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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: MCRyder on June 06, 2019, 11:15:12 AM
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OK, double-check question time.
I've done the valve check on my RT. #2 and #3 exhaust valves need to be adjusted. The #2 will allow a .24mm blade to squeeze through, definitely needs adjustment. #3 will let a .25mm blade through, which is in spec but I'd like to back it off while I'm in there. The OEM shims come in at 2.48 and 2.47 respectively. I'm looking at getting 2.45 shims from New Motorcycle Parts. Both of those should back off the tightness to well within tolerances, right?
Thanks.
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What's the difference between "squeezing" and letting "through." How much greater gap allows "letting through" compared with "squeezing"? Will excess clearance cause valve rattle that will fill your nights with dread?
By "OEM shims come in at 2.48 and 2.47respectively", do you mean to convey "the shims that were on the buckets when I took the clearance measurements"? If you do, then going by what you have measured:
Allowed exhaust valve clearance range = 0.25–0.30mm. Replacement shims calculated to be 2.45mm for both #2 and #3 exhaust valves.
#2 with 2.48mm shim = 0.24mm clearance space 2.48 - 2.45 = 0.03mm increase of clearance space 0.03 + 0.24 = 0.27mm clearance space
#3 with 2.47mm shim = 0.25mm clearance space 2.47 - 2.45 = 0.02mm increase of clearance space 0.02 + 0.25 = 0.27mm clearance space
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Not sure about what the others have seen, but my experience with valve shims is that when they are tight*, going to the next thinner shim gets everything back in spec. For example, if the valve clearance is tight at the bottom of the spec, and the shim is a 2.40mm, going to a 2.35mm shim will bring the clearance back into the upper part of the spec. If the valve was so tight that the next thinner shim doesn't get it in spec, then I would be concerned that the valve may be damaged or burnt, especially exhaust valves.
* this assumes that the valve is at or just a tiny bit tighter than the spec, in other words, the "go" feeler just barely goes with a lot of force. Even if it is very tight and won't go at all, the next shim usually gets things at the proper gap again.
Hope this makes sense. I am calculationally challenged, and doing the math to get shim sizes makes me want to take a nap.
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Thanks for the replies. The OEM shims meant the shims on the buckets when measured. I wasn't clear on that, thanks for pointing it out. I began to get cloudy thinking what next shim I'd need and it helped getting input :clap:
"Hope this makes sense. I am calculationally challenged, and doing the math to get shim sizes makes me want to take a nap."
I know the feeling :hehehe Thanks.
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Check with your local Yamaha and/or Kawasaki dealer for shims. The 29mm are the size we need and in my case they just swapped them out for free.
As noted in a previous thread, Suzuki has a 29.5mm shim - these will not work.