Troubleshooting air leak near the head with bonus: cylinder stud pulled out

[2017FLHTK]

I recently picked up a 1993 FXDL off facebook marketplace that has sat for a few years.  I cleaned out the carb, put new spark plugs in, and she started right up.  However, I could feel relatively cool air pulsing out of the front head area (see picture below for where I noticed the air pressure / movement).  The bike has unknown mileage on it (odometer is inop), but I'd guess it's a higher mileage motor that's had a rough life and the motor might be getting tired and in need of new rings.



I sprayed starter fluid all around the intake manifold with the bike running and noticed no change in RPM, so I don't think the issue has anything to do with that area.  It almost seemed as if the pulsing air was coming from the hole where the front cylinder intake pushrod inserts into the head. 

I decided to pull the head to see if I could see any issues, and was half-expecting to see a blown head gasket.  However, the cylinder head gasket seemed to be in good shape and I can see no obvious issues with either the head or the cylinder.  I ran a straight edge along along the surfaces of both the head and cylinder and see no evidence of cracking or warping.



The o-rings were present in the heads for the pushrod tubes, but seemed slightly hard and permanently squished in a flat-ish shape, as opposed to the rounded / tubular shape they have when new.

A few other items of note:
-A few days ago I hooked up a leak down tester and it seemed as if air was escaping in to the intake tract when I had it hooked up to the front cylinder with the piston at TDC.  When hooked up to the leak down tester to the rear cylinder / with the rear piston at TDC it was noticeably leaking air into the rear exhaust pipe.  However, even with me holding the rear brake to keep the rear wheel from spinning while a helper hooked up the leak down tester it seemed like the engine rotated such that the valves changed position and were partially open (the PSI indication on the cylinder leakage dial was rhythmically rising and falling even though the supply dial gauge indicated a steady flow), so it's hard to draw definitive and accurate conclusions.  Perhaps it's also possible that air was escaping past a valve and entering the intake / exhaust tract but then partially re-pressurizing the combustion chamber causing the cyclic PSI readings.  If I was doing it all over again I would have taken the time to remove the primary cover and jam the engine / transmission sprockets together and lock the motor in place.  Regardless, I'm suspicious that the the valves aren't fully seating the same way they did when brand new.
-The previous owner had the carb setup waaaaaay lean (165 main jet / 42 pilot jet).  The bike has drag pipes, so I changed over to a 185 main / 45 pilot jet while cleaning out the carb.  I'm wondering if previously running lean caused the temps to run high, burning off oil in the cylinder and prematurely wearing out the piston rings??
-I pulled the freshly installed spark plugs while taking the front head off and noticed that they already had signs of fouling on them after less than 5-10 minutes of run time while idling on my lift.  To me it looks more like oil deposits than carbon:

-When I pulled the front head the piston top in the cylinder showed a fair amount of carbon buildup.
-All the head bolts required significant force to break free (tapping on a wrench with a deadblow hammer was the only way I could initially get them to budge).  I suspect it was simply rust and corrosion, but it's always possible that at some point they were over torqued by another mechanic.  However, one of the head bolts stuck to the engine stud and spun the cylinder stud all the way out of the engine case.     I was able to get the head bolt off the stud on my workbench, but damaged the stud in the process.
-The cylinder walls seem to be in relatively decent shape, although I can see one small scuff mark



Obviously a few items have to be addressed no matter what. 
-The cylinder stud has to be replaced.  I don't see any damage to the threads in the case, so I should be able to install via the "double-nut" method.  I'll of course run a chase into the case first to make sure the threads are straight.  Are there any other considerations?
-The "puffing air" that originally led me to tear in to the top end isn't really definitively solved for me.  Obviously I'll replace the pushrod o-rings with new, and of course I won't reuse the old head gasket, but since I don't see any obvious signs of what was causing the problem in the first place I'm hesitant to bolt everything back up until I can diagnose and solve the original issue.


So, I'm at something of an impasse here. I bought the bike to flip it after getting it running again, so I don't want to throw a bunch of cash at the problem.  With that said, I have a Jims valve spring compressor tool, so I can put in new valve seals relatively inexpensively.  It's not the end of the world to also instal new Wiseco rings, but obviously that cuts down on my profit.  My biggest concern is tearing into the rear cylinder head bolts and encountering more issues with the cylinder case studs.  I have an induction heater that I can use to warm them up ahead of time, so that should hopefully help them come loose without any drama. 

With all of that said, I'm not sure that new valve guides / rings will solve the "puffing air" problem that started this whole debacle.  Any thoughts or suggestions?

