So I picked up this 84 LT50 from a friend the other day for $100. He couldn't get it running and was gonna scrap it and I couldn't let that happen.
First thing I noticed was the carb. Every single screw on this Mikuni was boogered up and it was leaking fuel like a sieve.
I bought a cheap ebay replacement carb, cleaned out lines, checked the petcock, and filled with a fresh tank of gas (premixed because I don't know if or how well the oil injection works). Then I noticed that the intake has had the restrictor plate removed, so as per my research I also removed the primary pilot jet from the replacement carb before installing. I put in a new plug and checked to make sure it's firing. It has great compression when you pull it.
I also had read in my digging that these models are known to have the exhaust clog up and keep it from running. So I also removed the exhaust and cleaned it all out the best I could. I also removed the spark arrestor from the muffler.
So what I have is "what should be" a fully derestricted quad with fresh carb that has good compression, good spark, gets fuel, but won't start at all. I'm beating my head against the wall. Any tips,advice, or suggestions would be greatly appreciated !

 

Sounds like you have your arms around it well, but I think your missing one of the three......If your sure you have good spark and fuel, then I would go a step further and do a compression test even tho it may feel good ( to the pull ) as the comp could be low. I can't remember, but does the 50 have reeds? That could be a problem area.....if it has them. Could be stuck closed, cracked...etc.

 

I am definitely missing something. I don't have a manual, I'm getting all my info from the internet. What values am I looking for if I compression test ?
Also, it's been suggested that even though I see the plug firing, there may still be an issue with ignition. How can I check this? What should the coil be putting out ? Anyone know ?

 

See in red.

There won't be any issue unless the magnet or pick up coil has moved or the flywheel key has been sheared...and none of these are likely....but are possible. IRT to what the coil puts out...you just want a good bluish spark. Otherwise you would require a "spark tester" which you may not want to invest in.

 

Compression should be in the 130psi or higher range.


They can be hard to start...have you tried using starting fluid with cylinder protection? If it runs on that and dies then it's a carb issue...if it doesn't fire then it's a ignition/spark/compression issue...in any case it's a good idea to check the reeds...


You mentioned you pre-mixed the gas...but didn't mention removing the oil injection...does it have both or did you remove the oil injection?


Let us know if it runs on starting fluid...it's always my first step with a no-start...

 

Okay I will check compression
I have not tried starting fluid, but when removing the plug and spraying fuel right into the cylinder it wouldn't start either, which would point to spark or compression right ?
I did not remove the oil injection. I was under the impression that it ran off vacuum, and therefore would not affect startup conditions with the petcock in the prime position. Am I wrong to think that ? Do I need to take it off ?
I will repost with updates

 

The fiche don't show a reed cage. Only a inlet tube.
My idea on comp::: anything under 90= no good.

 

Yeah that's a big 10-4......no reeds.
I did end up hooking up a tester and checking compression. It was definitely way low ( 40-50psi) even after about 20 or 30 pulls.
So it looks like I'm gonna be ordering a top end kit. Luckily they are not that expensive for this make and model, it's just a little more work than I was hoping to do.

 

Thank you everyone for the assistance . I appreciate the help of fellow enthusiasts !
I will update with progress

 

piston set: .5 over:
Part # 12100-35611-050
I use Suzuki parts.