1988 LT80 won't start...

ggaspo13

Member
Jan 20, 2013
74
2
34
S. Jersey
Hey guys, I picked up this project 88' LT80 and have it pretty much ready to go but it won't run. When I first got it there was no battery, a bad cdi, the wrong size fuse in it, and a lot of missing parts. Long story short I bought all of the missing parts (still waiting on the battery to get here this week), put it back together, and it turns over with a jumper box hooked to the battery terminals but doesn't run. It has fuel in the bowl, new spark plug, spark outside of the cylinder when plug is grounded, 120psi compression, but won't start with pull start or jumper box. It'll turn over fine just not starting. Also when I hook it to the jumper box and try to start it, I blow the 5A fuse instantly. Any thoughts would be greatly appreciated...my son was in tears this morning when he saw all this snow and his quad not ready....DAD NEEDS HELP !
 
Ok so I'm thinking I'm blowing the fuses bc of the jumper box hooked to the terminals directly. The jumper/charger box has a setting for 50A engine start and that's what Im using for my powersource, which I believe to be too much....??? I always used this for my previous LT80 but the terminals were hooked to a battery, not sure if that diluted some of the power...not very versed in electrical, but 50A running thru a 5A fuse seems like it is bound to blow....?
 
Also, the LT80 has a foot brake which needs to be engaged to start the quad and mine will turn over, with spark, regardless of the brake being set.
 
if you are blowing the fuse while cranking then the starter is pulling too many amps, or the red wire that goes from the battery to the starter is rubbing the frame, i've had it happen once, and kept tripping the breaker (newer models have breakers) also check the starter mounting bolts, as they are the ground, they are on the clutch cover, two forward most bolts

as far as starting, sounds like you need to re clean the carb, they are a bit(h to clean, must use compressed air in every port on the front, there is like 3 i believe.and if you lost or dropped that o'ring that goes between the carb and black plastic insulator it will create a vacuum leak and not allow the engine vacuum to "pull" the fuel out of the carb and into the engine.

how is the plug after you crank it a few times and not start? wet? dry? they stock petcock likes to leak while sitting and will flood the engine, if the plug is wet after trying to crank it, keep the plug out, crank and crank with the throttle wide open, then put the plug in, hold the throttle wide open (with the parking brake on) and either crank it or pull start it.


i have tons and tons of lt80 parts, so if you need anything let me know, i have barely used boyesen reeds for them too.
 
Thanks for the response Kevin...I will check the grounds and red wire to try and resolve the fuse issue. So the latest - I took apart the top end to investigate...the piston is scorn and it looks like I will be rebuilding the top end for piece of mind. Not sure why the compression test showed 120psi unless I tested it incorrectly. Needless to say this quad will be waiting on parts and I'll move to the other LT80 I have torn apart waiting for me. I thought this one was going to be a much easier fix...thats what I get for getting my hopes up and believing the PO that it would be an easy fix !
 
Thanks for the response Kevin...I will check the grounds and red wire to try and resolve the fuse issue. So the latest - I took apart the top end to investigate...the piston is scorn and it looks like I will be rebuilding the top end for piece of mind. Not sure why the compression test showed 120psi unless I tested it incorrectly. Needless to say this quad will be waiting on parts and I'll move to the other LT80 I have torn apart waiting for me. I thought this one was going to be a much easier fix...thats what I get for getting my hopes up and believing the PO that it would be an easy fix !


i can almost bet that the compression was that high due to the carb flooding the cylinder.

quick question, when you push the start button, can you hear the relay clicking? im wondering if the starter relay is corroded inside and stuck, i've heard of it before, if you know how to read a wiring diagram and have a multimeter you should test that too, if you have a multimeter and cant read the diagrams well let me know and ill let you know what prongs on the relay to test

make sure when you put a top end in it, you point the arrow on the piston towards the back of the quad (exhast) cuz my first rebuild i learned the hard way.

i see that you are in jersey, i just moved to pa from jersey a year ago, lived in south brunswick.

if you need any parts or machine work done on the 80 i have to recommend moore racing, you can find him on atv connection under the kids atv section, he is from pa, his work is the best, and his prices seem to be set back in time lol. he does all kinds of modifications to lt80's, porting, clutch mods, carb mods, and he does offer boring and top end kits
 
IMG_0928.jpg IMG_0929.jpg Here's the piston...
 
another thing i noticed in the pic is the oil pump is removed, did you remove it during the tear down? or did the previous owner remove it and you didnt know?
 
