YZ465/490 conrod

[sleepy]

Don't recall if I've talked regarding this before but was playing with a couple of Maico rods recently that are advertised as being replacements but are slightly different in length.
The YZ465 rods available from Mitaka in the UK are advertised as 137mm center to center but the correct length for a YZ big-bore is 137.5mm. All other dimensions are correct and it would be a relatively simple job to machine .5mm off the base flange.

[Big Scotty]

I not long rebuilt mine I used genuine rod still available from yamaha

[sleepy]

Original is a good choice. The Mitaka one have been sold for a few years now and it is the only aftermarket one around. There are probably quite a few been fitted in Australia without anything down about the different length.

[Nebo]

  I think the YZ400 rod is the same length as the Maico one.  The only other difference is the Yamaha Big end pin is longer.
  Very easy to shorten the pin. How are you going to Machine .5mm of the cylinder barrel without removing the sleeve ?.
   The easy option to get the correct deck height is by the base gasket . They vary from .3/.5/.8 /1mm or make your own.   



   Contact Stacker Motorcycles. They have done many of these conversions.
   Also Royal Rods may have a Kit that is a direct replacement.

 

[sleepy]

  I think the YZ400 rod is the same length as the Maico one.  The only other difference is the Yamaha Big end pin is longer.
  Very easy to shorten the pin. How are you going to Machine .5mm of the cylinder barrel without removing the sleeve ?.
   The easy option to get the correct deck height is by the base gasket . They vary from .3/.5/.8 /1mm or make your own.   



   Contact Stacker Motorcycles. They have done many of these conversions.
   Also Royal Rods may have a Kit that is a direct replacement.

 

We used to fit the Yamaha rods YZ465/490 to the Maico 400,440 & 490's going back 20 years or so when the Maico rods were unavailable but the Yamaha is 137.5mm making it .5 mm longer than the Maico. That was easy to correct with a 1 mm thick gasket. The other difference was the width of the rod at the bigend and from memory it's 3mm different so a bit of machining was required.
Now the rod availability is reversed with the Maico easy and cheap to get but the Yamaha got difficult.
The rod being sold by Mitaka for the YZ465 is actually the later Maico 490/500 rod which has the wider bigend but still the same 137mm as per the early Maico rod.
The YZ400 has a 130mm rod which is even shorter than the 250 Maico rod but have seen one used in a 250 Maico but it required 1.5mm machined of the bottom of the barrel and the piston skirt chamfers increased to miss the crank wheels. Not a good conversion and I only got involved when they couldn't work out what the knocking sound was when they started it with the piston smacking into the crank. This was also done many years ago when 250 Maico rods were hard to get. Incidentally the latest batch of 250 Maico rods now available from Mitaka are listed as being 132mm centers but are in fact .5mm to long. After informing Mitaka of this error the only comment was that they have sold lots and nobody else had complained. Again that is easy to fix with an extra .5mm base gasket.

Machining the bottom/base flange of a barrel is easily done in a lathe without removal of the sleeve. I would allow about 1/2 hour for the job plus a little extra to remove the head studs if fitted.