[SixShooter14]

I've had small air leaks around damaged pushrod tube O-rings, so that is definitely a possibility.

1993 should be a head breather, perhaps the breather hole in the head wasn't sealing to the intake back plate? Nothing definitive on that without having it sealed up and tracking down the leak.

[2017FLHTK]

I've had small air leaks around damaged pushrod tube O-rings, so that is definitely a possibility.

Hmmm... thanks for that feedback.

1993 should be a head breather, perhaps the breather hole in the head wasn't sealing to the intake back plate?

Can you help me understand how to check that?  What would be the indication?

The umbrella valves are present in the rocker boxes, without any visible cracks.  I'm not sure how pliable they're supposed to be, but these seem pretty stiff.

[2017FLHTK]

For those following along at home, a user on another forum reminded NOT to chase the cylinder stud threads in the case because "the threads have an interference fit. The studs have a rolled thread."  Glad I didn't screw that one up....

Here's the guidance in the service manual for the stud installation:


 

[SixShooter14]

I've had small air leaks around damaged pushrod tube O-rings, so that is definitely a possibility.

Hmmm... thanks for that feedback.

1993 should be a head breather, perhaps the breather hole in the head wasn't sealing to the intake back plate?

Can you help me understand how to check that?  What would be the indication?

The umbrella valves are present in the rocker boxes, without any visible cracks.  I'm not sure how pliable they're supposed to be, but these seem pretty stiff.

If you felt air with the engine running, then it would be between the head and the air cleaner. Either there's no seal or a poor one allowing the air to get out instead of flowing into the intake tract.

[2017FLHTK]

If you felt air with the engine running, then it would be between the head and the air cleaner. Either there's no seal or a poor one allowing the air to get out instead of flowing into the intake tract.

FWIW, when I put the carb on to the bike I used fresh OEM HD gaskets.

I felt the moving most distinctly down and to the right of the air cleaner and intake tract.It was strongest between the pushrods, approx 5 inches below the head.  While the bike was running I held a lit cigar in that vicinity and could see the smoke moving about, but couldn't determine anything definitive as to the direction of where it was coming from. 

[SixShooter14]

It could definitely be any of the pushrod cover o-rings. If the bike has been sitting awhile they'll get dry.

A breather leak could be blowing any direction, so it's definitely nothing to rule out... Also don't just assume it's not an exhaust leak coming around the heat shield and that's just where you felt it.

[JW113]

Since this a '93, be aware that the 90-94 era Evo cases had a tendancy to crack on the right side area at the apex of the spiggot holes. See attached, this was my '92. There was a somewhat funny saying back then, there are two types of 90-94 cases. Those that have cracked, and those that are going to.


The symptoms of this can bee quite strange. The heads can torque down, but they are NOT held to the case at that area, just the broken chunk, and who knows what can get squeezed out the base gaskets.

-JW

You cannot view this attachment.

[FSG]

a good post and a good use of imgur   

[2017FLHTK]

It could definitely be any of the pushrod cover o-rings. If the bike has been sitting awhile they'll get dry.

A breather leak could be blowing any direction, so it's definitely nothing to rule out... Also don't just assume it's not an exhaust leak coming around the heat shield and that's just where you felt it.

Well, the puffing air felt shockingly cool (essentially room temperature) whereas the exhaust pipes got toasty very quickly from the hot exhaust gases.  Also, these are straight drag pipes with no heat shields over the top.

[2017FLHTK]

Since this a '93, be aware that the 90-94 era Evo cases had a tendancy to crack on the right side area at the apex of the spiggot holes. See attached, this was my '92. There was a somewhat funny saying back then, there are two types of 90-94 cases. Those that have cracked, and those that are going to.

Why you gotta stress me out? 

[2017FLHTK]

I swung by the dealership and purchased the new revision stud, part number HD 16837-85C:


The procedures I posted above (out of the 1993 Factory Service Manual) is only applicable to the older style studs.  The new revision studs mount differently.  HD Tech Bulletin M-1043 has the installation instructions:
�������[i

[kd]

I'll take a crack at a couple of things.  First off, you have to understand the crankcase venting system beforew you can epect to diagnose it.  Very simply, when the pistons go down (and because the rods are on a single crank pin) they compress the air in the crankcase.  That air ecapes up the pushrod tubes into the heads.  The umbrella valves open under that preasure and the air gets moved to and through the galleries and vent out the breather base mounting into the breather to be reconsumed and burned (emission control).  Alternatively when the pistons are going up the lower crankcase pressure is negative and the umbrella valve acts opposite under negative pressure. The puffing you felt likely was in fact a leaking pushrod cover o-ring.  The stain on the head fin seems to support that. The head probably could have been left on (at least for now). 

