I just bought a used 1990 LT 80. I got it running today and it makes a vibration/knocking noise when idling and not moving. Once I give it gas and get it going the vibration/knock goes away. Is this normal? Also, where can I get a factor service manual? I need a good source of service information on this quad.

Thanks for the help,

Matt

 

It might be your starter, the spring gets weak and it will make noise. Other than that just start looking for loose or missing bolts.

 

piston slap??

 

my sons did the same thing when i got it,and is now doing it again,does noise stop when you put weight on it/sit on it??,took mine to the dealer,it's an old one '87, and they told me it was the shocks, after they milked me for 300.00 and it still did it they said they were stumped & wanted to charge hourly to figure it out. no way,i replaced the front bushings & it stopped, now its doing it againthere are 3 sets of bushings,2on the frame,2on the motor mount,&2 on the front of the engine case,the first set are the ones i replaced the easy ones,i now beleive the other ones are bad,if you have the same problem as mine you can grab the grab bar in the back and shake the lt80& feel slop, it should feel pretty rigid,i can also take a prybar and lift the engine away from the frame an inch or so,that's were my rattle comes from,the bottom of the motor tappin the frame, i dont know an easy way to replace those other bushings yet, the 2 dealers near me wont give a price they just say hourly,& i wont do that again. anybody out there thats changed those bushings??, i would love to know the best way.

 

Sounds like the rollers to me. This happened to my sons LT80, one was stuck and it make a bad noise at idle, once the clutch moved it no longer made the noise, I discovered that one roller was stuck and the other rollers were banging around. Hope this helps

 

Welcome to the forums lt80racerdad.
Quadnut: the bushings press in and out. It's not a complicated thing, just time consuming.

I agree with lt80racerdad, the clutchs need to be serviced to eliminate that aspect of it.
The piston slap post was a good idea also. Compression reading?? I've taken LT motors out and put a next size piston in WITHOUT boring. They seem to run forever. This is why piston slap "may" be it.
Quaduck makes a good point too. The starter will make a bell ringing noise if the gear comes out and hits the starter gear.
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Thanks for all the ideas. I think my problem is the bushings. It looks like the engine is vibrating against the frame. I will look into replacing the bushings.

Thanks,

Matt

 

hey GB, if you get those bushings out,let me know how it worked,when i tried i didn't want to dissasemble the whole thing,take the pieces to a shop etc., i removed the long bolts, nuts ,washers, and tried to drive them out with a deep impact socket/hammer& they wouldn't budge so i stopped,worried about cracking something, i read in a post last year that this would work by heating it up ,i tried map gas and they still wouldnt budge, i dont have a press, so i was trying what i had, if i have to take it all apart,&take the pieces/motor to a machine shop i guess i'll just have to,if you succeed i'd love to know what worked ,what tools you used etc. thanks

 

hey LT80, i would like to say, that i consider you to be the #1 authority on these lil' quads,from everything i've read on here, to all the help you've given me, the clutches ,carbs,chain roller,sprockets etc. , so i take your advice as gold, if you could list a few details on those bushings that would be great, i'm a fairly mechanical person ,but on a limited budget,& i hate to be forced to take anything to a dealer/shop because of my limited skills/tools because in my area they rob you every chance they get, i am yet to walk away from a shop of any type satisfied, i have never had anything work as good or better than it did before it broke, from auto trans to atv's to outboard shops,they just fix it good enough to get paid,then when it fails a week later they wont repair it, so i have been forced to become a mechanic,& i do enjoy repairing things it's what i do for a living" building trades", it just really sucks to have to spend every free moment repairing things that i could afford to drop off, if i knew they would repair them properly. it is nice to have sights like this,& people like you & alot of the others on here to give honest advice to help people like me. thanks again for your help, and back to my question, do i need to invest in a shop press for those bushings??,i can get one for about 100 bucks, i'm sure the shops in my area would charge that or more to remove/install those 4 bushings. thanks again my kids get alot of joy out of those 2 lt80's we keep running for them, thank GOD they're not daredevils or racers.