Dyno baseline

Right boys n girls,

As those of you who were involved in the earlier discussions know, I want to do a back-to-back Dyno comparison of my bike before and after cylinder head work.

Today I got the baseline done, I didn't adjust anything or fiddle around, just a couple of straight forward runs to get the figure and see what the carburation is like.

The carbs were pretty good, a tad rich on the top end which is probably fine, the surprise, and what will need looking at, is they are quite weak on the needle. These are FCRs as supplied by Matt and of course could be quite different on a different engine set up.

Well, the baseline figures are 56bhp at 6200rpm and 50ft-lbs torque at about 5300rpm.

Power curve was very linear, although the peak was at 6200, it is flattens out considerably from 6000. Torque is very flat, above 46 from 3300 right to 6200rpm which I was impressed by.

I'll be very honest, I was hoping for a little more than this, it certainly feels like more. Although this is on a Dyno that I have used for several years and I know to be 'conservative ' compared to some others.

As some have noted before, I would suggest that mine was quite a lot less than 40bhp before any work was done, so 56bhp is probably still quite healthy in all relativity.

The head is a stock RH10, so I am hoping for some tangible increase with changes in that area. It certainly looks to me like something is holding back the way the power levels off so distinctly.

So we'll see what the 'after' run looks like, hopefully that will be sometime early in the new year.

Fast Eddie wrote;

they are quite weak on the needle.

Click to expand...

Nigel, the needle as far as I am aware is effective from approx. one third to three quarters? Is this the area you're referring to?

Fast Eddie wrote;

Well, the baseline figures are 56bhp at 6200rpm and 50ft-lbs torque at about 5300rpm.

Click to expand...

Your bhp figures are quite close to mine, and I had a 2-1-2 exhaust, stage 2 Steve Maney head on, and my engine has 11% more capacity. A friend of mine had his Combat dyno'd on the same rig and it registered 38bhp at the rear wheel. He wasn't very happy about that, but even so it went quite well on the road.

I'm still very interested to see if the Full Auto head does make a significant difference, and I'm not just talking about oil escaping.

Check out the sheets I posted in 'Head Flow Testing , page 34.
That is with BD valves which are near standard size and a little port massaging and volume balancing.
I used 32 mm Premiers and standard length manifolds for these tests
This is bench flowing and not dyno, although it shows the potential of the RH10 head.
Will post dyno results once motor is back in the bike probably this week.

head-flow-testing-t8640.html
Regards Mike

Reggie said:

Fast Eddie wrote;

they are quite weak on the needle.

Click to expand...

Nigel, the needle as far as I am aware is effective from approx. one third to three quarters? Is this the area you're referring to?

Fast Eddie wrote;

Well, the baseline figures are 56bhp at 6200rpm and 50ft-lbs torque at about 5300rpm.

Click to expand...

Your bhp figures are quite close to mine, and I had a 2-1-2 exhaust, stage 2 Steve Maney head on, and my engine has 11% more capacity. A friend of mine had his Combat dyno'd on the same rig and it registered 38bhp at the rear wheel. He wasn't very happy about that, but even so it went quite well on the road.

I'm still very interested to see if the Full Auto head does make a significant difference, and I'm not just talking about oil escaping.

Click to expand...

Now then Martin, false modesty doesn't become you, if I recall correctly, yours is more like 62rwhp?

The air fuel ratio shows as very, very lean between approx 3800 and 4200. It was the Dyno guys estimation that it was the needles. At least it is an easy thing to try.

Indeed, it will be very interesting to see the after results. We shall see!

That's impressive. If I see you on the road I'll know not to take you on!! As a matter of interest would that have been GP in Dorchester?.
I de-tuned mine last winter and pulled the PW3 but would still like to get it on a Dyno to sort the carbs etc. I've not found anyone local to take it on. Cheers.

Keith1069 said:

That's impressive. If I see you on the road I'll know not to take you on!! As a matter of interest would that have been GP in Dorchester?.
I de-tuned mine last winter and pulled the PW3 but would still like to get it on a Dyno to sort the carbs etc. I've not found anyone local to take it on. Cheers.

Click to expand...

Hi Keith,

Why did you pull the PW3 cam?

