LT80 turns over but won't start - ATVConnection.com ATV Enthusiast Community



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Old 01-22-2003, 03:22 AM
Weekend Warrior
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Default LT80 turns over but won't start

Help!

I bought a fixer-upper 1989 LT80 which had a bad starter relay on it, and hadn't been started in a long time. I've fixed the relay and it's turning the motor over good now. Drained the old gas out of the tank and carb bowl and put in new gas. Checked the spark plug and have a good blue/white spark. Tried ether down the spark plug hole, and through the carb. Removed the carb and checked the reeds and they visibly look ok (no visible cracks as i have read in this forum is a common problem). The only question is the compression, I only have a cheapo compression gauge that you hold against the spark plug hole when you're cranking and only get 60-70 psi. Anyone refresh my memory if I need to have the throttle all the way open during a compression test and isn't the actual compression on a two stroke higher than what can be measured on a normal gauge? will oil increase the compression enough to start it and let me know it needs a top-end rebuild?

Do the CDI's go bad and still spark? I'm not getting even a hint of an explosion.

hey LT80 any suggestions?

thx

jay



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Old 01-22-2003, 09:17 AM
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Default LT80 turns over but won't start

when you cleaned the carb and put it back on, did you put the fuel petcock on "prime",otherwise it won't fill the bowl very good, it is vacuum operated,and would take a while to get the carb to fill up cranking it. Try taking the air box off and squirt a little fuel in the carb,if it catches, you may have a blocked fuel line. The petcock has a tiny screen filter in it, if this quad sat a long time,it could be full of crud. If the compression is low enough, it won't fire, I'm not real sure on what you should see on the guage,you are correct, 2 strokes read lower than 4 strokes. Start with the basics, you have spark, give it a little squirt of gas and if it fires, you've narrowed it down. if you can get gas in, but no fire,(the plug stays wet) then it could be a piston or bad air leak problem. I never had a lot of problems with my son's LT80, so I've only done the basics to get it running. Hope some of this helps, and yes, LT80 -- where are you !!!!
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Old 01-22-2003, 09:32 AM
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Default LT80 turns over but won't start

It sounds like you did a good job of getting it ready to run. I suspect the compression to be the problem here.
Use spray wd-40 not ether [img]i/expressions/face-icon-small-wink.gif[/img] Yes putting oil in the spark plug hole will increase compression,but it isnt a fix.
Compression should be more like 130 (minimum). A better gage is allways recommended,but it sounds like yours is working.
If you have spark then thats prolly OK,ALTHO it wouldnt hurt to remove the flywheel and clean (I use an 80# sandpaper)seeins' that it's been sitting [img]i/expressions/face-icon-small-smile.gif[/img]
Let us know [img]i/expressions/face-icon-small-happy.gif[/img]
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Old 01-22-2003, 02:23 PM
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Default LT80 turns over but won't start

The spark plug is getting wet and at one point it got so much gas in the motor it was dripping out of the exhaust manifold gasket. That's when i removed the carb and checked the bowl, then i learned about the "prime" on this bike. That is new to me. I've had several motorcycles and atv's over the years and i've never seen that before. Does the ON and RES positions require the carb to pull the gas down to the carb then via vacuum? i see a second hose going up to the back of the petcock, i'm assuming this is vacuum and not a gas line? After leaving it on prime and figuring out what THAT does, I removed the spark plug and turned it over a couple of times to blow out the excess gas and let it set overnight to dry out.

So, i don't think it's fuel problem. I've taken the carb off and tried straight gas and ether through the intake (reeds) with my hand over it to control air (which I am pretty good at) and tried straight gas and ether in the cylinder too.

I had a 1986 LT250R that would be very hard to start when it got low on compression and needed boring, but it would still fire with a little ether and a couple of kicks. Is this LT80 so cold that it won't even try if the compression is that low? I can feel it sucking good on the intake side and it seems to be enough compression that it puts a good strain on the starter motor.

