3 were designed to use flat followers. I use a different cam which was also designed for flat followers, and in 30 years racing I have never had cam or follower wear, despite using heavy valve springs and revving to 8000rpm!
Some other cams (all Dunstall, some Megacycle for example) were designed to use radiussed followers. Maney cams are designed to run with flat followers
All "proper" norton race cams i.e. 2S, 3S and 4S as well as the PW3 were designed to use flat followers. I use a different cam which was also designed for flat followers, and in 30 years racing I have never had cam or follower wear, despite using heavy valve springs and revving to 8000rpm!
Some other cams (all Dunstall, some Megacycle for example) were designed to use radiussed followers. Maney cams are designed to run with flat followers
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hi rennie,i was not aware that dunstall called his cam a 4s, the timings of the cam you posted are different to my 4s cam,cant remember exactly but my inlet timings are 65 open btdc 89 close abdc and the exaust is something like 89 bbdc and 60 atdc with 16 thou clearance for checking and 16 thou running on inlet and exaust and the recomended flat faced followers ,i do know that dunstalls 810 big bore kit used a65 type followers which were radiused ,i dont know the timing details for the maney cam but i am led to believe it is his development of the original norvil 4s cam refined over the years on the dyno.so if yours is a genuine dunstall cam that requires radiused followers then thats what you should do,i dont think there is a wear issue with flat versus radius ,its to do with valve acceleration and flat followers accelerate the valves quicker
Thanks for explaining and getting me back on track. I was reading too much into the Maney site thinking regrinding meant radiusing rather than just "new cam = new followers or regrind".
Wish I'd bought the radiused followers too back when I bought the cam
Wish I'd bought the radiused followers too back when I bought the cam
Thanks again for the extra info. However, both minor and major problems attempting to hinder my progress!!! Prior to getting around to fitting them, I had only unpacked one of the two pairs of followers - they were fine, but look at these:
I was told 'nothing unusual' and 'they are fine'. Anyway, I made them change that pair - I don't think there would have been anything wrong with the security of the Stellite pad, but (not shown well in the photo) there is a proper open edge between the excess brazing metal and the pad. Just looked like another piece of metal that could have ended up in the oil, so why risk it? So no dummy fit of the top-end over the weekend, but I thought I would try the barrels for size..........this is when I got really pissed off!!!
The joys of building a special I expect, but the sleeves would not fit into the apertures in the Maney cases. I had fitted all the studs, and at first thought that that was the problem, so took them out but no way would the barrels come close to sliding in. The sleeves are the correct diameter, I doubt if the CNC machining is wrong on the cases and so I am left with the actual position of the sleeves being skew. I reckon mine was a 'Monday morning' job or one left to the apprentice to practise his skills on. Anyway, with the missing honing and a few other problems in the past, I've decided where my confidence lies. It is of course possible, that the tolerances are greater on the standard cases and the barrels would fit without any problem.
So, what to do? I could only see a long drawn out process if I tried to apportion fault, as each could blame the other ad infinitum, while my project dragged on and on. There was no chance that I would try and hog out those lovely cases, and pretty costly to have everything properly measured and accurately machined. Added to this, every Norton specialist seems to be up to their eyes with work and I may have ended up with a pup anyway. So, you guessed it, I have gone way below the depths of my pockets and will soon be the proud (and highly annoyed) owner of a set of Maney alloy barrels. When I called, he had just finished a batch so I thought I'd better strike while the iron was hot and before they all got shipped off to the States :lol: - I remember with affection, the days when CNW stuff seemed a snip :cry:
I was told 'nothing unusual' and 'they are fine'. Anyway, I made them change that pair - I don't think there would have been anything wrong with the security of the Stellite pad, but (not shown well in the photo) there is a proper open edge between the excess brazing metal and the pad. Just looked like another piece of metal that could have ended up in the oil, so why risk it? So no dummy fit of the top-end over the weekend, but I thought I would try the barrels for size..........this is when I got really pissed off!!!
The joys of building a special I expect, but the sleeves would not fit into the apertures in the Maney cases. I had fitted all the studs, and at first thought that that was the problem, so took them out but no way would the barrels come close to sliding in. The sleeves are the correct diameter, I doubt if the CNC machining is wrong on the cases and so I am left with the actual position of the sleeves being skew. I reckon mine was a 'Monday morning' job or one left to the apprentice to practise his skills on. Anyway, with the missing honing and a few other problems in the past, I've decided where my confidence lies. It is of course possible, that the tolerances are greater on the standard cases and the barrels would fit without any problem.
