How Screwed am I? Stripped Gearcase oil plug?

Crap.

Changing out all the oils in my GRiSO.  The gearbox oil plug was in there pretty tight, but it came out - though it was binding, and I had to use a box wrench to get it all the way out.

Drained the oil, went back to put the plug in...and it bound again as it was being screwed in.  Fingers wouldn't work, so I had to use the box wrench again.  And it never stopped...it just kept going and going...

I tool it out, and this is what I saw:

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The plug looks fine.  The metal you see was embedded in the threads.  I'm guessing the threads in the crankcase itself are compromised.

Thoughts?  What are my options here?

Crap.   

Wow that sucks. Only things I can think of at the moment are tapping new threads (larger diameter of course) along with a drain plug to match your new thread pattern, or replace the oil pan (probably the more expensive option).

Also, if I had to purchase a new oil pan, I would also spring for a new drain plug just to be safe - there appears to be some galling just after the starter thread, wouldn't want to botch the new pan!

Tim

You could try inserting a Helicoil in the oil pan. You drill out the hole and screw in a stainless steel helix. In effect, you get new threads in the hole, which are at least as strong as the old aluminum threads. It's pretty easy to do, and requires no power tools. Kits are available where automotive tools are sold. Should cost you a lot less than a new oil pan, at least!

I did this on my truck when I stripped the threads for one of the bolts holding the transmission sump in place. Worked perfectly. If the old bolt is damaged, replacing it will probably save you from future problems.

I would even remove the oil pan to do it, saves getting any crap in the sump and you can clean it out at the same time.

Us old air head 2 valvers have to do this to change our oil filters, no biggy.

If the oil pan removal isn't rocket science, I'm game to try.

Is is just a bunch of bolts to remove, drop the pan, do the work, reverse the first step and ride?

Do yourself a favour and buy a new sump - they are not expensive. The current one you can use as a spare - I would not recommend Helicoil, as oil will seep past the thread too readily. Better to get someone to weld it up and tap a new thread the correct size, then you have a spare if you ever ride off a gutter (like I did) and you need another sump pretty quickly. If you have a spare you will never need it - if you don't, you will - this is the way of the world, unfortunately...

ghezzi wrote:

I would even remove the oil pan to do it, saves getting any crap in the sump and you can clean it out at the same time.

Us old air head 2 valvers have to do this to change our oil filters, no biggy.

Seconded.

Oz1200Guzzi wrote:

Do yourself a favour and buy a new sump - they are not expensive. The current one you can use as a spare - I would not recommend Helicoil, as oil will seep past the thread too readily. Better to get someone to weld it up and tap a new thread the correct size, then you have a spare if you ever ride off a gutter (like I did) and you need another sump pretty quickly. If you have a spare you will never need it - if you don't, you will - this is the way of the world, unfortunately...

Sounds a little like your Friday night dream Tony, better get yourself a spare GRiSO mate!

And to NorthBayGriso, if you drill, tap and helicoil the hole, use Loctite 515 on the outside of the helicoil. Allow it to dry/harden etc overnight and I guarantee it will never leak and it definitely will not come out. Next day clean any excess 515, especially from the inside of the helicoil. Oil the threads of your new bolt before installation.

Correction gents: it's my gearbox plug, not the plug for my engine oil. As noted in the correction on the OP, I'm an idiot.

And: is the plug supposed to be a standard 3/8-16 tpi bolt? 'Cause that's what I had installed in my bike. The only difference between the plug and anything I can get at a local hardware store is the magnet on the end.

Remove the pan. This is no big deal but you will require a new gasket.

Drain the oil and disconnect the return pipe from the back of the sump. Then remove the 14 6mm Allen bolts around the outside of the pan and then the four more that are around the filter.

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These also hold the sump on and are in wells beside the filter, feel for them with your finger. They have to come out before the sump will drop. 6mm allens also.

Once the sump is off it will be much easier to helicoil. If you don't know how to do a helicoil? Take it to a shop and have them do it. They HAVE to go in square or you'll get leaks as the plug won't seal.

Once the helicoil is in just bolt the sump back on, re- connect the return pipe, install the plug, fill with oil, go ride.

