NGC:73 r 60/5 BMW Stripped Spark Plug Hole

[Tkelly]

Bike running fine until one of the plugs loosened up leaving half the cylinder threads destroyed.  What’s the repair procedure for this?  Any recommendations?

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[Zoom Zoom]

Pull the head and helicoil. What you do not want is metal shavings in the cylinder.

ZZ

[oldbike54]

Pull the head and helicoil. What you do not want is metal shavings in the cylinder.

ZZ

 Most machine shops will do the repair for less than 50 bucks if you take them the cylinder head .

 Dusty

[Lannis]

Bike running fine until one of the plugs loosened up leaving half the cylinder threads destroyed.  What’s the repair procedure for this?  Any recommendations?

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Back when I were young and inexperienced, I stripped out the spark plug threads on my 1970 BSA Lightning.

An "old experienced" guy at the local machine shop said it would be fine to re-cut threads for an insert leaving the head in place as long as he could use heavy grease to catch all the shavings.   So I said go ahead ... and it didn't work ... shavings stuck under the valves, no compression, and I had to pull the head on the sidewalk, give it to him, and let him fix it.   He felt bad about it, and did a free valve lapping on all the valves while I waited.  Ran great when he was done, but I'd recommend skipping the middle step of trying it with the head on the cylinder.

Especially on the easiest bike in the world to pull the head!!

Lannis

[wirespokes]

Pull the head. Install a timesert with red loctite.

I can do stuff like that, but it's a job requiring precision I'm not capable of since the plug needs to seal. I'd have the machinist do it - and that's saying something since I tend to do all my own stuff. But in this case I'd take it to the shop and have an expert do it. If it's not done expertly and well the first time you might end up looking for a new head.

[lucky phil]

Bike running fine until one of the plugs loosened up leaving half the cylinder threads destroyed.  What’s the repair procedure for this?  Any recommendations?

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Timeserts are far superior to Helicoils and worth the extra effort. Here's one I did on the Rear main bearing attach hole.




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Ciao

[wirespokes]

I've heard of helicoils failing in the spark plug area. The machinist I know even stakes the timeserts (hope I'm remembering correctly) when repairing spark plug threads. He's local but does the best exhaust thread repair for the most reasonable price. In fact, it's impossible to tell it was ever damaged when he's done. Guys send him heads from all over the country, including dealers, and is one of a few who works on the really old parts. He's retired many years now but will probably be doing this till the day he dies - or is unable to do it any more.

[creaky99]

Timeserts are far superior to Helicoils and worth the extra effort. Here's one I did on the Rear main bearing attach hole.




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Ciao

True, Timeserts are the only way to go.

[acogoff]

   Well I suppose timesets are fine, but I will stick with what Lycoming has had in their sparkplug holes from the factory for 70 years. Helicoils.
 Is this like an oil Thread?

[lucky phil]

   Well I suppose timesets are fine, but I will stick with what Lycoming has had in their sparkplug holes from the factory for 70 years. Helicoils.
 Is this like an oil Thread?

As a retired certifying aircraft engineer on commercial jets you need to be aware that in the aviation business esp the light aircraft end things dont necessarily keep up with the latest technology/best practice. Reason being that that area of aviation baulks at the expense of getting advancements Certified. It's cheaper and easier to stick with what you've been doing for years even though there have been advancements. Even the big end of aviation suffers from this to a certain extent.
Add to that the fact that not everything thats good for aviation is good engineering for the auto/motorcycle application. Tig welded CRMo steel tube frames are a good example. Great for fully triangulated light aircraft space frames but not as good for racing motorcycles frames as Bronze welding. Not everything translates.
Timeserts are technically better than helicoils and are used by high end manufacturers for brand new components. Professionally and personally I've had Helicoils fail.They used to give quite a bit of trouble on CFM-56 jet engine fuel filter cover retaining bolt holes. A real PITA on a night shift service.

Ciao     

[acogoff]

As a retired certifying aircraft engineer on commercial jets you need to be aware that in the aviation business esp the light aircraft end things dont necessarily keep up with the latest technology/best practice. Reason being that that area of aviation baulks at the expense of getting advancements Certified. It's cheaper and easier to stick with what you've been doing for years even though there have been advancements. Even the big end of aviation suffers from this to a certain extent.
Add to that the fact that not everything thats good for aviation is good engineering for the auto/motorcycle application. Tig welded CRMo steel tube frames are a good example. Great for fully triangulated light aircraft space frames but not as good for racing motorcycles frames as Bronze welding. Not everything translates.
Timeserts are technically better than helicoils and are used by high end manufacturers for brand new components. Professionally and personally I've had Helicoils fail.They used to give quite a bit of trouble on CFM-56 jet engine fuel filter cover retaining bolt holes. A real PITA on a night shift service.

