Looking for pistons or piston options! '81 SOHC

[thebeardedone]

So the first few years of riding, I borrowed my dad's XS. The problem is I didn't maintain it (oil, filter, plugs etc.) and after letting it sit for a year, I started it and after 200 yards down the road it died and spewed oil out the exhaust on the right side. I finally gave in and took it to a shop for lack of time. They said the leakdown test was well below acceptable. In their catalogs they can't find pistons and can only find 3rd over rings. I've searched all over online and found pistons to be quite spendy and sometimes hard to get a pair (but you all knew that).

So I bought another bike built in 2/77 to swap the engine, but I'm re-thinking it because of head fin differences, the fact that my dad doesn't want another vin engine in it, and the excellent condition of the '77-78. It doesn't have a title, but my dad has a title for his '79 parts bike and thought that would do the trick.

Anyway, I am considering doing the rebuild. I found a site (sohc4.net) where they were talking about using pistons and sleeves from other makes. The only problem is that the bores were significantly larger, and I want to give back a stocker.

Has anyone here done a rebuild to stock bore in this way? And what parts did you use?

 

[thebeardedone]

Generationmx.com has 1st over rings for $46.60. Boats.net has 1st over pistons for $69.17 each. I finally had some time to do some research, but I still would like opinions/advice on what to do. Obviously could pay for the re-build by parting out the 400 I just picked up, and I'll obviously have problems in the future if I ever decide to sell a ride-able bike with a different title. I can't apply for a title in Wisconsin without finding the last registered owner, and even then that person needs to be willing to apply for a lost title. I got lucky with my RD350 and the last registered owner (from almost 20 years ago) was still alive and was willing to carve out a portion of a day and go to the nearest DMV that issues titles. From the sound of it, the last person to register the 400 is not so available or compliant.

 

[thebeardedone]

Tons of sites out there with the same layout/look to them. Although they all look the same, the price differences are all over the board. As high as $106 down to $61.19 at stadiumyamaha.com. Pretty soon you'll know everyone's prices just from this thread if I don't stop bombing this thing with replies!

 

[xschris]

There is a guy on ebay that sells standard size ring sets for the sohc xs400 from time to time. If all you need is a hone that would be a good option. As for oversize piston/ring combos you either spend big money or get lucky on ebay. Yamaha has nothing for these bikes anymore. Another place to look but pricey is yamtopdog.com (speed and sport) they have a lot of stuff also. There has been a lot of discussion on other brand/model pistons that could be fitted to this bike but none have been posted with end results as of yet. If you have a running spare motor put it in. You only need to have a title for the bikes frame. Unless the motor is stolen and someone is looking for it All sohc xs400 motor parts 77-82 will interchange.

 

[xschris]

http://www.ebay.com/itm/Yamaha-XS40...amaha|Model:XS400&hash=item5411f4d509&vxp=mtr Link for the rings.

 

[XS400Cup]

http://www.scheuerlein-motorentechnik.de/motorenersatzteile/motorrad/Yamaha/400-499-ccm-y4/-0-360/

 

[xschris]

At $190 for a set of rings with shipping to the u.s. I don't think so I do like the complete piston and ring kits but that's $400 Maybe someday there will be a u.s. supplier.