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Discussion Starter · #1 ·
I had the spark plugs out and was wanting to perform a leak down test since my bike isn't running too well. I have a Lang Tools leak down tester and it has only an M14 short and long adapters. However I have a compression test kit that has several adapters and happens to have an M10 x 1.0 like this:

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So it is a short reach. I thread it on either the short reach M14 hose or the solid long reach M14 and try to thread it in to the engine and the threads won't start. I assume it is a short reach and the threads aren't engaging. Anyway, I would be concerned if I threaded it in all the way because if I tried to unthread it and the M14 hose come out, I wouldn't be able to remove the M10 adapter because it requires a 17mm socket and none of my 17mm sockets will fit down the recessed hole of the engine.

Sorry for what is likely a dumb question, but what am I missing here?
 

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Tighten the piss outta the two & shove it in you don't need to tighten the adapter all that tight in the plug hole that's what the O ring is for
 

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Discussion Starter · #3 ·
Yeah the problem is that I can't even get the 10mm adapter to start threading in the hole. Never had this problem before on car engines.
 

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Discussion Starter · #4 ·
I have looked down the hole with an inspection camera and also felt what happened when I put the spark plugs in. If I let the bottom the spark plug sit on the lip at the bottom and then slide it off of that lip, it drops a fair amount before it hits the top thread. So I am think the first thread is recessed in the threaded bore enough that the short reach 10 mm adapter I have won't reach the first thread. So something like this:

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So the bottom of the M10 adapter bottoms out before the first male thread on the adapter can engage with the first female thread in the head. The problem is that ever M10 adapter I see appears to be fairly short like mine. Mine appears to only have 4-5 threads and the most I have seen is one from Innova with 8 and it seems to only be available by buying a compression tester kit.

 

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Discussion Starter · #5 ·
That ended up being the problem. I went to the local auto parts store and they had a set of cheap adapters. The 10mm one had about 3-4 more threads on it than mine did and it threaded in just fine. Thanks.
 
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Let us know what leakdown numbers you came up with I've never leaked a desmo engine & often wondered without valve springs & no cylinder pressure if it would be better than 10%

A valve spring engine with that much leak has issues
 

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See what I had to do to my adapter, it was too large to fit the plug well. Be sure your new is small enough to fit in there otherwise it will not seal perfect.
1013659
 

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I guess you could call that a spring........a clock spring

I was referring to a coil spring with 130lb closed pressure or more
 

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Discussion Starter · #10 ·
See what I had to do to my adapter, it was too large to fit the plug well. Be sure your new is small enough to fit in there otherwise it will not seal perfect.
I haven't had the chance to do the test yet, but it appeared to seal at least moderately. But maybe that was the problem all along and I could have turned down my old adapter. Do you happen to remember what size you had to turn it down to?
 

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Discussion Starter · #12 ·
Let us know what leakdown numbers you came up with I've never leaked a desmo engine & often wondered without valve springs & no cylinder pressure if it would be better than 10%

A valve spring engine with that much leak has issues
Unfortunately I was unable to do the leakdown test properly with a warm engine. By the time I got everything off and obtained an adapter that worked, the engine was long since cooled and I wasn't ready to put everything back together to get it warmed up. So take these values with a grain of salt because a warm engine would give a little better numbers from my experience.

I got 12.5% on both cylinders. I listened for leaks at the exhaust, radiator, and at the intake valves and I heard nothing. The only sound I heard was out of the oil fill. So the rings were the major source of leakage, which has been the case on every healthy engine I have ever tested.

You have heard an engine with 10% leakage has issues? I have heard anything above 20% you still wouldn't lose much horsepower and that 30% is where you might start thinking of a rebuild. I have never tested a newly rebuilt engine, but I am not sure I have ever tested an engine with less than 10%. The Snap-On leakdown tester shows 10-40% as low leakage, 40-70% as moderate. I think that is a bit extreme myself. But I was pretty happy with 12.5% on both cylinders with a cold engine.
 

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That's not bad for a springless motor (yea I know about the puny clock spring) our LS race engines leak 6 to 8% after a freshen up, after a good 100 hours of beating on them somewhere around 15% anything over 20% it's time to send it off to the builder for another freshen up

I'd like to know why it's going past the rings has it been hot or late oil changes?
Squirt some oil in your plug holes while cold spin it with the starter button a bit & test it again if it goes down (it should) nothing really wrong if nothing changes you have a stuck ring or two possibly cylinder wall scoring now it time for the bore scope I don't know about Ducati's chrome bores but KTM's chrome is the shits & always peeling off
 

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Discussion Starter · #14 · (Edited)
That's not bad for a springless motor (yea I know about the puny clock spring) our LS race engines leak 6 to 8% after a freshen up, after a good 100 hours of beating on them somewhere around 15% anything over 20% it's time to send it off to the builder for another freshen up

I'd like to know why it's going past the rings has it been hot or late oil changes?
Squirt some oil in your plug holes while cold spin it with the starter button a bit & test it again if it goes down (it should) nothing really wrong if nothing changes you have a stuck ring or two possibly cylinder wall scoring now it time for the bore scope I don't know about Ducati's chrome bores but KTM's chrome is the shits & always peeling off
This bike is low mileage (7500mi) and had the oil and filter changed every 1000-1500 mi or less (because it isn't ridden much). The oil and filter have never gone over 1 year. Also it has never been hot..maybe 225F max. Doesn't every engine leak past the rings a bit?

I most recently used this gauge on an old Mazda B2300. It was 15-18% when I did a cold test and 12-15% when I did it warm. So I wouldn't be surprised if this one was 10% or better if it had been warm.
 

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Try the oil trick & see What happens

Another thing if it has been used alot on short trips not allowing oil not to get get fully warmed up for a length of time like 180° plus degrees to burn off any condensation from a prior short not so warmed up ride, also startup cold enrichment (aka choke) allowing cylinder wall glazing from always being cold & rich from short rides. Just starting it up to hear the motor/exaust for "just a minute" is a bad thing especially if it happens alot.
 

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Discussion Starter · #16 ·
Try the oil trick & see What happens

Another thing if it has been used alot on short trips not allowing oil not to get get fully warmed up for a length of time like 180° plus degrees to burn off any condensation from a prior short not so warmed up ride, also startup cold enrichment (aka choke) allowing cylinder wall glazing from always being cold & rich from short rides. Just starting it up to hear the motor/exaust for "just a minute" is a bad thing especially if it happens alot.
Mine typically sits for a long period of time, then goes on long trips of between 100 and 500 miles. It has rarely had short trips or even stop and go driving. I will try the oil trick.
 
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