Leak Down Test (Don't Laugh!!)

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If the vertical scores are not that bad (as you describe) then I’m gonna guess your pistons will be quite badly damaged, and as I already mentioned, have possibly closed up on the rings. I say this because I’ve been quite surprised in the past about how well my bikes have behaved and performed even with many relatively deep scores!

Regarding your honing marks, they look more like someone has cleaned up the bores with a flap wheel to me!

I still see no reason why you should consider changing your barrel if suitable OS pistons are available?

If you really want to change them, why not ‘go for it’ and fit Maney barrels?

You could use nice Maney pistons too. But you’d have to bush the little ends back down and perhaps the crank would be out of balance for lighter pistons?

You gotta draw the line somewhere (NOT something I’m good at BTW). Like-for-like OS pistons from Norvil seem like the most economical solution I’d say.
 
According to a video I found on YouTube, horizontal honing marks like that can lead to broken rings, and over oiling due to oil retention.


cliffa.
 
Fast Eddie said:
If the vertical scores are not that bad (as you describe) then I’m gonna guess your pistons will be quite badly damaged, and as I already mentioned, have possibly closed up on the rings. I say this because I’ve been quite surprised in the past about how well my bikes have behaved and performed even with many relatively deep scores!

Regarding your honing marks, they look more like someone has cleaned up the bores with a flap wheel to me!

I still see no reason why you should consider changing your barrel if suitable OS pistons are available?

If you really want to change them, why not ‘go for it’ and fit Maney barrels?

You could use nice Maney pistons too. But you’d have to bush the little ends back down and perhaps the crank would be out of balance for lighter pistons?

You gotta draw the line somewhere (NOT something I’m good at BTW). Like-for-like OS pistons from Norvil seem like the most economical solution I’d say.
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Really appreciate your insights :)

Can't wait now to see the pistons!!!

It's amazing how well, apart from the smoke, the bike was running, perfect tickover and when I put the head on for the first time I did some high speed testing and the bike just kept pulling all the way to 90mph when I backed off! but the engine felt it could easily keep going. All done on private roads of course :rolleyes:

Makes total sense about the pistons, if I can get oversize ones I'll get a rebore done etc.

I'm just aiming to get the Norton back on the road, just for touring & plodding around!;)
 
cliffa said:
According to a video I found on YouTube, horizontal honing marks like that can lead to broken rings, and over oiling due to oil retention.


cliffa.
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Interesting, unfortunantly the chap who rebuilt this engine is no longer with us, so I can't ask him any questions.

I know he got the liner & piston kit from Norvil & got somebody to fit the liners. I'm unsure if the liners from Norvil come pre-honed or is it more typical that liners, once installed have to be honed/machined to fit the rigs/pistons???
 
Don’t know if you can try this, you could hone out the vertical groves yourself with an low speed electric drill and fit new piston rings, but the piston / bore clearance will be bigger than stock, as long as it’s not bigger than a .005-6 tho. feeler gauge in there you should be all right.
 
hobot said:
Wesley and I learned not to use the oil moistened hot rod cool KN type filters d/t too soon rings/scoring smoking so not unreasonable to suspect similar as mentioned.
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We tested the K&N s on Dan Smith's Rapide with the Vancouver to Tierra Del Fuego run in 2000 . It was 8,000 miles each way with 800 miles of gravel each way. The following year the same bike did Vancouver to the Arctic Circle ,2200 miles each way, several hundred gravel on that run too.
The bores were fresh before the start of the South America trip.
On examination after the Arctic Circle trip, the bores were still perfect.
K&Ns work, have no fear.

One problem was recently encountered on another bike fitted with some off brand Pod filters. The problem was filter disintegration.
The filters were a few years old but looked OK from a couple of feet away . On close inspection and when held up to a light it became obvious that the filter material under the wire mesh had disintegrated in places. So not only was road grit getting sucked into the engine, those pieces of oil soaked, grit covered filter material went thru the engine.
This did quite a bit of bore damage.
These were not proper K&NS, they were some eBay special copies that turned out to be a less than stellar deal.

Glen
 
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Not doing much useful around here either. I forget click's details of prior behavior before smoke showed up.

Smoke source still a mystery but shows how far either side of TDC leak down must be done. The good psi reading/holdings supports the view scoring is mostly visual burnishing new dry rings might burnish out themselves. If scored to matter one would expect more carbon/varnish on piston sides. Maybe just too much smoke to ride that much to show up. Can't wait to see rings pistons in hands to deepen the plot. Craig alerted us-you to check piston/bore gap and feeler method too crue to bother with. Take barrel to decent engine machinist to check bores/piston clearance before buying anything yet. Tricky part of hobby is making good efficient choices w/o always knowing where to throw money at first.

