71 norton top end break in now?

concours · Sep 26, 2012

Rule 1) DON'T OVERHEAT IT. Like get stuck in a traffic jam. The rings need to have compression load to seat properly, use repeated bursts of 1/2, 3/4, then full throttle roll ons lasting 5 seconds, on up. Don't redline it, but pampering is not good either.

iceteanolemon · Sep 26, 2012

ok heres the ride report....

came home today to beat the sun as fast as I could. I didnt have tons of time to ride around but I wanted to get it up to operating temp and get 5-10 miles on it.

turned the chokes on and gave it a kick. Fired up right away and sounds decent. I noticed some white puff coming from both pipes. This happens fotr about 30 seconds. I proceed to warm it up for two min and turn the choke off. While the bilke is idling I turn it around and get ready.

Riding down the street everything is normal. Bike seems to be running well.

I roll out through the gears adding more load to the motor with a roll on accellerating up to about 50mph. I approach a stop sign and decellerate to a stop. I hold the clutch in and listen to the bike settle down. As I rill out from the stop there is a long 5% grade and I accellerate up the grade with healthy throttle shifting about 35-4000 rpm. Bike sounds good. when in fourth gear on the throttle I turn around to see if I am smoking and the exhaust doesnt show signs of smoke at all.

I proceed down country roads and over a hill, this riding is going through the gears and accellerating and decellerating over transitions from 30mph to 50mph.

I get the bike to about 60mph at the most. On the downhill runs I get a pop but it sounds nice.

I come to stop at the bottom of the hill and let the bike settle down. I let it idle a bit and I watch the traffic going by. The bike idles down and when I add throttle to go I notice it dies on me. I stalled it but this happens without me letting the clutch out. I dont know if my idle is too low or what. I place the shifter in neutral and kick it over. Starts first kick and no smoke.

I take off back for home and the bike runs well. I take an extra run around the block just to feel the bike accellerating a bit. A few more turn arounds while accellerating and I stil ldont see smoke.

I do notice a sound of an exhaust leak coming from the header to muffler. When I get home I check and notice there is exhaust blowing from the right side mating from header to pipe. I also notice my right rear tank mount is messed up.

No leaks not even the valve covers!

I take the plugs out while its warm to do a compression test. I notice my compression tester rubber oring is eaten away but I do the test anyways. I have to kick a few times but on each cylinder it is about 160psi. They are even so I am happy! The plugs are a little light. I hope they are not too lean.

Other than that thats the ride for my first "break in" session....

motorson · Sep 27, 2012

I know I'm jumping in late here but I want to comment on the piston/bore clearance issue discussed earlier in this thread.

All the pistons I have ever fitted called for a certain clearance from the piston to cyl wall. The ring end gap is also specified and is to be set by the mechanic. All the old engine rebuilding courses and manuals would show a picture of the ring end gap grinder. You can also use a flat file to shorten the ring if necessary.

One shop where we got some engine work done wanted the cylinder and the top compression ring. They would bore until the end gap was right! Almost always made a sloppy bore. I would drop off my work with the piston only but then they used a feeler gauge :cry: (South America) I finally went to dropping off work with just a piece of paper with the size and tolerance written on it and got some perfect work out of them!

The zero tolerance thing comes up on Honda cam ground pistons. The measurement is at the widest part of the skirt on the bottom of the piston ninety degrees to the wrist pin. The theory is that when it is all hot the piston is parallel and fits the bore just right. I did a Honda XL250 that way (not zero but .001) and it never seized and lasted for 14 years that I know of.

Cheers, Dan.

DogT · Sep 27, 2012

Icetea, when you come home from your ride, let the bike idle for a bit, and then slowly open the throttle. Make sure you don't have a dip or one side or the other is breaking down. Adjust the idle pilot for a tiny bit rich, or if one side stops hitting with increased throttle, adjust for that. A slightly rich idle can compensate for the dip coming off idle, but not if it's bad. It took me a while to get mine adjusted, and I still notice the idle changes a bit with the weather and it's very sensitive. This is with the Amals of course.

