Head gaskets, what's the trick?

[GGRider01]

So, a couple months ago I did a top end job on the EC 300. I tried warming and massaging the o-rings so they'd relax into their grooves naturally. I ended up using plain old semi-synthetic industrial use grease to make the o-rings stick into their grooves. I think the grease contributed to a recent catastrophic failure where the inner head gasket blew and caused the bike to seize. I also didn't have a torque wrench so warping was likely a factor as well.

I'm just curious what tricks you guys have utilized in getting these gaskets in place.

[gasgasman]

Along with massaging the o-ring, I use 3M spray trim adhesive.

[swazi_matt]

I used grease to hold them in place - 100hrs and no issues

[GGRider01]

During the rebuild I also installed the N3EJ needle in the middle position and just went to town riding it. I will likely go up on the pilot (currently a 38) to a 42. It has a 172 main in it.

The weird thing is, I took it up about 7 thousand feet higher than I normally ride it, so I assumed it would just be so much richer than normal I wouldn't even bother reading the plug until that trip was over.

Locally, I ride around 4,600 feet. I had it up to 13,000 feet and as low as 7,400 feet while riding it on the fresh top end.

That leaves only cylinder head torque as the contributing factor to the engine's premature failure.

Thankfully, it made it 4 days of long hard riding and died in a giant cloud of sweet steam at the end of the last day only a couple miles from camp.

[Jakobi]

Which year model bike? Which particular carb? Did the bike show any signs of lean running prior to failure?

I've used a few dabs of grease to hold the O-rings down in the past and never had any issues.

If you're using an older AS1 carb you'll want at least an N3EG needle. The J diameter is too lean, even with bigger pilots.

[Zman]

I use dielectric silicone grease or synthetic brake caliper grease while gently stretching the O-rings. They tend to retract after a short period of time so I have a couple screws ready to go into the head so I can assemble it quickly after the last stretching.

[Zman]

O-Rings work best with a lubricant. Using the correct lubricant helps them seal better and last longer. I found this recently about O-Rings. http://www.parker.com/Literature/O-R...rature/FAQ.pdf

[pscook]

I roll the outer o-ring on the outside of the cylinder to stretch it out, then gently stretch the inner by hand. It's about timing- I drop the outer o-ring onto the grooves, and as it gets close to the right size I quickly drop the inner o-ring. The split second they are in the grooves I install the head, rotate it to make sure the o-rings aren't out of the grooves, and run two bolts down.

Timing the retraction of the rings takes a bit of timing, but you can do it.

[GGRider01]

Originally Posted by Jakobi

Which year model bike? Which particular carb? Did the bike show any signs of lean running prior to failure?

I've used a few dabs of grease to hold the O-rings down in the past and never had any issues.

If you're using an older AS1 carb you'll want at least an N3EG needle. The J diameter is too lean, even with bigger pilots.

This is good to know. I did a google image search on the AS1 and the AS2, and don't see anything to identify mine with. It's a 2001 EC 300, so I'm going to assume it's an older design, the AS1.

I'll try to find the N3EG this Monday. I went up on the pilot to a 42 and a 175 on the main in the mean time. Likely won't run the bike until I get the proper needle, no reason to seize up a brand new cylinder and piston.

Float bowl was out of spec. Bike was very responsive up until 12,000ft and become a bit doggish but wasn't smoking as much as I expected. It's hard for me to believe it was lean but all indications say that it was. The head gaskets completely melted and blew out into the combustion chamber in 2 locations.

If the needle was too fat, then it all makes sense.

Got the o-rings in dry today but will likely try grease again, next time.

[motopsycho87]

The only greases I reccomend for using on a motorbike are red rubber grease (OK) or Dupont Finish Line.

I've spent ages lurking forums etc and looking at tech spec sheets, Dupont Finish Line is;

Waterproof
Rubber friendly
Thick
Anti corrosive
High melting point
Mid - high pressure

There are no other greases on the market like it as PTFE as a lubricant still has patent. Cost me ?15 a tub, but now I only need 1 tub!

So yeah, use that on your head o-rings. Lithium grease or most others will cause the o-rings to swell and fail, if you manage to fit the buggers in the first place!