Bill Hoddinott - VA (guest) View all posts in this topic  
Sun Jan 21, 2007 1:30 pm
Re: At some time will you check the valve clearances...        

True that I don't beat my equipment real hard, because I want it to last. I do use the 9-11K range whenever I want maximum torque at full throttle for some reason - including just because I feel like it. But I never exceed 11K.

I have heard a few case histories where the valves had negative clearance, in other words were being held a tiny amount off their seats due to misadjustment of tappets or other reason. Just as SOON as the valves are not making solid contact with the seats, the compression will be going away or gone altogether, depending how much clearance there is, and you will know something is wrong. The engine won't run well or at all if the compression is not up to the minimum figure required. It is conceivable that the exhaust valves could get eroded or burned on their sealing faces as this negative clearance thing is developing, but I haven't seen any actual cases of this reported on this forum. It has been reported long ago that with air-cooled aircraft engines, where the heads and the valves run at super high temperatures anyway, a slightly leaking valve like this would get burnt on the face of it. Here we have a water-cooled engine where the head and the valves run much cooler, so it would seem the risk is not very great.

Part of my experiment here is to verify for myself that 5w-30 non-synthetic car oil lubricates adequately to keep wear away in the top end, and so far it has, evidently. I don't plan to check the tappet clearances unless I get some symptom of distress or engine malfunction, but I will when the spark plugs eventually show evidence of large gaps which will cause hot-starting problems; and I have to take the tank off anyway to replace the plugs.

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