NO exhaust gasket...really? By evilgenius (Read 9,887 times)

[evilgenius]

Suspecting that I may have had a leaky exhaust gasket (head to pipe), I take off the pipe this morning only to discover that my problem is not that the gasket isn't sealing correctly...it's that the gasket is not effing there!

Wow. Really?

Not only that, the left stud was apparently stripped inside the head, just to sweeten the deal.

First order of business is a trip to the local Yammy and Honda dealers...neither of which seems to have one in stock. Honda parts guy actually tried to tell me that "he doesn't know what this GY6 he always hears about online is, because Honda doesn't make an engine with that designation". Thanks for nothing yet again, crappy Honda dealership.

So, without delay, I've got an order in to Absolutely Scooters for one of these jewels:
absolutelyscooterparts.net/catalog/exhaust-gasket-150s-p-112.html
Hopefully it'll get here before the next monsoons hit, and fit the recess correctly. Design looked superior to the little copper donut, anyway.

Too bad that, after no scooting all weekend due to downpours of biblical proportions, I'll be still 'not scooting' until this can get here. Of course, blue skies and sunshine called for all week. Grrr...here's hoping that AS and Priority Mail get it here PDQ.

And of course, there's still the issue of the stripped out stud to deal with. Brushed the aluminum out of the threads, and the stud itself seems to be in fine shape. Testing with another bolt finds that there are still threads enough to bite in the hole. (Strangely, it would seem to be that the bolt only stripped in the "middle", leaving thread at top and bottom). My thought is just to re-fit the stud in there with a copious amount of threadlocker (or even considering JB weld), cross my fingers, and hope for the best. Providing I can get the old nut to let loose of course, which has thus far been a losing proposition. Hopefully a little soak in the ultrasonic cleaner tonight with some rust remover will coax it loose. Otherwise, I'll be off hunting for a substitute at the hardware store (I've just about given up asking for anything at the local shops due to repeated disappointment, and I've already checked advance auto to no avail).

All of this ON TOP of hoping that the engine hasn't been damaged by this already too. Luckily, I see no signs that it has, but still. No telling what kind of stresses and temps this subjected the poor thing to. It has been running just fine, so I'm hoping it's OK and will pull through.

There you have it Docs, my daily adventure in scooting (or, more precisely, lack thereof). Had to rant to somebody, so here I am. Any input from fellow Docs on this one is welcome...

[hiskid1973]

When I pull the exhaust off Lois' RX200 there was no flat type of gasket..What I did find was like a thin raised ridge like one side of a thin donut..I put it back together and no leaks...One nut came out with the stud attached and the nut just came off the other side..

[Bashan]

Just curious, what kind of damage could a leak at that point do? Rich

[Alleyoop]

Well I know you will probably get backfires when you crank on it and let it come down say when your going to stop or slow down without any throttle on. You will hear a POP.
Alleyoop

[Bashan]

Well, that's what I was wondering, would it just be a noise issue or could it actually do some mechanical damage by, say warping a valve due to heat differentials. Rich

[zugzug]

Well if you run an engine too long like that you can burn the valve, maybe the piston, the exhaust port area. Its usually pretty obvious damage.
-Zug

[mthomas]

If it was me, I would avoid using thread lock and especially JB weld. I would buy either one or two bolts to replace the studs. Just my .02

[evilgenius]

Well, it would seem that I've avoided any significant damage, but that all remains to be seen I suppose. I'm hoping that I at least had the flange polished and secured well enough that the leak wasn't terribly bad. I was getting only just a little bit of 'putter' when letting off the throttle, which was what tipped me off to look in the first place. Only physical signs I see is a little chalkiness on the flange on that side (already re-stove blacked ;D) and a little melting of the plastic on that side of the shroud (which was there when I bought it).

Will probably go to Ace and/or the local auto parts houses tomorrow to see if I can find some new exhaust studs. I have the old one, but threads were slightly damaged and I just don't trust it based on a) suspecting it's cheap steel and b) in a state of highly dubious structural integrity due to the aforementioned cheapness combined with 2.5km's worth of heat cycles. Not exactly a promising combination for long-term integrity.

Failing that, I did get some high quality stainless 6mmx30 machine screws I can cut the heads off of to use in a pinch. I've heard both ways about using SS in aluminum, but I'm thinking for my purpose having it weld itself in place might be just the thing...

In the head itself, I've got approximately 15mm of thread, with 5 missing/damaged smack dab in the middle. My goal for repair is to do the best I can to hold it together without pulling the head. If I pull the head, I'm just going to put a new one on, and that would be a huge PITA for me, so repair in place is the hands-down preferred option. I want to just get another stud in place, lock it down, and *hopefully* have it remain there for the remainder of the life of the engine. This made SS an attractive option, and probably either red or possibly even green loctite up in there. (No offense, mthomas, I'd normally agree with you but this situation calls for it, IMHO.) Theoretically, that'll hold the stud securely in place. Then use either brass/copper, or failing that, heat treated steel hardware to secure. I'm thinking double-nutted with a lock washer for maximum adhesion and thread protection.