Dave
69S

concours · Sep 27, 2012

motorson said:
I know I'm jumping in late here but I want to comment on the piston/bore clearance issue discussed earlier in this thread.

All the pistons I have ever fitted called for a certain clearance from the piston to cyl wall. The ring end gap is also specified and is to be set by the mechanic. All the old engine rebuilding courses and manuals would show a picture of the ring end gap grinder. You can also use a flat file to shorten the ring if necessary.

One shop where we got some engine work done wanted the cylinder and the top compression ring. They would bore until the end gap was right! Almost always made a sloppy bore. I would drop of my work with the piston only but then they used a feeler gauge :cry: (South America) I finally went to dropping off work with just a piece of paper with the size and tolerance written on it and got some perfect work out of them!

The zero tolerance thing comes up on Honda cam ground pistons. The measurement is at the widest part of the skirt on the bottom of the piston ninety degrees to the wrist pin. The theory is that when it is all hot the piston is parallel and fits the bore just right. I did a Honda XL250 that way (not zero but .001) and it never seized and lasted for 14 years that I know of.

Cheers, Dan.

yes, half a century ago or more, the piston ring manufacturing process was not as precise. They (ring grinders)are hardly used today, except in special cases. Sing with me, again... if the bore is correct, the ring end gap falls right in spec. The "bore her out nice and loose and she won't seize" crowd has created a problem that doesn't need to exist.

IT-L, glad she's running good!

iceteanolemon · Sep 27, 2012

concours said:
motorson said:

I know I'm jumping in late here but I want to comment on the piston/bore clearance issue discussed earlier in this thread.

All the pistons I have ever fitted called for a certain clearance from the piston to cyl wall. The ring end gap is also specified and is to be set by the mechanic. All the old engine rebuilding courses and manuals would show a picture of the ring end gap grinder. You can also use a flat file to shorten the ring if necessary.

One shop where we got some engine work done wanted the cylinder and the top compression ring. They would bore until the end gap was right! Almost always made a sloppy bore. I would drop of my work with the piston only but then they used a feeler gauge :cry: (South America) I finally went to dropping off work with just a piece of paper with the size and tolerance written on it and got some perfect work out of them!

The zero tolerance thing comes up on Honda cam ground pistons. The measurement is at the widest part of the skirt on the bottom of the piston ninety degrees to the wrist pin. The theory is that when it is all hot the piston is parallel and fits the bore just right. I did a Honda XL250 that way (not zero but .001) and it never seized and lasted for 14 years that I know of.

Cheers, Dan.

Click to expand...

Yeah me too! I still need to nip up that header to muffler leak, i can hear it. And I suppose another valve check of course. I think the wonder of riding it around gets lost quick with me though. I am more and more quickly enjoying performing the work.

yes, half a century ago or more, the piston ring manufacturing process was not as precise. They (ring grinders)are hardly used today, except in special cases. Sing with me, again... if the bore is correct, the ring end gap falls right in spec. The "bore her out nice and loose and she won't seize" crowd has created a problem that doesn't need to exist.

IT-L, glad she's running good!

Rohan · Sep 27, 2012

concours said:
yes, half a century ago or more, the piston ring manufacturing process was not as precise. They (ring grinders)are hardly used today, except in special cases. Sing with me, again... if the bore is correct, the ring end gap falls right in spec. The "bore her out nice and loose and she won't seize" crowd has created a problem that doesn't need to exist.

Hepolite rings, that came with Hepolite pistons for Commandos in +0.020 oversize were far too complete for their own good - took a lot of filing to get the ring gaps big enough to meet the specs in the Commando Workshop Manual. Seizure material there, for sure.
Although these pistons/rings haven't been available for a few decades now though.

