'69 CB350 dowel pin o-ring question???

[1969Honda]

So I'm finally getting around to the final assembly (again :) on my engine and I seem to be missing some o-rings. My clymer's mentions (and I remember installing at one time) an o-ring to go around the 4 locating pins for the top and bottom of the cylinders (2 at each end) but the factory service manual only mentions the o-rings around the base of the cylinders. Does any one have some dimensions for these o-rings by chance? I also seem to recall reading that a few people run their engine with out the cylinder base gasket, if so do I need the lower rings?

 

[nograv1]

I'm in the same spot with the same engine. During dis-assembly, I did notice some thin rubber pieces (may be an old o-ring? It looked more like a piece of electrical tape wrapped once or twice around the cylinder bolt but it had some sort of logo on it that seemed to come from in the dowel pins). Alright, I was curious enough to go out to the garage and get a pic. FYI, I think the dowels are also known as "knock pins" according to a Honda parts search.

Here's a pic of the rubber thing that was wrapped around the cylinder bolts when I pulled the cylinders off.

As you can see, the little rubber piece appears that it could fit between the dowel pin and the cylinder stud (bolt). It also says "NOK" on it. Bottom line, what are those things, where did they come, and if we need them for reassembly, where do I get them? I say where did they come from because I found them still wrapped around the cylinder studs after taking the top end all the way off, so I'm not sure where they go exactly.

Sorry OP for the long reply with no answer, but hopefully this will help us both in the end!

 

[1969Honda]

Well in haste to put things back together a took a pin to the local hardware store and started to fit o-rings until I found one I was satisfied with. If I remember correctly it was a 3/8" ID with a 1/16th thickness. I'm going to install them and hope that it doesn't leak or cause problems.

As for the rubbers around your studs I don't recall seeing anything like that on mine during dis-assembly, maybe they're some type of vibration isolator or guides for the studs due to the open space between the stud and the inside of the dowel? Good luck on that one.

Maybe CrazyPJ or Greg from Ohio Cafe Racers will chime in and clue us in as to what we're dealing with.

 

[nograv1]

Where did you put the o rings? On top/underneath the dowels?

How many o rings did you wind up getting? I've got 6 dowels... you too?

 

[1969Honda]

4 dowels, one o-ring per dowel. Two dowels on the bottom and two dowels on the cylinder head side, both of them towards the front end of the motor.

I'll try and get some pics tomorrow night and post them up.

 

[nograv1]

I'm good on where the dowels themselves go. I'm talking about where the o rings go. Did you put them down in the bottom of the hole before putting in the dowel or are you putting in the dowel, then putting the o ring around it and setting the next piece on top so the o ring is around the middle of the dowel and sandwiched between the case/cylinders or cylinders/head? As you can probably tell, I'm very confused... haha

 

[1969Honda]

I'm gonna try the no base gasket thing, if I were running a gasket I'd install the o-ring on the dowel after the gasket.

 

[1969Honda]

Well after breaking an oil ring on one piston last thursday night I got my new ones in yesterday and started to assemble the engine tonight. I'll keep you posted on if I have any problems leaking oil or anything.

 

[DrJ]

I'm gonna try the no base gasket thing, if I were running a gasket I'd install the o-ring on the dowel after the gasket.

These o-rings are not needed at the base gasket. It may even leak if you install them. The base gasket alone will seal the cylinders to the base. You do need to install the large o-rings that fit around the bottom of the cylinder flanges.

 

[nograv1]

So are the orings needed on any of the dowel things?

 

[1969Honda]

Thanks Dr J! I'll see how it does and if needed I'll take'em out. I did get the ones around the base of the liners installed .

 

[DrJ]

So are the orings needed on any of the dowel things?

Not on the CB350, I've never used them when rebuilding the motor.