Absolutely Scooters got my package shipped PDQ yesterday, and confirmed that it will fit the 1P57QMJ. If the USPS cooperates, I will hopefully be back on the road for the weekend.

Took the opportunity to have a closer look at the exhaust while it was off...my, my, my...bad form! Lots of ugly 'weld boogers' disrupting my airflow both coming out of the pipe and going into the muffler. A few minutes with a rotary tool and a carbide burr took care of all that silliness. Damn 'pig iron' pipe had already started rusting back in spots, so it got another generous helpin' of stove black, as did the muffler where it had gotten scratched when dismounting. All is shiny and well again there. ;D

There was indeed a gasket present between the pipe and muffler, thankfully. A bit questionable how well it was sealing due to waviness on the muffler face, so I hit it with the 'ol mouse sander to try and smooth it out, as well as rough up the surface a bit for a better seal. Going to run a bead of gasket maker around the outside before reassembly just to help make sure everything goes back together and seals well. Polished the flange with some fine grit too, for the same reasons.

So, there's today's update. I'm cautiously optimistic as to repairability, and looking forward to being back on the road. This weather taunts me so...

[evilgenius]

Gasket's on the way, One of these jewels...



...thanks to Absolutely Scooters & Supply (that's right, Doc-approved vendor!). Might be in as early as tomorrow, but I'm guessing Friday.

Again, that's fine, it'll have me back up and runnin' for the weekend. ;D

I might get some material and make a new gasket for the muffler while I've got it all apart, but that's not really a 'must have' at this moment - the old one should do just fine for now, especially with an extra bead of sticky around it. Depends on what I find at the parts houses/hardware store tomorrow.

[evilgenius]

Well, AS got my gasket in Friday afternoon - sweet! So much fuss over such a simple little thing...

My trip to Ace got me a new heat-treated 6x30mm stud, a roll of some hi-temp gasket material, and some loctite 'red'. One-stop shopping, indeed.

Used the old pipe/muffler gasket to make a pattern on the new gasket sheet, and bolted the exhaust back together. New gasket material isn't as thick, but hopefully will do OK.

Against my better judgment, I decided to listen to everyone's advice and forego any type of sealer inside the stud hole in favor of anti-seize. I figured this is going to be a progressive repair, stepping up in degrees of severity until something 'sticks', so that was the place to start.

New stud went in, manifold went on, held in place by a heat treated lock washer and double nutted with standard steel nuts. Nice.

Fired it up and all seemed well. After a week of 'not scooting', I was tickled to be back on the road for a test ride! Things seemed to go well...sound was 'normal' on accel...deccel was not 'poppy', just a nice "grrr" sound, which I took as indication that the gasket was doing its job and exhaust gases flowing properly. Rode about 10 miles this way and brought it home to cool off while I went out for some Chinese food (no, the irony is not lost!).

Waddled home from the buffet and decided to have a look-see to find out if any of the nuts needed tightening up after the ride. Got about another 1/4 turn on the muffler clamp bolts, as expected. Looked at the flange and found that, to my horror, the new stud was gone. Yep, that's right, just fell right the eff outta there. About every swear word I know escaped my lips at this point, and I believe I may have actually created some strange new ones (urban dictionary said they'd get back to me on that).

So...not enough thread there to hold it in place, vibrated loose, and fell out. Boo on this, both because it left me back at 'point A', and because I gave a whopping $2.50 for the stud that's now road debris somewhere.

I had thought the thread O.D. and depth on the new stud looked a bit thin to begin with - yeah, it's M6 blahdeblah, but it just seemed a bit fine to me. Thought perhaps the failure might have been due to a combination of thread size variation and the lock washer putting undue extra pressure on the threads, so I replaced with a stainless 30mm allen machine screw with flat washer and double nuts as spacers. All looked well, so I fired 'er up and went for another test ride.

Behavior was again fine on the ride, good sound and no problems. Unfortunately, when I got back to the garage and had a look-see, the bolt was gone just like the stud. Barring the possibility of exhaust-stud-munching gremlins, it would appear that there just isn't enough bite left in there to secure a standard M6 anymore. The anti-seize might be working a bit *too* well also.

So...I have a gasket now, that is functioning and holding in place courtesy of the remaining stud, and a half-stripped hole full of anti-seize. First step's getting that anti-seize goop outta there. Next step is up in the air...

I can thread M6 into the hole and have it hold just until heat and vibration enter the picture, at which point it lets loose and vibrates out. I'm still tempted to use some kind of goop to try and fill the gap between and solidify the seat. Bad thing is, there would seem to be very little in the way of goop that can stand up to this kind of heat.

Speaking of which, anybody know for sure how much heat we're dealing with here? I've read up to 1200f, but I don't know how accurate that random internet factoid may be. Most goops, even hi-temp goop, will only hold to about 500f. This includes JB weld and Loctite products.

