I have been monkeying with a 2003 LT80 for about a month now. I have to have 40 hours and $150 into this thing not that I am too worried about the money. Being a purveyor of vintage golf carts I know my around 2 strokes pretty well. With the LT80, I think I may officially have a parts quad on my hands. This is the first time I am pretty close to admitting defeat with a 2 stroke. Before I put it on Craigs List as a parts quad I need one last sanity check:

The thing just won't run. It will occasionally fire a time or two with the starter turning but won't come anywhere close to actually running.

Here is what I have done:

New head and piston. Compression is 115 psi.

Two new China carb attempts and a rebuilt original carb attempt. No change with any attempt.

Spark is there as it should be.

I thought I may have had a fuel issue so I checked both crank seals. Both looked fine but I went ahead and changed them anyway. No change. I checked the reed and it looked ok. I went ahead and replaced it anyway. No change. When I check the carb's air draw it is pretty strong. The plug is getting wet during the starting process so it's getting gas. Additionally, starting fluid has no effect.

It's the oddest thing. The old adage of gas + spark + compression = running engine simply isn't applying to this machine. Is 115 psi ok on this? Again, the cylinder and piston are new and I torqued to spec which is around 8 pounds if memory serves me correct. Not sure what else I can do if 115 psi is too low.

Again, this thing is on it's way to being a parts donor. I think my fear is that someone else gets it does something simple to it and I am out my time and money. This quad is probably only worth $200 running. Maybe $100 for parts as the tires are new. Just by way of my time I am already pretty far behind on it, though.

Before I go ahead and post an ad, can someone give me a sanity check? Is there anything I could be missing or is this truly a basket case?

 

Thinking this through. I am pretty sure that I have good vacuum in this cart. I still think I am having a fuel delivery issue. It hit me that these quads really don't have fuel pumps on them and those petcocks things somehow act as the fuel pump. How do those work? Do those go bad?

 

Petcock is just a tap, but on RUN the tap is opened by the vacuum provided by that pipe just in front of the cylinder. So when you turn the starter, the vacuum opens the tap and fuel can flow until the engine stops, so no vacuum, tap closes. There is a PRIME position where fuel flows all the time, for that first start after you have emptied the carb of fuel. However, if you leave it on prime and the float needle leaks, you get a cylinder full of fuel and the engine with a hydraulic lock the next time you want to use it.

In my experience the LT80 can be bad to start after a long lay up, but once running, they seem to start OK afterwards. I squirt butane gas from a blowlamp up the intake, most use starting fluid, but butane doesn't "dry" the cylinder walls (and bottom end on a two stroke) and I can often get the engine to fire up on butane.

 

Plugged pipe?

 

There is something up with my petcock. I happened to have a 3 line vacuum pump for a golf cart on hand. I replaced the petcock with it and hooked up the cart pump's vacuum line to the carb's vacuum nipple. Presto, it fired up and is running good. The golf cart pump probably can't serve as a permanent fix as they have no way of stopping the fuel flow. Gravity would flood it out. I'll go ahead and order me a petcock and will post up results but, really, this has to be what the issue is.

I still don't understand why it wouldn't fire with starting fluid into the cylinder but who knows with these things. Yes, I use the starting fluid with lubricant in it.

 

Even with a good petcock, I install a on/off valve (lawn mower section at auto store) and install it close to the carb.
Shutting off the flow and running the carb dry has eliminated a bunch of problems Plus you can use your golf cart pump then.

 

Thanks LT. Even with the on / off valve inevitably a kid will forget to turn it off and I will have hydro-locked engine, which actually happened earlier this year.

New petcock is here and installed. Indeed, that was the issue. Engine is running fine now. No CraigsList for this machine quite yet.

 

Your welcome but my reply stays the same. When the float needle sticks, the fuel in the line will flood it.
Running the carb dry when done riding (except for the time or 2 it's forgot about) seems to be very important these days.