Leak Down Test (Don't Laugh!!)

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Grumpy knob said:
Does anyone with crank balancing experience have any comments regarding the difference in weight of the pistons? I`ve also included a picture of the small end modification.

http://s628.photobucket.com/user/sk...[user]=100741386&filters[recent]=1&sort=1&o=0

http://s628.photobucket.com/user/sk...[user]=100741386&filters[recent]=1&sort=1&o=1

http://s628.photobucket.com/user/sk...[user]=100741386&filters[recent]=1&sort=1&o=2
Click to expand...

Thanks for posting the pics/info.

I must admit, looking at how much material is removed from the small end for the larger gudgeon pin is food for thought!
 
I hate Photobucket !!

click, I finally got to see the comparison between the small ends, and as you say, it is food for thought, mostly "what if "...
 
cliffa said:
I hate Photobucket !!

click, I finally got to see the comparison between the small ends, and as you say, it is food for thought, mostly "what if "...
Click to expand...

Has anyone heard of a early 920 conversion loosing a small end?

And yes, photobucket is a pain, is there an easier way?
 
Lately I've been using Google drive (although I don't like Google much either) but at least folks can see the pics you've shared with them.

Good question about the 920 failures. it seems that some people are very happy with them, but i don't know if they are the Norvil conversions.


Cheers,

cliffa.
 
Although it goes against the grain for most of us to think about hacking out a little end eye like that, I for one, haven’t heard of a little end letting go as a result.

Has anyone else?
 
Fast Eddie said:
Although it goes against the grain for most of us to think about hacking out a little end eye like that, I for one, haven’t heard of a little end letting go as a result.

Has anyone else?
Click to expand...

Fast Eddie said:
Although it goes against the grain for most of us to think about hacking out a little end eye like that, I for one, haven’t heard of a little end letting go as a result.

Has anyone else?
Click to expand...

I'm ringing Mick Hemmings,Steve Money & Pete Lovell for advice today, I'll ask them about the small end & see if they have any experience of it letting go with the 13/16 pins.
 
Well be warned...

If you ask 3 independent experts the same question, you’ll get 4 different answers !

More seriously, here’s my guess:

Mick will tell you that 920s are complete junk.

Steve will tell you he wouldn’t trust those rods.

Pete will tell you it’ll be fine.
 
Fast Eddie said:
Well be warned...

If you ask 3 independent experts the same question, you’ll get 4 different answers !

More seriously, here’s my guess:

Mick will tell you that 920s are complete junk.

Steve will tell you he wouldn’t trust those rods.

Pete will tell you it’ll be fine.
Click to expand...
+1, that's exactly what I will say if you don't ....! go for one and do it .........!
 
marinatlas said:
+1, that's exactly what I will say if you don't ....! go for one and do it .........!
Click to expand...

Interesting, I'm aware all these experts have a particular way of doing things & will not endorse something they have not done or do not offer as a service now.

Sometimes you pickup little 'bits' of info. in between the party line being spoken which can help in the decision making process.

I'm also talking to RGM which, from a Norton point of view, are quite agnostic and will give a fair appraisal of the options open to me. I've dealt with them in the past & have found their work to be of the highest standard.
 
You could also give a call to Norman White, great bloke with unparalleled experience of all things Norton.

So, you would have 4 experts and 5 answers to choose from...
 
No updates, Friday must be a bad day to contact some of these guys, had a limited amount of time to ring but couldn't get through to anybody!! Maybe they're reading this thread :)

I removed the other piston & took some pictures of the crank & cam. I can't see any markings on the cam. I'm going to measure the lift in the cam over the weekend & identify from this measurement, or should I say you guys will :)

Anyway, here's the pics, I just hope your educated engineering eyes don't see any problem with the cam :rolleyes:

Leak Down Test (Don't Laugh!!)
Leak Down Test (Don't Laugh!!)
Leak Down Test (Don't Laugh!!)
Leak Down Test (Don't Laugh!!)
Leak Down Test (Don't Laugh!!)
Leak Down Test (Don't Laugh!!)
Leak Down Test (Don't Laugh!!)
Leak Down Test (Don't Laugh!!)
 
Based on what I see from the pics, the cam looks OK to me. Make sure the tappets go back in the same location they came from; if they don't, the cam WON"T be OK for very long! ;)
 
You're going the right way to piss a machinist off, you've gone and engaged a very talented man and then asking everybody else for advice, fast eddies comments are probably very correct on their opinions
 
So you really need to answer the fundamental question of "why did the pistons scuff"?

If not mentioned already, try finding an undamaged and minimally worn portion of piston skirt and corresponding barrel and check the clearances with a feeler gauge to get some idea of where these piston/bore combinations started out at. My hunch is inadequate clearance but you don't know that until you or someone checks (if possible). I can speculate all sorts of other exotic reasons for the scuffing but no point in going there ...yet. Hopefully it was just inadequate piston skirt clearance. If you cannot do the checking then definitely have the machinist conduct the checking.

When you removed the pistons, were any of the rings hung up (stuck)? Though I saw the skirt damage I don't recall seeing any heavy smearing of the skirt into the ring lands.

Apologies if some or all of these questions have been asked already.
 
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