Tach cable leak caused by internal damage

[ChrisMA]

So, one of the items on the to-do list for my 80 GS1000G was a very slow leak where the tach cable enters the front of the cylinder head. I ordered both seals, then removed the tach cable and sleeve to replace them. I found that there had been some damage done to the inside of the head, in the wall of the hole where the sleeve is seated (see pic below). There was also a little gouging to the sleeve itself, and some minor damage to the gear teeth (though the tach itself works fine).

I assume that, at some point, the screw securing the seal must have come loose while riding, and the spinning gear pulled out, causing the gouge. I'm guessing that a PO must have more or less plugged up the leak with gasket seal (which you can see caked on the side of the head).

I did replace the seals and put it all back together, but the leak has progressed from maybe a drip a day to almost a flow when the engine is running - basically to the point where I can't ride it (it starts smoking as soon as the pipes warm up).

Any thoughts on the best way to reseal this? Maybe cleaning up the oil from around the sleeve and applying some hi-temp gasket maker (I have some Permatex Motoseal that's supposed to be good up to 450F)? I'm afraid that anything short of a head swap is going to be a hack, and that the leak will keep coming back until I swap the head, but I'm also in no hurry to do that...

IMG_20180829_125710a.jpg

Thanks,
Chris

[hannibal]

I have no experience with something like this, but JB Weld was my first thought.

[ChrisMA]

I have no experience with something like this, but JB Weld was my first thought.

Good point, thanks. Yes, that would hold up better than a gasket maker. Though I'm nervous about the sanding I'd need to do to smooth it out, resulting in grit in the engine. Probably something I'd hold off on trying until the next time I have the valve cover off, so I can find a way to plug it from the inside as a precaution.

[ChrisMA]

Here's a view of the gear - though the damage to the teeth doesn't seem nearly bad enough to explain the amount of gouging to the passage through the head. It's a bit of a head-scratcher (pardon the pun)



For now, I think I'm leaning toward giving the MotoSeal a try just to fill the worst of the gouges, then another thin layer around the outer lip where the sleeve will mate. Maybe I'll luck out and that will be good enough. Though I'm skeptical, as I assume I need a pretty good contact with that inner ring seal in order to prevent oil from dribbling out through the cable connector (which is probably exactly what was happening before I disturbed the old layer of gasket seal).

Long term, JB Weld is probably the only good fix (or at least, the only one I'm capable of doing at home). Though I'm not sure I trust myself to get it smooth enough for that sleeve to fit in, which is already a pretty snug fit.

[Burque73]

What a mess. I'm wondering if the P.O. snapped off that sleeve at some point, then drilled or pried the thing out.

[ChrisMA]

What a mess. I'm wondering if the P.O. snapped off that sleeve at some point, then drilled or pried the thing out.

Ugh... just the thought of all the metal shavings that would have left behind (shudder). Though otherwise, the engine seems to be in decent shape internally. Whatever happened, it somehow seems to have avoided any other damage.

[ChrisMA]

Closing this out, in case someone else is researching the same problem in the future (though I do hope that damage like I have is pretty rare).

After cleaning off the oil carefully, I slathered some Permatex Motoseal around the inside of the head opening, as well as all of the outer surfaces of the tach sleeve, then reassembled. I let the bike sit on the centerstand for a few days (to keep the seal away from the oil). Finally, after a week and a long ride, there are no signs of any further leakage. If I do have problems later, I'll likely wait until I get the valve cover off, then try again with some JB Weld.

I read on a Honda forum how a CB owner with similar damage repaired his: rather than dealing with sanding down the surface, he smeared on the JBW just like I did the Permatex, and inserted the sleeve. Sounds simple enough, but also seems pretty much permanent.

[Uncamitzi]

vacuum cleaner running while sanding...? just a thought

[ChrisMA]

Well, the permatex seal held for a couple rides. But then the leak started back up. Slow at first, maybe 1 drip per day. Now it's back to the point where I can't ride it. It seemed to get worse after high revs (around 8k). So, maybe it was vibration in the tach unit that messed up the seal. Anyhow, looks like I'm going to have to break out the jb weld if I'm going to salvage the rest of the season.

So... To grind, or not to grind? That is the question.

Pros:
- No grinding
- No risk of engine debris (and I'm more worried about sand from the grinding material than the jb weld, which, being an epoxy, I assume is softer than the valves/pistons/etc)
- Better chance of tight seal (and I'm not sure that I'd be able to grind a perfect opening for the sleeve anyway)
- I don't have to remove the valve cover (which I would do if grinding, if only to follow Uncamitzi's vacuum suggestion)

Cons:
- When I pulled the tach unit, I found that I'd gotten some permatex in the teeth of the gear (because it's near impossible to thread it through the head hole without contacting the wet seal). If I do the same with jb weld, I'd end up introducing some debris in the engine one way or another.
- Good luck getting that sleeve back out without a torch.

[Steve]

Why all the concern about removing the valve cover?

That is a pretty much routine task, and very easily done. I would think it would be easier to remove the valve cover and be able to get to both sides of the hole. Besides, how long has it been since you checked valve clearances?

.

[Burque73]

Just a thought but what if while the valve cover is removed, you tap that hole and just plug it with a bolt? The damage looks pretty bad and may not seal. Of course you lose the tachometer but it's non essential anyway. JB weld may work, but if not this may be an option...

[ChrisMA]

Why all the concern about removing the valve cover?
.

You're right of course, but it's only been several hundred miles since I adjusted the valves, and while I know that my new oem gasket SHOULD stay intact, with my luck, I'll be waiting on yet another part order when I just want to get out and ride. But even if I do remove it, the other concerns remain.

Decisions, decisions...

[ChrisMA]

Just a thought but what if while the valve cover is removed, you tap that hole and just plug it with a bolt? The damage looks pretty bad and may not seal. Of course you lose the tachometer but it's non essential anyway. JB weld may work, but if not this may be an option...

Yeah, that may end up being my last resort option. Though at that point I may end up seeing if the local shop could weld a more permanent solution, retaining the sleeve and tach gear. I'm just not sure I'd want to go without a tach permanently, though I know some riders get by just fine without.

[GregT]

Don't weld it - you risk head distortion. The mechanically correct way to fix it is to remove the head and machine the hole to a clean diameter on the same center. Then a thin sleeve with the correct ID is pressed into place. But it's a lot of work. I'd only do it if it was a rare head or one I had a lot of work already sunk into...

In your place, I'd clean out the permatex and use epoxy or JB Weld. Don't smear it in the hole - put it on the tach drive insert OD and you won't get it on the gear. If it ever has to come out, it's easy enough with an electric heat gun.

[ChrisMA]

Don't weld it - you risk head distortion. The mechanically correct way to fix it is to remove the head and machine the hole to a clean diameter on the same center. Then a thin sleeve with the correct ID is pressed into place. But it's a lot of work. I'd only do it if it was a rare head or one I had a lot of work already sunk into...

In your place, I'd clean out the permatex and use epoxy or JB Weld. Don't smear it in the hole - put it on the tach drive insert OD and you won't get it on the gear. If it ever has to come out, it's easy enough with an electric heat gun.

Thank you Greg, good warning on the welding.

In fact, your JB suggestion is exactly what I did on Saturday. I just applied some around the OD of the insert, tightened it up, and let cure. Haven't had a chance to take it out yet, but... fingers crossed.