Another valve check question! - Suzuki SV650 Forum: SV650, SV1000, Gladius Forums

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SV650 Gen2 (03-15) Tech Info, advice or questions specific to the 2003-2015 model SV650.

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Old 07-02-2019, 06:53 PM   #1
mercuryae
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Join Date: Sep 2013
Bikes: Suzuki SV650SA
Miles Kms: 14000
Posts: 8
Another valve check question!

Alrighty, I got in there with the feeler gauges and the results are in:

*Front Cylinder*
-Intake Left: .005 in (.127mm)
-Intake Right: .006 in (.152mm)
-Exhaust Left: .008 in (.203mm)
-Exhaust Right: .009 in (.229mm)

*Rear Cylinder*
Intake Left: .004 in (.102mm)
-Intake Right: .005 in (.127mm)
-Exhaust Left: .009 in (.229mm)
-Exhaust Right: .008 in (.203mm)

Acceptable range is:
Intake: .004 - .008 in
Exhaust: .008 - .012 in

So, as you can see I'm running on the tight end across the board. My bike has 18,000 miles and I'm not sure if the valves were ever checked or adjusted by the previous owner. I'm also not a mechanic, and I've never attempted anything this invasive. Knowing I'm in spec, but just barely, I'm torn on how to proceed. As I see it my options are:

A. Tear it apart since the covers are already off and attempt to adjust the valves closer to the middle of the spec.
B. Close it back up, ride it for the rest of the summer, and then either check it again in the off season or take it to mechanic that would be more knowledgeable than I am.
C. Call it good and ride it until I sell it or it hits the normal checking interval again in the future.

Finally, assuming that option C is reasonable, would there be a performance benefit to adjusting the valves away from the limit anyway?

Thanks everyone!
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Old 07-03-2019, 07:56 AM   #2
zacbarlow007
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Join Date: Jul 2008
Location: Austin, TX
Bikes: 2008 Suzuki SV650S
Miles Kms: 43000
Posts: 997
Re: Another valve check question!

In spec is in spec. The measurements simply being out of spec doesn't mean your bike will immediately stop working, it just means that before the next interval but as soon as possible, some action will need to be taken to ensure proper operation.
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Old 07-04-2019, 02:25 AM   #3
Craig380
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Join Date: Jul 2015
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Bikes: Blue 650 AL7, replaced my K6S (RIP)
Miles Kms: New bike: 1,610 and rising. K6S had 21,380 until it was killed by a patch of diesel
Posts: 343
Re: Another valve check question!

+1 to the above. In spec is in spec. My 2 pennies worth is, if it ain't broke ...

You mention performance benefits of adjusting the valves. If they're at the tight end of the spec, you get ever so slightly more valve lift and overlap, which generally benefits higher-rpm breathing & running.

At the slack end of the spec, you get slightly LESS valve lift and hence less overlap, which is generally better for street / everyday riding when you're using less than half throttle and lower rpms.

But the differences either way are not huge, maybe 1 or 2bhp here or there if measured on a dyno, which falls within the variations you would also see from changes to ambient air temp / pressure / humidity etc.
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Old 07-04-2019, 05:31 AM   #4
RecoilRob
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Join Date: Feb 2011
Location: Uniontown, PA
Bikes: '07 SV1000S
Miles Kms: 41688
Posts: 6,588
Re: Another valve check question!

Going from tight limit to loose limit will change the timing about 4 degrees and in my case this increased the idle rpm by about 300 with no other changes.

The clearance specs are made from a durability and emissions standpoint and the engine will run within them, but if you're interested in the best running engine then you'd likely want to set the clearances toward the middle or loose depending on the shims you have available.

One of the 'old school' tuning tricks to see if your camshaft is properly timed is to vary the lash and watch the power production. If going tighter increases power you need a bigger cam....and vise versa. Race type use often will benefit from loose clearance specs not because of any power gain at high rpm (makes little difference way up on the tach) but because of the extreme heat of extended hard running makes things expand so it's good to have the extra clearance for durability reasons.

The old saying 'A tappy valve is a happy valve' comes to mind. Running at the tight limits won't hurt anything, but they're only going to get tighter and if you're riding on the street you will see a gain in torque and mileage by widening the clearances to at least the middle. The engine will often run a bit smoother if all clearances are set to the same respective range and the synch and TPS will stay in proper adjustment. Most cases of TPS being out of adjustment is caused more by valve adjustment drift than anything wearing in the throttle system IMHO.

Doing a DIY valve adjustment isn't rocket science...but there ARE lots of ways to make mistakes that can be frustrating and costly if you make them. If you aren't confident in your ability to DIY then the services of another will be needed....which can cost you a bit of money. If you are going to have to pay someone it wouldn't hurt to wait until you hit the minimum before being forced to do it....just be aware that you're not getting all the goodness the SV can give if the valves aren't adjusted precisely.
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