suzuki rm125a oversized pistons.

[basil44]

re old topic does pro x ts125r oversized pistons fit rm125a and if so has any one got the contact number for them? If it fits does it need any modifications. what viscousity oil and how much for rm125b forks. thanks

[Doc]

Basil, I do remember that thread and specifically the later (90's model) TSR125 using the same larger gudgeon size. I remember the model this piston is from was watercooled and i asked the question then but everything seemed to point to it being ok to use with the ring locating pins moved into new positions. Never heard any more about this issue sorry and I can't remember who it was that was doing it    I believe bbimporters in WA supply them but I don't have a contact number. Check eBay UK as these TSR125's and other small bore models were very popular over there due to licensing restrictions. Many we didn't get to see here. You could try this site http://pro-x.com/eng/default.htm go to the catalogue 4th item down in the option list at the right, you'll find them listed there. TSR125 not TS125R 

[crs-and-rms]

rm 125 a forks 223 cc per leg and thats  taken from genuine suzuki workshop manual as for what for oil weght to use depends on how heavy you  are

[TM BILL]

rm 125 a forks 223 cc per leg and thats  taken from genuine suzuki workshop manual as for what for oil weght to use depends on how heavy you  are

I think he asked for 125B fork oil capacity 

RM 125B 264cc per leg as per owners hand book sae 20w/20

[crs-and-rms]

opps so he did thanks tm bill lol at me

[crs-and-rms]

what size piston are you looking for there is a .50 piston on the usa ebay part number12110 41740 listed as .50 and its item number 350067129330 hope this helps

[basil44]

Thanks fellas.What about final drive gearing?.

[crs-and-rms]

for the rm 125 a its 14/57 thats from ome manual the rm 125 b is 14/59 got that from parts book

[basil44]

OK next problem,I have bought a Woosner TSR125 piston 57.5 mm size.These are flat top pistons and the RM125A Suzuki piston is domed,does anybody know an easy way to work out how much to machine out of the head and or the barrell to keep the compression back to original?.I also need  a front braking plate and brake arm to suit the RM125B forks I am putting in it.Thanks fellas.

[Lozza]

Yes If you have a lathe no if you don't. But well worth doing as flat tops are the go 

[LWC82PE]

what about a piston from a TS125X of around 84-86. im pretty sure they used pretty much the same watercooled motor as the RM 125 81-83. Is this motor the same as the late 80's/early 90's TS125R?

[basil44]

The original thread went dead and I suspect it was because of this.The problem with the RM125A is the 56mm bore and 16mm gudgeon pin.I think most of the later motors are 54mm bore and stroke.It would be nice if you could go and by a new barrel and piston and be done with it.ARRGH the fun of vintage bikes!There must be other frustrated RM125A owners out there that have come accross this problem or is there a bunch of A motors sitting in sheds waiting for the miracle cure to happen,could that be why you dont see any racing?Would it be smarter to convert it to an RM125B motor?Has any one got anything for sale out there.CHEERS BIG EARS.

[Lozza]

I have found a bearing that will allow the use of modern pistons with 15mm pins in rods designed for 16mm pins.Then you can go to the 2mm+ oversize  54mm pistons.What is the compression height of the piston(top of pin bore to timing edge before you ask).Failing that just swap the rod to a modern one that accepts 15mm pins.Also found bearings that will allow theuse of a 14mm gudgeon in a rod designed for 15mm pins. There's no real dramas.

[Doc]

Basil, I'd reckon you'd be best converting it, at least you could then get the 1.50mm and 2mm oversizes a little more easily. In the meantime you can keep your ear to the ground for the right parts which Murphy's Law states 'will turn up as soon as you've spent your fundings on having it converted'  least it could be ridden 

[vandy010]

i'm not real sure what i'm doing here in the world of Suzuki guys but this snippet of info may be of some use.
AT1 125 Yamaha pistons are,
 56mm std bore,up to 2mm o/s,
 16mm gudgeon,
 30mm from centre of pin to timing edge of piston,domed crown,
with the AT1 being a piston port motor {no reeds}, the piston would be a full skirt jobbie. would it be possible to trim the skirt {if nessecary} to suit the RM125a?
just a thought.