Author Topic: T35 Mk1 Pistons and Rings  (Read 3502 times)

0 Members and 1 Guest are viewing this topic.

Offline Benny

  • Member
  • *
  • Join Date: Jan 2012
  • Posts: 6
  • Location: Melbourne, Australia
T35 Mk1 Pistons and Rings
« on: 04 Jun 2012 at 08:33 »
Hi Everyone,
I'm in need of some Mk1 Pistons and Rings for my bike as I've just found out the excessive smoking has been due to damaged pistons from a partial seizing at some point. The Barrels look good but I need to replace the pistons etc..
Does the club have any pistons that would suit or is there someone on the forum that has a pair I could purchase from them?
Also are there any modern pistons say from a honda that would do the job?. Something with a high dome?
Thanks
Benny.

Offline Doug

  • Administrator
  • ****
  • Join Date: Mar 2004
  • Posts: 4334
  • Location: Glen Mills, PA, USA
Re: T35 Mk1 Pistons and Rings
« Reply #1 on: 04 Jun 2012 at 12:26 »
Benny,

If just localized seizing on the pistons, such as a burnished spot without significant galling, it can be eased down with a fine single cut file and light oil. Pistons do not have to be perfect, so long as they hold the rings true and the rings can seal. After all, most of the piston does not touch the bore (or that is the idea anyway.)

If the seizure has scuffed the bore, then you may be going up a size in any event.

Doug

Offline aggettd

  • Full Member
  • **
  • Join Date: Jul 2004
  • Posts: 69
  • Location: Nova Scotia, Canada
Re: T35 Mk1 Pistons and Rings
« Reply #2 on: 18 Jun 2012 at 12:09 »
Pistons from the SOHC Honda CB750 and the Suzuki GXS650 are 62mm in diameter. The Suzuki pistons are slightly more domed and there seems to be a bit more piston above the gudgeon (wrist) pin. They won't give you quite the same compression ratio, but the burn efficiency inherent in flatter pistons would probably make up for any power loss. They are both lighter than the originals. To fit them you would have to either bore the barrels or turn down the pistons.

Offline eddie

  • Master Member
  • ****
  • Join Date: Mar 2006
  • Posts: 1726
  • Location: Hampshire, UK
Re: T35 Mk1 Pistons and Rings
« Reply #3 on: 18 Jun 2012 at 14:08 »
Benny,
          Be careful when attempting to use oversize pistons in a Mk1 or Mk3 - Mr Douglas only went up to +.030" for these barrels as they are thinner in the wall than later barrels. When overbored, they have been known to crack and lift away from the base flange.
 If your barrels haven't been excessively scored from the pistons nipping up, you could try another set of standard pistons from a generator engine. Or as Doug says - ease the high spots on your pistons - also make sure the seizure hasn't drawn aluminium over the rings and trapped them in their grooves. This often happens, and may be the reason for your engine smoking, the damage to the piston skirt is unlikely to have much effect on the oil consumption.

   Regards,
                 Eddie.

Offline Benny

  • Member
  • *
  • Join Date: Jan 2012
  • Posts: 6
  • Location: Melbourne, Australia
Re: T35 Mk1 Pistons and Rings
« Reply #4 on: 21 Jun 2012 at 09:44 »
Thanks everyone for there advice. It appears after consulting a specialist that I'll be needing to get .20 thou over size pistons, rings etc... as one of the bores is scored deep enough to warrant boring it out further. +10 may do it?
The bores where on there original size, but it appears the pistons had been modified oversize pistons.
Or damaged and repaired.
Any ideas where to get +20 pistons, rings, gudgeon pins? Anyone got some they'd be willing to help me out with?
Or is it best to have someone make some pistons up for me?
Any help would me most welcome!
The only bonus is it's the middle winter here. So it's not great riding weather.
Thanks.
Benny.



 

motorcycle