Scraching at straws on inhaled causes. Carb slide pieces leave pock marks in chamber, grit and carbon excess scores bores. Glad couple 1000 miles gravel travel with K/N protected the big Vtwin and many live a long time with them so don't know what might account for that. Type of gravel/dust levels traffic/winds, placement of intake dodging most particle blasts. Commando's split air to slap back together right where Norton put ham can or bell mounts of racers. In Ozark Gravel cases we are going below hi way speeds, usually in walls of close trees allowing long lingering dust ya can't see but can feel on face/eyes. Wes/me would not follow each other in same line or had to hang far back not to choke. Not following same best line on THE Gravel is bad juju. At times Wes and I had single carbs on so used standard /common smallish K/N's but put layer of ~1" thick filter foam around them after early ring replacements with only lightest 2 seconds in/out hone clean up.

What's the hemi chambers look like?
 
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Interesting comments about what you guys are seeing in the pictures. I can't explain what could have caused these marks. Although it's a 1975 MK3 it has the MK2 ham can air filter using a paper element.

As stated earlier & a comment was made about the bike being left for long periods & the oil maybe deteriorating. The longest it tends to be left is 9 months, so not sure if that's an issue?

In a few hours I'll be tearing into the barrels.

I was thinking of setting up a pay per view channel so you guys would have to pay to see the pistons :)
 
Mr. Rick said:
I was surprised to see the vertical marks extending all the way to the top of the bore, implies the top ring is getting all the way up to the gasket level?
Is this typical?
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The chunk of alloy on the bore would suggest the ring land and other parts of the piston have big smeary pickups on them
 
I'm going to be an optimist! The left side wasn't smoking. So the bore can't be as bad as we imagine from the photos. Can you feel those grooves in the right side? Maybe your rings are broken and causing the scuffing (euphemistic word for gouges) and it was the rings after all that were passing the oil. I don't think you should assume the worst until you see the pistons and get a chance to start measuring stuff. Maybe the original clearance was too tight and you are gonna get away with honing this.

(OK so maybe this is how I sleep at night. Don't knock it!)
 
and the prize goes to . . . . . . . . . .Fast Eddie "If the vertical scores are not that bad (as you describe) then I’m gonna guess your pistons will be quite badly damaged"

So this is it boys feast your collective eyes on the pictures below.

I did some spanner work on a mates Susuki RGV 250 (2 stroke) he raced, this is the last time I saw pistons like this from a seized engine!!!

Can't figure out what the heck caused this? I've REALLY looked after this bike, changed the oil way before it needs to be changed, toured over in Wales & all over Ireland & it has never missed a beat!!! Can't imagine the first 500 miles did this damage so it must have taken place on my watch (I purchased the bike with 500 miles on the bore)

Have the bottle of whiskey out, purely medicinal!!!!

BOTH PISTONS BACK OF PISTON

Leak Down Test (Don't Laugh!!)


BOTH PISTONS FRONT OF PISTON

Leak Down Test (Don't Laugh!!)


RIGHT PISTON BACK AND FRONT OF PISTON

Leak Down Test (Don't Laugh!!)
Leak Down Test (Don't Laugh!!)


LEFT PISTON BACK AND FRONT OF PISTON

Leak Down Test (Don't Laugh!!)
Leak Down Test (Don't Laugh!!)
 
Ouch !!!

Pistons too tight in bore, or judging by the honing job maybe the bores aren't round ?
 
Perhaps there was something less than 4.5 thou skirt clearance set when the cylinder was fitted for the pistons?

Glen
 
worntorn said:
Perhaps there was something less than 4.5 thou skirt clearance set when the cylinder was fitted for the pistons?

Glen
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I think you said this earlier that modern watercooled engines tend to have much tighter clearance and some guys doing reboring work who are not use to older air cooled engines don't leave the clearance required??

I've had this puppy well over the ton on occasions!! This is what I find strange to my inexperienced brain, the bike ran REALLY well, plenty of power & poke and once I sorted the carbs, ticked over like a clock!!!

I'm sure a bit of wet & dry on the pistons and bore will sort everything out, or maybe a course flap wheel:rolleyes:
 
Has it ever nipped up or felt sluggish on a big climb, hot day?

Glen
 
worntorn said:
Has it ever nipped up or felt sluggish on a big climb, hot day?

Glen
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Can't say it ever did, if the engine had acted strange I would definitely pull over & investigate.

I chased way over rice running for quite a while & eventually replaced the needles & needle jets.

I also had some oil seals coming off the valve guides but eventaully got this sorted (not this head)

Apart from that a few leaks here & there, issues with sprag but apart from that nothing to report!!
 
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