DISASTER! Averted

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phliparoonie
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DISASTER! Averted

Post by phliparoonie » Sat Jun 18, 2016 2:33 pm

So, I needed to replace the base gasket on the left cylinder. Got the parts from Gene (along with a Ducati ignition...another story), and started to dig into it today. The head came off OK, but the cylinder was a little balky. Nothing new there. Repeated, judicious blows with a rubber mallet at 12 and 6 on the fins while pulling out loosened it up and it started to come off. Great!

Unfortunately, the cylinder did NOT slid off the top rear stud. It came with it, as the threaded insert pulled from the engine block (see previous post on this repair a couple of years ago viewtopic.php?f=5&t=22014). This. Is. Not. Good.

I never torque the heads more than 36 ft lbs. Re-torquing over the last two years to adjust valves had, apparently, NOT threaded the stud deeper into the insert, but drew the whole works into the face of the cylinder casting. Inspection showed that the lower front insert was beginning to do the same thing.

$hit Fire.

Here's some pics. I am bummed. IF I can find a helicoil product to re-do the hole, that will work in the limited wall space I have left in the engine block, I will certainly need a new cylinder (B size)

$hit Fire. New engine=$3500; New engine case=$400. The Monkey is not happy.
threaded insert attached to cylinder 01 small.jpg
threaded insert attached to cylinder 02 small.jpg
threaded insert damage to cylinder 01 small.jpg
threaded insert pulled out of block 02 small.jpg
threaded insert with engine block alloy imbedded in threads 01 small.jpg
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Last edited by phliparoonie on Fri Aug 05, 2016 6:47 am, edited 2 times in total.
It is important to keep an open mind. But not so much that your brain falls out. Carl Sagan
I am old, but I'm happy. Cat Stevens
It's a tractor, not a Ferrari. Holopaw Gene

2004 Tourist "Charlie" 25,036 km - 18/04/24
stock: pipes, carbs, airbox, fuel petcock, tractor seat
new/add: windscreen,hack headlight,4 head stud holes,pistons,rings,starter,FD splined hub,clutch actuator bearing, clutch arm,donut,drive shaft,Ducati ignition,tank xover dscnect

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Re: DISASTER!

Post by jchoby » Sat Jun 18, 2016 2:45 pm

Try a timesert....I think they have "over size" repair kit for just this kind of issue. Expensive but they work
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Re: DISASTER!

Post by phliparoonie » Sat Jun 18, 2016 2:53 pm

Used timesert the first time. Those are the ones with the staked threads. Not a whole lot meat left in the engine block to re-drill and re-tap.
It is important to keep an open mind. But not so much that your brain falls out. Carl Sagan
I am old, but I'm happy. Cat Stevens
It's a tractor, not a Ferrari. Holopaw Gene

2004 Tourist "Charlie" 25,036 km - 18/04/24
stock: pipes, carbs, airbox, fuel petcock, tractor seat
new/add: windscreen,hack headlight,4 head stud holes,pistons,rings,starter,FD splined hub,clutch actuator bearing, clutch arm,donut,drive shaft,Ducati ignition,tank xover dscnect

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Re: DISASTER!

Post by Snakeoil » Sat Jun 18, 2016 3:17 pm

Geez, I feel your pain. Regardless of what kind of insert you use, the real issue is the silly putty they used to make that engine case.

I think jchoby is talking about a timesert that is oversize relative to you first timesert to allow you one more correction.

Just for reference in reading your original thread on the first repair, a bottoming tap is not intended to be the original tap used to cut a thread in a hole. You use a normal tap with sufficient lead. Then go back in with a bottoming tap to cut the final threads to the bottom of the hole.

I seem to remember others here saying that head torque should be around 26 ft-lbs. Probably worth you doing a seach.

Another option is machining an aluminum plug threaded to accept the stud on the ID and threaded to a size that will just clean up your buggered hole. Put it in with a good epoxy and you could even pin it to be doubly sure.
Last edited by Snakeoil on Sun Jun 19, 2016 10:11 am, edited 1 time in total.
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Re: DISASTER!

Post by phliparoonie » Sat Jun 18, 2016 6:53 pm

All good points. Pretty sure 36 is the number I've seen on this site, anyway. The hole does look like it could be cleaned up with the tap. I have used high temp/strength epoxies before, and they drilled/took a tap at least as well the the ural aluminum alloy. Not saying much, but I'm feeling a little desperate. A new jug is $250, but that buggered up hole in the old one could be epoxied and 'machined" flat, too. Maybe.
It is important to keep an open mind. But not so much that your brain falls out. Carl Sagan
I am old, but I'm happy. Cat Stevens
It's a tractor, not a Ferrari. Holopaw Gene

2004 Tourist "Charlie" 25,036 km - 18/04/24
stock: pipes, carbs, airbox, fuel petcock, tractor seat
new/add: windscreen,hack headlight,4 head stud holes,pistons,rings,starter,FD splined hub,clutch actuator bearing, clutch arm,donut,drive shaft,Ducati ignition,tank xover dscnect

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Re: DISASTER!

