"Heading" Out..

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I wouldn't even think a bike would run for more than a few cycles without the piston pockets aligned with the valves. I could see the bike possibly running if the pistons were installed backwards on the opposite cylinder, so the intake valve aligned with the exhaust pocket, and the exhaust valve and intake pockets aligned as well, but it's mind boggling that the valve could carve it's own pocket in the top of the piston without something blowing up.

How does that cam and valve train survive the piston punching the valve back into the head?... It's amazing that a bike that screwed up ran at all. I'd like to see the cam and followers if you get a chance to post a picture.
 
I should have the engine here in 4 to 6 weeks. Step one in rebuilding a customer engine for me is to strip it down to component parts and examine all for obvious anomalies then to measure clearances. I will post pictures and my notes after that.

You would think that with the current configuration that the engine wouldn't even fire up due to bent valves, never mind run long enough to set the timing; a great mystery.

Best.
 
A little more information. The pistons were stamped incorrectly and the Commando managed to get down the road between 300 and 400 miles.

Best.
 
ludwig said:
You can't get that amount of carbon built up in 400 miles.
Click to expand...

The same person who "rebuilt" the engine may have put the rings in upside down, decided that .010 skirt clearance was too tight, installed the rocker shafts 180 degrees out and neglected to install the intake valve seals, or used the ones that have the same flexibility as a condom. Any one of these, and more, would have coked up the piston tops.

I can only assume, at this point, without tearing the engine down, that the valve guides must have an oval shape to have "survived" the intimate contact with the pistons.

Best.
 
So, hypothetically speaking, in a court of law, who would be at fault...

Professional mechanic who installed pistons incorrectly (but correct to the markings) ?

Or the piston manufacturer who marked them incorrectly ?
 
Fast Eddie said:
So, hypothetically speaking, in a court of law, who would be at fault...

Professional mechanic who installed pistons incorrectly (but correct to the markings) ?

Or the piston manufacturer who marked them incorrectly ?
Click to expand...


Interesting question, you ever live in the sue-happy States? One of the reasons I do not "get it running" for customers, who want no other repairs, is that such vehicles usually need brakes, tires an a host of other safety related items looked after just to get the motorcycle up to the point where it is merely dangerous in its own right; the condition it was in when it came out of the manufacturers shipping crate.

I suppose that if a person had enough time and money the attorney retained for this would sue them all and concentrate on the party with "deeper pockets".

Seems to me in this day-and-age that fewer people are willing to take responsibility for their actions and more inclined to becoming a victim. No one lies anymore, but will admit to being "truth challenged". I think I was born too late...

Best.
 
[
Fast Eddie said:
So, hypothetically speaking, in a court of law, who would be at fault...

Professional mechanic who installed pistons incorrectly (but correct to the markings) ?

Or the piston manufacturer who marked them incorrectly ?
Click to expand...

This...
'the attorney retained for this would sue them all and concentrate on the party with "deeper pockets".'
 
That looks like it has more than 3-400 miles on it. So the current owner bought the bike like that? It must have sounded... loud. Or did the current owner replace the pistons recently, it made a lot of noise and decided they needed professional help?

The mismarked parts is a real pisser. You really have to blame the piston manufacturer initially. But this shows the importance of claying every engine that comes apart.



Do some manufacturers consider the left and right differently? Or perhaps in Asia? Or is this just a simple cock up?
 
Nice video, thanks for sharing. My only suggestion would be that both center fasteners, bolt and nut, be installed and snugged prior to rotating the engine for the clay check.

Fixing blame, at this point, IMO is wasted time. What if the "re-builder" offers to make good; he has shown the depth of his experience; would you want to risk the introduction of new problems? Taking any action outside of doing a proper evaluation and rebuild will only consume time and money; the precious resource is time, of course.

Best.
 
Fast Eddie said:
So, hypothetically speaking, in a court of law, who would be at fault...

Professional mechanic who installed pistons incorrectly (but correct to the markings) ?

Or the piston manufacturer who marked them incorrectly ?
Click to expand...

A "professional mechanic" would
1. install them correctly
2. Call/notify the manufacturer AND point of sale of their severe screw up. If the mfg can't mark them correctly then DON'T MARK THEM AT ALL.
If you don't know what is front or back (left and right)on this desaxe engine, then hire someone who does...

3. Just because someone offers to take your money does not make them qualified to do the job.
4. Why pay someone to screw it up, when you can screw it up for free.
:D
 
While certainly a bit loud initially, once the valve has beat the piston into submission and created a new pocket, it will get less noisy. Some spirited high rpm runs later, it may quiet down even more. The builder may just have told the owner that it was a matter of ‘break in’ and it would get better over time and miles....and so it appeared while riding it

The valve pockets on the 750 are huge. You can see by the witness marks how shallow they could have been to give the valve enough clearance. There doesn’t even appear to be any marks on the exhaust side. Of course, cam choice and lift will make a big difference as well

Many of our loved Commandos have been through some hard times but here we are 50 years later, giving them the attention needed to run Well into the future. Pretty cool I think
 
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