HS40 intake valve seizing

[cncsparky]

After a complete rebuild of my Hustler's HS40 I've been having trouble with the intake valve seizing open. First time, I ran the bike in the yard for quite a while then died and had no compression. After pulling the head I was able to push on the valve and it seated. Took the block back to my machinist, he looked it over and couldn't find anything wrong with it. The valve guide clearance seems good. He has done lots of small engines and I trust his judgement.

I get it put back together and running, just idling in the garage and it does it again! Not sure what to think or do. Today I'm going to take the block back to him and have a new valve and spring setup in it. Maybe he could pull the guide and put a new one in?

Could ignition timing be causing the problem? I reset the timing after rebuild according to the Tec. repair manual. See my photos for a pic of the setup. I'm thinking maybe the timing is off causing the intake valve to heat up and seize. Any thoughts??

 

[Jay Wrix]

Hello,

Im sure he could put in a new valve, spring, and guide, I would get new guides when rebuilding but,

Did you get a new valve? or was the valve dropped? or hammered on at all?

If your valve stem becomes un-true it could cause sticking problems and jam up,

I suppose ignition timing could be a problem, But I dont think that's the case for the intakes, as they are normally cooled from the flow of cold air coming in, Id expect a exhaust to warp before that, thou it is possible

Im assuming you run it with an aircleaner, and that the engine did pick up a stone, and bend the valve? even a little bit of runnout could cause it to stick

 

[cncsparky]

I took it back to the machinist today and he is perplexed as I am about it. He agreed to install another new valve guide after discussing the problem he said maybe a chance the guide he installed earlier didn't go in straight. I gave him a new valve and spring to install also.

 

[brians306]

valve sticking

I wonder if he finished honed the guide after replacement. when you install new guides they compress around the circumference. and they lose clearance. I set all mine about .0015
or like jaywrix said maybe a bent valve. just some food for thought.

 

[cncsparky]

I got the engine back together today. The machinist installed a new guide and set the clearance a little looser than normal but within spec. He installed a new valve and spring, also. So far, so good. Hopefully, it will stay good because its running awesome now!

Tom.