Hey everyone, I've discovered that all my valves but one are way too tight. I know the suzuki specs, but I was wondering if anyone has any advice on a set of ideal clearances. My bike has some trouble when it's cold (coughs and spits) and read something about running tighter clearances on the exhaust can help. Any ideas?
Graham
the cold starts are due to too-tight valves. I run the intakes to suzuki specs (.03mm-.08mm), but i run me ex valves on the loose side per recommendations on here (.08mm-.13mm)
as a rule of thumb, ex valves tighten up more often than intakes.
Run them mid spec should be alright.
There's a big difference between the intake and exhaust valves. The cool fresh fuel/air mix flowing into the cylinder around an open intake valve feels refreshing compared to the red hot burning just exploded mixture flowing out around an open exhaust valve. The exhaust valve needs more time on the seat between explosions to transfer some of the heat from the valve to the seat or the process of the hot exhaust valve receeding into the valve seat over much time will be accelerated.
It's been my experience over many tens of thousands of GS miles that the intake clearances rarely change while the exhaust valve clearances get tighter due to this recession process. One of the exhaust valves in my 97 GS that ran on the tight side of tolerance began an accelerated process of recession and required more and more shim changes after 40k miles and was down to a min 215 thick shim before 80k miles with no place to go. When the tighter exhaust valve in my 02 GS began the same process around 40k miles I began setting the exhaust clearances wider to allow more cooling seat time and the valve recession progress was all but stopped. Now at 97k miles on the engine I expect to go over 100k miles on mid size shims, if I last that long.
I set my valves now at the stock .001-.003" for the intakes and a larger .003-.005" (.08-.13mm) for the exhaust and my stock GS engine is very happy with it. The stock .001 (.03mm) minimum specked clearance is unusually tight for mc engines. If your going to run redline all day long on a modified engine you might want to give some consideration of the possibility of throwing a shim if the clearance is too great and also there is the cosideration of possibly noisy valves with too much clearance. There's no need to run a stock GS over 9500 rpm since power drop off is fast after the 8500 redline. At least I'd suggest setting your exhaust valves to the loose side of the stock specs if you don't want to go wider. If your going to use your GS for only a year or two before moving "up" don't worry about it. Here's the whole log of my experience:
http://img.photobucket.com/albums/v443/jcp8832/GSvalvelogs.jpg