Bob's 920 Special 666
- Thread starter BobV
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The Norton Domiracer of 1961 vintage used needle bearings on the cam. That was the same technology used in the commando with the oil through the rockers right from the pump. All that technology was sold to Paul Dunstall. He was a big fan of needle bearings on the Norton cams.
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did you read all of those instructions,what a lot of crap to get some theoretical advantage over a plain bush,now with the chance of the shaft bearing surface breaking up. Whats all that stuff cost, still using a bolt up crank as a performance item? seems a bit out dated to me,after an expensive incedent on my t160 I no longer like alloy rods.That photo of those barrels are they what you are goning to use,as they dont appear to have any crosshatch on the bores,could just be the photo.thats is sure some nice stuff though, isnt jealousy an ugly thing.
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Nice project. Thanks for sharing.
Gotta chime in on the roller bearings as well. Keith Johnson walked me through the discussion in minute detail. In short, the load bearing abilities of bushings is superior to needle rollers. He also said he's measured no difference whatsoever in power output between them.
I have to say that if a guy who builds some of the winningest and most durable brit bike motors says they provide no benefit and MAY be a liability, I leaning toward taking his advice.
On another issue, and while you've got all that cool stuff - don't forget to get yourself an automatic cam chain tensioner. Through-bolted heavy duty barrels are nice as well, but then you'd have to bore and sleeve a perfectly good set of new barrels... probably not what you want to do.
Gotta chime in on the roller bearings as well. Keith Johnson walked me through the discussion in minute detail. In short, the load bearing abilities of bushings is superior to needle rollers. He also said he's measured no difference whatsoever in power output between them.
I have to say that if a guy who builds some of the winningest and most durable brit bike motors says they provide no benefit and MAY be a liability, I leaning toward taking his advice.
On another issue, and while you've got all that cool stuff - don't forget to get yourself an automatic cam chain tensioner. Through-bolted heavy duty barrels are nice as well, but then you'd have to bore and sleeve a perfectly good set of new barrels... probably not what you want to do.
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i,d like to chime in on the roller cam bearings too ,as stated in an earlier post the 500 domiracer of 61 used them to set the first 100 mph lap of the iom with a pushrod engine,paul dunstall used them in his racers very successfully,steve maney also does this conversion,NUFF SAID
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I only put that clipping in because it conveyed Dunstall's opinion on this issue. Keep in mind the tuning manual was written around 1970 (no date in it). It also covers 500, 650 and 750 twins and both Atlas and Commando so a lot of the prep work doesn't apply to Commando engines which have benefitted from all this effort from the earlier engines.
The whole is only equal to the sum of it's parts. Every component you can squeeze an ert out of is pertinent. To quote kebra's post here:
http://southsiders-mc.blogspot.com/2009 ... rt-ii.html
Where do you look for 4/10ths. of a second?
Many of us here are content to ride an original stock commando but others enjoy spending the time and money and taking the risks and pushing the envelope by following the likes of Maney, Dunstall, Dreer and the Norvil team. Different strokes for different folks.
I WANT A 920! .......but I'm not jealous, no-sir-ee
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I can never connect to:
http://www.stevemaney.com/
Every time I've tried to access this site in the last couple of months I can't connect. Any one know what's up or where one can browse the Maney offerings?
THX
http://www.stevemaney.com/
Every time I've tried to access this site in the last couple of months I can't connect. Any one know what's up or where one can browse the Maney offerings?
THX
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- Jan 7, 2009
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Hi guys, sorry to be a little slow in responding, but a busy weekend. Unfortunately not Norton related.
Yes, this did happen, just a small amount at the lower front behind the fins. After painting the barrels it is now invisible.
I think this has been more than well answered already, but roller bearings did cross my mind because of the desire for reliability. However, I ran my last Commando for nearly 50k miles before rebuilding the engine and the cam bushings required no attention. As I was pretty hard on that bike and maintenance was hit and miss, I reckoned that the plain bushings would be fine despite the exta (I hope) performance.
You won't be surprised to hear that it is a Maney cam. Steve assures me that it gives good, useable everyday road performance. An important reason for my choice was that it should be hardened adequately. Only time will tell if it suites everything else I will have done to the bike.
