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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No power valve. :)

Sorry whats a power valve?

To explain you have to understand that when the height of the exhaust port is low you have more torque and less rpm's. To increase rpm's we raise the exhaust port but suffer low end torque loss as a result.
A power valve in this plunger like thingie that sits in the exhaust port which makes the top of the port low thus more torque. Once a certain rpm is achieved, the power valve will retract thus raising the exhaust port for higher rpm's. It's to give you the best of both worlds.
Hope that helps. :)

Just seen pic.. WOW.. Not supposed to be like that!!!!!
OK, Let's make communication a lil more used friendly. I'll tell you the name of the part and you call it that.
Rear clutch: part w/weld is the post/fixed face. The other is the sliding face. Only discs are those flat/thin/fiber things that went on the rear clutch hub. :)
Front: Front outer is the fixed face and the front hub that hold the rollers is the movable drive face. Most call it a variator tho.
THe variator is stuck. I'd bet the previous installer let the notch slip off the keyway thus pinching it when tightened. Pry it off as careful as possible. Fair guess you'll be getting most all those parts new.
I prolly have everything you need here.

I really appreciate all the help. I would like a little more explanation of what to do with the power valve to fix it and once I get the variator off and get it pulled apart Id like to give you a call and see what you have. Probably most interested in maybe just buying two whole new clutch assembly's at this point. Just a whole host of problems in here LOL

Finally got the front off. Its also been tampered with before and the screws are semi stripped. I dont have time to get it apart before I go to work but I will tonight to see the condition of the rollers and see if anything can be salvaged. Definitely looking like im going to need all new. Man its bad lol.


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No powervalve. in rm250 motors and such. :)
We'll look at the variator when you get a chance to post pic. Your doing well.

So as you can see in the first picture I posted I bent that back cover piece with a pry bar removing it.

Got the screws out that hold it on, had to shock them with a chisel and ruin them but they came out one last time. Grease is rock solid and came out in formed chunks and the rollers are flat spotted and overall destroyed. Above and beyond that you will see in the pictures. It is a horrible horrible mess.

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It's just as I suspected. Prolly seen it 100 times.
Is the roller tracts in the variator gouged any?

Sorry to intrude in your thread mr jack but I been trying to find you for the longest time lol.
I got an lt80 I been working on for a couple days now I got it for 80 dollars in rough shape but I couldnt pass it up it had no airbox and plastics were rough sat for a long time. I have installed new crank bearings and oem suzuki seals and sealed cases for peace of mind and no air leaks. I also will port the reed and I have new boysen reed.
I was going to remove 2 of the rollers from the front clutch
and hold on the rear until the little one gets more comfortable riding this thing.
I got 14-26 428 sprockets and #40 chain with half links to make it tight
now the questions are the following.

what is the price for you to bore and port and mill my oem head?
I'm installing a chinese top end for now the bore was good on it and will be just to get it running to start it but I'd like a ported top end from you so I'll send you my oem cylinder and head.

Also should the clutch with the rollers be completely packed with grease or just enough to keep the rollers in place?

I removed the bottom plug of the pipe I will burn it off to clean it. I read that the stock one is a good I'm not interested in upgrading it if difference is minor.

Would running a pod vs a airbox be a problem?
. I have various machines and clean. My filter after every 2 rides

Aldo what else do you recomend doing for more power other than shoes in secondary to 175-180 and better spring?

Thank in advance jack.

Ps I know I'm working in the floor but I can spread my parts better there lol

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Its scratched as in a finger nail can feel the scratches in it but its not majorly gouged it doesnt appear with any chunks taken out

If you have a Dremel handy you can smooth those out...you just want to ensure the rollers have a smooth surface to operate as designed and shift properly...

It's not cool to hi-jack someone else's thread...especially a lengthy hi-jacking...be fair to this poster and start a new thread please so that we can address your specific queries...

I dont have a dremel but I have a die grinder I will find a softer wire wheel to clean it up and maybe smooth out some of the scratches in the soft aluminum. When I get the time I am going to sonic clean it and we can go from there.

When reassembled what is the deal with taking rollers out. I am using it for the time being till my daughter gets older and some friends and I race minis. Should I pull 2 rollers out like I often see people doing or just leave it factory with all 6? Thanks

Take a small round bit for your Dremel and rough up all the tracts. I use side to side motions. I prefer them a lil rough as opposed to a fine surface.
Leave all 6 rollers in.

Okay well maybe it's roughness is just right and I won't mess with it then.

So the surface the belt rides on is not perfect smooth anymore. It's not gouged but you can tell it's had alot of use and the belt as kind wore in in a few spots. It's still smooth and I don't think the belt will catch but it isn't perfectly flat. Should I try and surface that a little with an angle grinder and a fine resin disk or let it be?

Kind of odd the fronts are aluminum and the rears are steel. It was easy to clean the rears

Thanks

I could have missed it in the manual I downloaded but what is the best grease for the rollers? Or since grease hardening is a problem would any kind of a dry lube be better?

