Author Topic: BS350 lab seal?  (Read 298 times)

0 Members and 1 Guest are viewing this topic.

Offline CL-100

  • Trade Count: (0)
  • Expert Registered Bridgestone Member
  • ****
  • Posts: 275
  • CL-100
BS350 lab seal?
« on: July 31, 2018, 03:39:10 PM »
I thought some of the more experienced members of the site might be able to offer me some advice.  I have a 350 crank assembly that I suspect needs a rebuild.  I've only had one other 350 engine completely apart and the crank lab seal didn't make the noise and move like this one does (see video).  Also, but not mentioned in the video, the two inner bearings seem to have a little slop in them and when wiggled will rock back and forth on the crank slightly, as I show at the end of the video.

Let me know what you think!  Thanks.  (Click on youtube link below).

« Last Edit: July 31, 2018, 03:41:19 PM by CL-100 »

Online moonpup

  • Laidback Purist
  • Trade Count: (0)
  • Master Registered Bridgestone Member
  • *****
  • Posts: 2079
Re: BS350 lab seal?
« Reply #1 on: July 31, 2018, 04:19:45 PM »
Couldn't tell you whether it's good or bad, but I can tell you that I just checked a lab seal on a crank I happen to have out and it makes the same sound when slid sideways like that.

So....   popcorn

Confucius say... "Better to have Bridgestone than Kidneystone"

Offline hgzumanity

  • Trade Count: (0)
  • Registered Bridgestone Member
  • **
  • Posts: 21
Re: BS350 lab seal?
« Reply #2 on: July 31, 2018, 11:20:14 PM »
That labrynth seal is probably good. When the engine cases squeeze together it will not move side to side anymore. I don't know how you are going to get the o-ring that goes around the lab seal over the crankshaft counterweight though. You just want to make sure you cant move the seal up and down on the crankshaft. You don't want too much clearance between the seal and the shaft going through it.

Also, for your crank bearings. If there is a little bit of axial play (which you are showing at the end of the video) that is ok. To check the bearings, make sure they are oiled and clean and slowly spin each bearing all the way around, while putting slight pressure on it with your fingers, and make sure you don't feel any roughness or hear any noises. Each bearing should be quiet and smooth. Harry

Offline Jeff Bar

  • Trade Count: (0)
  • Expert Registered Bridgestone Member
  • ****
  • Posts: 402
Re: BS350 lab seal?
« Reply #3 on: August 01, 2018, 11:18:16 AM »
Personally I would replace the labrynth seal as they wear on inside not on sides, just way too much trouble to get to it later , I bought a spare from
Richard some time back, not sure if he has them or not

Jeff Bar

Offline slawsonb

  • Trade Count: (0)
  • Master Registered Bridgestone Member
  • *****
  • Posts: 1366
Re: BS350 lab seal?
« Reply #4 on: August 01, 2018, 12:41:44 PM »
I think this all boils down to whether you intend to rebuild the crank or not. If not, you can probably get away with using the lab seal and bearings as they are. I don't expect you intend to race/abuse this motor, so with proper lubrication they should do fine. I like the checking technique Harry recommends above before you commit to reuse.
There is a trick to stretch the o-ring over all the stuff that seems to large the get past. I have never done it myself and don't know the details, but I'm sure someone on here can add some instructions for that. Steve Reed did this o-ring stretch on a crank that he did a partial rebuild on for me.

Good luck Roland!

...bert

Offline CL-100

  • Trade Count: (0)
  • Expert Registered Bridgestone Member
  • ****
  • Posts: 275
  • CL-100
Re: BS350 lab seal?
« Reply #5 on: August 01, 2018, 02:52:44 PM »
Thanks to all for your responses to-date.

I did try and test the bearings as Harry mentioned and they all seem good.  I can't find anything obviously wrong to cause the wobble.  Also, I have set the crank in a lower case, leveled it, and set up my meter to measure wobble on the crank ends while I rotate the crank via the small ends of the connecting rods.  The crank rotates very well and both sides are well within the specs outlined in the Service Manual even though there's no O-ring on the lab seal to help stabilize the crank.  The connecting rod measurements are all on the low end of the specs too.  When I rotate the crank it actually looks like one of the inner bearings wobbles depending on which bearing  is closest to the lab seal.  I push the lab seal over toward one bearing or the other as seen in the video to get this result. 

I guess I'm trying to save some $ because a full rebuild/balance is $400-500 with my parts.  Fortunately, I have a conn-rod repro kit from Richard/Ray as well as all bearings, pins, lab seals, O-rings, etc.  I may explore the possibility of just replacing the the center bearings, lab seal, and O-ring.   All the other parts seem perfect and this crank came out of a bike with 1300 miles that broke a ring and got parked for a few decades. 

