I think I got the goody out of that one.

There is no detonation sensor. There is an input for a sensor but I have never been able to filter out all the normal Norton noises from detonation. A little ringing from the fins would fool the sensor and retard the timing. I may have to revisit this.

There are cylinder temp and fuel mixture readouts on the dashboard. They were all reading normal before and after the seizure. Any deviation from the correct fuel mixture would have been sensed by the oxygen sensor and corrected.

Engine pinging will absolutely cause a seizure in an air cooled motor. It causes major piston heating which causes the piston to grow larger than the cylinder bore. It is no surprise that the left piston seized first as that is the cylinder that normally runs hottest on a Commando. The major damage seen is from continuing to run the engine with excessive piston to cylinder clearance caused by the seizure.

The engine is high compression and pretty highly tuned. It has always pinged if the octane was not high enough. I could get away with 90 octane at my home elevation of 5000 ft but sea level required at least 92 to prevent pinging.

I have seized a couple Norton engines before with detonation. All it takes is a few seconds worth of steady pinging and a forged piston will outgrow the hole every time. If that would have been a cast piston it would likely have just broken. Jim

Wow, three blown engines on one trip! It is almost like the Combat Commando days. Maybe I will leave the old MK3 alone, just living dangerously with an extra half point compression and some open peashooters. Not too adventuresome I know, but it might be best to leave the experimental stuff too the Comstock brothers.
Were all of three engines of the high performamce variety?
I wonder if two plug heads would help with the pinging problem? As near as I can tell, two plug heads allow the timing to be pulled back about 5degrees from where it needs to be on a single plug head at same CR.

Glen

Here is what a detonation caused seizure looks like right after the seizure. This is probably what my piston looked like 3000 miles before the teardown. The excess clearance caused by the seizure of this piston sounded about the same as my bike did.

Jim, thanks for the deeper anatomy views of your extra special and the types of pathology we are all prone to. Discouraging that instrumentation gave no alert. We covered the knock sensor being overwhelmed by normal engine ringing for A/F EFI reference but maybe with head phones might detect while working up a tune, though not practical for the long hauls unless listening a while on each new gas top off. I assume TC's pistons were so extra special no way to have a spare sent to fix for return ride. I've learned we all ride around on faith alone till a show stopper, again.

1. What evidence on the still intact piston example revealed it suffered detonation damage?
2. Can the steel rod still be trusted?
3. Will your polished cases be compromised now like your Bro's prior traumatized Combat?
4. What CR did you run with?
5. Did oil pump have protective screen or got to chew on piston and ugh ring pieces?
6. Will you recover and reuse this engine before ya come up with another 'one in a row' engine?

hobot said:

Jim, thanks for the deeper anatomy views of your extra special and the types of pathology we are all prone to. Discouraging that instrumentation gave no alert. We covered the knock sensor being overwhelmed by normal engine ringing for A/F EFI reference but maybe with head phones might detect while working up a tune, though not practical for the long hauls unless listening a while on each new gas top off. I assume TC's pistons were so extra special no way to have a spare sent to fix for return ride. I've learned we all ride around on faith alone till a show stopper, again.

1. What evidence on the still intact piston example revealed it suffered detonation damage?
2. Can the steel rod still be trusted?
3. Will your polished cases be compromised now like your Bro's prior traumatized Combat?
4. What CR did you run with?
5. Did oil pump have protective screen or got to chew on piston and ugh ring pieces?
6. Will you recover and reuse this engine before ya come up with another 'one in a row' engine?

Click to expand...

1. It was a high compression engine and was broken in [350 miles or so] before the timing was "messed with" This was the result of the first ride after removing the ignition rotor and putting it back "just where it was before". He said it was pinging and then "just died". The timing was at 34 degrees when I checked it with a light.
2. I have no reservations about re-using the rod.
3. I don't think the cases were damaged although I do worry about fatigue from the high mileage.
4. If my memory serves me right the c/r was 10.2. I don't remember what the cranking compression was- but it was high.
5. There is the stock screen for the sump pump.
6. I will rebuild this engine unless I find other issues on teardown.

Main drive belt too? I didn't know anyone did that. Or am I seeing things?

Jim, I'm wondering if you are prepared to post details of your injection system ? It looks very attractive to me. A friend owns Motec which makes the EMS supplied to Porsche etc. - Might be a way forward ?

Your crankshaft is beautiful, however it looks too light. Back in the sixties the Triumph Saint had a very light shaft and did not perform very well.

DogT said:

Main drive belt too? I didn't know anyone did that. Or am I seeing things?

Click to expand...

http://www.quietpowerdrive.com/QPDhtm/F ... Drives.htm



Although Jim made his own. Like everything else.

I have tried to contact QPD several times. Now answer and they don't reply to emails.

