Did I install my rear main seal too deep??

Discuss all things 1970 & later Airheads right here.
Post Reply
CHEWY1219
Posts: 19
Joined: Mon Jul 11, 2022 12:49 pm

Did I install my rear main seal too deep??

Post by CHEWY1219 »

So I replaced my RMS in my 76 R75/7 with the cycle works tool. BUT I didn’t use the washers under the bolts...careless oversight. The RMS is seated a mm or so under the lip of the case and not flush. Will this leak? Should I pull the seal out and start over? Please advise. I already have the flywheel back on and the clutch.....
User avatar
gspd
Posts: 1041
Joined: Tue Aug 03, 2010 8:04 pm

Re: Did I install my rear main seal too deep??

Post by gspd »

The RMOS should be flush with the case...AND bone dry, with the flywheel flange perfectly clean and dry.
One mm further in should be OK, but I doubt anybody's ever (intentionally) tried that.
If you didn't block the crank, be sure you can turn the flywheel before you put the tranny back in.
You could always put just the carbs back on and run it a bit BEFORE installing the transmission to see if it leaks.
Mechanic from Hell
"I remember every raging second of it...
My bike was on fire, the road was on fire, and I was on fire.
It was the best ride ever!"
CHEWY1219
Posts: 19
Joined: Mon Jul 11, 2022 12:49 pm

Re: Did I install my rear main seal too deep??

Post by CHEWY1219 »

UPDATE....yes, 1mm is enough to make the RMS leak, and quite substantially. Tore back down, installed another seal with the tool from Boxer2Valve, buttoned back up and she is now as intended:)
User avatar
SteveD
Posts: 4909
Joined: Tue Aug 03, 2010 3:29 am
Location: Melbourne, Oz.

Re: Did I install my rear main seal too deep??

Post by SteveD »

CHEWY1219 wrote: Tue Oct 25, 2022 3:27 pm UPDATE....yes, 1mm is enough to make the RMS leak, and quite substantially. Tore back down, installed another seal with the tool from Boxer2Valve, buttoned back up and she is now as intended:)
Good feedback...thanks.
Cheers, Steve
Victoria, S.E.Oz.


1982 R100RSR100RS supergallery. https://boxerboy81.smugmug.com/R100RS
2006 K1200R.
1994 R1100GS.
Rob
Posts: 3088
Joined: Thu Feb 13, 2014 2:05 am

Re: Did I install my rear main seal too deep??

Post by Rob »

gspd wrote: Fri Oct 21, 2022 9:35 am The RMOS should be flush with the case...AND bone dry, with the flywheel flange perfectly clean and dry.
One mm further in should be OK, but I doubt anybody's ever (intentionally) tried that.
If you didn't block the crank, be sure you can turn the flywheel before you put the tranny back in.
You could always put just the carbs back on and run it a bit BEFORE installing the transmission to see if it leaks.
Excellent stuff, gspd, as always! I'm glad I knew about that before my first RMS replacement!
Rob V
ME 109
Posts: 7306
Joined: Tue Aug 03, 2010 3:00 am
Location: Albury, Australia

Re: Did I install my rear main seal too deep??

Post by ME 109 »

gspd wrote: Fri Oct 21, 2022 9:35 am
You could always put just the carbs back on and run it a bit BEFORE installing the transmission to see if it leaks.
That was your advice to me years ago when I couldn't find a leak. Turned out to be a small crack in the oil pump cover bolt hole.
Started the bike with no clutch in the way and there was the leak, saw it through the spinning holes of the clutch carrier. Bingo.
Lord of the Bings
Post Reply