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Author Topic: 2008+ Ninja 250 valves  (Read 383 times)

vance

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2008+ Ninja 250 valves
« on: March 21, 2017, 06:40:53 AM »

Can both the intake and exhaust valves be lapped? I'm reading that some valves are case hardened and should not be lapped. Cannot seem to find the info on the 250 valves.  Blew a head gasket, so I figure while I'm in there I will attempt my first ever valve job.  Purchased the gasket, but am wondering if I can use the stock valves or if I need to buy new ones.  Any additional advice appreciated.
On a side note, I've been told I have a "stuck intake valve" on my EX500 so I'm into the same process for that bike and found that the exhaust valves can be lapped, but the intake valves are case hardened and you should not lap an old (used) case hardened valve, as it will quickly wear through the hardening.  Is the majority in agreement with this?
« Last Edit: March 21, 2017, 06:46:06 AM by vance »

bruce71198

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Re: 2008+ Ninja 250 valves
« Reply #1 on: March 23, 2017, 09:35:16 AM »
I have lapped my 250 valves on several different heads without issue. I have never heard of the "case hardened" argument on the 250 or 300 but now that you have brought it up i will look into it. The other point is case hardening should be thick enough to allow enough lapping to clean up a valve seat, if lapping past this point is what it takes to make a clean seat you are probably ready for new valves anyway.

vance

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Re: 2008+ Ninja 250 valves
« Reply #2 on: March 23, 2017, 11:36:22 AM »
Thanks for the reply Bruce.
Been tough to find what material the valves are made of.  This will be my first ever valve job with a $5 hand lapping tool from AutoZone, so it will be a light lapping, reinstall and then test with fuel sitting in the head overnight to check for leaks (at least that's how the internet says to do it)  :biggrin:
Actually, now that I think about it, the overnight test should be done first to see if lapping even needs to be done, correct?

bruce71198

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Re: 2008+ Ninja 250 valves
« Reply #3 on: March 24, 2017, 11:35:08 AM »
Look at the seat and the margin on the valve, if there's any irregularities or discoloration in those surfaces, lap them to make a good seal. As far as material and construction? 1 step above Briggs and Stratton.