SDR Ossa

[VMX60]

Most hard reving racing ossas models Phantom etc will need the yamaha rod kit fitted all of the US dealers stock early/late model  crankpin sizes crank flywheels need to machined
SDR with std porting and used for fun enduro work std ossa rod should be OK

Cheers

[YUMASTEPSIDE]

.........so, whats the lowdown on this yamaha rod conversion ?? 

                 Roger

[Big John]

Try www.ossaplanet.com I'm sure they will have everything you need. www.ossaworld.com is another one that might comes in handy.
For a bike company that that folded 30 years ago parts are quite easy and reasonably inexpensive.

[YUMASTEPSIDE]

Anyone know what Yamaha rod is used in this conversion ??

              Roger

[T250K]

I'm told that the supply of that particular Yamaha rod has dried up.    Ossa workshops in the ' States now use a heavier rod and crankpin manufactured for their use and based on the original Yamaha parts.     Rod kit alone was around $150 US, and an exchange flywheel from Ossa Planet ,which includes the rod kit and all of the re machining and fitting was $300 US in mid 2009.

When I was buying stuff a couple of years ago Ossa World had a good range of parts at a good price and their service was excellent.

   

[firko]

I think it's the Yamaha 250 J rod Roger but don't take my word. I think that's the one we use on 250 Maicos and something in my subconcious tells me that it's the same. Whichever Yamaha rod it is, it's the one off model that varied from the 214 rod for a year or so.....the Yamaha blokes will know.

[evo550]

The conrod mod for the Phsntoms was a YB125 Yamaha road bike rod, where avaliable through pro-x.
Each crank half needs machining as the bigend of the Yamaha rod is slightly wider than the ossa's. May not be a necessary mod for a sdr but it's up to you.

[YUMASTEPSIDE]

The info' I got from Ron Bors and Keith Lynas is that the rods are no longer available (except through them) hopefully I can get enough information from them to buy a minimum amount of goods from the states and be able to buy the majority of it locally.
I can machine the crank halves here in my workshop, the details are supplied on the OSSA-World website and I can machine the stepped pin also.

                    Roger.

[JC]

Roger,

the Yam rod hasn't been available in US for yonks.  It still was available here a few years ago both from Yam sources & Pro-X so it'd be worth checking Oz suppliers. YA or YB 125 IIRC.

There was a guy in NSW who did the whole mod for $100 plus parts (he knows the part nos). Can't remember if his name was Michael Bevan or Michael Slater now (the latter I think) - yes, same as the cricketer but diff bloke. He could also recondition cranks w oversize bearings & proper heat treatment. He advertised in some of the early Club Bultaco newsletters which I could probable find if you wanted.

[YUMASTEPSIDE]

Thanks John, that'd be great , anything I can get locally, in Oz, is preferable.

[VMX60]

Yamaha conrod
model ya6
Part number 137-11651-00 rod only
                  93310-42433 b/end bearing
                  90209-24073 thrust washers x2
crankpin 24mmx 58.2 straight late model  style 74 upward

After market 137 kit the crank pin is to short  Plus the SDR will have the stepped style crankpin
Better to just buy the correct rod kit from Ossaworld
Cheers

[JC]

Yep thats the nos. My notes show Yam b/end pin is only 48.75mm long. Maybe best doing as VMX60 says & buy thro Ossaworld

Bigend of Yam rod is 15mm wide whereas Ossa is only about 11mm, hence machining of flywheels is req'd, so presumeably the crank should be rebalanced too

I also have a brief article from 10/77 Cycle Guide about a mod AMA national #34 Darryl Hurst was doing for hi HP hi rpm Ossa engines fitting a TZ250 rod & b'end w silver plated bearing cage, which also req'd some machining of the flywheels.

The chap I mentioned above is Mark (not Michael) Slater at Coff's Harbour - "specializing in con-rod refurbishing... we can make it like new".  It maybe an old mobile # by now that I have but PM me if y're interested

.

[YUMASTEPSIDE]

Thanks John........Mark and I actually went to school together, so I'll give him a call.

                  Roger

[EML]

A mate of my says he has two old Ossas lying in his shed and though I tried to keep a straight face and ask him if I could meet him at the dump I think he twigged to what I was up to.
He reckons one has an elec issue and he's trying to fit a PEI unit to it, would this be a goer??

[euro bikes]

A long way back you talked about grab rails at the back ,mine has two on it standard, the flywheel is same as the explorer so it doesn't rev fast like the phantoms.