As far as stretching an O-ring over the webs, I have done this successfully on my only other 350 build.  I did however buy Viton O-rings and wasted one of them practicing the technique for stretching the O-ring the least amount and for the shortest time.  I also warmed the O-ring with a hobby hand dryer first.  The Viton ring took about 3-4 days before it snugged up in lab seal again.  During assembly I used some sort of blue sealant on the O-ring as an extra precaution.  This process is outlined in a thread on this site between Steve Reed and Ziggy while Ziggy was restoring one of the two 350's he rebuilt. 

If anyone has anything else to add, please do.  I'm still studying these bikes and I enjoy the learning opportunities provided by those with experience.

Rowland

Offline slawsonb

  • Trade Count: (0)
  • Master Registered Bridgestone Member
  • *****
  • Posts: 1366
Re: BS350 lab seal?
« Reply #6 on: August 01, 2018, 03:44:59 PM »
A little birdie (named moonpup…;-) just pointed out that I misspelled your name in my earlier post Rowland. Just wanted to say sorry for that...doh!
...bert

Offline BRT-GTR

  • Brian
  • Trade Count: (0)
  • Master Registered Bridgestone Member
  • *****
  • Posts: 765
Re: BS350 lab seal?
« Reply #7 on: August 01, 2018, 05:48:29 PM »
          Rowland,
                        I'm currently rebuilding an engine, put the crank in today, from what I read in your post above your crank should be fine to reuse as is.
        My old crank was rusted solid, I'm rebuilding with an NOS Rockfords rebuilt crank from 50 years ago ! that I bought 2 years back. The centre seal and bearings exhibit exactly the same charateristics you describe above.
       As far as I am aware the crank bearings are generally very reliable and do not give trouble or wear abnormaly. All caged ball bearings rock slightly due to manufactured in running clearance. This reduces as the engine warms up.
        The lab seal runs with no metal to metal contact and in theory should not wear unless a bearing fails. You will have got better results from your runout tests without the oring. From what I see the oring stops the lab seal from fully seating until the top case is clamped on and compresses the rubber.
       I suspect the bearings have a small interference fit so that the cases grip them when bolted together. I can't explain the apparent wobble you see on the centre bearings , while in the lower case, and I'm sure you will have carefully seated the knock pins. I've just spun my crank on the rods and the center bearings appear rock solid but I can move the lab seal slightly. Can you move the bearings sideways or radially by hand. Are there any signs of wear on the case bearing seats?                                                                            Brian.

PS. Without the oring fitted, it is possible the lab seal is moving slightly. Is that where you observe the wobble.                                                                                    Columbo ;D
« Last Edit: August 01, 2018, 06:08:19 PM by BRT-GTR »
Unspoiled by progress.

Offline CL-100

  • Trade Count: (0)
  • Expert Registered Bridgestone Member
  • ****
  • Posts: 275
  • CL-100
Re: BS350 lab seal?
« Reply #8 on: August 02, 2018, 08:11:02 AM »
Bert, I take no offense at the misspelling of my first name.  Not sure why my parents chose to spell it that way.  I've only met one other person with the name spelled as mine is.  To complicate matters, my last name is sometimes used as a first name so throughout life many assume that my first name is my last name. 

Thank you though for acknowledging the spelling. 

Brian,  the cases I have are not the cases this crank came from, but no signs of any wear on the center bearings.  Yes, I made sure the pins are seated correctly.  I'll try and post another short video later today to show the wobble with the crank in the lower case. 

 


Gallery


Views:10
Comments (0)
By: harleywaynecycles

Views:15
Comments (0)
By: harleywaynecycles

Views:10
Comments (0)
By: harleywaynecycles

Views:5
Comments (0)
By: harleywaynecycles

Classifieds

Assorted Bridgestone Parts

Price: $0.00
Date: 10/16/2018 11:09 am
Time Left: 85d 0h 13m
Bridgestone 350 Carburetors (2nd. Set)

Price: $0.00
Date: 10/04/2018 04:52 pm
Time Left: 73d 5h 57m
1966 DT 175

Price: $1900.00
Date: 09/16/2018 07:14 am
Time Left: 54d 20h 18m
Bridgestone Jacket XL

Price: $0.00
Date: 09/08/2018 01:25 pm
Time Left: 47d 2h 29m

Recent Downloads added

11/01/1967 Factory Service Letter, RH shift/LH Brake conversion

Rating: (None)
Filesize: 92.56KB
Date: August 03, 2018, 02:49:08 AM
11/01/1967 Factory Service Letter, RH shift/LH Brake conversion

Rating: (None)
Filesize: 142.24KB
Date: August 03, 2018, 02:44:36 AM
350 GTR Wiring Diagram
Rating: *****
Filesize: 8604.23KB
Date: July 29, 2018, 12:29:25 PM
Bridgestone Motorcycles

Rating: (None)
Filesize: 3561.91KB
Date: June 05, 2018, 04:42:13 PM

Powered by EzPortal