R45 to R65 upgrade

[dogshome]

Hi all, the 860 kit is staying, so I may as well sell the 650 pistons and barrels. They are the 1981 plated type (1983) with base O ring groove.

I believe the block is the same on R45s, also pushrods etc, but don't know about the head or whether the 650 parts can be simply fitted or if some machining or compression reducing base gaskets etc are required. From photos it looks like the edges of the 650 pistons might hit the wider gasket area of the 450 head. The 650 pistons do have a flat band at the edge and don't pop-up, but it's hard to tell. Of course it might simply result in 15:1 compression......

Since the head gaskets on all are the same apart from the 1000 and combined with my rough pic below, this seems to confirm the head will fit the barrel. But will the piston hit the head?


I'd like to know as someone is bound to ask now!

[dogshome]

They look in reasonable shape.

Yes I can feel every original finishing tool mark all down both sides of the skirt. I never had a Yamaha piston like this after 30,000, let alone 60,000!

The bore though has some ring polishing marks at the top and I can feel a tiny ridge on the top of the first compression ring mark. So worn and a ring replacement not possible, but will do another tens of thousands I expect. She was losing no oil or smoking.

Collective thoughts? 

[Justin B.]

I'd just stuff the slugs back in the same jugs and run 'em!  When I freshened up the Junkyard Dawg the oil rings had an excessive end-gap and it smoked like crazy.  I just scuffed the cylinder walls with a Scotch-Brite and put in new rings.  Ran great!

[dogshome]

If I'd not just fitted some shiney new big ones, that's what I'd be doing. I think they are good for a few years, but not another 60,000.

Do they fit a 450? Would 450 heads then need a bit of milling to reduce compression or just base shims or fit right in?

[Justin B.]

I have no idea but there are a couple of 450 folks on here that might be able to shed some light.  Have you looked up the part numbers for both heads?  I would think that maybe a thicker head gasket or flatter piston top would get compression under control.

[dogshome]

Probably yes. But no-one seems to talk about it 

More on liners. This is ring gap in worst worn spot.

[dogshome]

The gap on the hardly worn area further down.

This is 0.05 smaller, so divide by pi gives 0.016mm. Wear (taper) limit is 0.02mm. I don't know if this is a wear limit or a manufacturing limit. Either way it ain't knackered. Worn, but not worn out.

[Justin B.]

Hopefully somebody will chime in.  The site traffic is down considerably this past year due to various issues but hopefully now that things appear stable people will start coming back...