As far as I know, and I happily admit to not knowing much, this is the only way I could have got a crank with this combination of lightness and strength. Too late now anyway!!! I looked into using the original rods quite a bit before deciding to stick with them and essentially went with the advice of virtually all the experts I consulted. Good call on the honing - I had assumed and not really looked until now. It will be attended to - thanks Norvil....... On the cost front - way, way, way too much.
I agree, but funds at basement level and it was overlooked at the start of the project, so I may have to end up putting it together with the standard adjuster for now.
It's a Maney cam as I said. Steve gave me more detail when I bought it, but I have forgotten - crap or what? His shop is closed for a few days, so I can't get a reminder. Maybe someone out there has the specs on the Maney cam? I have approached the 920 thing by assuming it would not be much good unless I could get more fuel in, so inlet and exhaust valves are both 3mm larger and ports machined to suite. I had planned to use 34mm Amal Mk11's, but then found a set of Keihin's for a really good price so I opted for these - from what I've read, I'll probably be overfuelled, but we'll see. Regarding the crankcases, yes, I may well have gone a totally different route if I had been more organised and circumspect at the very start. I am just hoping that I end up with a useable bike, that none of my mistakes end up being too expensive and that the end-product still feels like a Commando.
Next on the list is to rig up the top-end and see if those puny looking cut-outs in the pistons will allow enough clearance for the valves.
Cheers, Bob
Yes, this did happen, just a small amount at the lower front behind the fins. After painting the barrels it is now invisible.
I think this has been more than well answered already, but roller bearings did cross my mind because of the desire for reliability. However, I ran my last Commando for nearly 50k miles before rebuilding the engine and the cam bushings required no attention. As I was pretty hard on that bike and maintenance was hit and miss, I reckoned that the plain bushings would be fine despite the exta (I hope) performance.
You won't be surprised to hear that it is a Maney cam. Steve assures me that it gives good, useable everyday road performance. An important reason for my choice was that it should be hardened adequately. Only time will tell if it suites everything else I will have done to the bike.
As far as I know, and I happily admit to not knowing much, this is the only way I could have got a crank with this combination of lightness and strength. Too late now anyway!!! I looked into using the original rods quite a bit before deciding to stick with them and essentially went with the advice of virtually all the experts I consulted. Good call on the honing - I had assumed and not really looked until now. It will be attended to - thanks Norvil....... On the cost front - way, way, way too much.
I agree, but funds at basement level and it was overlooked at the start of the project, so I may have to end up putting it together with the standard adjuster for now.
It's a Maney cam as I said. Steve gave me more detail when I bought it, but I have forgotten - crap or what? His shop is closed for a few days, so I can't get a reminder. Maybe someone out there has the specs on the Maney cam? I have approached the 920 thing by assuming it would not be much good unless I could get more fuel in, so inlet and exhaust valves are both 3mm larger and ports machined to suite. I had planned to use 34mm Amal Mk11's, but then found a set of Keihin's for a really good price so I opted for these - from what I've read, I'll probably be overfuelled, but we'll see. Regarding the crankcases, yes, I may well have gone a totally different route if I had been more organised and circumspect at the very start. I am just hoping that I end up with a useable bike, that none of my mistakes end up being too expensive and that the end-product still feels like a Commando.
Next on the list is to rig up the top-end and see if those puny looking cut-outs in the pistons will allow enough clearance for the valves.
Cheers, Bob
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- Jul 14, 2008
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I was wondering how much torque you lose with the light crank and wether the bore kit gets the torque back,is the crank really meant to go with a 5 speed box?,one of the things I enjoy about my commando is the large amounts of torque.
RenneiK, my comment was directed at the part about cutting the end of the crank,and not at your opinion,I'm sure Bob wants to cut the end off his new crank.You don't think mums blocked your computer from the maney web site do you.
RenneiK, my comment was directed at the part about cutting the end of the crank,and not at your opinion,I'm sure Bob wants to cut the end off his new crank.You don't think mums blocked your computer from the maney web site do you.
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