You can check the breather operation with the engine running by feeling if it is puffing or sucking at the breater base outlet.  A search on here will walk you through that test.  BTW, it is NOT uncommon to find a breather assembly put together wrong.  They are in fact shipped improperly assembled to protect them from damage.

With the leakdown test, if you remove the pushrod covers you can visually confirm (and feel) the pushrods are in fact closed by the loose feel and ability to spin them.  Both must be in that position to be sure they are closed and on the seat with full valve spring pressure.  You have to lock the engine from turning either with a tool or whatever other method you decide works best for you. For example, fuel injected engine flywheels have timing notches on the left flywheel that can be locked in place with a threaded tool through the threaded hole in the left front of the case near the bottom end of the oil filter.  It engages with the flywheel notches and locks it from turning when you add air to the test gauges.  Your method with the cross lock bar is good too but it is still googood to have it in high gear and brake on hard..  If you don't take the time to get it perfect your results are garbage bin and you wasted your time.

Did you do a cranking commression test?  Dry first then wet. That's important engine health information.

Finally, as said, DO NOT use a thread die to clean the threads.  A brush, sovent and air maybe.  Be sure not to leave any particles, liquid solvent or oil in the hole before the stud goes back in.  A hydraulic lock from the stud being screwed in can and often does break out the case at the bottom of the hole.  Blow it clean and triple check it. Clean, dry and loctite,  That's the ikely reason they were so tight.  A little heat carefully applied to warm up the loctite seal before trying to turn them out goes a long way to making the job more normal. No hammer required.  The same goes for any stud being reused)  only a light drop of loctite.  Too nuch adds lubrication which cause overtorqued threads and case damage.  If any gets sqeezed of the threads on install you risk a hydro lock and case damage.   

[JW113]

Why you gotta stress me out? 

Those that don't study history are doomed to repeat it. Just sayin', it's quite well documented that a certain era of Evo cases were prone to cracking. There were a batch in the 80s that were prone to the left side case inserts coming loose. And let's not forget all the fun we had with INA inner cam bearings. Hey, us old geezers lived through this "drama" and survived.

Just trying to say, in my unique friendly way, take a very close look at that right side case while you have it apart...

-JW

[2017FLHTK]

The puffing you felt likely was in fact a leaking pushrod cover o-ring.  The stain on the head fin seems to support that. The head probably could have been left on (at least for now). 

I'm heavily leaning in that direction.  I have a complete James gasket set, so that will have new o-rings for the pushrods along with the head gasket / base gasket / rocker box gaskets.  I also picked up new (green) OEM HD breather umbrellas to install.  While I'm in there I'll slightly enlarge the oil drain hole in the rocker cover (although that of course has nothing to do with my earlier symptoms).

You can check the breather operation with the engine running by feeling if it is puffing or sucking at the breater base outlet.  A search on here will walk you through that test. 

I typed in "breather base outlet test" in google and limited search results to this site.  I wasn't able to find any threads discussing this topic.  Can you steer me in the right direction?  I'm not sure I'm tracking what you're trying to tell me.

The air is definitely puffing though.

With the leakdown test, if you remove the pushrod covers you can visually confirm (and feel) the pushrods are in fact closed by the loose feel and ability to spin them.  Both must be in that position to be sure they are closed and on the seat with full valve spring pressure.  You have to lock the engine from turning either with a tool or whatever other method you decide works best for you. For example, fuel injected engine flywheels have timing notches on the left flywheel that can be locked in place with a threaded tool through the threaded hole in the left front of the case near the bottom end of the oil filter.  It engages with the flywheel notches and locks it from turning when you add air to the test gauges.  Your method with the cross lock bar is good too but it is still googood to have it in high gear and brake on hard..  If you don't take the time to get it perfect your results are garbage bin and you wasted your time.

Interesting discussion on the flywheel notch locking capability on EFI bikes.  I wasn't aware of that, but I'll file that away for future reference.  Couldn't agree more with the part in red.  I have some half-ass results because I was going fast, which ultimately doesn't tell me anything.  Of course now that the head is off I can't repeat the test.

Did you do a cranking commression test?  Dry first then wet. That's important engine health information.

I wish I would have, but unfortunately did not do so.