Still read on these motorcycle lists way too often of pistons that have been bored too tight (car clearances ?) and then had problems. Much better to be loose than tight.... ?
(Factory grading for size is to ensure that a too tight fit doesn't occur ??)

Wonder what specs these new 'hepolite' pistons meet that are now available again ?
Anyone tried them ?

willy mac · Sep 28, 2012

Just had my Barrels bored out to +20 with new type Hepolites, paperwork that came with them gave a suggested 004" piston to barrel clearance, all rings required filing to get the correct end gaps as called for in the workshop manual.
Currently in the running in period using oil supplied by the machine shop that did the rebore with 125 miles on the clock and 2 head re-torques on the copper gasket.

iceteanolemon · Sep 30, 2012

Just took it out for another test run. Did another head torque and valve check. See that the intake valves were in spec but the exhaust valves were at 009. I re adjusted to 008 and then did the oil. The oil doesnt have much in it in the way of metal or anything so things are looking ok.

I do have a little shite smoke on idle but nothing coming when I am running the bike. Hoping this goes away. Otherwise I may find another reason to take this thing apart! I told my wife that I think in order to prepare for my retirement I need a bunch of bikes and a whole bunch of parts. Once I get the bike runnin I tend to want to work on something else for some reason.

Going to get some more oil in it and start riding it a little more seriously. Nothing too crazy, no top speed records but I am certainly not going to baby the thing anymore. I have about 50 miles on it so far....

concours · Sep 30, 2012

willy mac said:
Just had my Barrels bored out to +20 with new type Hepolites, paperwork that came with them gave a suggested 004" piston to barrel clearance, all rings required filing to get the correct end gaps as called for in the workshop manual.
Currently in the running in period using oil supplied by the machine shop that did the rebore with 125 miles on the clock and 2 head re-torques on the copper gasket.

NICE! Did you measure and file the rings yourself? :?:

Rohan · Sep 30, 2012

concours said:
NICE! Did you measure and file the rings yourself? :?:

Yes I did.

Realise this wasn't aimed at me, but thought would throw it in there for good measure.
Maybe we should ask if concours (name unknown...) does ?
And, how many here bore their own cylinders ??!

iceteanolemon · Sep 30, 2012

Rohan said:
concours said:

NICE! Did you measure and file the rings yourself? :?:

Click to expand...

Yes I did.

Realise this wasn't aimed at me, but thought would throw it in there for good measure.
Maybe we should ask if concours (name unknown...) does ?
And, how many here bore their own cylinders ??!

Bore em yourself? pfft... these days the street cred goes to you if you can cast the barrels yourself! Of course in your garage!

Rohan · Sep 30, 2012

iceteanolemon said:
Bore em yourself? pfft... these days the street cred goes to you if you can cast the barrels yourself! Of course in your garage!

Worth mentioning that not even the Norton FACTORY did this. !
Nor very few other motorcycle manufacturers, all through history even.

iceteanolemon · Oct 2, 2012

Rohan said:
iceteanolemon said:

Bore em yourself? pfft... these days the street cred goes to you if you can cast the barrels yourself! Of course in your garage!

Click to expand...

Worth mentioning that not even the Norton FACTORY did this. !
Nor very few other motorcycle manufacturers, all through history even.

For my next project I am ordering one 800lb block of raw steel. And a 1971 commando horn. Im gonna make it happen!

Rohan · Oct 2, 2012

And a file ?
or sandpaper....

Good Luck !

Now where did I put that wheelnut that is the start of the next project.

iceteanolemon · Oct 2, 2012

Rohan said:
And a file ?
or sandpaper....

Good Luck !