So, what to do? I could only see a long drawn out process if I tried to apportion fault, as each could blame the other ad infinitum, while my project dragged on and on. There was no chance that I would try and hog out those lovely cases, and pretty costly to have everything properly measured and accurately machined. Added to this, every Norton specialist seems to be up to their eyes with work and I may have ended up with a pup anyway. So, you guessed it, I have gone way below the depths of my pockets and will soon be the proud (and highly annoyed) owner of a set of Maney alloy barrels. When I called, he had just finished a batch so I thought I'd better strike while the iron was hot and before they all got shipped off to the States :lol: - I remember with affection, the days when CNW stuff seemed a snip :cry:
If the two back holes are the same size then you can see one sleeve looks about 1/2 mm closer to the hole than the other one,that may have been within original tolerance,or even rebored offset before,most boring bars only set up off the old bore. One of maneys 1000cc kit must be pissing you off right now.
Hi Bob,
Sorry to hear the bad news....but now you'll understand why I refuse to deal with Les Emery......I had LOTS of faulty, badly made parts from him, lots of arguments and just rudeness! By the way, these weren't faulty genuine Norton parts, rather the " special" stuff he did....vernier cam sprockets that were eccentric to the centres so you couldn.t set the cam chain etc, etc!
Sorry to hear the bad news....but now you'll understand why I refuse to deal with Les Emery......I had LOTS of faulty, badly made parts from him, lots of arguments and just rudeness! By the way, these weren't faulty genuine Norton parts, rather the " special" stuff he did....vernier cam sprockets that were eccentric to the centres so you couldn.t set the cam chain etc, etc!
Splatt - tell me about it!!! :evil: :cry: I had also noticed the slight differences in hole spacings from the sleeves, which are a little less than they look in the photo, but there all the same. I too thought 'should be within tolerance'.
Thanks Seeley. I have dealt with Les since he was trading as Fair Spares in Rugeley and I find it very convenient to just nip up the road to get the odd bit that I have overlooked. There is no way that I will argue with your sentiments or views - for example, what a change and delight it is to chat to Angie Hemmings when making an order or to discuss technical issues with Matt at CNW. It was a difficult decision to use Norvil for the 920 conversion - I really wanted to use Maney barrels and pistons, but didn't have the cash at the time - and it was convenience that swung it, as I didn't fancy posting off a set of barrels! I have to say that my heart sank with the first thing they did wrong:
I had already returned a set of Norvil fork sliders because the quality of the casting was diabolical and the words 'here we go again' were still running around my head, when I was presented with my old cam followers, which I had left in the barrels to be checked and refaced if they were still OK. They had refaced them and then discovered that they were made up of two (or three) types of follower and one mismatched pair. To add insult to injury, they expected me to pay for the refacing work, despite the mismatching being obvious to a five year old - one follower did not have an oil groove and the inner sliding surfaces were completely different shapes. To add further insult to further injury, I was kept waiting for months and months while the work was being done and left to chase up the machining work myself (they very kindly gave me the phone number). I won't reveal the reasons given for the delay, let's just say that this was when my opinions were confirmed :!:
:cry: I had also noticed the slight differences in hole spacings from the sleeves, which are a little less than they look in the photo, but there all the same. I too thought 'should be within tolerance'.Thanks Seeley. I have dealt with Les since he was trading as Fair Spares in Rugeley and I find it very convenient to just nip up the road to get the odd bit that I have overlooked. There is no way that I will argue with your sentiments or views - for example, what a change and delight it is to chat to Angie Hemmings when making an order or to discuss technical issues with Matt at CNW. It was a difficult decision to use Norvil for the 920 conversion - I really wanted to use Maney barrels and pistons, but didn't have the cash at the time - and it was convenience that swung it, as I didn't fancy posting off a set of barrels! I have to say that my heart sank with the first thing they did wrong:
I had already returned a set of Norvil fork sliders because the quality of the casting was diabolical and the words 'here we go again' were still running around my head, when I was presented with my old cam followers, which I had left in the barrels to be checked and refaced if they were still OK. They had refaced them and then discovered that they were made up of two (or three) types of follower and one mismatched pair. To add insult to injury, they expected me to pay for the refacing work, despite the mismatching being obvious to a five year old - one follower did not have an oil groove and the inner sliding surfaces were completely different shapes. To add further insult to further injury, I was kept waiting for months and months while the work was being done and left to chase up the machining work myself (they very kindly gave me the phone number). I won't reveal the reasons given for the delay, let's just say that this was when my opinions were confirmed :!:
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