Topic: Cylinder sleeve 0-rings on 890cc motor

[scondon]

 I'm ready to put the top end back together, and find that I can't quite squeeze the four thin o-rings into the grooves around the cylinder sleeves. These are the o-rings that prevent oil from seeping between the sleeves and cylinder block. First time I am putting together a motor with oversized sleeves so I'm not sure of the best way to handle this. When I took the motor apart I saw that they had just filled the gaps, and goddamn near every other orifice, with silicon liquid gasket stuff.

I have "semi-drying" Yamabond 4 gasket sealer, and "semi-drying" Threebond 1104 on hand, but I wonder if I should use some fully drying silicon gasket sealer. What are you guys doing in your overbore motors to seal this area?

[MCRider]

I'm ready to put the top end back together, and find that I can't quite squeeze the four thin o-rings into the grooves around the cylinder sleeves. These are the o-rings that prevent oil from seeping between the sleeves and cylinder block. First time I am putting together a motor with oversized sleeves so I'm not sure of the best way to handle this. When I took the motor apart I saw that they had just filled the gaps, and goddamn near every other orifice, with silicon liquid gasket stuff.

I have "semi-drying" Yamabond 4 gasket sealer, and "semi-drying" Threebond 1104 on hand, but I wonder if I should use some fully drying silicon gasket sealer. What are you guys doing in your overbore motors to seal this area?

I've got a few comments, but no conclusions and will be interested in what others say. I've been told to believe that the Orings you speak of are not necessary, so they could be left out. If you're doing an 890 as i am (67mm) you (or the PO) had new sleeves installed. The block is bored out for these sleeves and most of the groove for that Oring is removed. So the origianl ORing would not fit as the groove has now been reduced in size.  This is my second 888. I left them out of the first one and after 15 years and 50k+ miles I noticed no ill effects. That's what I intend to do again. Though I think i may try to source a smaller cross section ORing.

IMO, under no conditions should a silicone based sealer be used. This stuff will squeeze out and break off, enter the oil stream like an embolism and cause huge damage, most often restricting oil to the camshaft causing it to break in half.

[bwaller]

Hey Sean. The only fix would be to machine the groove larger with the sleeves removed. You're not likely to do that so like MCR I've heard you can live without em....and yea forget the sealant.

[paulages]

I ran into that problem with the oversized sleeves on my 735 build. If you hit porosity in the casting like I did, then you'll definitely have oil leak problems. I sent my block out to a place in Seattle that specialized in porosity sealing. Otherwise, you gotta mill the case like Bwaller said.

[MCRider]

I'm going to look for an ORing that will fit the smaller groove. I'll report back but it may be a while.

[scondon]

This engine has certainly been a trip back in a time machine. It's a '71 that has a lot of the bells and whistles of the day. Terry In Australia found it on ebay attached to a ARD magneto ignition he wanted, so i split the cost with him and drove 100 miles to pick up this $150 motor. I also got the Morris Mags in the sellers other auction. He threw in the Kerker exhaust, Dresda? box swingarm, Lockhart cooler, and a bunch of other stuff in a box that has sat in my garage for too long.

Worst part of this motor is that it had Del Orto carbs on it, and when those went on auction everyone bidding on them wanted to be sure they came with the manifold to mount them to the motor. The seller thought they were talking about the cylinder head, and just about pried the thing off with a crowbar. A bit of an exaggeration, but there are a lot of gouges on mating surfaces where a screwdriver was used to pry bits apart:P

Back to the issue of sleeve o-rings. I'm not so worried about the porosity issue that paulages encountered in his build, as I don't think that quite as much material is removed to fit 890 sleeves in a 750 block. What I want to avoid is having the increased crankcase pressure pushing oil up the sleeves and into the head gasket area. I am so determined to build a motor that doesn't weep after 5k miles that I am prepared to break the "no sealant" rule, and put some in just this one area. I have put a motor together, and forgot to put these o-rings in. It did not grenade, or smoke, or have any noticeable problems. I'm going to sleep on this one and end up flipping a coin in the morning

[paulages]

I'm going to look for an ORing that will fit the smaller groove. I'll report back but it may be a while.

let me know if you find anything... I couldn't find anything with a cross-section small enough, and was told by two seal suppliers in town (cal seal NW and Air-oil) that it was impossible to get viton o-rings in a smaller cross section than 1mm (if I remember that dimension correctly).

