jeepguy
XS650 Addict
just that i have my engine completely torn down how do i know if i need to get the cylinders bored and if so to what size and what pistons would i need. thanks
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catastrophe
XS650 Addict
You have to measure out the bore. You should get close to 75mm. According to what I read if your at 75.02 you should go for a bore up to 75.25 mikesxs sells the pistons and rings. How marked up are your pistons on the thrust side? What do the cylinder walls look like?
Read the Yamaha Service Manual for your model. Available on line at sites such as www.biker.net. Compare your engine to the specs given by Yamaha.
jeepguy
XS650 Addict
k thanks i'll have to do some measuring
Re. measurement of cylinders, it's not that simple. If the top of the jug is lipped from wear it has to be bored. If the cylinder is pitted it has to be bored. If the bores are in good shape it's possible they can be honed. Let a machine shop evaluate and measure the bores for you. You may be able to use your current pistons and maybe not.
If boring is required the shop will be able to tell you how much material they'd have to remove to get the bores clean, and based on that you'd select the appropriate oversize, obtain the pistons, bring the pistons to the shop, and then have the cylinders bored to them. Piston oversizes are specified in increments of .025 mm.=.010". If they tell you, for example, "We'll need to go twenty over," that means you'll need a piston .020" larger than what's in place--2nd oversize, if your current pistons are original.
If boring is required the shop will be able to tell you how much material they'd have to remove to get the bores clean, and based on that you'd select the appropriate oversize, obtain the pistons, bring the pistons to the shop, and then have the cylinders bored to them. Piston oversizes are specified in increments of .025 mm.=.010". If they tell you, for example, "We'll need to go twenty over," that means you'll need a piston .020" larger than what's in place--2nd oversize, if your current pistons are original.
jeepguy
XS650 Addict
great info thanks griz
Most places will measure for free or very close to it if they think you will have them do the work. I had the local speed shop do mine. Second overs, $35 per hole.
I would have gone just first over, but found a set of new old stock second overs for half the price of new first overs.
Shop around you might find a deal on the pistons.
I would have gone just first over, but found a set of new old stock second overs for half the price of new first overs.
Shop around you might find a deal on the pistons.
