Rebore question. xs360 to xs400

agent laraby

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Hi rebuilding my 77 xs360 engine and was wondering a crazy question. I am rebuilding the pots and was wondering instead of using the OS pistons available, (I am struggling to find and OS kit or all the components independently) (yes looked on Csmnl, ebay etc) can the 360 bore of 66mm be taken out to 69mm and i use a set of xs400 rings an pistons? I am assuming they use the same conrod and I would use a 400 head gasket ? piston length is the same 52.4

I am also assuming carb jetting would have to change as well. but both run Mikuni bs34s
 
Hi rebuilding my 77 xs360 engine and was wondering a crazy question. I am rebuilding the pots and was wondering instead of using the OS pistons available, (I am struggling to find and OS kit or all the components independently) (yes looked on Csmnl, ebay etc) can the 360 bore of 66mm be taken out to 69mm and i use a set of xs400 rings an pistons? I am assuming they use the same conrod and I would use a 400 head gasket ? piston length is the same 52.4

I am also assuming carb jetting would have to change as well. but both run Mikuni bs34s
worked that there is not enough meat in the bores i would only be left with 2mm if I rebored to take 69mm std 400 slugs. So the hunt for xs360 OS pistons and rings continues.
 
I am with rshutchinson with using the XS400 jugs also. There is going to be carb issues with jetting but you'll be happy with the finished product.
 
I would keep the xs360 carbs but use the xs400 cam with the xs400 jugs. The xs400 cam has larger lobes than the 360 ones. I would just replace the entire top end if you can find one.
 
thanks guys that makes a lot of sense, ironically whilst chasing down a bigbore kit for my gpz this morning I came across apair of OS pistons for the 360 but without rings. so I am still undecided I also know of a 400 block up the road that I can check out that may be ok. not sure is it is SOHC yet but will find out. Woud prefer the 400 route unless a set of 66.25 360 os rings apear.
 
no joy on the xs 400 jugs up the road. So seeking 66.25, or 66.50 xs360 OS rings. I did findout that my gpz 750 has 66 x1.4mm rings which would be perfect with a tiny bit of machining on one of the ring groves ....Except their OS are different ring diametres.. :(

Any ideas on sourcing OS 360 rings would be sweet
 
With them on non in stock parts there is a minimum amount to buy for them to make them. They will not do just one set. The price would be more than the bike at most times because of this. A guy did this a few years back with 400 pistons and they needed to get like five pairs.
 
True, but, with these 360 parts beginning increasingly scarce, there is potential for profit in selling the excess xs, unless the cost is astronomical, of course. Minimum order is 12 pistons, by the way.
 
thanks guys yes looked at wiseco and there isnt a similar thickness cross reference in 66.25 dia.
But will check out thes other links thanks. I really apreciate everyones help and suggestions.
i will keep posted,.the rest of the bike is done and ready for engine rebuild and fitting so the only thing i havent been able to source is OS rings. i will post some pics soon of the ol' girl
 
update - I had the prefix wrong on the part number when I looked at speed and sport. went through year and model and off the schematics listing and bingo! i have 3 OS kit options available. Thanks Drewpy and Speed and Sport !
 
Piston kit on way ready for rebuild motor is in pretty good nick but a couple of tiny scratches on the pistons and the beginnings of some piston slap so doing everything but the bottom end 32,000 ks on the bike. could probably have just run it for a while but I had to do the main seal so i thought i would do the the lot seeing it was going to be apart.
 
Did this ever become a thing? Did you use the xs400 head complete?

Did you find OS kits for the 360 head or for the 400 head?

What was the correct part number. Lol #revivesa6yearoldthread
 
I would keep the xs360 carbs but use the xs400 cam with the xs400 jugs. The xs400 cam has larger lobes than the 360 ones. I would just replace the entire top end if you can find one.

Is this a real thing? A direct swap? Where does compression end up?
 
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