On the XR 400 do I have to push the o-ring into the groove on the base of the cylinder or will it push into place when I torque the cylinder down. Pushing them in they seem to stretch as you work your way around and trying to tuck the last bit in is always a PITA.

you always want orings seated where they belong before mating 2 surfaces together less you have it move at the last second and get pinched/torn when tightening everything up. use a little vaseline or grease to hold it in place.

I just spent the last 1.5 hrs trying to get that o-ring in place.  I can't get more then about 1" started and then it has already stretched about 2 inches.  I tried it oiled, greased , even put it in the freezer for about 20 minutes .  I will have it destroyed before it fits.  I measured the old one and it is just shy of 2mm  and this new one is 2.12mm. Should still fit.   The old one split in half when I was trying to get it out.  

The honda dealership here is no help , they just say to bring it in.  No thanks at $100 per hour.   I have never had this much trouble with a o-ring, then again I have never had to try and fit one is such a tight place.   It's like trying to get a gallon of crap into a quart jar.

Consider the circumference of the groove as a clock face and try just pushing the oring in at 12 and 6 o'clock positions, then 3 and 9, 1:30 and 7:30, 10:30 and 4:30 etc. Keep going like that and you will end up with several small loops that you should be able to compress into the remaining spaces, rather than a big loop.

Ray.

Thinking about what I might try myself in this situation.......

Using a strip of cellophane tape or Scotch tape to hold the o-ring in place at several points. Of coarse the surface would need to be free of grease. Then just leave the tape in place when mating the cylinder. The tape is thin enough not to prevent good o-ring seal, Idea being that the tape will melt away on first run up.

Stupid or not?

I don't see it fitting.  Tape is not going to work. I have a feeling that it just goes in after the cylinder is torqued down.  It has shaved off the edge of the o-ring already .  I am going to try and phone a few dealers outside of my area and see if I can get any answers.

Well I talked to 4 different Honda Dealers across the province. Got 3 different answers, one had all new mechanics.
The answers I got were just put the o-ring on and then torque it down , it can't go anywhere. Second place said to put it in the groove somehow ( not really much help) and the third place said to stretch the o-ring  ( not needed) and glue it into place with some fast setting silicone.  Stretching the o-ring and gluing it into place tells me he has never worked on one either.  I need to shrink it to fit the groove.

I will wait until the end of the day and see if anyone else has a idea and if not I am just going to put it into place and torque it down and see what happens.

Are you sure you got the right part# o-ring? Service Honda shows it to be 91302-356-000.

Aftermarket part or OEM?

o ring in the freezer for a bit can make stretchy big ones fit up easier

XR8ed400, on 30 May 2012 - 05:42 PM, said:

It was a aftermarket o-ring that came in the Vesrah top end kit. It measured 2.11mm.  I got fed up and called the local dealer and lucky he had one in stock but I paid through the nose for it at $14.  The OEM ring measured 1.94mm.  Still did not stay in place but it would push in easy and then roll back out so I took a chance and put the cylinder on and hoped it would squeeze into place. Everything seemed to fall into place fine.  Buttoned it all back up , set the valves and called it a night.

One thing I did notice was that everytime I rotated the crank , every second full rotation I could hear a sound like something skruntching right after TDC on the compression stroke.  It almost sounded like sand grinding on glass. I thought it was maybe suction sound from the oil I had on the piston and cylinder wall.
, but I don't think that is it.  I can't figure out where it is coming from .  I thought it was in the front exhaust valves, but not there, next I will check the intake valve area.  By the way I was turning the crank CCW if that makes any difference.  Tomorrow I will check it turning CW and see if the sound is still there.