I have used Slime in my tractor and mower tires with good results.  It seals the holes that can come from thistles and sharp twigs, etc.

I once used a cheap "CAMEL" brand in the front of my lawn tractor tires, and it dissolved the rubber inside the tire and all the cords came loose - and the tires got all funny shaped as there was nothing holding them together.  When I took the tires off the inside was filled with sticky goo and strings.

On one group ride in TN/NC we pulled under the porch roof of an abandoned building to get out of the rain, and I got a piece of glass stuck in my tire.  Not knowing if the glass had gotten to the tube, we bought SLIME and put it in the tube of the front tire.  I didn't notice any ill effects from having it in the tube.  When I changed that tire I discovered that the glass had not gone deep enough to get to the tube - so the slime never had to seal anything.

I have never had tire sealer plug up a valve stem - but I have had it blow slime into my air gauge when checking tire pressure.

I put it in when I put my new front tire on last time … but it already had a couple of oz's in it … then months later I forgot I had put it in and put it in again … (maybe 12 ozs total was way too much) (4 ozs in a bike tire is a lot).


Well , when I got to Texas this year and tried ridding 70-75 mph on ruff Texas roads I found that too much slime is not good.


Apparently , the slime also blances the tire if there isn't TOO-MUCH of it  in there.  So best I can figure the tire would be rolling along blanced OK then a jolting bump would put the slim to moving out of blance.    

At the camp site I worked about 8 ozs of it out the valve stem and then things worked good for the next days ride and all the way home too , and still is good now !

I'm thinking 4ozs for the back and 3 ozs for the front is about right.
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The first time I used it 30 years ago I had found a product in my local motorcycle shop call "Sealer & Balancer" in a 12oz bottle.  
I had just had a flat (rear) on my CB500 while ridding double, down hill , with a curve at the bottom and running about 65mph on a 55mph road.   I didn't like the experience very much.    Back then I'd carry a patch kit and a basket ball pump , so I made it home Ok but was at the shop getting a new innertube when I saw this new product (Sealer & Balancer) , I had to try it...        

I haven't had a flat out on the road since .