I saw someone say something about the exhaust on these being clogged up and creating to much backpressure, but it should still hit and at least turn over a little eh ?

jay
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Old 01-23-2003, 01:08 PM
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Default LT80 turns over but won't start

The pipe could be a problem,but doubtfull. If in question,have it acid dipped. (I've ran them momentarily w/o the pipe)
The fuel going into the motor is from the float needle sticking.I presumed on the first post that you had cleaned the carb properly,I see it was not done,Hope it has been by now (you've had it off).If not,,,,,,,,clean it [img]i/expressions/face-icon-small-smile.gif[/img]
Cranking it over a few times and let to dry "MAY" work. I have found that it takes keeping the throttle on fully and cranking it ALOT, is how they start after the bottom end has been flooded out.
Yes the petcock needs vaccum to have flow on run and reserve.The 2nd hose does that.
So now that you've cleaned the carb,we're back to compression if it still hasn't started.
Get that WD-40 yet? [img]i/expressions/face-icon-small-happy.gif[/img]
Will it fire with that low of comp.?? I'd say no! Especially if your gage is correct.
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Old 01-24-2003, 03:47 AM
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Default LT80 turns over but won't start


I left the reeds out for some time to let it dry out inside and charged the battery fully last night. Put the reeds back in, sprayed some WD40 down the hole and got 120 psi on the compression test today. Put the spark plug back in and it sounded like it wanted to start but i have a feeling it's because of the oil in the WD40 making the rings seal? Tried to shoot a little gas and wd40 into the intake and it didn't want to run. I've ordered a new plug, and i'm going to go through the carb tomorrow night, see what it may need and replace the intake o-ring cause it's compressed. Maybe it will run with a little wd40 and the carb back on tomorrow or whenever i get the carb built.

Looked inside beyond the fan today and looked to see if the flywheel had spun and saw where someone must have had it off because the washer that should have been under the flywheel nut was sticking to the inside of the magento. Removed it, checked the woodruff key and it was ok and re torqued the flywheel down. No mud and it was actually pretty clean up in there.

How much would you spend at a shop to have this baby bored out? I've pretty much taken everything off so a pro could get to the cylinder pretty easy.

later


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Old 01-24-2003, 10:22 AM
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Default LT80 turns over but won't start

Well,, <G> there is no washer that goes under the flywheel bolt. Hard to say where that came from.
If all that spray/gas only got it to 120 then it's looking even more like the top end is bad.When I do the same thing I can get 180+ compression.
Boring can easily be 40$, the piston kit is like 50-60$, piston pin and brg another 10$, gaskets 10$
Get a B8HVX spark plug [img]i/expressions/face-icon-small-wink.gif[/img] (10 bucks but well worth it)
I have parts in stock (depending on what piston size you need)
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  #8  
Old 12-22-2016, 03:02 PM
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Default I have the same problem

Quote:
Originally Posted by LT80 View Post
Well,, <G> there is no washer that goes under the flywheel bolt. Hard to say where that came from.
If all that spray/gas only got it to 120 then it's looking even more like the top end is bad.When I do the same thing I can get 180+ compression.
Boring can easily be 40$, the piston kit is like 50-60$, piston pin and brg another 10$, gaskets 10$
Get a B8HVX spark plug [img]i/expressions/face-icon-small-wink.gif[/img] (10 bucks but well worth it)
I have parts in stock (depending on what piston size you need)
I know this is an old post so hoping someone is still on here. I have all of the above problems. With the exception that I have good compression 150 psi. Can you help lt80?
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  #9  
Old 03-03-2017, 05:26 PM
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Default Lt80

Lt80 can you help me? I just put an aftermarket pipe on my LT 80 and now it won't start. At first it started up and Idled just fine. Let it warm up. I got on it to take off and it just died and now it won't start at all. what could be going on?
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  #10  
Old 03-03-2017, 06:50 PM
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1st guess would be the carb is flooding the motor out. Or, no fuel at all. See if the plug is wet or dry.
I'd prolly clean the carb anyway.
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