Dyno readout of Mike Hamiltons 850 with JS parts

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jseng1

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Here's a dyno readout of Mike Hamilton's 850 Commando with JS lightweight pistons and JS stage 2 radiused cam kit.

64 HP is very impressive on an otherwise stock Nort.

Dyno readout of Mike Hamiltons 850 with JS parts
 
Could you explain , please . To lazy to look it up . :oops: ' Radiused Cam ' is it the cam radiused or the Lifters ? Bin Wondrin , thanks .

Seems to have the goods .
 
Matt Spencer said:
Could you explain , please . To lazy to look it up .
Click to expand...

Complete Radius Cam Kit - including our custom Radius cam, set of lightweight lifters, bronze lifter blocks, set of stronger, lighter, shorter pushrods to eliminate flexing (more info). For stage 3 cams the lifters must be ground to 7/8" radius. We provide this service (see below). Contact us to special order Atlas cams or cams for 90 degree cranks

Labor charge to radius lifters to 7/8" - for stage 3 cams only. You must buy a JS 3 cam kit for this service.

Norton radius cam for use with our "tested" lightweight radiused lifters and blocks. Will not work with stock lifters. Four cam grinds available

Gee Matt you look up and post all sorts of stuff here--his web site has the above info and more CJ :wink:
 
MPH and not RPM on a Dynojet, bike must have a Boyer.

Can you give us an indication of RPM range? I see "open pipes" but are the stock with cross over or....?


Dyno readout of Mike Hamiltons 850 with JS parts
 
Brooking 850 said:
Second one is the final run with the better jetting and OEM mufflers, unfortunately dyno operator didnt tab the recording until we were over 4000 rpm although after riding it , I know there is stacks of mid range from low down. We quit due to a slight leak in the rocker overhead feed pipe.
Dyno readout of Mike Hamiltons 850 with JS parts

Third pic posted is the speed run. Stopped at just ove 7000RPM , new motor and results were encouraging so no need to press it.
Dyno readout of Mike Hamiltons 850 with JS parts


1973 motor Std crank and cases, JS rods and pistons 0.040" over, std cast iron barrels ,JS Stage 2 cam , 32 mm Mk1 Concentric Premiers, RH10 head
std Commando manifolds. 21 tooth sprocket on 5 speed TTI box 44 tooth at rear wheel which I found the gearing to tall, so have changed that to 46 tooth at the rear
Regards Mike
Click to expand...
I would have liked to have seen a pull from 3000 RPM. That might give a better idea of street manners.

Very impressive. 64 RWHP is over 70 HP @ crank.
 
'I would have liked to have seen a pull from 3000 RPM. That might give a better idea of street manners.'

Not only 'street manners' - 'torque wins races'.
'
 
Hi Dances, I see that others have posted my dyno run, if you look at the bottom of the print outs, I have written my name free hand as the operator pulled up a previous Norton owners profile (he has Maney gear in his bike , I know him well and race with him)and forgot to change the parameters to suit my bike and profile, but I dont run a Boyer ignition, mine is battery less crank mounted.
As Jim comments , not bad for a very basic stock motor running std manifolds, std valves, RH10 head and 32mm Amal Premiers.
Headers are by Paul Bryant of Viking Exhausts here in New Zealand, have no crossover, are std length and bore size, although upswept into OEM peashooters.
Like I said in other threads, I have a great starting point and there is room for development, that will come although right now I just need to be quicker on what I have and get my gearing set right for each track
As for torque further down the rev range, shame the operator didn't tab the keyboard earlier in the run, although I know it is there after riding it, makes good power from the high 2000's to low 3000's and as the curve shows plenty all the way through the range.
Regards Mike
 
Thanks for sharing this Mike. Really nice build and a benchmark for others. What did the compression ratio come out to? What ignition advance was it happy at?

A Commando head performs so well with little to no work.
 
Dances, timing is set at approximately 5 degrees advanced of static timing as per a stepped key on TS and as recommended by JS to avoid valve clash at maximum lift , clearance is approximately 0.185" and ignition timing is 32 degrees BTDC, although Jim Comstock thinks I could be running 28 BTDC for the higher rpm.
As I say , I am really at the bottom of the development ladder, that will come, need track time now
Regards Mike
 
Brooking 850 said:
Dances, timing is set at approximately 5 degrees advanced of static timing as per a stepped key on TS and as recommended by JS to avoid valve clash at maximum lift , clearance is approximately 0.185" and ignition timing is 32 degrees BTDC, although Jim Comstock thinks I could be running 28 BTDC for the higher rpm.
As I say , I am really at the bottom of the development ladder, that will come, need track time now
Regards Mike
Click to expand...
Which J&S pistons are you using, the medium or high compression?