Ciao   

     Yup, an oil thread.

[Lannis]

Add to that the fact that not everything thats good for aviation is good engineering for the auto/motorcycle application. Tig welded CRMo steel tube frames are a good example. Great for fully triangulated light aircraft space frames but not as good for racing motorcycles frames as Bronze welding.

Ciao   

Now I would never have thought that.   I've often mused and fantasized about having a custom motorcycle that was built to aircraft specifications, including wiring, engine assembly and tolerances, and all like that.

So, you've mentioned that aircraft TIG welded frames wouldn't be "as good" as bronze-welded motorcycle frames for high stress.   In what way are they not as good?   And are there other areas like that?

Not challenging your expertise and conclusions, but seeking to learn ....

Lannis

[Tkelly]

Thanks for the unanimous advice not to try this at home,I am going with timeserts unless the machinist talks me out of it.

[bodine99]

I had a R/S plug blow out of my R-75. Did a helicoil plug kit fix,that worked for a few years. In Sept 2018 that went FUBAR'd. Company called The Brillman Co. in Mt. Jackson VA. 540-477-4112 has stuff. I bought x2 B9005-002 18mm (comes with a copper crush washer) to 14mm adapters. Also got an 18x1.50 tap from ACE hardware. Pulled the head off and retreaded the hole from the combustion side. J-B welded the insert & staked it from the outside.  Modified a 13/16th open end to fit into the sparkler recess to back up the adapter when tightening or loosing the sparkler. Since I was a kid (now a geezer) sparkler into an alloy head gets anti-seize.Coming up on 2 yrs. and 9000 miles and all good.

[lucky phil]

Now I would never have thought that.   I've often mused and fantasized about having a custom motorcycle that was built to aircraft specifications, including wiring, engine assembly and tolerances, and all like that.

So, you've mentioned that aircraft TIG welded frames wouldn't be "as good" as bronze-welded motorcycle frames for high stress.   In what way are they not as good?   And are there other areas like that?

Not challenging your expertise and conclusions, but seeking to learn ....

Lannis

Generally speaking because you rarely get the luxury of a fully triangulated design in a motorcycle frame the bronze welding with its large fillet radius is better at distributing lateral loads across the weld and into the tubing.
In most aircraft space frame applications you get to fully triangulate the design. In addition the reduced heat doesn't affect the Chrome molly composition. Bronze welding and brazing are different things.
Having said that I've owned a couple of MV Agustas with tig welded frames and they were lovely things.
I just came across this very good video while looking for bronze welded frame images. It really is very good and this guy knows how to weld for sure. The first tests between steel and bronze on a simple 90 deg fillet weld aren't surprising but of greater interest is the thin walled steel tube test. Remember that apart from ultimate strength with regards to the material use in the weld with reference to tubular motorcycle frames is that motorcycle frames need to flex a little and are subject to harmonic vibration loads and even static bending loads from imperfect engine to frame interfaces. The malleability and load spreading ability of the bronze welded joint in a tube frame is a distinct advantage here. I love engineering.

 https://www.youtube.com/watch?time_continue=646&v=wf-Cq5eQmt0&feature=emb_logo

Ciao

[lucian]

Why not just find another head like this one
 https://www.ebay.com/itm/BMW-R60-R50-R75-5-6-Cylinder-head-727/373093172467?hash=item56de1604f3:g:TH0AAOSw~A5e85Rp

 I'm sure there are alot of them out there.

[Canuck750]

I have repaired a couple heads with similar spark plug thread damage.

I would not use a helicoil for this, a carbon steel insert is much stronger and given that the spark plug is regularly torqued down and removed / reinstalled I would be concerned a helicoil could fail.

My local automotive parts supply shop carries a carbon steel insert in many SAE and metric sizes along with the required drill and tap. I feel the head has to come off and be clamped onto a milling machine bed or drill press plate. The drill must be aligned to the angle of the original spark plug bore and be properly centered. I also place the tap in the mill chuck after drilling to ensure the tap is true.

If you can get a shop to do it for you for under $100 let them do it. You get one chance to get it right.

