Tuning a different way.

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acotrel

acotrel

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I have just come back from Winton Motor Raceway where I watched Bob Rosenthat win a race on Geoff Clatworthy's 500cc ES2 Norton. In four laps of the 2 kilometer circuit, he lapped all but two bikes. I was talking to him a while back and he told me how he tunes the bike. He puts the bike on the dyno and tunes the jetting with the oxygen probe. He then assumes the jetting is correct and adjusts the ignition timing until he gets maximum power.

I have always done the opposite. I choose an ignition advance to suit the compression ratio and the fuel octane ratio, then lean off the jetting.

I think his way might be much better. My assumption is that I have chosen the right ignition advance. I base it on what has worked for me in other motors. It could be very wrong.
 
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I would be inclined to think that going back and forth a few times would insure the best of both A/F ratio and maximum ignition advance?

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RoadScholar said:
I would be inclined to think that going back and forth a few times would insure the best of both A/F ratio and maximum ignition advance?

Best
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I agree.

Plus those Clatworthy ES2s are amazing and after 20 plus years of development I should imagine that today his starting points for ignition and jetting are 19.5 years ahead of everyone else's best estimate.

Except for the Lodge ES2s of course.
 
Adjusting ignition timing to produce max power on the dyno is pretty much a standard technique in the engine-building world. Without a dyno the shade tree method of doing the same thing is to advance the timing until you get some detonation and then back it off two degrees.

Different OEM engines of the SAME model typically require different timing to achieve the same power output and most conventional (non-computer controlled) engines will increase power over stock settings by using that method. The disadvantage is that you have to be careful if you use a different gasoline than the one you tuned for - EVEN if the other gas claims to have the same octane rating. IOW, if you tuned using say, Shell premium rated at 93 (US) octane, you might get some detonation using Chevron premium 93...or visa versa!

Frankly, my engine building experience is that the timing from the factory is never optimum for maximum performance BUT the factory had to make sure that the engine can run properly on any gasoline of the appropriate octane rating. I personally have seen stock V-8 OHV engines gain over 35 HP simply by adjusting the timing for max output with "normal' pump gasoline as opposed to the factory settings - no other engine changes.
 
MexicoMike said:
..... The disadvantage is that you have to be careful if you use a different gasoline than the one you tuned for - EVEN if the other gas claims to have the same octane rating. IOW, if you tuned using say, Shell premium rated at 93 (US) octane, you might get some detonation using Chevron premium 93...or visa versa!

Frankly, my engine building experience is that the timing from the factory is never optimum for maximum performance BUT the factory had to make sure that the engine can run properly on any gasoline of the appropriate octane rating.....
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These points chime with me.

Only my personal viewpoint, but if I feel I need more performance, a different bike would have bèen cheaper (and probably, more reliable). I enjoy riding the Commando for a host of reasons and it's adequate performance is fine, on the road. I do get enjoyment from keeping it running as it should. I take an interest in practical mods that keep it sweet, make it easier to look after, or extend the lifespan of its internals, without starting to introduce new things to worry about, or turning it into a different bike to experience riding.

Just my way of enjoying it.
 
I thought advancing the timing must be standard practice, but what is the repeatability of oxygen probe like when you use it to set the jetting ? If you put the timing in a fixed setting then adjust the carburation, you do not know if the timing is right for the fuel. But comp. ratio, ignition advance, fuel octane rating and jetting form a balance. I think Bob's way of doing it gets you to the right place easier. i don't know how he selects needle tapers. I use the leanest needles.
 
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Mart UK said:
These points chime with me.

Only my personal viewpoint, but if I feel I need more performance, a different bike would have bèen cheaper (and probably, more reliable). I enjoy riding the Commando for a host of reasons and it's adequate performance is fine, on the road. I do get enjoyment from keeping it running as it should. I take an interest in practical mods that keep it sweet, make it easier to look after, or extend the lifespan of its internals, without starting to introduce new things to worry about, or turning it into a different bike to experience riding.

Just my way of enjoying it.
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I think that is the only sensible way to own an old motorcycle - love it for what it is. Road racing is silly stuff, but I really love it, and a Commando-based bike is slow enough to stay safe. Quicker in the corners, slower down the straights. Braking from high speed is where most big crashes happen.
 
Well you did start this by saying that Bob lapped all but two bikes… I’d suggest that’s a reasonable endorsement of his methods !

Also, in my own experience, moving the timing a few degrees either way of nominal makes no measurable difference in our old tech motors.
 
Fast Eddie said:
Well you did start this by saying that Bob lapped all but two bikes… I’d suggest that’s a reasonable endorsement of his methods !

Also, in my own experience, moving the timing a few degrees either way of nominal makes no measurable difference in our old tech motors.
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IMO Bob is probably riding the balls of his bike whereas a couple of other riders are not quite coming out of the corners as fast, that alone can give you an extra 10mph down the straight, if the engines were equal.
 
