Lasper01
XS650 Addict
Has anyone tried this kit?
http://www.ebay.co.uk/itm/74-81-YAM...pt=UK_Motorcycle_Parts_13&hash=item3a9bdb23fb
Lasse
http://www.ebay.co.uk/itm/74-81-YAM...pt=UK_Motorcycle_Parts_13&hash=item3a9bdb23fb
Lasse
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I think that same company sells that kit stateside. As I recall many have used it with good results.
You just need to get your cylinders bored to match the pistons.
Leo
You just need to get your cylinders bored to match the pistons.
Leo
Lasper01
XS650 Addict
Ok thanks. Its a lot cheaper than getting the 6. oversize(680cc) and it will give some more cc's. Is the a big difference between 680cc and the 706cc?
Will they go in the original cylinder?
Will they go in the original cylinder?
Jaydela180
XS650 Addict
Original sleeves, yes. 78 is as far as they will go though. My JE pistons from hoos measure 77.5 in the stock sleeve.
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Posted via Mobile
Nailbomb
Central New York XS650
No advertised compression rating? That's important info...
Lasper01
XS650 Addict
Thanks!
Does anyone know the compression rate on the pistons?
Does anyone know the compression rate on the pistons?
If those piston have the same dome as stock, then my guess is about 9.1. My guesstimate comes from these figures. A 650 with 8.4 C/R, 650 divided by 8.4 is about 77. This is cc's of head.
Now take 706 and divide by 77, this gives about 9.1.
These figures may be way off but I think they are fairly close.
Leo
Now take 706 and divide by 77, this gives about 9.1.
These figures may be way off but I think they are fairly close.
Leo
chizler62
XS650 Addict
I figure the compression ration isn't much different than stock. If it were they'd, being a good seller, would tell you to use higher octane, cam, jetting blah blah etc
The best way to find compression ration is CC the head with ATF and a glass plate with an old spark plug. Then push the piston down, say 20mm, and CC the cylinder. Do the math and it'll compensate for the dome and valve cut pockets. Don't for get to measure and do the CC of the head gasket and bond itself.
IMO, I'd only get as big of an oversized piston as you need. The power difference is not huge. You can get more bang for the buck other places and you will still have cylinder wall left for the next time you freshin the top end.
Most people will say that they seen a big power difference going to an oversized piston kit etc....truth is they're just feeling a fresh motor compared to their old wore out top end. If you'd dyno the a fresh stock piston'd motor and a 1mm over motor you'd hardly see any difference certainly not for the money.
The best way to find compression ration is CC the head with ATF and a glass plate with an old spark plug. Then push the piston down, say 20mm, and CC the cylinder. Do the math and it'll compensate for the dome and valve cut pockets. Don't for get to measure and do the CC of the head gasket and bond itself.
IMO, I'd only get as big of an oversized piston as you need. The power difference is not huge. You can get more bang for the buck other places and you will still have cylinder wall left for the next time you freshin the top end.
Most people will say that they seen a big power difference going to an oversized piston kit etc....truth is they're just feeling a fresh motor compared to their old wore out top end. If you'd dyno the a fresh stock piston'd motor and a 1mm over motor you'd hardly see any difference certainly not for the money.
Lasper01
XS650 Addict
Thanks alot!! Good math 
Lasper01
XS650 Addict
Ok, thanks for the advice chizler. Its just that the price of 1. oversize is more expensive than the 706 kit..
Cruzinimage 1mm oversize, (4th), is 55.20 Pound so a lot cheaper.
A thing you might consider..........Boring out to 706cc oversize means there is no more re-bore left in the sleeves.
4th oversize, (1mm), gives you about 670cc and also has the advantage of boring out the sleeves for another oversize or, (worse case scenario), damaged bore after rebuild, then the sleeves can be re-bored for the 706cc.
Unless the sleeves are damaged and can be cleaned up to only take the 706cc size, a step down gives room for mistakes/problems and won't cost a another set of sleeves
A thing you might consider..........Boring out to 706cc oversize means there is no more re-bore left in the sleeves.
4th oversize, (1mm), gives you about 670cc and also has the advantage of boring out the sleeves for another oversize or, (worse case scenario), damaged bore after rebuild, then the sleeves can be re-bored for the 706cc.
Unless the sleeves are damaged and can be cleaned up to only take the 706cc size, a step down gives room for mistakes/problems and won't cost a another set of sleeves
Lasper01
XS650 Addict
Thats a really good point Skull and I like the Price
Thanks for the link!
Thanks for the link!
As you are Copenhagen, it might pay to find out what rods you have first, as you might need these
http://www.ebay.co.uk/itm/YAMAHA-XS...pt=UK_Motorcycle_Parts_13&hash=item3ceba9807f
as these are the only pistons cruzin image do for the 533 rods which unless your bike is an import from the US is what your bike should have.
http://www.ebay.co.uk/itm/YAMAHA-XS...pt=UK_Motorcycle_Parts_13&hash=item3ceba9807f
as these are the only pistons cruzin image do for the 533 rods which unless your bike is an import from the US is what your bike should have.
Lasper01
XS650 Addict
Yes thats well spotted but my xs is imported (not by me) so its a 447. But thanks