Post by rivers » Sat Jun 18, 2016 8:01 pm

I'm no machinist but those threads for the head/jug bolts go are toast. You're not gonna get away with just running a tap into'm. If'n were me I'd have those holes bored out on a mill, refill them with alum weld re-bore and tap for std size or over-bore and tap for the next size up bolt. I'd mess with the stock block for less investment than buying a new block. That IS fixable and yet be reliable I'm just not smart/skilled enough to do it. A good alum pro could though. In a past life I've had a few Brit alum lumps resurrected from the scrap pile by real pros. If no qualified folks near you give Terry Crawford in MI a call and see what he suggests.
On a positive note 'you' didn't screw anything up with 36 torque, damage was likely done long before you bought your 04. Sucks for sure but call Terry.
edit: PS also fook epoxy fixes. :(
Joe
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Re: DISASTER!

Post by wooden nickel » Sat Jun 18, 2016 8:23 pm

When I re-torque Ural heads, I always set the click type torque wrench on 36 ft. lb. and check to see if they have loosened. I do not do the proper back off and reset. With a Ural you're just asking for trouble.
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Re: DISASTER!

Post by phliparoonie » Sun Jun 19, 2016 7:13 am

Will this work? Gene thought maybe the original insert wasn't long enough.

https://www.amazon.com/BIG-SERT-Time-Se ... go-ffsb-20
It is important to keep an open mind. But not so much that your brain falls out. Carl Sagan
I am old, but I'm happy. Cat Stevens
It's a tractor, not a Ferrari. Holopaw Gene

2004 Tourist "Charlie" 25,036 km - 18/04/24
stock: pipes, carbs, airbox, fuel petcock, tractor seat
new/add: windscreen,hack headlight,4 head stud holes,pistons,rings,starter,FD splined hub,clutch actuator bearing, clutch arm,donut,drive shaft,Ducati ignition,tank xover dscnect

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Re: DISASTER!

Post by Lee Pape » Sun Jun 19, 2016 10:06 am

Another tip once the head have been torqued you should not have to re-torqued or check them once they have settled in. Unless I find a valve adjustment way off I will not touch the head torque. I don't care if you back off and torque again or just recheck the torque you already have, you are still applying more stress on everything. Sooner or later something gives. I try not to fix my Ural until it breaks like some people I know have done. If it starts and makes no new strange noises then I just ride it.
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Re: DISASTER!

Post by Snakeoil » Sun Jun 19, 2016 10:38 am

Another option is machining an aluminum plug threaded to accept the stud on the ID and threaded to a size that will just clean up your buggered hole. Put it in with a good epoxy and you could even pin it to be doubly sure.
To be clear (and based on at least one response here it looks like I wasn't) when I said clean up the hole with a tap, I'm talking about selecting a tap size that will cut a new, clean, full depth thread into that buggered hole. Just running the same size tap into it may clean it up, but the helicoil pulling out removed material and hence strength.

The insert need only be as long as the major diameter of the thread on the insert. So, if you are repairing a 1/4-20 thread, the insert is normally about a 5/16"-20 so the insert only needs to be 5/16" long to obtain full strength based on the strength of the fastener being used. A little extra length does not hurt becauses more often than not the first couple threads on the repaired hole are a bit iffy from the original damage.

Welding up the hole would be a last choice if it were mine. Welding will probably require that the cylinder deck will warp and have to be skimmed to be flat again. The process is easy. The set-up is what eats up shop hours. Making a threaded aluminum plug would also cost a few bucks if you don't have a friend with a lathe and the skills to pin it in place after insertion. But I'd expect it to be cheaper than welding and remachining. Assuming these are 10mm studs, I would expect your helicoil hole to be close to 1/2" in diameter (major diameter of the thread). That would tell me that you could probably clean that hole up with a tap drill for a 5/8"-11 tap. This will give you deep thread engagement as the 5/8" thread is deeper than what you had for depth on the helicoil. So, you'll have better shear strength meaning the threads will have a lesser chance of failing as they did in your case. Your threads sheared off. If you have a local machine shop with a good reputation, I'd talk to them about a fix.

I would not expoxy the hole and drill and tap it to the stud size. Although I've done that on lawn mowers, it was not for fasteners with the stresses that head studs see. I've had great luck with that kind of fix. But still would not use it for a head stud/bolt.

I'm curious why you need a new cylinder? I thought the 750 engines used thru studs. So the cylinder should just have through-holes thru which the studs pass. Maybe I missed something in the photos and the helicoil backing out damaged your jug.

