Ignition timing advice

Status
Not open for further replies.
I don't worry much about the actual value of my ignition advance, as long as it does not change - because I set it, then jet to it. If I ever disturb the Boyer pick-up, I always check that the motor has not gone too lean. If it runs lean, I sometimes get a miss at mid-throttle. If I detect that, I stop and raise the needles a notch. My main jets with methanol are nearly 700 Amal. At full throttle, the motor never runs lean.
If you rum methanol at 12 to 1 comp., you use much more fuel. Theoretically if all the fuel is used efficiently, you should get more power. But there might be something else happening when you raise the comp. ratio. My 850 on methanol is quite quick enough. There is probably more to be gained in developing the gearbox and steering geometry than there is in raising the comp. ratio
I think the Commando engine was designed to run on methanol, I have never experienced any other which responds so well to it.
 
gortnipper said:
I use the strobe with my TS to make sure I am not a dumb ass. Well, at least regarding timing.
Click to expand...
That is a very good idea. I have done that, but usually I am too lazy. The actual value of the advance does not matter much, as long as it does not change. That also applies to the advance curve, if there is one.
 
If you have ever ridden an Indian which has the hand advance/retard twist grip, you find that as you wind the advance on the power reaches a very broad peak. I use to wind ithe advance on until the engine started to show distress , then back it off slightly. I do similar with jetting against a fixed advance. Lean it off until I get the miss, then raise the needles one notch.
 
" I don't worry much about the actual value of my ignition advance, as long as it does not change - because I set it, then jet to it "

Hi.

You have written this a couple of times now and sorry I have to say I 1000 % do not agree with you.

I'm not going to make the argument but just suggest reading Gordon Jenning on spark plugs and how to read them including getting timing right.

The section where he talks about the specks of soot on the central porcelain has been of tremendous help to me in tuning my bike. This is an old articles but it is absolutely excellent in my opinion.

 
johnm said:
" I don't worry much about the actual value of my ignition advance, as long as it does not change - because I set it, then jet to it "

Hi.

You have written this a couple of times now and sorry I have to say I 1000 % do not agree with you.

I'm not going to make the argument but just suggest reading Gordon Jenning on spark plugs and how to read them including getting timing right.

The section where he talks about the specks of soot on the central porcelain has been of tremendous help to me in tuning my bike. This is an old articles but it is absolutely excellent in my opinion.

Click to expand...
And, you know when you've got it very wrong when you find tiny sliver balls on the porcelain.
 
johnm said:
" I don't worry much about the actual value of my ignition advance, as long as it does not change - because I set it, then jet to it "

Hi.

You have written this a couple of times now and sorry I have to say I 1000 % do not agree with you.

I'm not going to make the argument but just suggest reading Gordon Jenning on spark plugs and how to read them including getting timing right.

The section where he talks about the specks of soot on the central porcelain has been of tremendous help to me in tuning my bike. This is an old articles but it is absolutely excellent in my opinion.

Click to expand...
John, I am with you, but.....

Have you tried reading plugs recently?, with current 98/99 Octane petrols....no Avgas added.

Whilst the detonation warnings still show, the general readings are much more difficult...

If you want to read plugs easily, you need some lead!
 
Bernhard said:
First, let me say that air/fuel ratio does not usually affect ingition timing, but octane ratings of the fuel does.
Didn't you get any timings advice with the camshaft?
......
25 degrees sounds too far retarded, how are you checking this, are you using a degree disc and a strobe?
Click to expand...
One, I missed this earlier, but I bought a PW3 from Norman White and I got ignition timing advice with it.

Clear and unequivocal, 31 degrees fully advanced, with the question, why would you use anything else?

Two, out and about the race circuits, I have found quite a few running Commando motors at 26 degrees!

These were mainly in sidecars, but they swear by it!

Rod length may have an impact if you are using non-standard parts, whereby less advance may indeed work.

What am I using today, with a different cam, a short stroke and long, long rods, about 28!