Bernhard said:
IMO Bob is probably riding the balls of his bike whereas a couple of other riders are not quite coming out of the corners as fast, that alone can give you an extra 10mph down the straight, if the engines were equal.
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I would argue that both points go hand in hand… someone with that talent and riding ability is highly unlikely to be tuning his bike ‘wrong’…
 
Fast Eddie said:
Well you did start this by saying that Bob lapped all but two bikes… I’d suggest that’s a reasonable endorsement of his methods !

Also, in my own experience, moving the timing a few degrees either way of nominal makes no measurable difference in our old tech motors.
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If you jetting is slightly rich, the motor will usually be slightly sluggish, but the rider does not usually notice the motor is slower because you do not know it is slow until you make it go faster. When you advance the timing or increase the comp. ratio on a motor which is jetted slightly too rich, it has a similar effect to leaning off the jetting. If you move the tuning into the right area, the motor will be faster. It is easy to be slightly off and live with the difference when the bike still performs OK, but not just as good as it can. A similar thing happens if you improve your motor's torque. You often do not know you have an improvement until you raise the overall gearing. and the bike performs better.
When I first started racing the Seeley, it performed OK, but I suspected it was not pulling as hard as it could. So I started raising the overall gearing and the bike accelerated faster. With the heavy crank, the motor seems to spin up at the same rate regardless of the gearing. But with a close ratio gearbox, that becomes less relevant.
 
Bernhard said:
IMO Bob is probably riding the balls of his bike whereas a couple of other riders are not quite coming out of the corners as fast, that alone can give you an extra 10mph down the straight, if the engines were equal.
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He looked as though he had 20 MPH in hand. Bob is an old A grade rider from the 1970s. He used to ride a sponsored Yamaha TZ750. So when he plays, he is fair dinkum. Even if his motor had been slow, he still would have won. The kids he was racing against are all good, but they cannot beat old age and experience. I was just amazed at the speed he has got out of an ES2 Norton. One of the things I have found, is a lot of bikes are never as fast as they can be. There are a lot of myths in road racing and most of the very fast guys will not tell you much. I do not consider myself tyo be one of them. I have never had that level of dedication.
 
acotrel said:
He looked as though he had 20 MPH in hand. Bob is an old A grade rider from the 1970s. He used to ride a sponsored Yamaha TZ750. So when he plays, he is fair dinkum. Even if his motor had been slow, he still would have won. The kids he was racing against are all good, but they cannot beat old age and experience. I was just amazed at the speed he has got out of an ES2 Norton. One of the things I have found, is a lot of bikes are never as fast as they can be. There are a lot of myths in road racing and most of the very fast guys will not tell you much. I do not consider myself tyo be one of them. I have never had that level of dedication.
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I would like to have seen that race is there any film would you know?
 
baz said:
I would like to have seen that race is there any film would you know?
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We have just had a federal election in Australia. Just prior to it, I shopped around looking for a grant to pay for the Historic Winton to be televised. The politicians are prepared to write letters in support of a grant application. I will persevere. Next year, the whole meeting might be televised. It is a bit different - I think you guys would really like it. If it happens I will get a copy of the video and upload it to Youtube. Bob will be riding Clatworthy's Norton again, as well as his own G50' The meeting is run by the Austin 7 car club at the end of May each year.
I will be talking with Bob. I will see if I can get a photo of the ES2. I don't even know if it has a featherbed frame, but it seemed to handle extremely well. It turned tight into the corners. But that was not important. It's speed was unbeatable.
 
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Bernhard said:
Did u see the YouTube film about practice at Scarborough riding I believe a pushrod Norton posted on this site a while back?
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Theoretically the only difference between a pushrod motor and a DOHC motor should be reliability. In our historic races Jawa speedway motors in featherbed frames have been as fast as Molnar Manxs.
I was talking to Bob's wife yesterday. She said Geoff Clatworthy has put a lot of work into the ES2. It is not something I would ever do with an ES2 motor. A Jawa motor would be quick enough for me.
One if my friends is Geoff Duke's nephew, Keith Campbell. His uncle was Keith Campbell - the Australian rider, who was killed while racing in Europe., Keith junior and his fasther George were playing with pushrod Matchless motors. I suggested he should try a Jawa motor, so he bought two. First time out he beat the $80,000 Manxes. But there is not much tuning you can do to a Jawa motor, they are fast as they come without doing mods.
I would never have thought an ES2 motor would get there.
 
I did not realise this report was on this forum. Apparently there is now a video of one lap of the race I watched at Historic Winton 2022. I am trying to get it - might be on Youtube.

www.accessnorton.com

Racing in Australia with an ES2

I would not normally share one of my riders reports, but after a little deliberation I have decided to provide an edited version as a bit of an insight for others who may never have the opportunity to race a single cylinder Norton. This is bike is essentially a short stroked ES2 in a Manx...
www.accessnorton.com www.accessnorton.com
 
Tuning on a dyno with a wideband A/F gauge is proper. Reading plugs is archaic

But who's got a dyno and wideband :cool:
 
I think that most of us street riders should be tuning for reliability and long engine life.
 
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