Guide Ring O-ring question

[R65Singh]

Hi all; Was replacing the leaking main seal on my bike and noticed that the O-ring for the Guide Ring from Motobins is black where as the one that was in the bike is red.  They seem to be the same thickness and diameter.   I hope it is the right one?
 I also replaced the oil pump o-ring (also red) with the new one from Motobins(also red).   Has any one replaced those recently?  May be the new ones are black rubber or it is just the color difference?

[Bob_Roller]

Most likely, just a different manufacturer is all .

[tvrla]

Any o-rings can be dyed. So who knows?

Do they have the same squishiness?

[R65Singh]

Yes..both O-rings looks and feels the same except the color...
Another dilemma I am having is....should I warm the new seal, or put in freezer to shrink a bit.  The little package it came in had a "no oil" sign on it, Snow bum site says it does not matter....I think little oil can't kill it?

[tvrla]

Are you asking about the rear main now? If it's the new style (which it should be), then freezing it doesn't help, as it'll warm up too quickly to make any difference. There are all sorts of stories of what, and what not, to do when installing these seals, and one of them is to soak in oil beforehand. I don't, but do put a film of oil on it, and stretch it for a few hours over the guide ring to help shape it. Make sure it gets driven in to an even depth - but I'm not sure if it's significant how deep it goes. I wouldn't set it any deeper than necessary. These seals don't wear the mating surface like the older spring tensioned seals, so it's not important to have the sealing surface positioned on a new area.

[Bob_Roller]

Warming the seal, will make it more pliable and possibly easier to install .

Always lubricate a rubber seal before installation, if you don't know what to use, lubricate it with the fluid that it is going to be exposed to .

Just about anything is better than installing it 'dry' .

[nhmaf]

I seem to recall seeing an article that the seal material and color had been changed some years back - perhaps it was on snowbum's website.  I think that the new kind is made with a PTFE type of rubber material - it is good to put some oil on it but shouldn't need other special pre-installation prep.  Be sure that you have first:
1) Block the crank at the front prior to removing the engine flywheel.
2) Put the engine&flywheel at TDC prior to removing the flywheel, so you can easily get it back in the same correct position.
3. Reinstall the guidering with the proper bolt orientation for the flywheel position to match up as in #2.
4) There are some special tools for making sure the seal is put in perfectly square and to the proper depth. I'd seat it to the same depth as the previous one was.   Snowbum has (LOTS) more to say about this on his web page (Scroll about 1/2 way down):


http://bmwmotorcycletech.info/flywheelremovalwarning.htm

[Mike V]

+1 on all responces.

Very important to block the crank before removing the flywheel.  Also, as maf has stated, it's a good idea to mark things before removing them so you can reassemble in the same order for continuity, not so much the  guide ring as the flwheel.  

My new Guide Ring O-Ring was red but I doubt it matters what color as long as the shape and thickness is the same.  Be careful to thoroughly clean the Guide Ring O-Ring groove.  I found a lot of baked-on crud in mine and it took a while to get it thoroughly clean with a soaking in Brakekleen and a plastic/wood pick.  I lightly lubricated it with clean engine oil during reinstallation.

The new style Rear Main Seal is very different in shape and composition than the original spring tension seal.  I measured the depth of the original seal before installing the new one but the configuration and contact point of the new seal is different than the old.  It seemed to me the contact surface of the seal was so great that the depth was not a big issue.  I still inserted the new seal about 1/16" inboard of the housing face.  No leaks after ±1500.

Singh, this is a good time to cleanup and paint your timing marks on your flywheel with some white paint.

Here's a couple of links with some pics, hope this helps a bit.

http://tinyurl.com/3pbn3o5
http://tinyurl.com/3ske5lm

[R65Singh]

Thanks Friends....I finished replacing the main rear seal today and seems like everything went well.  Still have to start the bike and see if there is any leaks.  I read the article on Snowbums site and some other tips and tricks posted on this site,  it was really helpful.
There was some crud in the O-ring groove as mentioned by Mike but I managed to clean everything out.  Also, I put some paint on the timing marks while it was all apart, a real good idea.  
Next on the list is to install new piston rings and new style cam chain tensioner.  

[Mike V]

Good work Singh.

Be sure to install the piston rings in the correct orientation.  Do you have Oak's Top End manual?  

-Mike V.

[Bob_Roller]

There is a correct and incorrect way to install the pistons on the connecting rod .

There should be an arrow cast into the piston, in the wrist pin area, it points forward .

Apparently the wrist pin hole in not directly centered in the piston, but offset a mm or two .

[Mike V]

Good point Bob, one I forgot to mention.  Here's a link to a larger photo showing the arrow on the piston dome that I have marked with black felt pen.  As Bob mentions...the arrow points forward.

http://tinyurl.com/7o3alz5

[tvrla]

There's an arrow on the top of the piston (pointing to the front of the bike) but you can also easily tell by the valve pockets. The smaller goes to the front since the exh valve is smaller. Don't know about the wrist pin offset - never heard that before. But that takes care of itself getting the piston oriented correctly.

There is a correct and incorrect way to install the pistons on the connecting rod .

There should be an arrow cast into the piston, in the wrist pin area, it points forward .

Apparently the wrist pin hole in not directly centered in the piston, but offset a mm or two .

[R65Singh]

Thanks guys for all your very helpful responses, you guys rock.  Finishing up installing new piston rings, cylinder O rings, new head gaskets and push rod gromets.  Everything went well, now on to adjusting valve gaps and adjustments.  The pistons had arrow marked on the top so that made it easy to reinstall.  Also the rings from Motobins had "top" marked on them so that helped to eliminate any errors.  
The bike itself does not have very many Ks on it (just 15000) but was sitting idle since late 80s. So I decided to give it a little TLC and hopefully it will be running better and worth the time spent.  Half of the fun is just working on it, specially in winter here.  Will keep you guys posted.
Thanks Mike, I looked at those pictures, are those valve covers powder coated?  I painted mine but the paint keeps flaking off and the finish was horrible.

[Mike V]

Singh,

Yes, I had the valve covers, airbox, airbox clips, and engine top cover all powder coated.  The timing chest I painted myself with Krylon High Heat BBQ paint.  The prep is the most important and most labor intensive part with painting.  If you choose to repaint the valve covers, be sure to apply the paint in numerous light coats after you have thoroughly cleaned the surface.  I use Acetone to prep my paint surfaces, then even soap and water if possible.  You may want to mask the ribs then after the paint has completely dried, take a sanding block with fine grit (maybe 220 or 320) to dress.