I think your engine uses a carb with a diaphragm. That's what I would change first.

Thank you for the reply but I have changed them already including with old carb and new carb. Diaphragm down first then gasket.

brad

I didn't notice about the new carb. Have you tried a small amount of carb cleaner to start it? Does it attempt to run at all? Is the plug dry?

I have tried starting fluid, carb cleaner, and a teaspoonful or so of gas and no luck. It acts like it wants to start and if I do get it started it runs about a minute poorly with no throttle response and dies. plug is wet but not overly so

brad

did you hit something with the blade?

No. Maybe it is just worn out.

Did you check to see if your flywheel key is intact and holding the flywheel and driveshaft in alignment? Otherwise it could affect the timing to an extent that you would get the symptoms your describe. The flywheel key is made from a light metal such as aluminum and is designed to shear if the lawnmower hits an object hard enough to stop the engine. Since the timing of a magneto ignition is dependent on flywheel alignment, the key is very important to inspect.

You say the "new governor spring does nothing." But it should be holding the throttle open, when the engine is stopped. The vane will pull the throttle closed, as it moves against the breeze generated by the flywheel.

To confirm spark, hold the plug end terminal in your hand. Have your daughter pull the engine over with the plug out. If you get a belt , you have good spark. If you get just a tingle, you dont. Yellowish spark doesnt bode well, you want a blue spark. Also it doesnt take much of a shear to the key, to throw the engine out of time. They cost less than a buck at the store. Buy a couple.

That's why I asked if you hit something. If your flywheel nut loosened, this could also happen.

Here is a link to at least look at your key without removing the flywheel.

http://forums2.gardenweb.com/forums/lmower/?11080

I appreciate all the suggestions and here is the followup:

flywheel key is intact
get a whallop when I hold the sparkplug cable
flywheel nut tighten to repair manual specs
new governor spring does nothing different than old spring does. Works as it should. Sorry I did not make that clearer.
See what I mean, this is making me go bananas. It should fire.

thanks for all the suggestions though, I'm going to figure it out if it kills me. I must be over looking something but I just cannot figure out what. Is it possible that cam lobes are just worn out or possibly something else worn out inside. Not much to these and this is why I'm going coo coo. At this point I thinking about gutting down to the block, taking measurements of critical parts and re-assembly. I've got the time and I enjoy the heck out of doing this kind of work but then again if not needed I dont want to spend time doing something I dont need to do.

thanks all

brad

I hate it when a thread is unfinished like this one. Brad, Brad,....post back man! What in the heck was wrong with that 3.5? It's like reading a good book only to get to a lousy ending.

check and see if the carb intake tube is cracked /broken had one do that to me .let me know

'Guess it might be time to take her out back and drop a few rounds in her'

Been there but never actually did it. You can find some vids on You Tube of shooting up mowers, complete with fires, etc. Of course it's better to shoot them while running, which sort of begs the question 'Why shoot a running mower?'. LOL

Just wondering if yours is old enough to have a mixture screw. Also, what is the condition of the fuel? Old, watery? Any crud in gas tank? Fuel pick-up tubes clean? Condition of air filter - clean and lightly oiled? Observe choke plate with filter off - does it move freely and spring back to choke position when released?

Just some random thoughts.

dont give, up just repaired a newer 3.5 and was doing the same thing found the plastic carb intake tube was cracked replaced tube ,not a hard job.runs like new.

I have not given up. I have actually completely torn down the engine. Taking measurements to see how far off critical measurements are according to service manual. Before tearing down I checked but did not see a crack anywhere on the carb including pickup tubes. I was able to try a new carb and still no luck getting her to fire. I'm thinking it a spark issue, possibly at the wrong time. I have adjusted timing many times and nothing. Anyway at this point engine is completely torn down and I'm taking measurements. Also waiting for gaskets so I can re-assemble. Have not had time to check but maybe a gear is broken or something to that affect. Unfortunately I do not have a mag that I can switch out with this one to determine how well mine is creating spark. I'm pretty much convinced at this point that it has something to do with sparking at wrong time but as said before adjustments did nothing. I am also going through mid terms next week so I wont have a chance to proceed on the work for a few weeks but rest assured I'm not giving up. Unless parts prices prohibit repair on this old puppy it will run again. Thank you all for your replies and I will be back after finals mid terms next week.

Brad

Now THAT is dedication!

I understand your determination, Brad. I'm the same
way. Even if it's something I know I can't fix, I HAVE
to tear it apart, (like the last computer hard drive that
went bad on me). And, if and when you do find the problem
and do fix it, there are sometimes mixed emotions. Fixing
the problem gives you a great deal of satisfaction. But
finding that the problem was a very simple one, and you
didn't have to go through all of that work, can result in
a sore forhead, but a good learning experience.

When reinstalling the carb/tank make sure the throttle on the carb is positioned correctly. I reinstalled one and the the throttle was in the choke position on the stop. Once installed you should be able to move it back and forth freely.

Ok all, here is where I am at now. A complete tear down and parts measurements has revealed this old engine is still within specs but a few of them are just barely making it past the rejection point. I mean .0005 and that is cutting it close. I will reassemble the short block next thursday at school and then bring it home and reassemble the top half. Will probably take another week or so past that as life gets in the way. Anyway I also plan on baking the mag/coil for 20 minutes at 200 degrees as I still think that is the problem. Dont have another to try and wont spend the money for this old engine.

Anyway still having a blast and learning. This is my first complete tear down and the simplicity of the engine is amazing. I have learned so much and never again will my machines go to a shop I hope.

I will report back when short block is done and keep this post going until she is back together.

Brad

Another natural-born mechanic; the best kind.

Ok for those following this thread, here is where I am at now. Upon closer inspection of parts I have found that the upper piston ring was stuck to the piston and not free floating if you will. This has been gently pulled away and believe it or not the rings are within specs. Found this a little hard to believe so had a friend measure them and they are good. I did find a small glob of what looked like solder on the ridge. It seems as if the engine has been overheated most likely from low oil.

First I took a honer or what I call a glaze breaker and ever so gently honed the cylinder. New measurements reveal I must have been gently enough. Then I took a ridge reamer and removed the glob of solder looking stuff. Cylinder looks awesome. Anyway this blob it seems to me was causing excessive blow by and this explains the ungodly amount of white smoke I got the few times I ever got this engine to turn over.

She will be going back together soon so stay tuned.

brad

"She will be going back together soon so stay tuned." Too cool... I'll get the popcorn! Pretty darn neat that you are sticking with this and keeping us up to date.

Rings are measured by 'end gap'. Use the piston to push the ring down towards the center height of the cylinder and measure the end gap.

In my earlier days as a Triumph motorcycle mechanic, it was always necessary to file the ends of their non-consistent rings.