Leak Down Test (Don't Laugh!!)

[click]

OK, I got 'Thor' out & gave the rose collars a serious pounding!! and the head eventually started to budge and came up very slowley.

I'm presuming becuase the Plibond was so new, I had no road miles on the head install, the 'grip' it had on the head was full on?

Anyway, I'll continue the removal of the head & start on the barrels!!!

 

[click]

OK got the head off with the usual flapping around with the pushrods

I used a method hotbot had mentioned a while back. I put the oil line bolts back into the head & using cable ties I was able to lift the head right up to the underside of the top frame member & suspended it from there.
This allowed me to access the pushrods, push them as far into the head as they would go, I used more cable ties to secure the pushrods, I then supported the head with one hand & cut the cable ties suspending the head. I was then, with a bit of flaffing around, able to tilt the head to the side & get one set of pushrods out, then the other then head off

I'll take the barrels off tomorrow & have lots of questions for you guys

Here's some pics of the bores, pistons, & head:

LEFT HAND BORE

RIGHT HAND BORE (THIS IS THE SMOKEY ONE!!)

PISTONS & HEAD

 

[Grumpy knob]

Looks like it`s time for a rebore old fruit.

 

[Madnorton]

To where? new liners more like.

 

[click]

To where? new liners more like.

Norvil do have oversized 920 pistons, +20, +30 & +40

I was thinking of bringing it back down to a std 850 BUT the conversion I have has larger than standard gudgeon pins + the crank has been balanced for the 920 pistons which are heavier, I would have to split the cases & go for an entire engine rebuild!

Is it possible to put another set of std 920 liners into the barrels? or is this a once off process?

Once I get the barrels off I'll check the ring gaps but the marks on the bore don't look good

 

[Grumpy knob]

I would think you would be able to fit new liners ok which would save you the crank work. I also have a 920 barrel with the old type heavier pistons which i need to get round to reboring before fitting to my cafe racer but will be able to use the new type lighter pistons which don`t require a crank rebalance but if your crank has already been balanced for the old type then the way to go is new liners and pistons unless your pistons are actually still good that is. fingers crossed for you.

 

[Dances with Shrapnel]

A couple of hard pulls WOT throttle uphill would have burnished those bore grooves out just fine.......not.

click, are you running an air filter? Looks like you took that bike through a steel mill slag yard w/o an air filter.

Early in this thread you wrote: "Because the bike has had VERY light use & ends up sitting for large periods of time unused, this is why I'm leaning towards the oil control ring being gunked up & is maybe stuck (unlikely I know!!)"

Used oil can go bad just from sitting unused for long periods of time in the bike. The fact that you have similar scoring on both bores makes me wonder what is the cause?

 

[texasSlick]

Nickel plating can repair the damage and bring a cylinder back to a standard oversize.

IMO, a less risky and less costly procedure than relining.

For reference ..... http://mxratracing.com/cylinder.html

Slick

 

[Hobot]

ah poo, just goes to show ya its waste of time doing misleading confusing tests so seasoned Nortoneers just dig in for unexpected faults to work around. 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. Speaks well of your lack of wet sump between starts to delay oil fill enough a few min before reaching bores. Still can't ignore gasket risk each/every time so hope ya make right decision this time. I get 3 *over* re annealing successes but lose bet on 4th time. Assume gasket blast bang beaten out of flatness by then. I'd rather have a V8 while riding.

 

[74850]

HI Click

Sorry to see the cylinder damage, Does it look worse in the photos than it actually is? I'm just wondering if the piston to bore clearance was right when the engine was originally assembled. when I had my cylinders bored to .040 over the I told the machinist I wanted clearance of approximately .0045, they came back with .002 which would have been fine if the bike was liquid cooled but not good for air cooled. Long story short is I did not measure and assembled the engine anyways (stupid me), ended up burning oil and scuffed pistons. took it apart the next winter and found similar vertical marking to yours, I was however able to hone it out to the correct clearance, replaced the pistons with new rings and all is ok now. This may or may not help you but get yourself a good bore gage and measure real good, maybe its saveable. I would not overbore any further if you can avoid it.

One thing to note, looking at the bores you can see some of the crosshatch pattern though the glazing and it is way too flat, It should be approximately 45degrees. When you have a very flat cross hatch it will cause the rings to flutter or break, and higher oil consumption as the rings will tend to hydroplane on the oil built-up.

Craig

 

[Fast Eddie]

Looks like you found the issue! I think you’ll find that your piston skirts will look even worse. You may even have tight rings due to closed up ring lands.

I think we can confidently say that my advice to give it a good thrashing was highly unlikely to have helped!

If oversized pistons are available, why on earth are we discussing new liners or nickel plating the bores? Just buy some new OS pistons, rebore, enjoy!

I agree with the above poster ref ensuring the engineer listens to your instructions, those more familiar with modern engines really do struggle to believe / accept our requirements!

You threw us a bit of a red herring here click. As you have only just re fitted the head, we had assumed that the bore must be in good condition, otherwise you’d have seen it and fixed it.

There is a lesson for you here to check more carefully in future. Whenever you intervene in an engine like this you should ALWAYS check EVERYTHING.