This is what I use for spark plug hole repair

https://www.ezlok.com/e-z-lok-solid-wall-threaded-inserts-automotive

[Tkelly]

I assumed that someone failed to tighten the plug but now Iam wondering what caused the blowout.I am also thinking  buying a replacement is the way to go.I never heard of this happening,is it a known bmw issue and is the  slash 6 head the same?

[wirespokes]

I'm pretty sure the R60 head is different than the R75. But I think an R60 head could be had pretty cheap.

BMW spark plug holes don't often strip out. It's not a common thing at all. I sort of recall some plugs, like Champions, having problems sticking or the threads not being quite right. Or maybe a plug got cross threaded in the distant past. Or how about this (I've never seen this before) a previous owner didn't want his spark plugs falling out so made damn sure they wouldn't. Or maybe he was a gorilla...

Treated right, spark plug threads don't strip out.

[ozarquebus]

I successfully drilled out out a broken off spark plug then retapped the spark plug hole on a mercedes 6 cylinder auto engine. I caught all the shavings I could by stuffing a rag down in the plug hole into the cylinder about 2 feet long, then used a large amount of oil in the process to immobilize the shavings and slowly pulled the rag out. Apparently either all the shavings came out or were small enough to get blasted out when the Unimog started..

[Zoom Zoom]

I assumed that someone failed to tighten the plug but now I am wondering what caused the blowout.I am also thinking  buying a replacement is the way to go.I never heard of this happening,is it a known bmw issue and is the  slash 6 head the same?

I'm more inclined to suspect the spark plug had been over tightened. I don't think this is a BMW issue. This is an owner issue. No offense.

John Henry

[Mike Tashjian]

I usually torque new plugs because it is so easy to do.  I can also tell you often spark plugs will loosen over time and it is not unusual.  Spark plug cap style can probably make things better or worse.  In this case you can see there are still what appears to be good threads on the blown out plug. There also appears to be good threads beyond the ripped out threads in the head.  So a good guess is the plug loosened over time and then blew out.  Repairing a blown out plug with a quality insert would bring this head back to full service.  Unless there are other issues involved, there is no reason to replace it.  There may even be better reasons to keep it as is. 

[Tkelly]

 Good points Mike,maybe we should all be checking plug tightness when we change oil.

[oldbike54]

 Tom , how many miles on this /5 ? Might be time for new valves and seats , this generation of airhead will break valve heads . DAMHIK.

 Dusty

[lucky phil]

I usually torque new plugs because it is so easy to do.  I can also tell you often spark plugs will loosen over time and it is not unusual.  Spark plug cap style can probably make things better or worse.  In this case you can see there are still what appears to be good threads on the blown out plug. There also appears to be good threads beyond the ripped out threads in the head.  So a good guess is the plug loosened over time and then blew out.  Repairing a blown out plug with a quality insert would bring this head back to full service.  Unless there are other issues involved, there is no reason to replace it.  There may even be better reasons to keep it as is.

Really? In 50 years working on everything from road, dirt bike car and road race engines I've never seen a correctly installed spark plug loosen. Maybe if the threads were already damaged but i've never experienced it in the hundreds of engines I've worked on.

Ciao

[PeteS]

FWIW, the Helicoil sparkplug repair kit has been using Timesert type inserts for at least 15 years now, not their classic helicoils. The special tap included is tapered so it starts off at the existing thread diameter and gradually increases to the size of the insert. Shouldn't require a machinist.

Pete

[Tkelly]

Bike has 38500 miles.We are taking the bike to a shop as removing and reinstalling the head may be too complicated for us and I don’t want to mess anything else up.

[Mike Tashjian]

 I can agree that correctly installed spark plugs should never loosen up on their own.  But I do find a few that are loose on bikes I work on. Why? Good question.  I don't know how these plugs were installed, but I usually look closely at the crush gasket to see if at least that has been seated.  Maybe people err on the side of too little torque but still manage to crush the gasket?  Warm engine?  Anyways as this thread shows, it appears the plug made it's way out about halfway before things went bad. 

[lucky phil]

I can agree that correctly installed spark plugs should never loosen up on their own.  But I do find a few that are loose on bikes I work on. Why? Good question.  I don't know how these plugs were installed, but I usually look closely at the crush gasket to see if at least that has been seated.  Maybe people err on the side of too little torque but still manage to crush the gasket?  Warm engine?  Anyways as this thread shows, it appears the plug made it's way out about halfway before things went bad.

In my experience the issue is more likely to be the ability to remove them intact, especially the tapered seal type. Modern automotive spark plugs generally have around an 80,000 klm replacement requirement per the manufacturers maintenance schedule and no requirement to check them for loosening.

Ciao