Now where did I put that wheelnut that is the start of the next project.

well actually I am digging a pit in the garage floor, going to start molting my tools immediately.

bluemax · Oct 29, 2014

I read this thread with interest
I have just been through fitting new JCC pistons and USA rings.
The hepolite/JCC pistons recommend 4 thou measured at right angle to wrist pin at the bottom of the skirt.
So measuring at the top of the piston would/may give a different reading.
I did mine to 4.5 tho as this was recommended by several people that were in the know.
I have 850 normal steel cylindes and +20 JCC/hepolites.
No aluminium cylinders and high silicon pistons or forged pistons that is a whole new argument on piston clearances.

The rings gaps if I were to listen to every one are on the large side.
At the risk of starting an argument the ring gap being too large is of little consequence with my new rings, as is the poppy cock about making sure that the gap are exactly 120 deg or something apart.
Just for convention I made sure they were not aligned, but would have made no difference it they were not.
Rings are their own identity and are free to do what they want and will and do move/rotate.
As mentioned in one of the lings below it's like lining up all your valve stems at 12 o"clock on you car wheels and driving around the block and expecting them to be in the same position when you get home.

Why do they put ring stop pin in two stroke engines, because the rings will rotate.
Plus imagine the effective area that a locating pin might make to blow by, but it doesn't.
With the ring gap and pin it could be up to 1/8 of an inch.
The key as I see it is tangential pressure from the rings to the bore.
When old engines smoke everyone says look at the ring gap that's the cause but in fact the ring has reduced in diameter and lost it's tangential pressure.

Here is an interesting read about ring gap and it effect

http://www.diagnosticengineers.org/jour ... 20Gaps.php

Also another interesting read about ring rotation.

http://kns.org/jknsfile/v31/A04803285773.pdf

For interest mine runs like a dream, sound solid , no rattling , no blowing smoke nor using oil

Anyway food for thought and just another view on the subject.

Cheers
Peter R

X-file · Oct 30, 2014

I'd read that a few years ago, about 0.060" ring gaps making no noticable difference. As long as the ring otherwise fits well and has correct radial tension, it's fine. I'd always agreed with that, even before I read that article.
Here's another about using a bigger ring gap on the 2nd ring than you use on the top ring. About 30% bigger ring gap on the 2nd ring seems to work well, make more power and use less oil. Some people are even claiming twice the ring life, before they have ring problems.
Most car manufacturers have been doing it on new engines for about 20 years.
See what Barry R has to say, about 1/4 way down the page in this link:
http://www.speedwake.com/forums/showthread.php?t=34413&page=4

mschmitz57 · Oct 30, 2014

bluemax said:
I
Why do they put ring stop pin in two stroke engines, because the rings will rotate.

I always thought the reason for 2 stroke ring pins is to prevent the ring gap from rotating into a port and getting caught on the port edge causing damage.
I never understood how the ring gaps lining up was any worse that having the gaps be positioned 90 degrees apart. Can't the blow-by pressure simply travel between the rings snd squirt out just as easily?

Nater_Potater · Oct 30, 2014

mschmitz57 said:
I always thought the reason for 2 stroke ring pins is to prevent the ring gap from rotating into a port and getting caught on the port edge causing damage.
I never understood how the ring gaps lining up was any worse that having the gaps be positioned 90 degrees apart. Can't the blow-by pressure simply travel between the rings snd squirt out just as easily?

Correct on both aspects. All I got from the old-school thinking was for when a brand-new engine lights; you want the top ring's ends close to the inlet cooling effects as long as possible. Once the rings break in and have good contact with the relatively cool cylinder wall, it doesn't really matter where they end up, as they'll continue to randomly orbit. As for the other rings, you scatter them to avoid causing any sort of wear pattern on a fresh bore.

In the case of two-stroke rings having a large end-gap, two different means of avoiding that are routinely employed:
1) Set the pin half-way into the groove, with the ring ends cut with a small 1/4-round that nests along the pin,

and
2) Recess the pin part-way into the groove, and have a corresponding notch in the ring ends that perch over the pin.

Either method is dictated by the piston manufacture, and requires like rings (which normally are supplied with the new pistons).
Nathan

71 norton top end break in now?

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