Leak Down Test (Don't Laugh!!)

Deets55 said:

Click,
Re: gasket thickness
I believe most standard copper and the old flame rings were .030”. New AN flame rings are .040”. Some people go even thinner than .030” on their copper gaskets. Depending what you are currently using a .043” will probably lower your CR slightly. Looking at Glen’s post about CR it will probably not make much of difference.
FWIW. There are a lot more knowledge people on this forum than me on things Norton, but if I were you and the head is off I would pull the barrels.
It’s not that much more work, you get to see the entire bore and rings. Take some measurements and put new rings in. One more thing, I had a blocked vent tube and had a similar problem, the way I found out was while the engine was running I opened the oil filler cap and heard a rush of air come out.
Pete

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Many thanks for the explanation on CH gasket thickness. I've checked all the vent & breather tubes & everything is clear.

I'd say the barrels will be coming off at some stage!!

OK, admittedly I might have missed this bit. But moving up to Part 2, you got the head back from Jim, put it on and the bike smoked the first time you started it after a few minutes?

Let's propose this. The oil didn't get hot enough to burn in part 1 until the engine warmed and was pumped into the muffler. Now the head and engine are fine but your muffler is still full of oil that smokes when it warms up! Take off the muffler, run the bike, if it smokes start tearing it down!

It's why we own wrenches.

Russ

Torontonian said:

Got the head off yet ?

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No, not yet.

My plan is to give the bike a good run on Friday, if I can get some time, get the engine nice & hot, give it a few blasts and get some heat into the engine & pistons.

If after doing that the bike is still smokey, I'll pull the head & look for leaks on the head gasket into the combustion chamber, I'll post some pics as we all like a good pic

I'll bit the bullet & remove the barrel also and see if I can get to the bottom of this smokey mystery tale!!

rvich said:

OK, admittedly I might have missed this bit. But moving up to Part 2, you got the head back from Jim, put it on and the bike smoked the first time you started it after a few minutes?

Let's propose this. The oil didn't get hot enough to burn in part 1 until the engine warmed and was pumped into the muffler. Now the head and engine are fine but your muffler is still full of oil that smokes when it warms up! Take off the muffler, run the bike, if it smokes start tearing it down!

It's why we own wrenches.

Russ

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Hi Russ, that is quite possible BUT I'm still seeing oil on the spark plug, I've run the bike 3 times on the bench for 4-5 minutes each time & oil is on the RH plug. The LH plug is dry.

I'll try it just to discount the oil in the muffler theory before I take a hammer, sorry, spanner to the Norton

I missed the oil on the spark plug. Heck, why wait for Friday. I'm not going to sleep well until you know for sure. Start wrenching.

rvich said:

I missed the oil on the spark plug. Heck, why wait for Friday. I'm not going to sleep well until you know for sure. Start wrenching.

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It's like a murder mystery who done it

Maybe it was Mr. Green in the garage with the oil can

Good things come to those who wait! (I'll stop now)

Do you have a security camera in the garage? Maybe a "friend" is coming over every night, pulling the RH spark plug and dumping tablespoon of oil in there...

And yes, I know people who do/have done stuff like that. NOT ME, of course...

MexicoMike said:

Do you have a security camera in the garage? Maybe a "friend" is coming over every night, pulling the RH spark plug and dumping tablespoon of oil in there...

And yes, I know people who do/have done stuff like that. NOT ME, of course...

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OK, where were you on the evening of the 28th January 2018 and do you have any witnesses to collaborate your whereabouts

If you decide to take it for a flog, just be careful and keep your ears wide open and fingers on the clutch. If the diligence has been done on the cylinder head I can't help but think that maybe the RH piston might have scuffed for some reason. Maybe even a broken or cracked ring land or piston.

click said:

OK, where were you on the evening of the 28th January 2018 and do you have any witnesses to collaborate your whereabouts

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Ah...that's the night I was draining some fuel out of an Electra Glide; owner can't figure out why his gas mileage is so bad Two Honda representatives can verify I was with them at the time.

I'm back!!

Minor update:

1. I did a compression test again, I was being a bit optimistic on my previous compression figures which were from memory. These are the latest results

LH cylinder 165 RH cylinder 170 (it's the RH that smoking!!) Slightly higher reading might be due to oil being in the bore.

2. I also did another leak down test. This time I had more hassle trying to keep the RH piston from moving under the air pressure. I put the bike in gear & held the rear break which allowed me to get a consistent reading. My poor little compressor, it only has an 8 litre tank!! it can just about get up to 100.

On the gauges I can hold a consistent 30 on the LH gauge (input pressure) & the right hand scale (leakage side) only drops by 5%

LH Cylinder 5-8% leakage RH Cylinder 5-8% leakage

So apart from me reporting incorrect compression figures the stats show I have a very healthy engine!!!

This just inforces my position that it's the oil ring on the RH piston that's not sealing but the compression rings are fine!

Hopefully the weather is OK for Friday & I can take the Norton out for a good spin! If its still smoking the head will come off and then the barrels

Ay up Click, You could swap your silencers over before you go for a blast, that would put that one to bed and keep you in good books with the neighbours. Just to confirm, the carbs haven`t been touched have they? I went through all this a while back with a plug fouling problem. I did the stem seal rope trick, RH crank seal, then replaced rings all to no avail. Obviously i`d been through the ignition first then checked every thing inside the new premiers was marked correct to spec which they were. I even dropped the RH needle down but no different. Finally I swapped everything out of the carbs over to the other side and the fault transferred to the LH cylinder, swapping the needles back again first and the fault returned to the RH cylinder. On close inspection, the RH needle taper was slightly different even though it was marked up the same number. I put a needle out of an old carb in and it was cured. I`d had the new premiers on a while before I really noticed the fault so didn`t suspect brand new carbs would be the fault. Yours is very noticeable though and does appear to be rings looking at your video, smoking when it`s on the throttle but as stated before, sometimes there is more than one culprit. Hope this info is helpful to anyone else with similar issues as a carb swap is a lot easier than a ring change. Best of luck, Al.

