Reving beyond 8000 RPM

Occasionally I put my products to the test. I've been running my streeter to 7500 RPM but decided to take it into the all out screaming range. I took it between 8000 and 8500 but it had an ignition miss so I changed out the old points in the Joe Hunt magneto, then it reved cleanly througout. It was surprisingly smooth because of the lightweight pistons & longer rods but I did notice a change of character in the vibration - more of a fine buzz and tingle over 7500. It pulled strongly up to 7500 but then the power dropped off and I was just reving it for the numbers. The tac has been calibrated on a CNC lathe so its accurate. I could have run it past 8500 but I have stock cases and modified stock crank and going beyond 8500 and trying for 9000 would be insane (unless I was still racing where its normal to be insane). My main interest was the valve train with the lightweight radiused lifters and beehive valve springs. I've floated valves in the past on the track with lightened stock lifters and RD springs but I haven't seen any problem with the beehive spring/radiused cam & BSA type lifter arrangement. When racing I never had a tac and just reved it as high as it would go - the worst was missing a shift and causing the valves to rub each other. I'll never know what my peak RPMs were back then.

This is just a test report. Don't try this at home - these motors don't always survive this sort of abuse. I know a couple racers who are reving these parts over 8000 but their long stroke motors have all the trick bits.

The poor over-reved test bike below

My favorite part of the bike is the Sharpie on the tank reminding you what kind of bike it is. :mrgreen:

When out on the town - People would be standing by the bike waiting for the owner to return and tell them what it was. So I made it easy for them with the "Sharpie ID".

Jim

jseng1 said:

When out on the town - People would be standing by the bike waiting for the owner to return and tell them what it was. So I made it easy for them with the "Sharpie ID".

Jim

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Perhaps a proper Norton logo on the tank might help? :mrgreen:

I go to your web page Jim and I do the same thing I did back in '71 with Dunstall's catalogue . . . . . dreaming and wishing . . . . . it appears that about $2500 will get me rods, pistons, cam, lifters, push rods, valves, springs - the whole high output top end. A deal, really. Unlucky for us both, just before I discovered this site and your site, http://www.jsmotorsport.com, I re-built my top end.

You like it risky with cast iron flywheel,if that still part of this. Exam real close now for rotor to stator contact, especially the lower front and rear arch and might peek in on the cam tensioner as even if the inside can stand it the crank ends levering can sure bother accessories. I'd suspect the power drop off was carb restriction more than head, don't know of course. Might need to tweak cam degree to breath more at top end, if was racer out dyno test event. Ignition some times needs to be retarded a bit after some rpm threshold, don't know if that is being hit in your set up or even ever a Norton rpm range issue. Pistons and rods you supply sure ain't the limiting factor no more.

thatsa street bike? looks mean!

DonOR said:

thatsa street bike? looks mean!

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and loud.

jseng1 said:

When out on the town - People would be standing by the bike waiting for the owner to return and tell them what it was. So I made it easy for them with the "Sharpie ID".

Jim

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heheh... I guess most of us who have our bikes on the road have that problem in common too. You'd think I'd be used to it already, but it can get really annoying--- unless its a pretty girl asking me what it is, my replies get really quick and to the point! I'm thinking of printing up some business cards that have all the specs and details, and just pass those out. To the old guys, anyway.

DonOR said:

jseng1 said:

When out on the town - People would be standing by the bike waiting for the owner to return and tell them what it was. So I made it easy for them with the "Sharpie ID".

Jim

Click to expand...

heheh... I guess most of us who have our bikes on the road have that problem in common too. You'd think I'd be used to it already, but it can get really annoying--- unless its a pretty girl asking me what it is, my replies get really quick and to the point! I'm thinking of printing up some business cards that have all the specs and details, and just pass those out. To the old guys, anyway.

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The card with your cell phone number is for the girls...

The diameter of the flywheel has been reduced so its lighter & not as likely to explode at high RPM. The PTO shaft has been radiused to reduce risk of cracking. These mods have worked well. I've broken racing cranks & cases but I get plenty of years out of them on the street. I don't expect any more bottom end failures with the new lightweight - low vibe pistons/rods.



