Author Topic: CB250RS Drive Sprocket Seal  (Read 2820 times)

Offline andy_c101

  • SOHC Member
  • Posts: 140
  • Gone but not forgotten.....
    • View Profile
CB250RS Drive Sprocket Seal
« on: September 10, 2013, 10:16:36 PM »
I really can't believe it!
(Apparently) It seems that back in the 80's Honda designed an engine (the CB250RS) where you have to split the crankcase in order to replace and fit the final drive sprocket shaft seal!
Crazy!
- unless anyone out there knows a way of fitting a new seal without a complete strip-down of the engine bottom end & gearbox.

Andy
 

Offline Bryanj

  • Grogu
  • *
  • Posts: 10692
    • View Profile
Re: CB250RS Drive Sprocket Seal
« Reply #1 on: September 11, 2013, 08:47:56 AM »
i can't remember, is it a vertical or horizontal split crankcase mate

ka-ja

  • Guest
Re: CB250RS Drive Sprocket Seal
« Reply #2 on: September 11, 2013, 09:17:59 AM »
hi,
     Not so rare, the 400/4 final drive oil seal and a gear shaft blanking plug are trapped in by the crankcase halves, not such a bad idea if you think of how much oil you could loose if the seal "popped out" while running at speed.

Offline Bitsa (Ralph Wright - RIP)

  • SOHC Jedi
  • Posts: 2937
    • View Profile
Re: CB250RS Drive Sprocket Seal
« Reply #3 on: September 11, 2013, 07:00:20 PM »
Hi Andy
Yeah bit of a bummer but you can dig it out carefully and replace using a damn good fixing sealant like previous if it pops out big sh t.Have done it with other models only because customers did not want to pay for full strip.Engine was horizontal split cases.
Cheers
Bitsa
Long Live Best Bitter.Status Quo and Sohc Bikes and common sense which you can not teach

Offline andy_c101

  • SOHC Member
  • Posts: 140
  • Gone but not forgotten.....
    • View Profile
Re: CB250RS Drive Sprocket Seal
« Reply #4 on: September 11, 2013, 09:15:33 PM »
Yes, it has horizontal split cases.
I did try installing a new seal without splitting the cases.
I thought it was worth trying, (& yes with some Honda engine gasket sealant in the casing groove too), but the seal just got all chewed up!

Now reading up on the procedure for the engine strip n rebuild.
I hope I don't find any new 'horrors' inside, when I open it up!

All good experience I suppose!

Cheers

Andy

Offline andy_c101

  • SOHC Member
  • Posts: 140
  • Gone but not forgotten.....
    • View Profile
Re: CB250RS Drive Sprocket Seal
« Reply #5 on: September 22, 2013, 09:20:07 PM »
Managed to spilt the crankcase today.

Once the top-end, cylinder etc. was off, I was able to split the cases WITHOUT having to strip/remove all the side-case parts such as generator; clutch, oil pump and balancer shaft & its chain.
So that speeded things up quite considerably.
With the balancer shaft chain still on, the upper case doesn't completely lift away, but enough clearance to allow access to change the final drive seal.
While doing this I have also swapped the final drive assembly shaft, as the old drive splines (for the chain sprocket) had worn badly leaving much backlash (not uncommon on these old single 'thumpers').
 :)

Just need to button it all back together, top-end 'n all later in the week.
[I don't know why I was so hesitant in the first place; the moral is 'just do it!]
Andy

 

SimplePortal 2.3.5 © 2008-2012, SimplePortal