Author Topic: Crankshaft end seals-revisited  (Read 2552 times)

0 Members and 2 Guests are viewing this topic.

Offline Kenneth Pagel

  • Trade Count: (0)
  • Expert Registered Bridgestone Member
  • ****
  • Posts: 273
  • What, me worry?
Crankshaft end seals-revisited
« on: June 12, 2017, 10:04:05 PM »
I've just read an old thread regarding the 350 crankshaft end seals that says it's just fine to run without them. (Service bulletin BSG-0070) I have very low mileage 1967 GTR that  I'll be restoring shortly. This bike started and idled after sitting over 30 years when I acquired it.  It does put out white smoke from the rh muffler, and was told this is due to bad rotary valve seals, and not the labyrinth seal. My question is do I need to remove the crankshaft end seals due to the age of the motor to prevent possible distintegration and risking blocked oil passages?  The motor is still mostly together;only the carbs and clutch have been removed. Thanks in advance!

Offline BS Mechanic

  • Trade Count: (0)
  • Expert Registered Bridgestone Member
  • ****
  • Posts: 282
Re: Crankshaft end seals-revisited
« Reply #1 on: June 12, 2017, 10:23:08 PM »
Smoke from the right side is nearly always caused by a failed crankshaft seal, behind the primary drive gear.  It can be replaced in the bike by removing the right side transmission cover.  The seal is housed in the rotary valve cover, at least that's my memory!  Shop manual shows details.

I have seen no indication that the seals improve engine life.  My personal belief is that they were added not by engineering, but by marketing who at that time were trying to get out from under the poor reliability view many held about two stroke engines.

The seals do occasionally come loose, and can cause catastrophic damage.

So in my view, there is little to no benefit, traded against the very real potential to destroy a good engine!

Simple choice, at least for me at the time.  I'm not sure I'd take an otherwise sound engine apart just to remove the seals though.  That's a harder choice, but based on the potential harm, "probably" best.

My 350, purchased by new in 1968 had the seals for 45K miles, till a main bearing cage disintegrated (unrelated to the seals).  When I had Rockford rebuild the crank (1972) they removed the seals.  The engine now has about 60K miles, still  with no other issues.
« Last Edit: June 12, 2017, 10:32:01 PM by BS Mechanic »

Offline BRT-GTR

  • Brian
  • Trade Count: (0)
  • Master Registered Bridgestone Member
  • *****
  • Posts: 951
Re: Crankshaft end seals-revisited
« Reply #2 on: June 13, 2017, 08:00:03 AM »
          nysz1b,
                         Whoever told you about the smokin right cylinder may not have been fully familiar with the GTR engine/crank construction. To clarify :-

  The title of this Topic refers to 2 special 57mm seals that BS installed on the outer cheek of the outer crank flywheels, one either side. Theoretically, these 'encouraged' the injected oil to flow towards the big end bearings, whether they were ever effective is debatable. As BS Mechanic states above, they sometimes come loose, break up, and get sucked into the barrel ports !! It does require a full engine strip to remove them but can be done without pressing the crank apart. It's your choice. I'm leaving mine in but will peen the outer edge to improve retention.

 The seal that is likely causing the over oiling is set into the R/H disc valve cover, where the crank passes through and stops oil from the primary drive case being sucked into the right cylinder, again as stated above. (The left cylinder is not affected by this issue).  My GTO has a similar smoky right cylinder. As far as I can assess this is the only potential source of additional oil to the right Cyl.   Although an incorrect fuel mixture or poor combustion may also cause a smoky cylinder.  Correctly set up,  the 350 oil pump cannot send more oil to one cyl than the other, so can be ignored at this stage.

 The labyrinth seal referred to is in the centre of the crank and separates the two cylinders. Of all metal construction, it should never wear unless the adjacent crank bearings fail.

                 Hope this helps,  Brian
Unspoiled by progress.
I'm so glad I grew up in the 60s & 70s. I did so much stupid stuff and there's no record of it.............Anywhere !!

Offline Richard Clark BS parts

  • Administrator
  • Trade Count: (0)
  • *******
  • Posts: 504
    • Bridgestone Motorcycle Discussion Board
Re: Crankshaft end seals-revisited
« Reply #3 on: June 14, 2017, 10:57:47 AM »
BS friends

Rockford, years ago determined and recommended that those end seals  09090-117 be removed
or left out when ever one rebuilds a 350 engine

Hope this helps

Richard Clark
Richard  Clark, Owner and provider of this site
BRIDGESTONE MOTORCYCLE PARTS
New Albany IN

BS Shopping Cart- With just a few of my BS parts

https://6x6parts.com/bridgestone_motorcycle_parts/

Thanks
Richard Clark

bsparts@aye.net

Offline Jeff McBrayer

  • Trade Count: (0)
  • Full Bridgestone Member
  • ***
  • Posts: 125
Re: Crankshaft end seals-revisited
« Reply #4 on: June 14, 2017, 02:46:55 PM »
Good to know, just leave them out

Great BS site

Offline Kenneth Pagel

  • Trade Count: (0)
  • Expert Registered Bridgestone Member
  • ****
  • Posts: 273
  • What, me worry?
Re: Crankshaft end seals-revisited
« Reply #5 on: June 15, 2017, 12:12:15 PM »
Thanks for all the feedback!

gtrman

  • Guest
  • Trade Count: (0)
Re: Crankshaft end seals-revisited
« Reply #6 on: July 15, 2017, 07:24:11 AM »
Kawasaki had them fastened in place with three screws. No trouble. I did mine this way, but with two screws. They aren't really seals. They retain oil for the bearings..so they are oil retainers. I'd load a picture if i could of mine, but i cant seem to browse my folders. 

That BS service bulletin was retracted i think.
Doug

 


Gallery


Views:221
Comments (0)
By: Jon West

Views:1362
Comments (0)
By: rwgibbon

Views:1690
Comments (0)
By: Perry L Anderson

Views:1757
Comments (0)
By: Perry L Anderson

Classifieds

Gto
Date: 03/02/2024 06:49 am
Time Left:
Looking for a BS90 used or new luggage Carrier assembly

Date: 02/01/2024 04:19 pm
Time Left:
Gto
Date: 10/19/2023 01:08 pm
Time Left:
Urgent - l/end roller bearing & piston pins needed
Date: 10/08/2023 03:25 am
Time Left:

Recent Downloads added

Chibi, Chibi Deluxe, Tora Service Manual
Rating: (None)
Filesize: 20383.27KB
Date: May 01, 2023, 08:35:39 PM
Chibi_Tora_Parts_Manual
Rating: (None)
Filesize: 14301.44KB
Date: May 01, 2023, 08:25:53 PM
BS200 Mk II RS & MK II SS Exclusive Parts
Rating: (None)
Filesize: 358.29KB
Date: March 07, 2021, 07:30:10 PM
1970 sales brochure
Rating: *****
Filesize: 6753.33KB
Date: July 16, 2020, 10:01:18 PM

Powered by EzPortal