Leak Down Test (Don't Laugh!!)

cliffa · Feb 8, 2018

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 "...

Grumpy knob · Feb 8, 2018

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 "...

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

And yes, photobucket is a pain, is there an easier way?

cliffa · Feb 8, 2018

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.

Fast Eddie · Feb 9, 2018

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 · Feb 9, 2018

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?

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.

Fast Eddie · Feb 9, 2018

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.

Brooking 850 · Feb 9, 2018

Now I know why I stopped using photo bucket, whole page is smothered in ads!!!!!

marinatlas · Feb 9, 2018

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.

+1, that's exactly what I will say if you don't ....! go for one and do it .........!

click · Feb 9, 2018

marinatlas said:
+1, that's exactly what I will say if you don't ....! go for one and do it .........!

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.

Jagbruno · Feb 9, 2018

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...

Gilesy · Feb 9, 2018

Try Norman White, he knows as much as anyone.

click · Feb 9, 2018

Gilesy said:
Try Norman White, he knows as much as anyone.

Thanks Lads, Norman is now on the 'list'!!

Fast Eddie · Feb 9, 2018

Norman will say that 920s are good for pulling tree stumps out but not for motorcycles!

Jagbruno · Feb 9, 2018

Fast Eddie said:
Norman will say that 920s are good for pulling tree stumps out but not for motorcycles!

Yep, definitely sounds like him!! ;-)

click · Feb 9, 2018

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

MexicoMike · Feb 9, 2018

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!

splatt · Feb 9, 2018

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

worntorn · Feb 9, 2018

Machinists are pissed off already. Its part of the apprenticeship training.

Glen

Dances with Shrapnel · Feb 9, 2018

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.

click · Feb 9, 2018

splatt said:
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

Although I had a good chat with PL, I didn't make any definite arrangements with him. I explained I was not sure what I was going to do next. I've asked him a few more questions about the 850 option. Apologies if I gave the impression I had engaged with PL's services.

I've got two options as I see it & I'm looking for as much info. as I can before making a decision:

1. Get the existing 920 barrel bored out to +20, fit new pistons, bike is back on the road. Least expensive option.

2. Change back to a std 850, replace conrods, barrels, pistons. Bottom end needs to be split. More expensive & will take more time.

All I'm doing is asking the guys who are regarded as some of the top Norton machinists over this side of the pond what they think. As has been said I'll probably get 5 opinions from 4 machinists! but that's OK. Ultimately it's up to me to make my own mind up!!

Leak Down Test (Don't Laugh!!)

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