What would I recommend if you are going for a dyno run, 28! And assuming everything else is working fine, adjust for best power at the rpm you will use for most of your riding!

I might also have recommended not to run a PW3 on a road bike, but that is another story. PW3 is a great cam for a race bike.
 
SteveA said:
John, I am with you, but.....

Have you tried reading plugs recently?, with current 98/99 Octane petrols....no Avgas added.

Whilst the detonation warnings still show, the general readings are much more difficult...

If you want to read plugs easily, you need some lead!
Click to expand...
Hi.

I'm trying to remember. I probably tuned the bike using No 1 race gas which I used for a few years. But then it became very expensive and I used NZ pump 98 gas.

I determined the ignition timing on race gas and methanol and could see the pepper spots when I was a bit advanced.
 
SteveA said:
One, I missed this earlier, but I bought a PW3 from Norman White and I got ignition timing advice with it.

Clear and unequivocal, 31 degrees fully advanced, with the question, why would you use anything else?

Two, out and about the race circuits, I have found quite a few running Commando motors at 26 degrees!

These were mainly in sidecars, but they swear by it!

Rod length may have an impact if you are using non-standard parts, whereby less advance may indeed work.

What am I using today, with a different cam, a short stroke and long, long rods, about 28!

What would I recommend if you are going for a dyno run, 28! And assuming everything else is working fine, adjust for best power at the rpm you will use for most of your riding!

I might also have recommended not to run a PW3 on a road bike, but that is another story. PW3 is a great cam for a race bike.
Click to expand...
Interesting stuff there.
I wonder if there's anyone here who runs JS Motorsports high compression (~10.5:1) pistons, PW3 cam, std peashooters and carbs who has similar data?
While waiting for my belt drive kit, I want to recheck the accuracy of the timing scale, which leads me to thinking about what advance to aim for.
 
Joachim said:
The Trispark goes to full advance at 3500rpm.
This can be checked dynamically by strobing at >3500rpm or statically by slowly rotating the engine by hand and checking when the LED on the stator plate comes on. When I compared static and dynamic in the past it was always close enough. I just dont have access to my strobe light at the moment.
Click to expand...
Might be easier to rotate the crank. (Sorry, couldnt help myself)
 
texasSlick said:
Excessively retarded or late timing will turn the header pipes blue, which many interpret to be a hotter engine. Not so, .... the blue indicates the header pipes are hotter than normal, but the cylinder and head temps are cooler than normal.

This happens because late timing results in fuel being burned in the exhaust ports and header pipes, rather than in the cylinders. Of course, fuel burned in the exhaust port does not contribute to power or economy, but will raise the temperature at the headers.

Slick
Click to expand...

SteveA said:
One, I missed this earlier, but I bought a PW3 from Norman White and I got ignition timing advice with it.

Clear and unequivocal, 31 degrees fully advanced, with the question, why would you use anything else?

Two, out and about the race circuits, I have found quite a few running Commando motors at 26 degrees!

These were mainly in sidecars, but they swear by it!

Rod length may have an impact if you are using non-standard parts, whereby less advance may indeed work.

What am I using today, with a different cam, a short stroke and long, long rods, about 28!

What would I recommend if you are going for a dyno run, 28! And assuming everything else is working fine, adjust for best power at the rpm you will use for most of your riding!

I might also have recommended not to run a PW3 on a road bike, but that is another story. PW3 is a great cam for a race bike.
Click to expand...
This is good advice. Jim Comstock's dyno showed -5 HP @ 4500 rpm for PW3 vs a stock cam. It also showed +3hp @6500 vs stock. So good for racing, provided you generally keep the revs well above 5000. Not great for most road riders where we pull long 8% grades at 4-4500rpm, sometimes loaded two up with luggage.
On the other hand, it could add to the fun with a hooligan road bike. If you do short fast rides, no passenger, no luggage, then max midrange isn't so important. A midrange lull then a high rpm hit of extra power is great fun.