Finally, as said, DO NOT use a thread die to clean the threads.  A brush, sovent and air maybe.  Be sure not to leave any particles, liquid solvent or oil in the hole before the stud goes back in.  A hydraulic lock from the stud being screwed in can and often does break out the case at the bottom of the hole.  Blow it clean and triple check it. Clean, dry and loctite,  That's the ikely reason they were so tight.  A little heat carefully applied to warm up the loctite seal before trying to turn them out goes a long way to making the job more normal. No hammer reuired.  The same goes for any stud being reused)  only a light drop of loctite.  Too nuch adds lubrication which cause overtorqued threads and case damage.  If any gets sqeezed of the threads on install you risk a hydro lock and case damage. 

Acknowledge the guidance above, and will rigorously follow.  THANK YOU for taking the time to share this knowledge. 

[kd]

Confirm the breathers are assemble properly (not upside down) as often packaged and shipped before installing them.    on the oil drain hole enlargement.  It will reduce filter contamination and oil puking out of the breather.

What I meant was for you to go to the search section here on HTT.  Word your "head breather" searches a few ways and you'll find previous conversations that are very enlightening.  The HTT search feature is a great way to get an education or confirmation on your understanding.  This info is vetted by many highly qualified members hear.  Straight goods.

The EFI flywheel tool can be found in Jim's catalogue and in some others.



 

[2017FLHTK]

Confirm the breathers are assemble properly (not upside down) as often packaged and shipped before installing them.  on the oil drain hole enlargement.  It will reduce filter contamination and oil puking out of the breather.

The breather umbrellas appear to have been correctly installed.

I popped the black umbrellas and replaced them with ones I picked up today at the dealership (part number 26856-89A).  The new breather is green and noticeably more flexible.  I'm not sure if that's because it's made out of different material or because the old breather has been installed for so long and stiffened up, but there's a noticeable difference between the two.

What I meant was for you to go to the search section here on HTT.  Word your "head breather" searches a few ways and you'll find previous conversations that are very enlightening.  The HTT search feature is a great way to get an education or confirmation on your understanding.  This info is vetted by many highly qualified members hear.  Straight goods.

I punched in "head breather test" and "breather base outlet" in the HTT search bar and wasn't able to find the content you're referencing.  I am NOT trying to be spoonfed the info, but I'm not finding what you're talking about.  I appreciate the thought though!   

[FSG]

my tool of choice for blowing out those blind holes 

[2017FLHTK]

I have installed new breather umbrella valves in the rocker boxes.  I'm about to head out to the garage and install the replacement engine stud.

My game plan for tomorrow is as follows:
-Drill out the oil drain holes near the breathers in the rocker boxes.
-Replace the engine case to cylinder base gasket with a James gasket.
-Replace the head gasket with a James gasket.
-Place fresh o-rings into the heads to properly seal the pushrods.
-Reinstall rocker box covers.
-Perform dry, followed by wet compression test.
-Properly lock each cylinder at it's prospective TDC and perform a leakdown test.
-Finally, start the bike and see if the puffing air symptom has gone away.

My hope is to gather enough info to help determine if it's bad piston rings, worn valve seals, or both that's contributing to the fouled plugs / carbon build up on the pistons.  Anything else I should be thinking about or doing during this process? 

[Ohio HD]

If you can, take the leakdown readings at TDC, mid stroke, and BDC. That way if there's an isolated bad spot in the cylinder you should see it in the readings.

[Hossamania]

Since it's apart, does it make sense to lap the valves, or am I just reaching back too old school?

[2017FLHTK]

Welp..... one step forward and two steps back. 

No drama or issues when I installed the replacement cylinder stud in to the case. I hand tightened via the double-nut method and then used a torque wrench set to 120 inch lbs / 12 foot lbs (validating that the shoulder was touching the case).



Since I had the cylinder off and had easy access, I took a chase die to the other cylinder studs to make sure the threads were cleaned.  With the cylinder off I had a better view of the piston and could see oil stains on the sides:



The outside of the head bolts were cleaned on the wire wheel, the threads were cleaned with a chase, and then I poured some motor oil inside the bolts and set them to the side.

I cleaned up the old gasket off the bottom of the cylinder / engine case in preparation for the new base gasket.  I then cleaned the top of the cylinder and the the bottom of the head to prep for the head gasket.  While everything was on the bench I used a brass wire wheel with my dremmel to clean up the machined areas where the head bolts snug up against the head and checked that all threads in the head were clean with a chase.  Finally, I used an air compressor to blow everything off and make sure there wasn't any dust or crud left that could migrate inside the engine.

