What would GRM do?
This relates to my Montesa thread.
http://grassrootsmotorsports.com/forum/sprockets/montesa-315r-the-project-begins/54630/page1/
The hole for the (steel) coolant drain plug bolt in the aluminum water pump housing is stripped.
Should I:
-or should I just go ahead and drill a bigger hole, tap and use a larger bolt?
This is not a huge problem, since the drain is in the water pump, not the block. Worst case, I have to replace the tiny water pump.
You need a helicoil or thread insert. This forum has gone over spark plug thread repair a bunch of times, this is a very similar problem. It looks like it's easy to remove the cover/pump, I'd probably do that so you don't have to worry about metal shavings getting inside there.
Bryce
In order of preference for a professional, long-term repair:
1) Helicoil. 2) Drill and tap for a larger plug. 3) JB Weld, drill and tap for same plug. 4) Wrap Teflon tape thickly around it, screw it in as best you can, and pray.
+1 for Helicoil or Timesert.
If it's m6, you might be able to just go 1/4"-20 if you don't mind putting an SAE thread on a metric bike. If it were me, unless I had a helicoil already, I'd just go to the next size. If you decide on the epoxy approach, use something better than jb weld. one of the Devcon, or similar aluminum filled epoxy's would be best.
Update:
Okay, a closer look reveals that this is just a water pump cover and not the whole pump, but there's not a lot of meat on there. The drain plug is the dark bolt with the phillips head.
Bolt is in place in this photo:
You said it's a Honda engine, just buy a new cover. Or tap it oversized.
It's an HRC engine (Honda racing), so parts are a little harder to find. It has a Montesa specific part number and I don't have a cross reference to Honda part numbers. But, I'm going to the Honda dealer with cover and gasket in hand to see if they have anything.
I've found them on eBay UK for 33 pounds plus shipping if need be.
theres not alot of meat there, i'd drill and tap for 5/16x24 and use JIC hex plug -2 size. http://www.discounthydraulichose.com/product_p/6409.htm
44Dwarf wrote: theres not alot of meat there, i'd drill and tap for 5/16x24 and use JIC hex plug -2 size. http://www.discounthydraulichose.com/product_p/6409.htm
I'm starting to like this idea. Thanks.
It's aluminum, right?
Weld in new meat, drill and tap for std size.
It came to me in a dream...
Well, not really, but I did think of it while I was laying in bed at 4:30am.
There was never a heli-coil.
When I removed the water pump cover, I noticed that there were threads cut into the rough casting beyond the hole for the drain plug bolt. I realized that I did that when I was chasing the threads and that's where the bits of metal on the tap came from; not an old heli-coil. So the threads probably weren't as bad as I thought. I figured that it would be worth the chance to try and wrap the crap out of the bolt with tefon tape and see what happens. I wouldn't be able to get bigger plug until the middle of next week anyway and I'm really hoping to avoid drilling out that hole.
The cover, and its gasket, are Montesa specific parts and can't be sourced from the Honda dealership. I had some old gasket paper laying around from the '65 Mustang project (1997), so rather than get a new gasket from Europe, I made my own. I wouldn't mind safety wiring all the bolts, though that would mean making another gasket.
Woody wrote:44Dwarf wrote: theres not alot of meat there, i'd drill and tap for 5/16x24 and use JIC hex plug -2 size. http://www.discounthydraulichose.com/product_p/6409.htmI'm starting to like this idea. Thanks.
the striped out 6mm hole should be the right size for the -2 tap or darm close.
I will probably do that.
This is the one, right?
6409-02 6409-02 | Hex Socket Plug, #2 SAE/ORB (Steel)
whenever I have damaged threads in a not-so-thick casting, I usually go NPT. Straight threads require the tension of the bolt to hold a gasket seal against the housing. NPT seals as a function of the tapered threads getting pressed into the housing (often times along with a sealant.)
I think this is a perfect application for an aluminum NPT plug.
..... unless it gets removed/installed frequently... in which case I recommend a 1/4 turn ball valve that can remain stationary in the threads and be opened by other means.
I am watching this as buell decided that the clutch cable should be a 1/4 28 with about 1" of threads. I'm not taking it off again until I have either a time sert or helicoil. I only lost about the first 1/4" of threads.
curtis73 wrote: whenever I have damaged threads in a not-so-thick casting, I usually go NPT. Straight threads require the tension of the bolt to hold a gasket seal against the housing. NPT seals as a function of the tapered threads getting pressed into the housing (often times along with a sealant.) I think this is a perfect application for an aluminum NPT plug. ..... unless it gets removed/installed frequently... in which case I recommend a 1/4 turn ball valve that can remain stationary in the threads and be opened by other means.
How do you tap for NPT threads? Does the tap bottom out at a certain depth?
1/4 turn valve is not a good idea for this bike. The cover has already been rock bashed once.
I would recommend Timesert brand repair kit for sure. It puts a steel threaded insert into the aluminum, for the bolt to screw in to, much more durable in my opinion. Found our size on amazon. The kits are very well put together and have everything you need. We have a BMW e30 Chump car with an aluminum oil pan. Some previous owner had used a helicoil or similar to repair in the past, and it did not last. I did the repair very carefully with the pan on the car. I put bearing grease in the grooves of the cutting bit to collect the shavings and used some qtips with grease on them to collect the minimal shavings that were in on the bottom of the pan. Flushed with oil. Has worked perfectly for us.
Woody wrote: I will probably do that. This is the one, right? 6409-02 6409-02 | Hex Socket Plug, #2 SAE/ORB (Steel)
Yup thats the right one.
I'd stay away from NPT do to stress it makes as it tightens.
I used a Keensert from Fastenal to fix a stripped timing belt tensioner bolthole. Worked great! Highly recommend those!
Woody wrote: How do you tap for NPT threads? Does the tap bottom out at a certain depth? 1/4 turn valve is not a good idea for this bike. The cover has already been rock bashed once.
It takes a tiny bit of finesse, but you basically go as far as you need to. Start shallow. You might find that you can't get more than one turn on the fitting before it gets too snug. Go another turn with the tap and try again.
Another thing you could try is APT, which is identical to NPT except its not tapered. Earls and Aeroquip have fittings. Tap, dope up the threads, insert.
I might suggest (instead of a ball valve which wasn't a really smart idea) using something like a butterfly draincock valve or a knurled knob drain valve like you would find on a radiator or an air compressor drain (respectively).
Basically, I'm trying to suggest something that lets you put a stationary fitting in the housing and allow drainage by other means. Maybe even just an NPT reducer, say maybe a 1/4" NPT to 1/8" NPT reducer and 1/8" NPT plug, then you can just take out the small one and prevent future damage to the housing.
Or, even better... a 1/4" NPT reducer, drill out the center, tap for straight threads, and use a bolt/o-ring to seal the hole. That way you're affixing a "permanent" thing in the housing that has 1" of threads to hold your drain bolt.
Send me the cover and I'll Helicoil it for you.
motomoron (at) yahoo (dawt) komm
Thanks for the offer, but I like to learn new tricks myself.
1/4"-18 NPT tap requires a 7/16" ( 0.438") tap drill but measure the tap dia. w/ calipers first to be sure there will be enough meat in the casting. 1/8"-27 NPT uses a 'Q' ( 0.332") letter drill.
If the hole is blind you may need to start the tap till it bottoms out, grind the tap down, start threading again, repeat till tap is at it's full dia. or until the plug will screw in securely. 3 turns of the plug to finger tight are good threads.
If a through hole tap to where plug is finger tight as above. Use tap oil and clear the flutes.
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