What alloy does the MT9 engine use?

[Korto]

I'm not very optimistic about anyone being able to answer this, but I was wanting a welder to weld flanges onto the (badly rounded off) exhaust ports of the cylinder head (so I can use proper steel bolts instead of aluminium thread, and what moron ever thought aluminium thread was a good idea?), and he refused because he didn't know what type of aluminium alloy it was and so it was too risky. And I have to respect that. He's a professional, accredited welder who presumably knows his business.

So, is there anyone here, with the qualifications to know what the welder needs to know, who knows what kind of aluminium alloy they used on the cylinder head of a 1972 MT-9?


Alternatively, anyone know any good solutions for rounded off thread that doesn't involve me having to buy a whole new cylinder head?

[RC20]

I can't begin to help you, possibly no one can as the alloys could be anything and if he is not confident enough in a general type rod, then a specific rod for that likely not available either.

I find it beyond belief they used aluminum studs.

Likely the only way would be a blown MT-9 head to test with.

You might query on the process as it does not sound like the aluminum allow is crucial

https://www.esabna.com/us/en/education/ ... -steel.cfm

Picture would help as it would seem you could drill out the old stud and install a steel one in place? Might not be seeing what you have.

[Mr Wazzock]

Any chance of photos? I'm struggling to visualize it (well failing actually)

[stagewex]

Perhaps the welder really doesn’t want the job? I don’t know either but there are plenty of aluminum heads and engines out there both car and motorcycle and I’ve never had a question like that and believe me, I’ve had a lot of stuff welded over the years.

Absolute best solution is helicoil or time-cert, both come in kits. Always a debate of which is better. Why add more of a failed and weak alloy (whatever it is). I have a few in my engine due to the wrong torque settings being included in the owners manual (lots of folks know about this). Done by dealer prep... not by me. Covered under warranty and the helicoils are super strong for steel vs. aluminum. I was tempted to do all of the head bolts but why tempt fate after getting the right torque specs?

[sKiZo]

why tempt fate after getting the right torque specs?

And for the benefit of those of us not in the know, what might those be? I've always gone with, tighten the bolts till just before they snap kinda thing.

PS - the soft studs might be similar to what they did on my Aurora Northstar. That has a lot of single use fasteners that actually stretch when properly installed and need to be replaced instead of re-used. Why? I'm told that's supposed to lock them in tight at lower torques without seizing over time due to major heat fluctuations. I doubt the object isn't to stretch them in a Ural (which is probably why they go fubar in the first place as torques are typically a lot lower than a standard bolt), but they do keep weight down while providing about the same strength as a grade 2 bolt while providing a LOT more vibration resistance.

[Korto]

I don't know if helicoil do m48 x 2mm exterior thread repair

It's M48 x 2mm threaded pipe, one-piece head cylinder casting


You stick the exhaust pipe in it, and screw the big nut over the top to tighten it


So it ends up looking like this


The thread on the pipe is rounded. The thread on the nut is also a bit rounded, but can be replaced. I want to weld a plate on the end of the threaded pipe, and another on the exhaust pipe, so I've got two plates butting against each other. Put an exhaust flange gasket between,


and then use real bolts to bolt the exhaust and cylinder plates together

[jeffsaline]

Repairing the exhaust stub threads on the head is a common job on old airhead BMWs. If I was going to do some welding on the exhaust stub I would probably be using 4043 filler rod.

Best,

Jeff

[jaybird]

I would try cleaning up the threads on the head with a thread file, thread chaser, die, etc, and using a new nut with plenty of anti seize.
What you’re proposing to do will probably wind up costing more than a replacement head.
As far as the weldor and the alloy composition of the head goes, I would try someone else as the one you talked to either doesn’t want the job or doesn’t have the confidence to attempt it.
In my circle I see aluminum engine cases of unknown composition being welded all the time, most are quite valuable and some irreplaceable.
If the threads are that buggered, I would just replace the head in this case.
Good luck.

Happy trails,
Jaybird

[RC20]

Ok, that is a new one on me. Low cost production approach.

If you can clean it up you need to use aluminum specific anti seize.

[jaybird]

Ok, that is a new one on me. Low cost production approach.

If you can clean it up you need to use aluminum specific anti seize.

BMW airheads utilized that design for years.

Happy trails,
Jaybird

[Desantnik-VDV]

Exactly like a BMW airhead of 70's and 80's. I had a hard time unscrewing and removing that nuts. They were seized and like baked on both R80 and R100 when I was doing Ural heart transplants. But I was able to use old nuts with some aluminum anti-seize Permatex paste the one is used on spark plugs:
https://www.amazon.com/Permatex-81343-A ... 2548&psc=1

Also, a special wrench makes it easy removal and installation.