Leading candidate seems to be this Permatex metal compound, or putty, both of which claim to not only withstand up to 2000f, but to actually set better with the heat:
www.caswellplating.com/permatex/permrepairprods.html

Seems to be a ceramic, which is interesting. Explains setting with the heat, at least.

So, I suppose I'll saunter on back to the parts house and see what they've got that's comparable. If it doesn't hold, well, I'm no worse off than I am now. Either I try this and it works, saving me from having to drill/tap, helicoil, or replace the head, or I have to do one of those, which is exactly what I'm looking at now. If I go the retap route, I'll likely try and go for a 1/4". Mixing metric and standard is never good, but a stripped M6 is about perfect for a 1/4", and the 1/4" stud will likely fit the opening in the flange to boot, saving me the trouble of having to drill that out too (which is really no big deal anyway, but easier is easier any way you slice it).

Not that anybody cares about me and my half-stripped thread, but if I can find an easy fix for what's apparently a fairly common problem, it might help someone further down the line, so well enough to post here for posterity's sake. Helps my own thought process to document it too. If nothing else, I'm making a nice "won't work" checklist! ;D

[ootscoot]

Thanks for all the research - you are definately not alone w/ this. We get about one stripped/sheared/missing exhaust manifold bolt scoot repair each week. Often to the point of replacing the head - we have, if possible, re-threaded the head and went up a bolt size to the 1/4", and have used a green high temp locktight. Seems to work on some bikes (or else our customers had the same problem and went somewhere else)

[runningslow]

I had a stripped exhaust stud and the shop who fixed it for me used a helicoil. Worked great and it introduced some good quality steel to the problem. Of course, now that I'm getting a new motor, I'm not going to have that head on the bike. So, hopefully the new head won't strip. LOL.

[Bashan]

I used permatex copper gasket sealer/maker to fill some gaps when I put a blocking plate on my head when I removed the PAIR emissions system. It seems indestuctible but I believe that Permatex makes a remover if you decide to dismantle. Rich

CLICK ON IMAGE

[evilgenius]

Thanks for all the encouragement, folks!

Progress has been delayed until funding can be secured (read:payday).

I did however make a pretty swanky 28mm stud bolt from a 30mm stainless machine screw with a wet saw, so I suppose that counts for something. ;D

Bashan: how did that ultra copper set up? I.E. "spongy" like silicone, or hard, like cement? I'm still up in the air on which type of compound to try next...I like the idea of the ceramic, because I think it would make a good solid base when it cures, but then again something with just a little bit of flex to it might give it a wider operating range before failure.

I'll likely not know 'till I actually go to the parts house and see what they've got, so it's kind of a moot point I suppose.

That's the plan though...if this won't hold it, it's off to Harbor Freight for a 1/4" tap. And really, any excuse to go to Harbor Freight is a good one, am I right?

[evilgenius]

**walks back in from garage**

Well, it's done...here's hoping it works! They didn't have the ceramic compound I was looking for at the parts house, so I wound up with some of this goop:



Thermosteel..."cold weld" compound, used for patching up cracks/holes in blocks, heads, manifolds, and the like. According to the package, this stuff's good up to 2400f! That's hot! The mere 1200f coming out of the exhaust port should just cure it up nicely then. Says it gets stronger with heat too...we'll see about that!

I cleaned out the hole with carb cleaner and Q-tips, then mixed up the magic goo. Consistency is kinda like JB weld, with pulverized metal shavings in it. It was thin enough when mixed to get drawn up into a syringe, which I used to blow the stuff up in there. A lot of it ran out, but I was able to get a good bit up in there. Surprisingly, I found the stud that had fallen out on the garage floor, so I cleaned it up and used it instead of the one I made from the SS (hell, I gave $2.50 for this thing, I'm gonna use it!). Dipped it in some of the pastier stuff left and screwed it in using triple nuts on the external side to try and keep those threads clean as the excess goop squeezed out when threading it in. I could definitely feel the metallic bits 'crunching' as I was threading, which I took as a good sign. Pulled off the triple nuts and cleaned everything up with more Q-tips. Now to let it cure overnight...

When I pulled off the pipe, I was quite dismayed to find that the new gasket had fried itself to death on one side. Boo! I think I'll be making my own gasket this time, if I can find some material that will take the temps...we'll just have to see what wonders the parts house holds in the morning. Failing that, I might try to refurb the old one with some of the ultra copper, depends on how desperate I get.

On the bright side, the gasket I made between the muffler and the pipe is holding up nicely.

Picked up my poor workbenches a bit, they'd taken a beating over the last couple of months. Used the down time to throw a couple of body clips on that had been missing for a while too.

So...to the parts house in the morning for gasket material. Cut new gasket, bolt the pipe back up, and let her warm up at idle for a while to set the paste. Let it cool down...check the bolts...then if all's well I fire it back up and go for a ride! ;D