My street bikes have never been slow. Check out my first Nort. This bike was basically an early street tracker wihout even a kickstand. It was a dog until I went through it and ported the head etc. Then it was pulling 2nd gear wheelies (low gearing) and so I put it on the track and all my Norton trouble began.

Its inspiring to see your 'holey-ness exceeding my meager removals.
Your FeatherBed is similar to my P!!, which I lucked out to acquire not build. It had no power drop off to 9000 rpm except in 4th which I never ever reached. I did not rev it to that mark on its tach but once in a while mainly because rear street tire couldn't take it - just spun or smoke or slide right out from under if tipped even tiny bit. I can only assume it was a Woods or Axtel engine the cycle shop put in. Would like to see internal parts of those engines to model our own after.

Anywho mainly just want to remind you that the exterior items can limit rpms when the crank is jump roping its ends into a cone shaped orbital. I'd sure want a cast iron flywheel magnafluxed then cryo temped to relieve my gritting teeth a bit. My P!! was 2" low in front so no wheelie issue just floated level.

I found the Cdo can take more power before lift limits so could plant more than super bikes up to almost 100 mph in Peel, by gritting teeth in 1st and 2nd with tach mostly in red zone. Less than that I'd get out run in opens when no leaning involved. BTW 3rd gear seems the weakess teeth for some reason.
P!! shook me off holding it at high rpm, like Fwy speeds but my Peel was so smooth I couldn't resist red zone.

The original Domiracer valvetrain would rev this high. In the early seventies Chuch Dearborn raced the Kegler Domi, which was one of the original three bikes built at Norton under Doug Hele for the 1962 Daytona race. Kegler and Dearborn rented a track in New England and tested the bike to 9000rpm with S&W springs on the valves. For racing though the revs were kept down below 8K because of crankshaft problems. Bucket tappets, longer pushrods to suit, and a needle-bearing cam with oil pressure fed to the end coming out holes in the lobes to keep the tappet lubed. Bike still runs like a raped ape.

These three "daytona 88" bikes did well. They won the Canadian GP in 1963 and the amatuer and Novice at Laconia that year. The Kegler bike won the AAMRR 500cc championship more than once in the mid-sixties with George Rockett riding, and this duo qualified and placed sixth at the 1967 Canadian GP behind Hailwood, Agostini, and Duff.



Chuck Dearborn: " When you pull the primary
cover off let me know what he has on the outer clutch basket for
support. He put shipping strapping after it spread at Bridgehampton at
about 8500 rpm. We did tests in 500rpm stages to see where it stopped
making power - no dyno days. I remember going to 9000. We would go to
Bridgehampton on Fridays before the races and pay $25.00 to rent the
track for day. It was worth it. He would pack some German sausages and
rye bread and we were off in his big Buick, The German cowboy and I."




AMA rules would not let the Domiracer with it's special frame and engine castings race in the USA, so they built three bikes with standard Model 88 frames , cases and cylinders and stuffed those parts wtih all the other Domiracer parts including the special valvetrain and large rod-journal crank. The Domiracer alloy rods did not hold up, so Kegler used a standard 88 crank with Carrillo rods on it in later years. Also Mahle pistons. Bike has unique long-body right and left handed Amal Gp carbs.

Heinz Kegler, ex Norton Experimental Department, ex Berliner head technician, passed away in September 2010.

I like the bucket tappets - its about time someone showed those. Were they machined from stock items? But I don't like the longer flexier pushrods. The smaller cc domni motor would certainly help with the RPMs. But the "raped ape" sounds severely dangerous.

I would bet that the Domiracer tappets were machined starting with stock castings. You can see from the first photo of the whole valvetrain that they were radiused. Maybe someone could take an old lifter and cut it down, but the stock lightening holes in the sides would be bisected and it might be weak, or it might be fine, someone can try it who has a spare engine to blow.



Kegler said the factory tested the 650/750/850 crank with a light flywheel in 1962. They built a 1962 650ss with a model 99 flywheel, much lighter, and it also had a factory racing camshaft in it and high compression etc.. Kegler said it needed really good gasoline to run on and Norton tested it at 126 mph, this was a fully equipped street bike. Kegler rode it all over Great Britian and England testing it and running errands for Norton that year. He made a few trips to the Ace cafe with it to blow off the regulars there. The engine finally blew when he was on his way back from a bike show in Europe and got a tank of bad fuel in it....