[paulages]

I have been recommended a loctite product  for this by reputable people. I'll see if I can remember which product it is... PM Speedracer741 maybe, as the folks at his work spoke highly of it.

[MRieck]

I have been recommended a loctite product  for this by reputable people. I'll see if I can remember which product it is... PM Speedracer741 maybe, as the folks at his work spoke highly of it.

I'd say they are talking about green Loctite. I have no orings on my 915 cylinder. The same for my 1314 FJ. I've never had a problem Sean.

[Jerry Rxman Griffin aka MuthaF'er]

Sean,

I found 900 DOHC o-rings and have them in place just waiting to be torqued down.

[MCRider]

Sean,

I found 900 DOHC o-rings and have them in place just waiting to be torqued down.

According to the Fish, they are 2mm cross section, the same as the OEM for the CB750. That would seem way to thick for our purpose?

[MCRider]

I'm going to look for an ORing that will fit the smaller groove. I'll report back but it may be a while.

let me know if you find anything... I couldn't find anything with a cross-section small enough, and was told by two seal suppliers in town (cal seal NW and Air-oil) that it was impossible to get viton o-rings in a smaller cross section than 1mm (if I remember that dimension correctly).

1mm may be just right. OEM is 2mm.

[MCRider]

I knew my cylinders still had some of the groove left in them. So I took theORings from my new CycleX kit, which looked to be pretty small and attempted to install. No way.


So I'll call around Monday for some 1mm and see about them. 1mm may be too big also. Otherwise, I'll be content to leave them out altogether.

FYI: peering into the groove around the cylinder sleeves, one can see the taper is the sleeve which allows it to fit into the crankcase opening without boring the crankcase.

[paulages]

I'm going to look for an ORing that will fit the smaller groove. I'll report back but it may be a while.

let me know if you find anything... I couldn't find anything with a cross-section small enough, and was told by two seal suppliers in town (cal seal NW and Air-oil) that it was impossible to get viton o-rings in a smaller cross section than 1mm (if I remember that dimension correctly).

1mm may be just right. OEM is 2mm.

Come to think of it, 1mm is what I needed as well, and I couldn't find them that small.

[Jerry Rxman Griffin aka MuthaF'er]

Sean,

I found my SD card. Here's a couple pictures of the CB900 Cylinder O-Ring and with it installed. Rolls right into the groove.

[Retro Rocket]

You guys need a billet block like mine...aluminium bore nikasil coated, no sleeves.....

Mick

[Sam Green Racing]

Show off

[Retro Rocket]

 

[MCRider]

Jerry: I double checked and that is a 2mm ORing which definitely will not fit in my groove. Did your machinist open up your groove perhaps, to make up for how much was taken away? Your groove looks a bit larger than mine, but that's in a picture, can be deceiving.

[Jerry Rxman Griffin aka MuthaF'er]

Big Jay did those for me. I'm not sure, we'd have to ask. Jay, are you tuned in?

[Big Jay]

Have never run o'rings in big sleeve motors. The only exception is on our 1000cc block assemblies. When boring for the sleeves, if we break through in to the air passage, then we counter bore the bottom far enough to install two orings with a really tight fit.

[MCRider]

Have never run o'rings in big sleeve motors. The only exception is on our 1000cc block assemblies. When boring for the sleeves, if we break through in to the air passage, then we counter bore the bottom far enough to install to orings with a really tight fit.

Thanks Jay!

[Tom]

I knew my cylinders still had some of the groove left in them. So I took theORings from my new CycleX kit, which looked to be pretty small and attempted to install. No way.

Those are the early Sandcast Barrels and have more meat between 1&2  and 3&4. i did a 970 years ago and the sleves broke thru to the fins on a 74 barrel and leaked oil, i then used one of these early barrels and had it bored and sleves fitted and no brake thru between 1&2 and 3&4 end of problem Tom

[Sam Green Racing]

I guess the price for early barrels will go through the roof after that announcement.

Sam.

[Terry in Australia]

Just try to buy a set of K0 barrels now Sammy, they're like rocking horse manure, it'd be cheaper to buy a billet block! Cheers, Terry.