Pulling my hair out

We bought an LT80 in the fall that wouldn't start. After screwing with it a while it would run for about 10 mins with low power and would die. Compression was around 75 so I put a chinese pison and sleeve in it. Ran like a champ for 2 tanks of fuel but didn't idle very well each time we used it (in the snow). Last time it ran I ran out of gas in the yard. topped it up and it hasn't ran since. Took the carb off a couple weeks ago and the isolator was broken in about 6 pieces. New isolator and gasket are on. Pulled the reed and it has the stainless one still in it. tried the Boyssens and they didn't close properly, nor would it start. put the stainless one back on and i see no air around the valve. Cleaned bottom of carb today and idle jet looked clogged. Buttoned back up and still no luck.

Bike will sputter with starter fluid into the carb, or after pulling a few times with 2 fingers over the carb then held WOT. Fuel is pre-mixed 32:1 and oil tank is blocked off. spark plug has 4 hours on it. Current Compression is 110.

spark is good and it is getting fuel from the petcock to the carb and bowl is full when I open the drain screw.

Thoughts?

 

Can't say I have a solution at the moment, but for my own clarification, what is a broken "isolator"?

 

it's the black plastic part between the carb and reed valve. It must have been dried out I assume.

 

 

The insulators can break. Not too common. I suspect someone tightened one side too tight and then cranked on the other side.
When you took the carb off, did you remove the jets and clean all making sure you can see thru the holes in the carb body and jets?
Maybe a plugged pipe.

 

I'd try the following to completely bypass the carb...you need to pull the plug, shoot about 3 seconds worth of fluid into the plug hole, replace plug and then fire it up...if it runs for 10 seconds or so I'd say carb issue...if it wont start this way you have other issues...

 

Is that a good idea if you're depending on the fuel mix to provide lubrication? Doesn't take long to seize an engine.
But speaking of starter fluid, have you tried the old "spraying around the seals, gaskets, etc." to look for an air leak?

 

I see LT grandad and I asked the same question about jets. No answer yet.

 

I shoved this thing aside from frustration for a month and started playing with it again today. I just pulled all the jets out again and made sure they were all clear and made sure everything was cleaned up. Pipe is currently off the bike. Still no luck besides starter fluid into the carb.

I have tried 2 different carbs, I am at a total loss unless it is reeds.

 

Have you checked compression again? Those Chinese kits don't have the ports chamfered I believe, so you have to do it before assembly, if a ring caught on a sharp edged port it could do damage. Did you fit the rings the right way up. I didn't know they had a right way and couldn't weigh up why the rings didn't fit, Jack, on here, put me right.