Grumpy knob said:

Ay up Click, You could swap your silencers over before you go for a blast, that would put that one to bed and keep you in good books with the neighbours. Just to confirm, the carbs haven`t been touched have they? I went through all this a while back with a plug fouling problem. I did the stem seal rope trick, RH crank seal, then replaced rings all to no avail. Obviously i`d been through the ignition first then checked every thing inside the new premiers was marked correct to spec which they were. I even dropped the RH needle down but no different. Finally I swapped everything out of the carbs over to the other side and the fault transferred to the LH cylinder, swapping the needles back again first and the fault returned to the RH cylinder. On close inspection, the RH needle taper was slightly different even though it was marked up the same number. I put a needle out of an old carb in and it was cured. I`d had the new premiers on a while before I really noticed the fault so didn`t suspect brand new carbs would be the fault. Yours is very noticeable though and does appear to be rings looking at your video, smoking when it`s on the throttle but as stated before, sometimes there is more than one culprit. Hope this info is helpful to anyone else with similar issues as a carb swap is a lot easier than a ring change. Best of luck, Al.

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Hi GK (I refuse to use your forum name ;-) )

That's REALLY interesting. I was having general running issues, not holding a steady idle etc. & replaced needles, needle jets etc This was when I had a different RH4 head on the bike which a company in the UK worked on & I ended up chasing various issues with this head related to the overall poor assembly of the head (loose rocker shafts!!)

I'll double check the carbs and just for a laugh I'll swop over the needles & needle jets, you never know! But as you say the amount of smoke from the RH cylinder is more than an out of spec. carb!

Not sure if I can swop the silencers over, I think they're handed, I'll check later.

Good points but badly adjusted carbs can't make oil smoke UNLESS oil in ingested into the air box. Fuel smoke is black/dark while oil smoke is white-ish. What the video shows is oil smoke.

MexicoMike said:

Good points but badly adjusted carbs can't make oil smoke UNLESS oil in ingested into the air box. Fuel smoke is black/dark while oil smoke is white-ish. What the video shows is oil smoke.

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Fair enough, probably can't see it in the video but when I blip the throttle the centre of the smoke 'cloud' is quite dark/black but the outer part is white. I totally agree that oil in the combustion chamber is the problem (oil on plug etc.) I'll have a look at the carbs anyway, just in case it could be contributing to the smoke 'cloud'!!

over rich fuel is infamous for washing oil off bores so ring sealing grinds away.

Leak down testing: I have always done my LDT with an engine that was at operating temp no more than 20 minutes prior to the testing. I use 80 PSI with the cylinder under test at TDC compression. It has been my impression that testing a warm to hot engine with 80 PSI is closer to what the engine is actually experiencing when it is running. I lock the engine by holding the rotor fixing nut; the process is considerably more accurate if you have an assistant.

There was an illuminating thread about 18 months ago were Comnoz demonstrated the variance in LDT when the piston was 15 or 20 degrees either side of TDC. I don't recall the actual conclusion, but the LDT results were different. My take away was that the LDT was most effective (diagnostic) with the piston at TDC.

Click, you have plenty of homework suggested, I would add, only, that if you do pull the barrel off that you measure everything that has a spec listed and examine all sealing/seating/sliding surfaces for their characteristics of flat, round, square, concentric and parallel,

Happy exploration, this shouldn't be a mystery.

bore/ring sealing issue don't often happen a tdc but few degrees below either side of tdc which imposes sigifnicant torque to resist once off either side of TDC under even 80's PSI. If good sealing then even 80's PSI should over come mere brake resistance so blocks/chucks or brealer bar and wedge block trapping on crank nut needed to suffice holding for reliable results. If not shocked a the sudden lost of restrained crank motion then ain't yet done it right.

Thanks for the advice on doing a leak down test, this test is new to me as I've never done this before. When performing the test I did have to hold on to the kickstart as the rear brake was slipping. It took a few attempts as I couldn't hold the piston steady using the kickstart but eventually figured out a way of holding it in place, just!!

So I agree it is difficult to keep the pistons in place while pressurising the cylinder.

One thing I did notice, which might or might not be the correct method is, if I built up 80-100PSI on the compressor & connected the leak down tester to the quick connect extension in the spark plug hole, the piston would move from the sudden rush of pressure BUT if I connected the leak down test with the compressor at zeroPSI & built up the pressure gradually I had a better chance of keeping the piston at TDC.

I only did this test out of curiosity, the leak down tester I have is a cheap chinese type thing, I just wanted to see if there was any big difference between left & right cylinder. The actual empirical figures I'm getting, I'd say have no real meaning other than for comparison between left & right.

Once I get the long spin out of the way and even being optimistic I doubt it will make any real difference, other than I want to make it off my list of things to do.

When I get to stripping the head & barrels off I'll get somebody who has more experience & the necessary tools to check the spec of everything, I know my limitations!!

Interesting development!!

I contacted Norvil about composite gaskets for the 920 conversion that they supplied for this bike. I vaguely remember 10 years ago when I originally removed the head that it had a composite gasket but from then on I always used a 920 copper gasket as that was the only thing available for a 920 (|I know I never asked about the composite gasket at the time!!)

This is what I got back from Norvil:

Hi, Yes you can use 850 composite gasket, we never use a 920 one.
The big bore size will be big enough that's why the pistons are machined at the tops.

So, it looks like I can use an 850 composite gasket with the 920 conversion I have on the bike!!!! Dohhhhh!!!!

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