I ask because of the valve clash mentioned. Since advancing the cam was used to avoid VC, I assume that it's the exhaust valve/piston clearance that is the concern. The medium CR piston has shollower valve ctearance notches.

Advancing the timing is probably helping the low end TQ some.
 
The purpose of advancing the cam was not to avoid valve clash but simply to get the cam correctly timed. The cam grinder had located the keyway incorrectly so the cam would have been a bit retarded. Of course if the cam is too far out of time it will cause the valves to hit the pistons. I have been working with the cam grinder to fix this (and they are charging me for correcting their mistake). But the timing instructions come with the cam and its pretty easy to check if both valves have the same lift at TDC and preferably the intake has between .010" and .020 more lift than the ex at TDC. This can also be checked quickly by peering onto the ports to see which valve has more lift at TDC. In any case you should always check cam timing for best performance. 5 deg advance is achieved by re-meshing the gears and sprocket according to instructions. Cam gears/sprockets vary and each Nort comes out differently.
 
Brooking 850 said:
Hi Bitchin, 10- 1's 0.040" oversize
Std composite head gasket.
Regards Mike
Click to expand...


I thought the J&S pistons were either 8.5:1 or 10.5:1 W/a standard .040" head gasket.

When I talked to Jim he said that going W/the .003 head gasket would raise CR to about 9.5:1. The head would then have to me milled another .020 or so to get into the 10:1 range.

Likewise a .021" cylinder base gasket should drop the high compression (10.5:1) piston down to 10:1.

Just wondering which route you took? Or, perhaps there is there another option?
 
Just noting that various dyno's are notoriously inaccurate below 3000 rpm for a number of reasons so even if ya did get a graph that low its not trust worthy as seat of the pants or stop watch distance in that zone. Graph's meeting at 5225 helps keep fudge factors even on each dyno judgment.
 
Just for clarification, the JS cam series is JS0, JS1, JS2 and JS3. Is the stage 2 cam referred to here the JS2 or the 2nd one in the series which would be the JS1?
 
worntorn said:
I recall reading here on a recent thread that some dynos (I believe dynojet was mentioned) automatically add 12 % to the measured rwhp to give a graph of estimated crank hp rather than rwhp?

Here is a discussion on dynos that is quite interesting.

http://www.factorypro.com/dyno/Inflated ... epower.htm

Glen
Click to expand...

Pretty much any dyno can output a number with a correction for crankshaft horsepower. It is the default for most dynos. Some apply a standard value [like 12%] Some apply a value that is computed from a coastdown test.

Even comparing the numbers that are supposedly from the same setup, it is well known that the dynojet is going to give the highest readings of any of the dynos. Which dyno is accurate -the timeslip at your favorite track.

Dynos are a great tool for tuning and seeing the results of changes made.
As far as advertising and absolute numbers they are meaningless.
Any dyno operator can get whatever number he wants from a dyno. Not that most dyno operators would willingly skew the results, but it is easily done. Jim
 
I have heard about aggressive dealers offering free dyno days for motorcycles. Sportbike owners tend to flock to them in hopes of posting a really high number for bragging rights. The free dyno is set to show a conservative or perhaps honest RWHP number which turns out to be much lower than the advertised HP numbers. Disappointed owners are then easy pickings for expensive Dealer power upgrades on full display. These upgrades come with a guarantee of increased hp and another free dyno test. later that week the dealer bolts on the upgrades, does another dyno test with dyno now adjusted for a high reading, crankshaft hp or more perhaps. He hands the owner the new improved dyno sheet and the owner now has the bragging rights he was after.
The bike may actually have less power than before, but who can really tell when even 600 cc sportbikes have power way beyond anything fully useable for most riders. So everyone is happy!

Glen
 
I know one dealer who used to refer to his customers as 'wood ducks' in private.
About the cam timing. The first thing I did to my 850 motor was broach two more keyways into the cam sprocket at random. I look where the timings are using a degree disc, and adjust to the situation using judgment based on my own experience, and what others do with cam timings in relation to various exhaust systems. (have a look at the Megacycle web site) . Lift is not important when you are adjusting to suit harmonics and back pressure. I would never take the position of the keyway as being correct for granted.
If you buy a hot cam, always find out what pipe suits it, and the specified timings and the engine response they should give. In my own situation, I am currently working fairly blind with the 850 cam - it is quite surprising what happens when you advance it 12 degrees with a two into one exhaust and methanol fuel. My feeling these days is that the commando engine is lovely - fast enough to win races, especially on tight circuits using high gearing.
 
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