i can almost bet that the compression was that high due to the carb flooding the cylinder.

quick question, when you push the start button, can you hear the relay clicking? im wondering if the starter relay is corroded inside and stuck, i've heard of it before, if you know how to read a wiring diagram and have a multimeter you should test that too, if you have a multimeter and cant read the diagrams well let me know and ill let you know what prongs on the relay to test

make sure when you put a top end in it, you point the arrow on the piston towards the back of the quad (exhast) cuz my first rebuild i learned the hard way.

i see that you are in jersey, i just moved to pa from jersey a year ago, lived in south brunswick.

if you need any parts or machine work done on the 80 i have to recommend moore racing, you can find him on atv connection under the kids atv section, he is from pa, his work is the best, and his prices seem to be set back in time lol. he does all kinds of modifications to lt80's, porting, clutch mods, carb mods, and he does offer boring and top end kits
- If the cylinder was flooding the cylinder does that mean the crankcase oil will probably be fill with gas too?
- I do have a multimeter but not sure how to test the starter relay.
- I actually have another LT80 project going rt now and it needed a top end rebuild. Installed the new piston tonight, and yes the arrow is facing the correct way...but just went down and checked and the LT piston I posted pics on has the arrow facing forward...didn't even think to look at that when I removed the cylinder.
- the guy I just took my cylinder to charged me $65 for bore, and i got wiseco top end kit off ebay, but if your guy saves me money I'll send it his way
- Yeah I'm in s. jersey right across the bridge from philly
 
- If the cylinder was flooding the cylinder does that mean the crankcase oil will probably be fill with gas too?
- I do have a multimeter but not sure how to test the starter relay.
- I actually have another LT80 project going rt now and it needed a top end rebuild. Installed the new piston tonight, and yes the arrow is facing the correct way...but just went down and checked and the LT piston I posted pics on has the arrow facing forward...didn't even think to look at that when I removed the cylinder.
- the guy I just took my cylinder to charged me $65 for bore, and i got wiseco top end kit off ebay, but if your guy saves me money I'll send it his way
- Yeah I'm in s. jersey right across the bridge from philly


so it was the usual case of arrow pointing forward, that sucks, it does a good amount of damage when those rings catch a port.

the lt80 does not use crankcase oil, the premix lubes the entire crankcase, it does have trans oil, but they arent connected at all so there is really no way for the fuel to get to the trans. i will look up the wiring diagram and let you know what to test on the relay. of course if it was together you could have taken the relay off the other one to see if that changed the situation.
 
I know this is an old forum but folks like me do look at these for help so I'm going to add my experience. My kids have an LT80 and we have had most of the problems y'all have discussed. Here's my experience:
- make sure you have gas in the bowl. There's a little phillips screw that drains the bowl. When you open it gas should come out.
- make sure you have spark
- make sure the exhaust is not restricted. Remove the bolt on the bottom of the muffler to drain any spooge. Feel the exhaust while it's cranking to make sure it's clear.
- the auto oilers on these are notorious for leaking into the carb / cylinder. With the spark plug out, turn the motor over. If it's full of oil it'll blow out everywhere. Do this outdoors and have a fire extinguisher handy anytime you crank over an engine with the spark plug removed. I recommend disconnecting the auto oiler contraption and using premix.
- if the petcock leaks, and they usually do, it will overfill the bowl and flood the engine. When we get done riding I remove the fuel line from the petcock to the carb and drain the tank. If you ride often then make sure that petcock is sealing tight! A drop every few minutes is enough to flood these things and they'll never start.
- if the starter fuse is blowing you've probably either got oil or gas in the cylinder and locking it up.
- NEVER EVER use ethanol gas. It'll destroy any 4 wheeler, outboard, chain saw, etc.
- install a brand new spark plug. That simple thing solves a lot of hard-starting problems on 2 strokes.
- if the carb needs to be cleaned, and it probably does if you've got gas, spark, aren't flooded and it still won't start, make sure to clean out both jets. Pluck a wire out of a wire brush. Remove the jets and rod them out with that wire. Remove the choke assembly. In the bottom of the hole it came out of there are tiny passages leading to the throat of the carb. Make sure they are not clogged.
- finally, when you do get it running right, install an inline fuel filter. Never let it sit for weeks without draining the tank and the carb.

These machines are not hard starting by nature. When everything is right, it'll crank up instantly even after it's been sitting for months.