Glen
 
Last edited:
I said it before, all advance figures are given at sea level.
At higher altitude, say over 5000 ft, it is better to add a few deg.
In the Alps I set it at 33 - 34°.
(and leaner, of course..)
 
Last edited:
SteveBorland said:
Interesting stuff there.
I wonder if there's anyone here who runs JS Motorsports high compression (~10.5:1) pistons, PW3 cam, std peashooters and carbs who has similar data?
While waiting for my belt drive kit, I want to recheck the accuracy of the timing scale, which leads me to thinking about what advance to aim for.
Click to expand...
Bad form to reply to ones own questions, I know. However, I've just found a mail from Jim Schmidt, recommending 28 degrees on high compression engines, so I'll keep to that.
 
worntorn said:
This is good advice. Jim Comstock's dyno showed -5 HP @ 4500 rpm for PW3 vs a stock cam. It also showed +3hp @6500 vs stock. So good for racing, provided you generally keep the revs well above 5000. Not great for most road riders where we pull long 8% grades at 4-4500rpm, sometimes loaded two up with luggage.
On the other hand, it could add to the fun with a hooligan road bike. If you do short fast rides, no passenger, no luggage, then max midrange isn't so important. A midrange lull then a high rpm hit of extra power is great fun.

Glen
Click to expand...
I ran a PW3 on my race bike.

Not much help for a street bike but I found extending the inlet tract to 13.5 inches got the power back around 4500 and kept the top end gain as well.
 
SteveBorland said:
Bad form to reply to ones own questions, I know. However, I've just found a mail from Jim Schmidt, recommending 28 degrees on high compression engines, so I'll keep to that.
Click to expand...
I think that is excellent place to start. And probably finish.

My 100 plus dyno runs with a 500 twin Norton. Basically the same SS head casting as an 759 850 10.25 CR showed 28 to 29 degrees to be just right.
 
Last edited:
Without verifying the degree plate the advance could be anything and it is a bit of fluffing around to check it.
I would be surprised if running nicely with 26° was actually that, more likely more in reality unless mechanically verified.

Ignition timing advice
 
Time Warp said:
Without verifying the degree plate the advance could be anything and it is a bit of fluffing around to check it.
I would be surprised if running nicely with 26° was actually that, more likely more in reality unless mechanically verified.

Time Warp said:
Without verifying the degree plate the advance could be anything and it is a bit of fluffing around to check it.
I would be surprised if running nicely with 26° was actually that, more likely more in reality unless mechanically verified.

View attachment 80670
Click to expand...

I did say above that I checked the timing marks. That was done when the engine was apart with a dial gauge straight onto the pistons. Also, I set the bike to 32 degrees, it ran quite alright on the road with no pinging. So I cant imagine the timing marks being completely out.
Click to expand...
 
A dial gauge will not find an accurate TDC even a micron reading gauge.

My post was somewhat generic.

A waste of time but just to show how inaccurate that method can be.
That was repeated and was where the gauge said TDC was.

ps2.jpg
 
Last edited:
Time Warp said:
A dial gauge will not find an accurate TDC even a micron reading gauge.

My post was somewhat generic.
Click to expand...

Well, dial gauge used in the same way as shown in your photo as a way to determine a certain position of the piston before an after TDC. Then middle the degrees for an accurate TDC. Is that acceptable?
 
Status
Not open for further replies.

Similar threads

Dan1950
  • Locked
Verifying Ignition Timing Marks
2
Replies
32
Views
2,651
marshg246
marshg246
Schwany
P11 static ignition timing, getting it close
Replies
0
Views
913
Schwany
Schwany
Nortorious
  • Locked
Advice for new Commando owner (Duplicate)
Replies
16
Views
1,635
L.A.B.
L.A.B.
Nortorious
  • Locked
Advice for new Commando owner (2021)
2 3 4
Replies
72
Views
7,470
Starvingphotog
Starvingphotog
Richard Tool
  • Locked
Ignition timing
Replies
7
Views
1,499
L.A.B.
L.A.B.
Back
Top