[rivers]

Korto, I am NOT a mechanic or welder but suggest finding another alum welder. No clue on what alloy KMZ/IMZ used back in the day but you can bet it was the cheapest easiest casting method avail at the time. So on the exotic alloy scale...I'd explore the lower end. I've had lots of "old even older" alum mc castings welded/repaired and never had a problem with alloy content. Often done w/o question as to make/model year/alloy content. I'd guess for whatever reason your welder just doesn't want the job.
Next thought would be save your shop money trying to convert to flanged exh headers. The exh nut system you have was industry standard for decades. yup more maint but still worked well. "I" would try to fix what ya got before chopping off the spigots/buggering up other wise good useable heads. If the threads have serious deformities work them with a thread file best you can. Then smear the threads with valve lapping compound then work the nut back-n-forth to final match cut/shape the threads. Once done on assembly add a gasket or ring of asbestos etc rope in the seat of the finned nut. A thin dab of copper based anti-seize on the threads will aid in leakage prevention and later maint/removal. I done this method on many slip-ins (bmw/triumph/et al).
Slip-in headers are more maint than bolt-on but not bad or too often if you actually do it every few years or if you notice leaks or looseness. One of the key satisfaction factors is the integrity/surface of the exh pipe stub that goes into the head. Sure slip-in heads and exh pipes can be reworked to take later bolt-on connections but it's not cheap or quick if you're paying a shop to do it. You can always resort to that option if your spigots are seriously deformed and not salvageable. Give it a go. Good luck.

[Lmo]

Korto, welcome to the forums.

Are the threads on the exhaust stub totally shot? The threads on my BMW R75/5 are in pretty bad shape but once cleaned up (both male & female) they hold well. I use an anti-seize compound on them when installing.

If they are totally shot something like this might be an option to check out; they are also available for Dnepr MT10/11/16 and Ural https://www.sternmutterersatz.de/index. ... ng-anfrage


The old threads do not need to be complete, just enough for the clamp to grab onto.


EDIT - Looks like about $200USD [177E]. You will easily have that much in repair work.

Hinweis:

Wenn Sie die Teile für ein anderes Fahrzeug benötigen, lassen Sie es mich wissen, vielleicht lässt sich eine Lösung finden.
Ich habe z.B. auch passende Teile für die Einzylinder mit M45 Gewinde oder die Simson AWO 425

Also folgendes wurde bereits realisiert:
52/40 BMW R100RS ('77-'78) und vermutlich Krauser 4V
52/38 BMW R80/100 ('70-'94)
48/36 BMW R45/65 & Dnepr/Ural Mil Varianten
48/37 Dnepr MT10/11/16 & Ural mit Wulst im Krümmer
48/41 Simson AWO 425 1-Zylinder
45/37 BMW R12 & R25 etc. Einzylinder
45/37y BMW R25/2 etc. Einzylinder

übersetzt/translated

Note:

If you need the parts for another vehicle, let me know, maybe a solution can be found.
I have e.g. Also suitable parts for the single cylinder with M45 thread or the Simson AWO 425

So the following has already been realized:
52/40 BMW R100RS ('77 -'78) and probably Krauser 4V
52/38 BMW R80 / 100 ('70 -'94)
48/36 BMW R45 / 65 & Dnepr / Ural Mil variants
48/37 Dnepr MT10 / 11/16 & Ural with bead in the elbow
48/41 Simson AWO 425 1-cylinder
45/37 BMW R12 & R25 etc. single cylinder
45 / 37y BMW R25 / 2 etc. single cylinder

More information > https://forums.bmwmoa.org/showthread.ph ... ead-repair

[jaybird]

Korto, welcome to the forums.

Are the threads on the exhaust stub totally shot? The threads on my BMW R75/5 are in pretty bad shape but once cleaned up (both male & female) they hold well. I use an anti-seize compound on them when installing.

If they are totally shot something like this might be an option to check out; they are also available for Dnepr MT10/11/16 and Ural https://www.sternmutterersatz.de/index. ... ng-anfrage


The old threads do not need to be complete, just enough for the clamp to grab onto.


EDIT - Looks like about $200USD [177E]. You will easily have that much in repair work.

Hinweis:

Wenn Sie die Teile für ein anderes Fahrzeug benötigen, lassen Sie es mich wissen, vielleicht lässt sich eine Lösung finden.
Ich habe z.B. auch passende Teile für die Einzylinder mit M45 Gewinde oder die Simson AWO 425

Also folgendes wurde bereits realisiert:
52/40 BMW R100RS ('77-'78) und vermutlich Krauser 4V
52/38 BMW R80/100 ('70-'94)
48/36 BMW R45/65 & Dnepr/Ural Mil Varianten
48/37 Dnepr MT10/11/16 & Ural mit Wulst im Krümmer
48/41 Simson AWO 425 1-Zylinder
45/37 BMW R12 & R25 etc. Einzylinder
45/37y BMW R25/2 etc. Einzylinder

übersetzt/translated

Note:

If you need the parts for another vehicle, let me know, maybe a solution can be found.
I have e.g. Also suitable parts for the single cylinder with M45 thread or the Simson AWO 425

So the following has already been realized:
52/40 BMW R100RS ('77 -'78) and probably Krauser 4V
52/38 BMW R80 / 100 ('70 -'94)
48/36 BMW R45 / 65 & Dnepr / Ural Mil variants
48/37 Dnepr MT10 / 11/16 & Ural with bead in the elbow
48/41 Simson AWO 425 1-cylinder
45/37 BMW R12 & R25 etc. single cylinder
45 / 37y BMW R25 / 2 etc. single cylinder

More information > https://forums.bmwmoa.org/showthread.ph ... ead-repair

Nice post Lew, that's helpful

Happy trails,
Jaybird

[Mr Wazzock]

OK I get it now, identical to the BMW screw on finned clamps. Never had a problem with these (I had an R80) apart from originals seized, had to cut slots in the finned nuts to loosen them. Replacements always went back on with copper grease. That ensured they could unscrew again.