Didn't he pass?

Here is a picture of my crankshaft. It is no lightweight at several pounds heavier than stock. I have been down the lightweight crank road before also -with not so good results.



Tha camchain tensioner was doing its job. The chain was at the correct amount of play and there was no measurable difference between the new heavy duty chain and the chain with 3500 miles.







The camshaft was good for wear but unfortunately it is bent about .005 inch. It was hard to turn in the bushings by hand. That goes along with the bent pushrod I found.





The rod bearings look good for the mileage.



The superblends don't show any wear but the drive side inner race is no longer a press fit on the crankshaft. They are the original bearings that were in the engine when new.



The cases look pretty good aside from a little shrapnel blasting.



Now for decisions. Maybe it is twingle time. Jim

bwolfie said:

I have tried to contact QPD several times. Now answer and they don't reply to emails.

Click to expand...

To say he is not good at communication is putting it mildly... having said that though, Ozzie is getting on, and looking to wind down!

I worked with him on a final drive for my slimline featherbed, but have had to do a ton of additional work to get clearance... not easy!

swooshdave said:

DogT said:

Main drive belt too? I didn't know anyone did that. Or am I seeing things?

Click to expand...

http://www.quietpowerdrive.com/QPDhtm/F ... Drives.htm

Although Jim made his own. Like everything else.

Click to expand...

I believe Leia had a QPD rear belt on her bike for a time. She was back to a chain at Barbers due to some kind of issues.

I will never go back to a rear chain. The zero maintenance bit with no mess has me spoiled. Jim

worntorn said:

Wow, three blown engines on one trip! It is almost like the Combat Commando days. Maybe I will leave the old MK3 alone, just living dangerously with an extra half point compression and some open peashooters. Not too adventuresome I know, but it might be best to leave the experimental stuff too the Comstock brothers.
Were all of three engines of the high performamce variety?
I wonder if two plug heads would help with the pinging problem? As near as I can tell, two plug heads allow the timing to be pulled back about 5degrees from where it needs to be on a single plug head at same CR.

Glen

Click to expand...

My brothers engines were both stock, low compression with a single Mikuni carb. The first motor obviously had a compromised case and the second motor was an unknown used motor he picked up cheap somewhere. He had never looked inside beyond pulling the cylinder head.

Twin plug heads are normally useful on a large bore slow burning combustion chamber. I doubt that it would be of much help on a fast burning chamber like a Norton and would be a real challenge to implement. Jim

acotrel said:

Jim, I'm wondering if you are prepared to post details of your injection system ? It looks very attractive to me. A friend owns Motec which makes the EMS supplied to Porsche etc. - Might be a way forward ?

Click to expand...

The fuel injection on my bike is all built by me and uses an ECU based on the Megasquirt system and is tuned with Tuner Studio. It has some custom firmware and a special ignition system with both low and high resolution pickups added to allow kickstarting. It has been a really good performer.

I have done some work with the Motec system but I never was able to get it to work on a kickstart bike. The processor took more revolutions than a kickstarter would provide before it would sync to the crankwheel and provide a spark.

I am not presently building any more injection systems as tuning them is beyond the means of most riders and there is not enough of me to take care of a bunch of systems. Jim

i had ozzies starter and rear belt system on my bike but continually had issues to resolve... i have the starter system working well now but it is virtually all my own design although based on oz's... much like old britts did (i am guessing) for their starter kits...... there is only one bracket of oz's original kit that is stll on my bike.... and even it has been 'tweaked' numerous times... all other parts including bendix, ring gear, clutch basket, motor sprockets and belts have been replaced with other items from other suppliers and/or been modified to work by me... to ozzies credit though... he did supply me with a lot of stuff to try and get me through these issues

same is true of the rear belt system... i had new sprockets machined to match the super torque pattern belts supplied by oz but was still having issues with excessive wear and squeaking... finally got fed up with fixing and modifying things and went back my 520 o-ring chain setup so i could get out and do some riding.... but like jim, i would much rather have a rear belt than a chain

Hi Leia,
It was good to finally meet you at Barbers [sorry I screwed up the spelling of your name] Jim

Hi jim

it was good to see you again as well and get to talk to you at length... glad you made it home.... sorry your motor became a problem... i had a few problems on the way home... my clutch hub notched itself pretty good and caused some issues but nothing too serious... and my battery side cover went for a solo ride on one of the alabama interstates... its nice and flat now... will hang on the wall real well ..... hope to start following up with you on that other issue asap

comnoz said:

It is no surprise that the left piston seized first as that is the cylinder that normally runs hottest on a Commando.

Click to expand...

So I'll ask. Why is it that the left cylinder normally runs hottest on a Commando?

By the way, that case of beer you left in the paddock was excellent!