The Dyno I use, and have for a long time, is at Aston Clinton, just outside Aylesbury. Check 'em out at:

http://www.msgracing.co.uk/home/

They do a lot of race work and the Dyno is just a part of their overall business.

BTW, they race 600s and get over 120bhp out of them... Kinda put the Commando into perspective !

The reason i use is that the head has been overworked by previous owners a long long time ago and she jjust hasn't any torque, even for a 750. The pw3 did give more power but only over 5.5k. At 1500 rpm in top it shudders before making progress, not that i ride like that regularly but sometimes you get lazy!
It has a combat head and 32mm mk1's with no base gasket. I've ridden 750's with small carbs and they aare chalk and cheese to mine. Ill take a look at that outfit. Tks.

I'm surprised that a near standard road going commando has near 60 BHP at the rear wheel. I think that is pretty good. My own bike feels as though it has 80 BHP when I ride it, however I've concentrated on getting more torque out of it. I suggest it is not the ultimate power figure which is important but how much gearing the motor will pull and still spin up quickly through the rev range . If you think about it, the claimed rear wheel power figure for a 1962 500cc Manx Norton was 50 BHP. Anything more than that in a road bike is plenty as long as it doesn't all happen in the top 2000 RPM of the rev range.
About jetting lean on the needles - lean is good as long as the motor actually runs on the mains at full throttle, and the mains should be slightly rich. If you fit the next size mains and don't get a richer reading on the plugs, you can get damage if you thrash the bike. If you lower your needles one notch you should be able to induce a cough in the motor as you change up and down through the gears around a twisty road - that is what I always look for, then raise the needles one notch. If you cannot get that miss to happen, the bike will usually be sluggish through being too rich at mid throttle.

acotrel said:

I'm surprised that a near standard road going commando has near 60 BHP at the rear wheel. I think that is pretty good. My own bike feels as though it has 80 BHP when I ride it, however I've concentrated on getting more torque out of it. I suggest it is not the ultimate power figure which is important but how much gearing the motor will pull and still spin up quickly through the rev range . If you think about it, the claimed rear wheel power figure for a 1962 500cc Manx Norton was 50 BHP. Anything more than that in a road bike is plenty as long as it doesn't all happen in the top 2000 RPM of the rev range.
About jetting lean on the needles - lean is good as long as the motor actually runs on the mains at full throttle, and the mains should be slightly rich. If you fit the next size mains and don't get a richer reading on the plugs, you can get damage if you thrash the bike. If you lower your needles one notch you should be able to induce a cough in the motor as you change up and down through the gears around a twisty road - that is what I always look for, then raise the needles one notch. If you cannot get that miss to happen, the bike will usually be sluggish through being too rich at mid throttle.

Click to expand...

I think needle jet setting is more crucial on a road bike than a racer. On a racer you're always accelerating through the needles range. On a road bike, you may cruise for miles on a steady throttle opening ON the needle!
Depends what you mean by 'near standard'... To remind, mine has JS1 cam and radiused followers, JS rods and 10.5:1 pistons, 35mm FCR carbs, Tri spark with Crane coil and a belt drive and clutch combo that takes many lbs of rotating weight out of the primary. The head IS standard though... But not for much longer.

If your weak spot is at wide open throttle, I'd be surprised if it's the needles. I don't know much about those carbs but I assume they have an air corrector jet? That might be worth looking at.

" Depends what you mean by 'near standard'... To remind, mine has JS1 cam and radiused followers, JS rods and 10.5:1 pistons, 35mm FCR carbs, Tri spark with Crane coil and a belt drive and clutch combo that takes many lbs of rotating weight out of the primary. The head IS standard though... But not for much longer."

How much experimenting have you done with ignition and cam timing?

And then exhaust and inlet tuning.

My experience is that this is what make the difference.

If I looked at my own 500 Norton - all on the same dyno - rear wheel.

Blue printed engine with street /race style exhaust, 4 S cam 10.2 :1 compression and normal SS head and carb manifold etc. - 34 bhp - actually a very good number for an almost standard Norton 500 SS.

Change to home made racing megaphone exhaust, plus retune carbs - 42 bhp.

Change to PW3 cam and head work at a good shop in New Zealand plus retuned carbs. 47 bhp.