Appreciate the reality check 9000 rpm Nortons were old school by time I got the '68 P!!. About everything Norton can be brought up to modern rpm ranges but for the dang old jump rope crankshaft.

Thanks for the insightful education on lifter mods that lighten and also relieve the load with the push rod contact right over the bearing surface, cool. Maney has light steel push rods. On my Chevy hot rod V8 push rods had slotted guides to keep them in line near top out.

Bores an be shifted off center, usually forward of crank bearings to get a bit more rev ability I've read in other engines, don't know how useful in Nortons.

W/o rev limiter you can be just one missed shift or start up stuck throttle in N to suddenly be back to start...

Talk about revving a standard stroke 750 Commando engine to 9000 rpm always scares me. It's very difficult (I'd almost say impossible, but you never know what someone will come up with) to build a streetable 750 with the horsepower peak much above 7000 rpm. Unless you're road racing, and winding the engine tighter lets you skip a gear shift in a corner, all you're doing is stressing the engine parts for no good reason. Revving the engine higher will not make the bike go any faster, unless you have it geared too low to start with. I know several Norton racers, including our own comnoz, Steve Maney, and Herb Becker, who have built 750 race engines that made serious horsepower at well over 7000 rpm, proven on the dyno, but I doubt if they'd be much fun on a street bike in stop-and-go traffic.

I don't mean this as a criticism. The fact that Jim (jseng) can safely rev the engine that high is a great testimony to the durability of his piston rod package and his valve train setup. My experience with standard 89 mm stroke 750 engines is that raising the horsepower peak much above 7000 rpm requires some pretty radical head work and a seriously lumpy race cam, along with high compression, big carbs and tuned mega exhausts, not the greatest combination for street riding.

Then again, maybe I'm behind the times. If so, this forum is where I'd expect to see the data. You gotta love that.

Ken

Revving the engine higher will not make the bike go any faster, unless you have it geared too low to start with

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Yeah Man that is so so right on I've NEVER gotten over nor come down off the high a certain P!! delivered in spades yet was a pussy cat at 600 rpm in 4th trolling girls in city or lolly gagging in deep sugar sand ruts. Believe me or don't but I rev'd it to the shop added tach mark as it both made more power and got tranny ratio torque advantage. Bad ass as current racers are I still had more on street bike straight line performance than them. Back in those days the only thing that could keep up with me on hwy was the over bored big kit 1%'r Harlelys 'choppers-bobbers'. If you ain't ever seen a Norton safety wired up like WWII radial then ya don't know what ya missing out on art deco power house. It did NOT go vaaroOOMM niether it went BLATTTT to 9000 exactly like you hear too hot to street dragsters at X-mass trees. 10.49 best ET recorded which I never attained on non flat profile slick but boy howdy I broke under 11 any time I dared.
Could not be opened up till in 3rd over 70 mph or just smoked in place. Dual Amals to rub in in more too.
2nd was good to over 70, but w/o a speedo hard to tell but by the traffic I passed lines of at once.
I was young and more stupid then so didn't know anything about Norton rpm allergies but got away with it.
Heck I see 9000 rpm Harleys so how special can we feel putting them down as tractor like : (

I've posted with real vintage off road desert racers that told me they pull 8500 to beat the new fangled inline 4's in straights and Captain Norton sight has very long discussion on what dragsters did to hit 8500, using the thinnest flex cases [Combat] with stiffest cranks to absorb the jump rope whip. Its where I read cast iron flywheels were rpm taboo.

After I figure out compression release and get some track times in and bored I want to attempt an 11,000 version w/o piston pins or center bearing. Sir Eddie in Oregon is building up 11,000 500cc Norton land speeder that looks like Swiss watch work. Next Ms Peel will not be a hi rpm machine thank you.

what balance factor did they use?

Given the "flexible" crank, is rpm increase the only way to go for more power?
Perhaps street riders would be better off just increasing the engine size and
have more enjoyable bike at the same time?