Pete

PS. OK, your bike has been butchered. The plug should be a 10 x 1.5 metric. Gearbox plug is a bastard to helicoil. Same deal but you have to remove stuff to get a clean run at the hole. It might just be better to tap it out slightly bigger and fit a standard size bolt without magnet.

My gearbox [the real one this time; the one with the engine oil in it] has an identical plug. No leaks, though. Wonder how this happened?

Pete Roper wrote:

PS. OK, your bike has been butchered. The plug should be a 10 x 1.5 metric. Gearbox plug is a bastard to helicoil. Same deal but you have to remove stuff to get a clean run at the hole. It might just be better to tap it out slightly bigger and fit a standard size bolt without magnet.

Sorry, can we clarify which plug has stripped? Is it part#22 in the image above? That's the engine oil plug.

The gearbox plug.

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Is identical but is part#13 in the above pic.

If its #22 drop the sump.

If its #13 it's a bit more involved and involves grovelling.

Pete

If it was me, I would use a key insert rather than a helicoil in aluminium.

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They are available at any decent nut and bolt store.

It is indeed part #13 in your schematic.

Though, to be clear[er]: the plug itself looks fine; its threading appears intact.  I believe it's the threads in the case itself that have stripped.

I am not above groveling to get my bike operating again.

And what is part #9? I think I need a couple of those too.

Pete Roper wrote:

Sorry, can we clarify which plug has stripped? Is it part#22 in the image above? That's the engine oil plug.

The gearbox plug.

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Is identical but is part#13 in the above pic.

If its #22 drop the sump.

If its #13 it's a bit more involved and involves grovelling.

Pete

Ugh. That's a much bigger job than dropping the sump... What a bugger. Gives you a great opportunity to grease up your swingarm bearing though.

I'm leaning really heavily towards some sort of Helicoil-ish/key insert solution. I'm not really looking for [and certainly can't afford] what is essentially a rebuild.

I still find it...odd? vexing?...that the wrong plug was installed in my gearbox, and possibly in my crankcase too.

how did this go so pear shaped....gee whiz...it is the tranny drain screw that stripped, as per first post, you do have a problem with that one as the access sucks.  

IT IS an M10 THERE IS NO STD THREAD ON THIS BIKE.  so you have a lot of stuff to remove to get a clear shot at the drain plug, if you can at all with the engine in frame.  

You need to install a time sert with retaining compound:
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the real problem is there is a gear shaft right over the drain and drilling and tapping is gonna be a bitch as the tap cannot project into the transmission very far,  you may have to thread partially and the shorten the time cert tool and go a bit further, and repeat this process several times then set the time cert with a retaining compound to ensure no weeps...it is a bitch to destroy a time cert tool set to do this but it beats pulling the tranny.

these are the best inserts for this application, helicoil being the worst (due to layout ) and kingcert wedge lockers will be too large in dia for the boss to seal later

make sure to coat all the tools with grease while you work it will pick up the debris and carry it out of the case with the tool do not get in a hurry and go slow keep the insert straight during the repair otherwise the plug will not seal.

and remember when a screw goes into the bottom of a case like this it is lefty tighty righty loosy  

it is the correct plug, who has serviced the bike befor this? they did not realize that the left and right reversed with the screw in this orientation and tightened the plug and damaged the threads. then stuck the plug in and kept their fingers crossed it would be ok when they did the re-fill

Hmmm:

1. Serviced at Rose Farms in IL, before I brought it home. This is the first service since then. God only knows who serviced it beforehand. If they even noticed the incorrect plug, I'm thinking the Rose Farm folks used what was already installed, as this kind of repair certainly wasn't budgeted.
2. I see Timesert.com has 2x m10 x 1.5 kits: headbolt [#1015 or #7580] and oil pan [#1015a] repair kits. I'm figuring on #1015a...?
3. Neither part show any retaining compound.
4. Access to the tranny case drain plug/hole didn't seem all that tough, if the bike is lifted enough to slide underneath. Did I miss something?