Six month of experimenting with cam ignition and inlet and exhaust lenghts. - 51 bhp. (The tune of this bike would be impossible on the road however - almost no hp below 4000 rpm- so only suitable for racing)

So if you add that up out of 17 bhp only 5 bhp came from new cams and head work. All the rest was exhaust/inlet experimenting and detailed ignition, cam and carb tuning.

I say this because when you talk about a "base line" you really need to be sure your baseline really is the bikes real potential as at set up 1 versus the bikes potential as at set up 2 PLUS a lot of tuning.

Half the amount you now atribute to your new head or cam or carb for example might have been available anyway had you experimented with ignition and cam timing plus a bit of increase of inlet tract lenght for example.

The Combat with 38 bhp probably had a good 50 bhp in the engine without any major change if it had been tuned properly. (Unless the motor was worn out , bad compression etc)

Having said all that 56 bhp rear wheel is pretty good for any Commando without a race type exhaust.

Good engines like Nortons should be good for 1 hp per cid, 750 = 45 cid, 920's 55 cid. Great engines hit 1.5 hp/cid and more.

johnm lays out the facts of surprising power adders that shocked me and others on Peel disappointing falling on her Combat face sluggish response till 2-1 mega super trap end cap shot open - then so unbelievable I almost had Peel run out from under me in my driveway as could not believe it and thought it was my deep depression made me lax as stuck with obsolete money-time waster Combat to be rid of soon while still road worthy, so got angry, positioned low tight like a drag racer launch but shocked again as still ended up on back of seat instead of tail light before it sunk in with huge evil smile cracked ear to ear as knew I could now hunt down elite sports bikes acceleration wise to the ton and not loose ground till over 130 mph.

Peel wt'd ~350 lb by then and me 170 suited = 520 lb. My 70 hp 365 lb SV650+me = 635 lb, add 4 gal of gas ~25 lb, so 545 Peel, 560 SuVee. So ~8 lb/hr on SuVee, factory wet Combat 445 lb/45 hp = ~9.8 lb/hr. SuVee and bone stock Trixie are neck and neck pullers till almost 90 mph then Trixie will out pull SuVee to over 115, with both good to about 120 max if waiting that long on SV or daring to risk a factory Combat to redline. My Trixie Combat, 2000 SuVee and others SV650's could not keep up with the real sportsbikes after 1st 10th mile open - no way they could catch the 600's to 1200's sports maniacs but Ms Peel sure could and most often got into their games by running up on them watching them dragging knees on her mere commuttes while sitting bolt upright. As ridiculous as sounds even to me Peel had to be making 70's hp to perform like she did. What I did find out in spades dicing with super bikers was they could only use their power/wt advantage in bee lines, poor corner cripples. Peel performed as if only upper 6lb/hp to shove. Next Peel hope to get ~ 4 lb per hp.

Peel had 3 unique power adders, bigger single carb, crude rough edge intruding manifold gasket with a step down lip edge into standard 750 low CR head and the 2-1- hollow Dunstall mega. I want to reproduce Peel's engine set up again and send to comnoz to find its pecking order so others may be tempted to mimic going against the grain rather cheaply simply while straining to stay in saddle. Only faster cycle I've had was the P!! which would out pull the NInja 900 and BMW 1200's to over 140. My P!! would not wheelie, just leap forward or smoke, Peel would not wheelie only leap or smoke, poor sportsbikes trying to keep up with Peel would have to back off d/t front lifting too much, similar to deer I've out accelerated by throttle snap seeing them leap front hi while falling behind peripheral vision. I don't take any credit for being a knowledgeable engine builder just frustrated trial/error experimenter with Commando memories to last a life time. P!! could break under 11 sec 1/4 m on street tire if careful throttle use, Peel maybe below 12 sec w/o spin to snap WOT, but I'd still rather ride Peel for the harsher G hits cornering like a dragster that required hugging Peel knees tight and body low not to get left behind while not feelling any engine vibration distraction.

johnm said:

" Depends what you mean by 'near standard'... To remind, mine has JS1 cam and radiused followers, JS rods and 10.5:1 pistons, 35mm FCR carbs, Tri spark with Crane coil and a belt drive and clutch combo that takes many lbs of rotating weight out of the primary. The head IS standard though... But not for much longer."

