I'm starting spring riding season (1928 101) off with a problem: the front exhaust valve lifter push rod guide is rising up out of its press-fit. This is holding the exhaust valve open. It’s risen up twice which means it’s now increasingly, and hopelessly loose.

This heavily used engine will need a major overhaul this next winter. But I don't want to stop and take time out of my other shop work or riding around to do that now. 

I'm contemplating a quick fix: drill into the aluminum case at a strategic location until the side of the hardened (iron?) guide is reached (should be easy to feel that), thread hole with a bottom end tap, and thread in a pressure pin against the guide. Fill the hole when the engine is eventually disassembled.  When the guide is reached it may be possible to drill with a cobalt or carbide- tipped bit a shallow indent for the pin to go into it - however the risk of breaking the brittle drill bit in the hole would be cause for great care.

The reason for threading is to repeat pressure if needed or to back it out if the trick just totally fails.

Do you think that is crazy to try? 

Would you buy a motorcycle from this man?

Bob

The guide must be being pushed up by crankcase pressure - we were just discussing that with a member. I’m meticulous about maintaining optimal oil quantity in the crankcase and so there would not have been too much oil to raise the pressure. And I did Check the vent disc and it’s free to move. All I can think of is:

it has not been ridden since installing new rings on the pistons last year. The old rings were quite worn and so the engine had been running under low crankcase pressure. That, coupled with the primitive breather system for crankcase pressure may be the twin causes that revealed a compromised guide fit.

I think I will first remove the vent disc and install a Krank Vent I was holding for a Chief. These automotive valves were popular as Indian improvements for a while, not long ago, maybe still, to improve crankcase ventilation making it more steady and reliable. Then I’m going to insert one self-tapping sheet metal screw in the telescoping cover for that front exhaust valve to keep it closed down and preventing any upward movement of the valve lifter push rod guide. That’s damage done to a cheap part and a replaceable part when the cylinders come off again.

This engine was a wreck before its rebuilding by the notable George Hood of California. He may have not pressed in new push rod guides. This one guide may have been compromised much earlier. And then it’s had a lot of use over the years - the cylinders have been replaced once and these are now five over. 

Anyone ever tried a loctite bearing fit here ? The  loose bearing fit can take up a good few thou, ( think specs may be 10 or 15 ), expands a bit, could crack case ? Loctite tech dept may be worth an ask.

Thanks Phil, appreciate the update, so now we know it can work, and is surely a better option to try rather than drilling or otherwise damaging anything.

Robert, if you really want to keep riding the bike as is, you can remove the valves without removing the cylinder by using an old fashioned scissor valve spring compressor. Then you can lift the loose guideblock, clean both it and the surface of the hole, and use Phils recommended green loctite or similar retainer. These can come in either close or loose fitting , the loose fitting version will expand into a gap with considerable force created if the compound has nowhere to go, and can damage parts. I think loose fitting specs run to between 0.010" and 0.015". Please check what you use is appropriate.

Tim Raindle wrote:

"... you can remove the valves without removing the cylinder by using an old fashioned scissor valve spring compressor...."

Thanks Tim,  I will try that, with cleaning and the adhesive, using the Briggs & Stratton valve spring compressor #19063 I use for valve removal/installation. But first, I just pushed it back down with a wooden rod and hammer, then installed a Krank Vent on a tube extension to the original pressure vent tube, and removed the tiny control disk. I waiting for cold and rain to pass to give it a run. Maybe the crankcase pressure will now be better regulated with that. But still, there is a loose guide to deal with sooner or later.