630 wont start

as

Member
Hi, I have a 630. Its always started good, however, it runs on one cylinder until it warms up.Last night it would not start, even pulled it. there is a spark and compression. But it seems there is not fuel getting into the cylinder. the carburator has gas in it. I was wondering if both valves could be stuck shut, is this possible? If I pulled the valve cover, could I tell? Thank you for any help.
 
I havn"t changed the plugs yet. I took both of them
out and checked the spark. There was spark on each
of them.
 

Drop the Float-Bowl off, clean it well.

Then, maybe you will be able to blow (Brake Parts Cleaner) out the idle passages well enough to get it to Idle..
Sometimes there is enough rust, dirt and scale in there that you should drop the Main Jets and make sure all the holes in them are clean.

You really should do a Complete cleaning and re-build, to do it right..

Ron..
 
think of the mechanics involved - if you have valves that are stuck shut, you've got major problems!

A valve can't stick closed without a push rod being bent, a rocker arm being broken, a valve stem bent real bad - etc.

It CAN happen, but unlikely enough to go much further down on your "things to check" list.

Sticking open is a different story - but then compression wouldn't be there.

MUCH more likely that your carb is the problem.

I may sound like a broken record because I always reply with this answer but...

Spray some starter fluid in and see what happens.

If it fires, even just a little, you can be pretty sure the problem is in your carb.

(yes a weak spark may still fire on the fluid and not gas - but that's a relatively rare situation).
 
That running on one cylinder that you mentioned - I'd swap the plugs side for side and see if the problem moves with the swap. It never hurts to pop in a new set of plugs to see if there's an improvement. Three minutes and you've eliminated a possible bad plug issue. If no improvement, then get out the wrenches. Easy stuff first. Now that it won't run, I'd still try new plugs before I tinkered with anything else. A marginal plug will fire in the open, but might not fire well under compression. Good luck - you'll figure it out. Post back so we can all learn something.
 

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