Sucking valves

[OldWrench]

One of the folks here had the valve keepers come loose and put the valve through the piston. Was working on the wing last night, and got to thinking about this problem.

Over the years I have rebuilt many engines, mainly truck. Many years ago I built a few racing engines. There are a few reasons for valve keepers separate. A broke valve spring will do it. But what happens most of the time is high rpm, and the valve starts floating, meaning the valve spring isn’t expanding fast enough, generally caused by a weak valve spring. The valve stem actually comes out of the spring and the keepers separate.

Our wings are old, and with that age the valve springs weaken. I won’t run my wing over 6000 rpm for that very reason, I know the red line is 8000.

I have an 83 engine I’m rebuilding and I checked the valve springs last night, they all should be replaced, but most likely won’t be able to find new ones, so I will need to shim them.

I don’t know if any of you guys have had experiences like this.

 

[joedrum]

yes i have ... i have some vw performance springs but there a little to big around and would need bottom and top pans big enough ... still got them ...

 

[mcgovern61]

When I pulled my '81 engine apart a while back, I found all of the springs out of spec. I did find replacements but the cost was more than the value of the machinery! (Plus, I needed new valves, new conrod bearings, new main bearings, new pistons and the heads needed to be rebuilt.) :hihihi:

 

[OldWrench]

I did find replacements but the cost was more than the value of the machinery!

That is a very good point. I comes down to how much you like your bike because you most likely won't get out of it what you put into it. I know shimming valve springs is not recommended and it is considered shade tree, but sometimes one just needs to do what you go to do. It is going to cost me seven to eight hundred to rebuild the engine, and when you think about it, that is cheap compared to automotive engines.

 

[Steve83]

When I rebuilt my '83, the springs also were out of spec. I had purchased 2 used, low-mileage heads on Ebay for the '80 I was originally going to rebuild, and the springs checked out good, so I got lucky.

I don't plan on redlining this 31 year-old machine, even with a rebuilt engine. I'm always leery of metal fatigue, which won't show up in measurements, plus I'm not into high speed anyway. I just want smooth, quiet comfort, with enough power to get me out of trouble if need be. If my vision was better, it would probably be a different story...