My apologies for the long wait to whomever might still be inexplicably paying attention...
In short: Ghetto gasket = FAIL.
I cut two nice diamonds out of the aluminum flashing, and bound them together with about 3mm of ultra copper for a primo-looking ultra copper sammich. This was a pretty badass ghetto gasket, IMHO. Bolted it up and was good for about 70 miles, then I heard it get louder and louder as I was riding...got it home and looked under the scoot to find ultra copper was forcefully blown right out the side and all over the shroud like a sneeze on a buffet - seriously, this stuff went straight to hell. I had expected a little more from the ultra copper, really.
Unbolted to try to find the failure mode, to find that only *half* of the gasket was still there! By that, I don't mean that the plates were left, no no...the aluminum and all burned clear in half, on both plates! Gotta say, I was impressed. Half of the entire gasket was completely GONE. Road litter somewhere, I would imagine.
Failure mode was apparently that the ultra copper just burned out, so no use investigating further.
This left me scootless for a while. Ordered 2 different types of ring gaskets, hoping that I would have better luck. Ordered from a vendor on Sunday night, paid for priority shipping. Monday was a holiday, that was all fine and dandy, but the damn things didn't ship out until THURSDAY NIGHT. Fat lot of good priority shipping does when it takes 3 days for a vendor to put 2 rings in an envelope. Bad form, unnamed vendor! USPS then proceeds to hose me by claiming they "attempted delivery" on Saturday. Pfft...
Finally got my parts the following Monday, one copper donut and one 'OEM' (aluminum?) donut with some mystery thermal goo around it. Chose to go with the OEM 'mystery goo' first, as it was slightly thicker and seemed to fill the recess a little more snugly.
Cleaned everything up, started bolting back together, and was giving the nuts one final twist when *pop* - out comes my thermosteeled stud. Needless to say, I was not happy at this point. All my ghetto engineering had failed. Not a high point in my personal scooter chronicle. Thermosteel looked like it had done it's job, there just wasn't enough thread left for it to grip to.
So, I procured a 1/4" tap from the parts house and proceeded to clean and re-tap. This was slightly tricky, as I had to tap from underneath with the pipe still attached - I'd already started crushing with the other stud and didn't want to waste the gasket. Unfortunately, the tap seemed way too easy - not sure if tap size was a little off, or if the hole was just a little too wallowed out. At any rate, I decided to use a high quality stainless steel 1/4" Allen head cap screw instead of a stud. This twisted in with little fuss, and is now extremely secure - I really think it may have finished tapping it's own thread. Tripple nutted both studs, crossed my fingers, and hoped for the best...
So far, so good! Bolts appear to be holding, and gasket appears to be...well, 'gasket-ing'. 4 or 5 good rides in now and nothing appears to have either loosened up or sprung a leak, so I'm tempted to call this repair complete.
One thing I noticed was that the casting in the flange area on the head was piss-poor. Convex areas from the fin ribbing ran clean across the flange face. You'd think they would have at least went to the trouble to grind the face flush, but nooOOOooo...pretty much any flange gasket would have been doomed to failure from this alone. Guess that's why Lifan went with the ring instead, eh?
In conclusion, EG's thinking points from this adventure:
1. If it's stripped, it's just stripped. Re-tap it by whatever means.
2. Never assume a mating surface is actually flat, even if all engineering logic dictates it will be. A good reminder that this IS Chino-fab we're dealing with, after all.
3. Thermosteel is good stuff. It can't hold pressure in absence of good thread though. See point #1.
4. Ultra copper also good stuff. Screamin' hot scooter exhaust gas is just a bit much for it - it can and will re-liquify under heat and pressure. Seems to make great ghetto loctite, though!
Thanks for all who have read and/or contributed to this thread. Mods, you might want to move this to the exhaust section so it might help someone out later down the line...