As Uzidzit said earlier, this is the correct plug, I think you may have mistakenly spec'd it out. It seems that someone either cross-threaded the plug or over tightened the plug and buggered the threads. It happens easily enough when a ham fist pits steel vs. aluminum.

Wow - we spec'd out the plug as .977 mm 16-tpi last night. Who'da thunk that m10-1.5 was virtually identical to 3/8-16 SAE?

OK, so its the gearbox plug. Bad news as these are a bear to do.

Before we start though let me just say that occasionally they do seemingly strip for no apparent reason! I have a customer who accused me of stripping the plug in his Norge and not telling him. Well, it was fine when I did it up and he claimed not to of touched it, (Shrug?) so perhaps it was over tightened at the factory and heat cycling caused the thread material to fail. I have no idea but they are a coarse thread in aluminium, you do have to be careful with them.

As mentioned the worst thing is getting a good run at the hole. Best bet with the GRiSO would be remove the footrest hanger plater and master cylinder assembly and then go in with first a taper tap and then, after you have it started, a bottoming tap, in the next size common thread above the 10 x 1.5 . The problem with heli oils in this situation is breaking off the tang and where it goes! Time sert is good but the issues there have been described!

Very important to get the repair square though otherwise you'll always have leaks.

Pete

pS the other part is simply a dowty washer.

The last time I checked mine with a magnet, GRiSO's dowty washers are made of steel.

If the person who tighten it using muscle memory from a more compressible aluminium washer, he will keep on torquing it down until until he felt the washer is crushed. That "crushing" sensation may came from threads pulling of the aluminum case.

It's steel bolt vs steel washer vs aluminum threads.

the washer on this one is a rubber lined sealing washer, they are avail from mcmaster carr I just suggest using retaining compound on the outside of the time sert to make 100% sure of no leak...the time sert is the best of the best for thd repair like this..they do not mention using retaining compound in their instructions but it is good for safety

just as a fyi time sert also is the only company that make inserts with bottoms so if you need to do a blind hole in a spot that has oil behind it they will not leak along the threads as they form a blind hole  they are expensive but are worth the extra dosh

and yes the m10 1.5 is very close to the 3/8 16 , as 10-32 is very close to m5 .8  we call these high risk exchanges in engineering and never mix the two in a single assy as they will thread into each other and fail...

and yes sometimes the threads in aluminium parts will gall for little aparent reason and come out with the fastener...you can avoid this by using COPPER or NICKEL based antisieze  DO NOT USE THE SILVER aluminium stuff it is for steel in steel or steel in cast iron only...most of the time in cast parts it will happen sometimes

this plug is vaunerable as it is very difficult to get to and it has a big head...so usually only a big box or open end wrench will get to it, and that means a long handle and easy to overdo the torque without trying hard

that neck on the screw is supposed to allow the screw to fail before the threads in the case but it does not always work

I suggest changing all crush sealing washers to the rubber lined ones if you can as they do not require as much torque to seal and have less tendancy to vibrate out hit the pressure sealing option below and scroll to the bottom for metrics, they also have larger ones match the diameter of the metric to a std size, other sources have them up to 30mm dia

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OK - to sum up:

1.  Sometimes stuff happens
2.  It just sucks it was this particular drain, because of access and depth issues
3.  Uzidzit likes Time-sert
4.  Pete, not so much
5.  Lots of folks, but not Uzidzit, like Helicoil
6.  Applying retaining compound and proper anti-seize compounds seems like good advice
7.  Of critical importance is getting the re-threading efforts square.  Otherwise, it'll leak  
8.  And for God's sake don't go too deep

Did I miss anything?  If not, I'll need to find someone for this job.  Too fiddly for me.  A friend has a local shop [non-Guzzi] that feels comfortable doing it, so I'll have a talk with them.

I was just having a look at the blown-up schematics for my y/m bike over at Harper's [http://www.harpermoto.com/parts-by-motorcycle/2000-up-moto-guzzi-motorcycles/GRiSO-v-8v-1200-2007-2009.html] - I don't have a CARC oil plug washer, nor do I have a tranny oil plug gasket or a CARC breather sealing washer.  And it looks like all for of my rubber-lined sealing washers need replacing while I'm in there.