How much experimenting have you done with ignition and cam timing?

And then exhaust and inlet tuning.

My experience is that this is what make the difference.

If I looked at my own 500 Norton - all on the same dyno - rear wheel.

Blue printed engine with street /race style exhaust, 4 S cam 10.2 :1 compression and normal SS head and carb manifold etc. - 34 bhp - actually a very good number for an almost standard Norton 500 SS.

Change to home made racing megaphone exhaust, plus retune carbs - 42 bhp.

Change to PW3 cam and head work at a good shop in New Zealand plus retuned carbs. 47 bhp.

Six month of experimenting with cam ignition and inlet and exhaust lenghts. - 51 bhp. (The tune of this bike would be impossible on the road however - almost no hp below 4000 rpm- so only suitable for racing)

So if you add that up out of 17 bhp only 5 bhp came from new cams and head work. All the rest was exhaust/inlet experimenting and detailed ignition, cam and carb tuning.

I say this because when you talk about a "base line" you really need to be sure your baseline really is the bikes real potential as at set up 1 versus the bikes potential as at set up 2 PLUS a lot of tuning.

Half the amount you now atribute to your new head or cam or carb for example might have been available anyway had you experimented with ignition and cam timing plus a bit of increase of inlet tract lenght for example.

The Combat with 38 bhp probably had a good 50 bhp in the engine without any major change if it had been tuned properly. (Unless the motor was worn out , bad compression etc)

Having said all that 56 bhp rear wheel is pretty good for any Commando without a race type exhaust.

Click to expand...

I hear you John. I say 'baseline' cos I had no intention of maximising everything you say with current set up. None of those other things / settings will change between now and the 'after' run. So that will be an 'apples to apples' comparrison.
Then, with the new head, I shall start dialing in the things you mention.
The level of improvements you saw on your 500 are very impressive! That gives me hope for more gains in the future!
I have a Steve Maney race exhaust lined up to borrow for Dyno runs, but the guy who owns it reckons they don't add much. Others say they add lots. So there's a lot of careful trial and error ahead I guess.

I've lucked out on a few variety of engines but all of them were expensively frustrating trying this and that disappointing till last few tweak in this and that > shit eating grin pleasing improvement. Can anyone list what to dial in first then next etc then back to first again and so on. Spark, fuel, intake track or exhaust system cam degree? Some day we may have enough data points to just order up the hp per cost with predicable results.

" Can anyone list what to dial in first then next etc then back to first again and so on. "

In my opinion the very first part of creating such a work flow is to decide what the target is.

A touring bike, a street race bike, a track race bike, etc. Then if you wish to push the engine a long way in hp terms you need to bite the bullet and build a blue printed very strong engine. Its a waste tuning a weak motor.

One piece crank, new rods, either the Carrello or one of the racing quality aluminium rods. Go through all the bearings and rollers rockers etc checking them all for cracks etc. Probably the easiest way to acheive this for a Commando is to talk to Jim Schmit. Degree the entire cam lift on all lobes to check it is made properly as per the published figures. Will you use air clearners or bell mouth. If you use a bell mouth read Dave Vizard for the profile.

Set the bike, ignition, cams carbs etc exactly as per the book.

Then check your ignition timing on a track using the methods described by Gordon Jennings in his spark plug articles.

Then for a race bike make a megaphone as per any standard formula (eg Jeffrey Diamond aka Panic ) go to the dyno with telescoping tubes for the header pipes and inlet tracts and establish first past lenghts for the exhaust and inlet tract lengths. You will need to do general carb adjustments but dont worry if its not perfect yet.

Then do cam timing sensitivity and recheck exhaust and inlet. Usually advancing about 5 to 8 degree will improve the midrange. With a megaphone you are unlikly to have much below 3500.

Then check ignition timing again. Final carb tune

After that you probably have 95 % of the gain and after that its just a question of going around and around. Im a very big fan of checking ignition timing is perfect and matched on both cylinders. With electronic ignition this may not be an issue but with magnetos it can be a big deal.

So in summary

Strong engine
Set up per book
Confirm ignition
exhaust and inlet
cam timing
reconfirm exhaust and inlet
re confirm ignition
get carbs perfect
repeat