Also im buying some new parts for the front clutch and the key is almost completely buried under the starter gear. There is in no way sufficient key to mount the movable drive face too it. There is keyway though so do I need to take it off and inspect or can I just hit the starter gear back?

I'd use the Dremel and go over the tracts. Side to side motions.
Don't grind on the front clutch pieces. You can take a coarse (60) sandpaper and in lil circular motions break the glaze on them.
I only use a dab of grease on each roller to help hold them in place during installation.
The key only sticks out a smidge. That's where the roller plate notch goes. Once together and tight, it holds fine. You can remove and clean it up (I sand both sides to clean) but it prolly won't stick out much further if any.

Okay thank you.

On the keyway and key how much is a smidge? Can it be measured? I have less than 1/8 inch of key. I don't even know if there is 3/32 it doesn't look to be enough to engage the variator key hole. I took a picture and it doesn't even show up.

I can take a measurement with Calipers if you could compare it with a known good one because I do not find a spec for it in the service manual.

OK, I know it doesn't seem like much.. It isn't. Put the roller plate on the crankshaft and see if the notch/key grabs. I'm betting you will feel it grab. Like I said, you can pull the starter gear off and clean the key up. It may stick out far enough to satisfy your worries...
If you can measure it.. I'd say it's good.
Proper installation and tightening is more important.

Makes sense and I see what you are saying. Actually after further inspection it appears that what happened is the movable drive face rotated about 10 degrees and sheared off the corner upon further inspection. I only noticed this after cleaning off the rust and taking a good look at the plate. Its too late to order a new one because I already made an order and I dont want to pay 10 dollars shipping on such a tiny part that is only 3 dollars to begin with.

I think it still has plenty of length to it and just needs reset and turned 180 degrees. Ill pull the starter gear and file the key smooth and get it turned around. It is missing .005 of an inch so not a ton but it is enough to not let it engage the movable drive face anymore. Just needs the fresh corner on the outside.

I apologize I didnt mean to be rude just have been trying to find lt80 for a while I was not aware he was still active in forrums. Because I had planned to get my kids an 80
I have made a new post.
to continue with the thread do you carry lighter rollers for the primary 2 of mine are flat in one spot.
and a better spring for the secondary?
I'd like to give you bussines for all your 80 help vs finding them cheaper on ebay or else where.

again I apologize for hi jacking the thread.

I use rocky mountain atv for oem parts they're great with having stuff I got the keys as well and they have heelguards in stock for 22 which idk if yours are good or not but I just added to 75 and for free shipping.
idk if you wanna take that route or not.
if not I ordered 4 keys I can ship you 1 on saturday when I get home. I order parts for my quads often and can replace them as extra anytime I make an order.

I mean that would be great if you don't mind but if it's an inconvenience you don't need to worry about it. I can get one I just need to do the same as you and order enough to make it worth it.

Right now I don't have enough to buy to make it worth it though lol.

Side note I'm having a hard time getting the starter gear off since it's a little smashed into the key as well and also just slightly indexed off it. What does everyone else use to remove it? Slide hammer or puller? I don't have a jaw puller that seems to fit in the holes so I'm not sure what to do yet. It's buried too deep to pry it out.
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Maybe it's seized to the crankshaft...I'd heat the gear near the shaft and lightly tap with a dead-blow hammer...maybe also soak with penetrating oil...

I had no issues getting them out on the 2 machines I worked on...

They can be tough. You'll get it with enough swearing and a big enough hammer..LOL. :D :D
If you bend it (which I haven't seen in a loooong time) I have others here.

Well I was a little afraid to put heat to anything so close to a seal. I can try and do that though. I was thinking welding a piece of tube over the shaft and on the gear with a tab on the end to hit off.

Guess we will see how much I can ruin to get this thing off. LT80 I sent you a pm regarding the rear clutch if you haven't seen it yet just FYI.

Thanks to everyone again for all the help

Got the starter gear off and key out. Never seen a key torqued like this before. I thought I could turn it around and reuse it but not with the twist in it so I am going to get a new one coming. Too bad because I got all my new parts to rebuild the front clutch too.

LT 80 can you check your private messages please.

If your daughter isn’t old enough to ride it yet, 18mph is probably pretty damn fast. Most likely go much faster with a 40lb kid on it.

had a similar experience with an KFX50. Thought it was a dog, removed all the restrictors, shaved the head, got it cooking thinking I could slow it down with the throttle limiter. Nope. With a 40lb kid, the bare min throttle required to increase the rpm from idle will accelerate it up to a far to high speed for me to run behind. I have a 20’ tow rope hooked to the bumper that I hold him back with. Amazing how fast you can run while being pulled

Yeah well I mean technically I did buy it for her. But I've always had a little rig and I'll use it till she can. My buddy has a flat track we race minis on. This is making me want to convert from pit bikes to mini quads.