1987 Suzuki LT80 speed problem
 

Hi there,

I just recently bought a non running 87 LT80. Its been a fun little bike. Clean the carb, new petcock, new boyesen 2 stage reed and battery and we were in business. After a little riding I feel like it just didnt have the speed it should even for a kids quad. Looked up top speed and sure enough they should do about 30. I cant get mine past 18. I bought it for my daughter who isnt old enough to ride yet so I have some time to work on it which is no big deal but now im getting frustrated. I just want it to work as intended and it doesnt seem to want too.

Thought the belt might be worn to the point it wouldnt engage any faster. Took the secondary clutch off and replaced the belt. Used belt was worn and skinnier than a new belt. It had been messed with before and the left handed nut that holds the assembly together was welded on and the back disk around the bearing was welded (weird). Anyways I grind the nut off and inspect the clutch disks and clean the rust, grease the shaft and resassemble. Had to do a light tig weld to hold that retaining nut on again. New clutch is in order but for now thats not the biggest issue. Get the clutch back together with a new belt and still wont go faster than 18 MPH. I can turn the secondary clutch by hand the full range of motion. However when running the quad with the case cover off it looks like the clutch disks only used 3/4 of their travel under full engine RPM (as much as I could get) on a stand.

The machine can be a little cold blooded when starting but its also been 20 degrees here for a while. When warm it runs awesome, takes off great, great midrange power. But what happens is it just flat lines. Just stops revving. Its not slipping and the engine doesnt seem to be limiting out. Thought it was being starved for fuel somewhere. Checked the plug and not as oily as I would like to see. C clip at the needle in the carb was all the way at the top. Well put it in the middle and it didnt change much and put the c clip at the bottom of the needle to open it all the way up and it changed my top speed to 15 mph. Seems like it over fueled it. Replaced the c clip at the needle in the second space down which seems to work best for now and it got me to 19 mph. Jets are factory sizing.

Above and beyond that I am stuck and I dont know what to do. Can anyone give me any insight where to look next?

I didn't see where you serviced the front clutch. You will find that the rollers is the problem. There could be other damage in the front also depending on the conditions you find.

Well I did not service the front clutch. I have never had a cvt machine before and I didn't know much about them. In the last few days reading it appeared to me that the rollers and weights had more to do with the stall and take off of the machine. But I have not dug into it yet. Really because I don't know what I'm doing there.

What should I look for and what parts should I buy for the front? Should I get new oem rollers? Do I want to take any out like people do?

Thanks for the response. After reading lots in the last week I want one of your engines eventually.

Suzuki used to pack the front clutch with grease. The grease hardens and stops the rollers from traveling. This is why you have no speed. Plus you don't know what the previous mechanical wizard did.
You'll need new rollers at least is my guess. There is also a good chance you will need the roller plate and possibly the variator (piece that holds the rollers). Clean and inspect for gouges and such.
I recommend you look at a online fiche so you can understand the parts involved. Most dealers have them. Transmission 1 (front) Transmission 2 (rear).
Other than the crank, tranny (gearbox), and post bearings, I only use Suzuki parts.
Oh yea.. Weld on the back disc. That part is the post and it does look like that. You needed all that new anyways. I'm presuming you got a new post. Did you get the 2 bearings for it (big and small)? FYI: there is a clip inside the post that holds the little bearing in place. Go in the closet and dig out the ol' hemostats to get that out.. LOL! :D :D

Well thanks I'll get it torn apart and see what I need now that I have a place to look. I wouldn't have guessed that. Mostly didn't understand it so I appreciate the help.
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Well good to know the post on the back of that disk is supposed to be like that. Looked weird because it's just a bunch of tac welds. No matter what I do need a new one eventually because that top nut is welded on. There is slight pitting low on the disk too from where the rust is indicating this has been a problem for a while. The bearings are not great but spin freely. I did not replace them yet in anticipation of new clutch disks. I just went through it quick to see if the rust was the issue mostly which if ass not. The drum and pads look good so I think I just need a new set of the disks. Because they work for now I will look into the front clutch and report back first.

My only issue is even though the front clutch may not be working correctly it still doesn't Rev enough in my opinion. I have a digital tac that runs off the spark plug wire which doesn't seem to work either or else I could confirm rpms. But what I mean is that I doesn't slip at all. It's not like I hit the power band and it doesn't turn. It feels limited on how abruptly it stops power. It's so close the power band and sometimes you get a small surge in power like it's about to pull more and then doesnt. Just kinda weird. Can't wait to look into the rollers though and get this thing moving quickly.

"what happens is it just flat lines. Just stops revving."

Jack knows a lot more than me about LT80s, but are those not the symptoms of a plugged exhaust?

LT 80 my last post didnt post so I will try to recap what I was thinking earlier tonight. But anyways I will get that taken apart asap and report back and get parts coming for what I can tell is messed up.

The weld on the back of the post looks odd like a bunch of tac welds. Doesnt quite look factory. Ill try to get a picture tomorrow or the next day when I get a chance to work on it again.

I have not got a new post yet because it still works. I did not get new bearings yet I am waiting to figure out this speed problem and order the rest of the parts I need at once. But as of right now the secondary clutch while stupid, works. Bearings spin, disks move freely. I actually have all the parts picked out in my shopping cart at partzilla to the tune of about 220 dollars just in clutch things. Waiting to see what else I need to buy in the way of parts to get it all here at once.

merryman, I checked the exhaust at the head for the restrictor plate or washer and did not find it. Other than that it seems to be flowing out the back as well as it can for as tiny of a pipe that comes off the muffler. When I dig into this bike again I can take that off and run air though it to make sure there is nothing in it.

When you remove the pipe, stick it in a fire and get it red hot. Blow air thru it. Careful, it'll throw flames.
The parts you are referring to is the post and sliding face (rear clutch). I agree, if it's working now, use it.
The rust on the post or sliding face is ok. I see them pitted all the time. The pic of the weld would be nice.

Exhaust pipe blockage ... I had a KX 125 that screamed, then one day wouldn't. Tore the carb apart twice before taking a screwdriver and knocking the mud dobber nest out of the tailpipe.
Little bugger built it in between weekends, spooge and all.
You also never know if the last owner left a rag in it (done that too:rolleyes:)
Also had a a "gimmee" that had all the factory correct jet sizes, but the previous owner had run a drill bit through one. Couldn't tell until you held two similar jets side by side. Obscure and not likely, but possible.

Since I am not familiar with this particular two stroke, does it have power valves that change the port timing? That would limit peak rpm's.

Well I have not removed the pipe and stuck it in a fire yet. Need to go to a friends house I can start a fire and get it done.

However I did take apart the case again, and the outside disk of the primary clutch was easy to get off but the back disk and little spacer ring on the shaft seem to be stuck. After some working it I got it to move almost a 1/4 inch out but not enough and its stuck on there good. There seem to be wear on the disks. I hit the stuck disk with penetrating oil at the ring which is why its greasy it was clean when opened up.

Also in the pictures posted here is the condition of the rear clutch. Those tac welds I was talking about and the stupid stripped nut I had to grind to get off and then tig weld very gently on again for fear of heating the bearing. Which is bad and it all needs replaced anyways but at least it allows me to use it for testing purposes. Clutch is rotates freely and smooth.



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