With the base gasket installed, I compressed the rings on the piston with a compression tool and slid the cylinder down onto the piston.  A James MLS (multi layer steel) head gasket was put in place, and then head was emplaced onto the cylinder.  I took the head bolts, emptied them of the oil that was placed inside them earlier, blew out any reaming liquid with the air compressor, and tightened them to finger tight.  Bolts were then tightened in a star pattern to the torque values specified by James (7-9 ft lbs, 12-15 ft lbs, 22-25 ft lbs, and a final torque of 38-42 ft lbs).

I rolled the engine to TDC on the front cylinder and removed the ignition timing cover to validate that I was precisely set at TDC.  I then removed the primary cover and used a Jims tool to brace the engine sprocket / clutch hub together and lock the motor from turning. 

With all of that complete, I hooked up my leak tester to the front cylinder and turned on my air compressor.  Almost immediately I could hear air hissing out from the back of the head, on the portion nearest the front of the bike. 

The James MLS gaskets have two brass rivets holding them together.  With the gasket installed and the heads torqued, here's what it looks like next to the intake:


And next to the rivet by the exhaust:


You can clearly see the brass rivet deflecting downwards off the head.  I don't know why James wouldn't locate those rivets out further another fraction of an inch!!! 

So, I pulled the heads off, cut the brass rivets out of the gasket, and re-installed / re-torqued the heads down.  It's still leaking air when the leak tester is applied (although not as stronlgy), but now the leak has moved and is coming from the rear side of the head in the vicinity of the back portion of the intake manifold.

I feel like I'm chasing my tail here.  Any suggestions for next steps?

[kd]

Are your pushrod out so the valve springs are holding the valves on their seats?

The staining on the piston below the rings is a sign of them not seating.  The carbon buildup on the head and piston top "may" be as a result of that.  There is more going on there.  Reassembling it with out further investigating the rings and heads may not go well.

[2017FLHTK]

Are your pushrod out so the valve springs are holding the valves on their seats?

Correct.  Pushrods are not installed, there is no pressure from the rocker arms being transferred to the valves.

The staining on the piston below the rings is a sign of them not seating.  The carbon buildup on the head and piston top "may" be as a result of that.  There is more going on there.  Reassembling it with out further investigating the rings and heads may not go well.

What are your suggestions on next steps?

[JW113]

Dude.... something is very wrong here. Are you 100% sure you have the gaskets oriented correctly? I just looked at my '92. The MLS head gaskets have the rivets on the left/right side of the cylinders. In your pictures, they appear to be pointed to the front/rear.

I would call James Gaskets and talk to them about this. They make thousands of these, I can't imagine the problem is with the design of the gasket.

-JW

[2017FLHTK]

Dude.... something is very wrong here. Are you 100% sure you have the gaskets oriented correctly? I just looked at my '92. The MLS head gaskets have the rivets on the left/right side of the cylinders. In your pictures, they appear to be pointed to the front/rear.

I would call James Gaskets and talk to them about this. They make thousands of these, I can't imagine the problem is with the design of the gasket.

-JW

I feel pretty damn confident that I had the James gaskets correctly oriented.  Because the gasket indexes off both the cylinder studs and the dowels, it's not possible to incorrectly install them rotated 180 degrees out of phase. The instructions provided by James don't even mention the rivet, and certainly don't mention one side or the other being needed to be "up" vs the other side.  I took the head off today and saw no indication that the gasket had moved or slipped; they were locked in place on the cylinder dowels and appropriately posistioned.

As a hail Mary, I went to the dealership and picked up an OEM HD head gasket (part number 16770-84F).  Side note: my factory service manual has a caution that states "Install new O-rings over the cylinder dowels before installing the head gasket.  Install the O-rings first to ensure alignment of the head gasket and prevent gasket leaks".  I didn't catch that until I was back at the house with my new HD gasket in hand, so I went back to buy the O-Rings (HD part number 26432-76A).  However, with the O-Rings in place my HD gasket would NOT fit flush with the surface of the heads.  As it turns out the MoCo has changed the construction of their evo head gaskets (as compared to what was in use from the early 90s), and now are designed to be used without the cylinder stud O-rings referenced in my older service manual. 

Good news: with the OEM gasket installed and torqued down to the specs in the service manual the head seams to have sealed up!  With my leakdown tester installed I was able to pump in 100 PSI of air on the supply side, with 92 PSI indicated on the cylinder gauge!

Unfortunately I got called out of town on a work trip, so I didn't have time to perform a leakdown test on the other cylinder, but I feel confident that I'm headed in the right direction.