One last point. Keep in mind that the helicoil might have pulled out because it was poorly done in the first place. From what others have said, the alloy in these cases is a bit gummy and does not produce a clean chip when machined. That means a proper tap lube is required to get a clean, sharp, full depth thread with a tap. Needless to say, the tap needs to be sharp and well made. Failure to do so will cause the material to tear, adhere to the tap and make for a very sloppy thread and loose fit for the helicoil. Like anything else, the success of any job is based upon a good foundation.
Regards,
Rob
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Re: DISASTER!

Post by phliparoonie » Sun Jun 19, 2016 11:03 am

Lots of great input everywhere. Need to clarify that the original fix wasn't a helicoil product it was a timesert with staked threads. The BigSert fix see above seems appropriate.
It is important to keep an open mind. But not so much that your brain falls out. Carl Sagan
I am old, but I'm happy. Cat Stevens
It's a tractor, not a Ferrari. Holopaw Gene

2004 Tourist "Charlie" 25,036 km - 18/04/24
stock: pipes, carbs, airbox, fuel petcock, tractor seat
new/add: windscreen,hack headlight,4 head stud holes,pistons,rings,starter,FD splined hub,clutch actuator bearing, clutch arm,donut,drive shaft,Ducati ignition,tank xover dscnect

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Re: DISASTER!

Post by Albuquralque » Sun Jun 19, 2016 11:41 am

One question on your original timesert fix....did you use red loctite when installing the timesert or just relied on the staking?
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Re: DISASTER!

Post by wooden nickel » Sun Jun 19, 2016 1:06 pm

Darrell,
Do you know what temperature the cylinder base gets when running? I ask because red Locktite is only rated to 400 degrees. McMaster Carr lists some high strength, high heat lockers but they ain't cheap.
I just found Permatex red on Amazon that says it is rated at 450.
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Re: DISASTER!

Post by Albuquralque » Sun Jun 19, 2016 2:35 pm

wooden nickel wrote:Darrell,
Do you know what temperature the cylinder base gets when running? I ask because red Locktite is only rated to 400 degrees. McMaster Carr lists some high strength, high heat lockers but they ain't cheap.
I just found Permatex red on Amazon that says it is rated at 450.
With my CHT, the heads haven't been above 425. I would think the engine block is considerably cooler.....but it is a good point you bring up about the temp rating of red loctite.
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Re: DISASTER!

Post by phliparoonie » Sun Jun 19, 2016 5:23 pm

Yes, Darrell, red loctite. Regarding the staked inserts, it almost seems like the cutting of the threads by the stakes created a plane of weakness that allowed the engine block material to just peel away stuck to the threads when I pulled the cylinder. The last photo in the first post shows the threads of the insert choked with block material. The staking worked well (I guess) in keeping the insert from turning. I never saw the stud turn when checking torque before checking valves (4 or 5 times) on this stud, but it always got an 1/8 of a turn or so before clicking at 36. Also, I never loosened the nuts to re-torque, just set it at 36 and gave it a little pressure. Plus, what gets me is how deep the insert was drawn into the base of the cylinder mating surface. (3rd photo in 1st post) It's quite a chunk that is going to be hard to gasket. I think comparing the material to Yak cheese is an insult to hard working Yaks everywhere.

Rob, We (I had help) were pretty careful keeping the drilling and tapping chaff out of the operation: bearing grease in the flutes of both tools caught all the chips (there was no "curl" with this parent material), more grease on the end of a cable tie for the fines, then electrical contact cleaner to blow out the micros and clean up the grease (no residue), air gun to dry. The insert and the stud both screwed in with no chattering or stalling. Go figure.

I'm hoping the BigSert fix for buggered insert jobs will work. It's $90, and the Monkey said OK to the outlay.

Here's a question: What if I used a high strength/high temp epoxy to set the insert in the block AND to set the stud in the insert instead of loctite. I don't know what else to do to keep the torque from pulling the insert into the cylinder base. Not being able to ever remove that stud doesn't interfere with any other repair/maintenance functions I can think of. I don't know, just flailing, I guess.

Again, thanks everyone for their input. Means a lot.
It is important to keep an open mind. But not so much that your brain falls out. Carl Sagan
I am old, but I'm happy. Cat Stevens
It's a tractor, not a Ferrari. Holopaw Gene

2004 Tourist "Charlie" 25,036 km - 18/04/24
stock: pipes, carbs, airbox, fuel petcock, tractor seat
new/add: windscreen,hack headlight,4 head stud holes,pistons,rings,starter,FD splined hub,clutch actuator bearing, clutch arm,donut,drive shaft,Ducati ignition,tank xover dscnect

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