Topic: CB550 pistons (edited from CB500)

[MotoRico]

I was wondering if there is a current source for pistons for the CB550?  I can find WiseCo pistons for the 750 on their website but nothing about the 550. 

I recall reading one of the articles on this site about using 750 pistons in a 550 and there needing to be some machine work done.  Do new sleeves need to be used?  Is there a newer sleeve that can be made thinner given any advances in the last 30 or so years since these motors were designed?

I have a second engine that I bought and I'd like to rebuild it.  There are a few kits floating around that are NOS and I was wondering if I should get my hands on one of those, thereby testing my wife's patience with my new obsession, or if there was another option that can be pursued later on.

[bill440cars]

                    You can find some piston sets on ebay but, I haven't seen any Wiseco products. Maybe
        someone else can be of assistance. Later on, Bill

[SteveD CB500F]

David Silver has NOS 605 kits for sale.

http://www.davidsilverspares.co.uk/cgi-bin/dss2-cgi/ProdSel.pl

[Einyodeler]

There is a 605cc kit on e-bay right now with a B.I.N. of $135.00 U.S.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=4619189218&rd=1&sspagename=STRK%3AMEWA%3AIT&rd=1

[MotoRico]

I see the kits on there from time to time, but I was wondering if there was a source for the pistons alone.  I know that those kits will all go away some day. 

How hard is it to get the 750 pistons to work?  I realize that a machine shop will be involved.  I seem to recall the diameter of the 750 pistons is about 1.5mm over that of the 550 piston.  Can that much safely be taken out of the sleeve on the 550?  Would a new sleeve be required?  If so, where does one obtain those?

[bryanj]

Now are we talking 500 or 550 cos the header sez 500 and you is asking 550--makes a big difference!

[MotoRico]

Yeah, it's 550, I made a typo on the initial post.

[volz1fsu]

The 750 pistons are actually 2.5mm bigger than the 550,  61mm as opposed to 58.5.  The stock 550 sleeves can be bored this big safely and there is still room for one oversize, 61.5 max bore on the stock sleeve.  Sleeves from 650s or 750s can be used but there is HEAVY machining work to be done and I am sure you are not looking to go that route.  The 605 kit would probably be best for you since I think it comes with its own sleeves.  And I CAN NOT stress the importance of precisely pressing in those sleeves if you must.  For some reason everyone thinks they have to be pressed in but the truth is that it is much better and easier to put them in by heating the assembly and dropping them in and out, aluminum expands 2.5 times that of iron or steel.  They will slide right in at 400 degrees.

[bryanj]

Right I think you will find that the 605 kit is standard 750 pistons machined to fit the 500, from an aged memory i think the skirt has to be altered slightly to clear the crank, buying the 750 kits then the machining could well cost you more than buying the 605 kit but on the 550 you will probably get away without having to fit the 605 liners which are a must for the 500 (plus case machining) Many moons ago i had a 500 bored to take the 605 pistons and the standard liners were increadibly thin at that point but were ok to run but not for long life so the 550 SHOULD be even better although i aint tried it.

[MRieck]

The 750 pistons are actually 2.5mm bigger than the 550,  61mm as opposed to 58.5.  The stock 550 sleeves can be bored this big safely and there is still room for one oversize, 61.5 max bore on the stock sleeve.  Sleeves from 650s or 750s can be used but there is HEAVY machining work to be done and I am sure you are not looking to go that route.  The 605 kit would probably be best for you since I think it comes with its own sleeves.  And I CAN NOT stress the importance of precisely pressing in those sleeves if you must.  For some reason everyone thinks they have to be pressed in but the truth is that it is much better and easier to put them in by heating the assembly and dropping them in and out, aluminum expands 2.5 times that of iron or steel.  They will slide right in at 400 degrees.

Absolutly right about heating the cylinder block to remove the sleeves. If you press them out you gall and smear the aluminum badly. It's a good idea to give the sleeves a press after they have been istalled and cool down just make sure they haven't walked out of the bore a little while cooling. The deck should be milled too just to make sure everything is flat.

[bwaller]

There appears to be a few of these so called 605 kits still available, but I'm not sure about extra rings. The pistons are the same size (61mm) as the std. 750, and the top two 750 rings will work but the oil ring for these kit pistons is narrower, so don't break one!