You removed the head to fix the head... rather than remove the head to investigate the problem.

In fact, when intervening in an old engine, we should see it as an opportunity to look for early signs of any / every problem we can find, in order to fix it before it happens.

Not preachin’ ... jus’ sayin’ ...

 

[Mr. Rick]

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?

 

[click]

Looks like you found the issue! I think you’ll find that your piston skirts will look even worse. You may even have tight rings due to close up ring lands.

I think we can confidently say that my advice to give it a good thrashing was highly unlikely to have helped!

If oversized pistons are available, why on earth are we discussing new liners or nickel plating the bores? Just buy some new OS pistons, rebore, enjoy!

I agree with the above poster ref ensuring the engineer listens to your instructions, those more familiar with modern engines really do struggle to believe / accept our requirements!

You threw us a bit of a red herring here click. As you have only just re fitted the head, we had assumed that the bore must be in good condition, otherwise you’d have seen it and fixed it.

There is a lesson for you here to check more carefully in future. Whenever you intervene in an engine like this you should ALWAYS check EVERYTHING.

You removed the head to fix the head... rather than remove the head to investigate the problem.

In fact, when intervening in an old engine, we should see it as an opportunity to look for early signs of any / every problem we can find, in order to fix it before it happens.

Not preachin’ ... jus’ sayin’ ...

Totally agree about checking the engine/bore which I did not!!! Lesson learnt.

 

[Fast Eddie]

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?

Probably caused by crap / debris above the rings

 

[click]

HI Click

Sorry to see the cylinder damage, Does it look worse in the photos than it actually is? I'm just wondering if the piston to bore clearance was right when the engine was originally assembled. when I had my cylinders bored to .040 over the I told the machinist I wanted clearance of approximately .0045, they came back with .002 which would have been fine if the bike was liquid cooled but not good for air cooled. Long story short is I did not measure and assembled the engine anyways (stupid me), ended up burning oil and scuffed pistons. took it apart the next winter and found similar vertical marking to yours, I was however able to hone it out to the correct clearance, replaced the pistons with new rings and all is ok now. This may or may not help you but get yourself a good bore gage and measure real good, maybe its saveable. I would not overbore any further if you can avoid it.

One thing to note, looking at the bores you can see some of the crosshatch pattern though the glazing and it is way too flat, It should be approximately 45degrees. When you have a very flat cross hatch it will cause the rings to flutter or break, and higher oil consumption as the rings will tend to hydroplane on the oil built-up.

Craig

Thanks for your comments, gives me a little bit of hope.

I did run my finger & finger nail around the bore & there's no scratches I can detect (not very scientific I know!)

I'll get a chance to take the barrels off this evening & I'll put some pics up of the pistons, hopefully their not toast!!

Worst case, I'll need to get a rebore (+20), new pistons, rings etc. (that's if I have the correct pistons!!, I think Norvil did two types of 920 pistons, ones with cutaways for the valves & ones without. According to their site the ones with cutaways have oversize pistons available, the other type does not. I'll ring them once I investigate further!)

The other option is to swop out my barrels for another set of 850 coverted to 920 barrels std bore from Norvil, again further investigation required!

Interesting about the cross hatch pattern. Most, if not all, of the other pics I've seen have a greather angle on the crosshatch (45degrees etc.) I can see that the crosshatch on these bores is almost horizontal. Is this just a different honing tool was used?

As I said I'll have the last part of the puzzle unravelled later today

 

[cliffa]

Hi click, sorry to see this. I agree with Dances with Shrapnel, it does look like something has been ingested. Do the pics make it look worse than it is?

From your pictures It also looks like the head gasket was leaking at two spots. One by the oil return, and on the other pot ( which looks to be running very rich) by the barrel bolt recess.

cliffa.

 

[cliffa]

Click, good point about the honing marks, it looks like the honing tool wasn’t moved in and out enough so the pattern is not right.

Cheers,

cliffa.

 

[click]

Hi click, sorry to see this. I agree with Dances with Shrapnel, it does look like something has been ingested. Do the pics make it look worse than it is?

From your pictures It also looks like the head gasket was leaking at two spots. One by the oil return, and on the other pot ( which looks to be running very rich) by the barrel bolt recess.

cliffa.

I think the pictures, I hope the pictures!!, make it look worse than it is. In the pics it looks like vertical 'gouges' in the bore. I can't detect any 'scratches' using my finger or finger nail but I've had very little dealings with engine strips! so what would I know.

Obviously I'll get the barrels decked whatever I end up doing to ensure flatness.

I also need to check the drain hole to ensure there are no obstructions. I did already have a look at this & used thin wire & compressed air to ensure it was clear, but you never know!

 

[click]

Click, good point about the honing marks, it looks like the honing tool wasn’t moved in and out enough so the pattern is not right.

Cheers,

cliffa.

Craig noticed this & mentioned it in his post, otherwise I would be none the wiser!!!

 

[click]

Overall there's a lot worse that could be going on in your life!!

Some money & time will get all this sorted!

What I find the most difficult is finding somebody on this side of the pond who you can trust to do a good job!!!