My daughter was riding her KFX80 last weeknd and every now and then I would hear an intermittant rattle coming from the cover, like a rock was bouncing around in there. It ran strong, and I figured, "What the hell? I'll run it until it dies then take it apart..." The bike stopped running at the dunes last weekend, and when I got it home I just started pulling things off of it. When I was looking at the head, it had pieces of plastic melted in it. I could not figure out where it was coming from!!! I finally pulled off the air box covers and looked down inside the right side cover to see a fan. I was curious how it kept the engine cool, and now I had my answer. When I looked closer, I noticed that EVERY fan fin was broken off, and that was what had been flung up on the head and melted into the fins. Now that I know that, I'm pretty sure that the it overheated and now it will have to be rebuilt. It has about 30lbs of compression on it before the started can't push it anymore, but the battery is probably low too.

Has anyone ever seen the fan on the right side of the motor shear off all the fins? I bought this used, so god only knows what was done to it by the pervious owner, but he said it was all done at the dealer, and he had a K&N and FMF installed. I'm fairly well mechanically inclined, so I'll probably do it myself, but I need to find a service manual for it. Is it necessary to pull the engine to rebuild it?

Any thoughts are appreciated.
Thanks

 

I've seen plenty of fins missing. I'm not saying this is a problem area but for some reason it happens. Put a new fan on and it'll prolly last forever.
The cylinder was prolly bad. Doubtfull the heat did it all.

No need to remove the motor.
They make a manual?? LOL

FYI: use Suzuki parts...115 inch pounds on the head nuts...the head gasket can go either way.... arrow toward the exhaust...
No rocket science here. I'm sure you can do it.

 

As far as the fins go, what could have caused it? How they just break off? This is an '05, and it's all sealed up in there, so what could have caused it?

Do they make an after market manual? I have a LTZ400 manual from Suzuki and it's garbage, I had to go buy a after market one but I've looked around for a manual for the LT80 and the only thing I can find is the OEM.

When you say the cylinder is prolly bad, what do you mean? How did it get bad? It ran really strong but then it died. The plug looked likke it was spakled white, or ash coated so to speak, but it doesn't rub off, I've never seen a plug like it. How much compression should it have?

There's a guy locally that will rebiuld the whole thing for me for $500. That includes porting, milling the head, boring the cylinder I think, doing a clutch mod that allows the bike to downshift and work better etc. I've considered it, but I don't know what I'm going to do.

Can the cylinder be bored? You said use OEM parts, not aftermarket pistons? I've heard I should mix my gas and forget the oil pump, any thoughts on that?

 

Well I called the guy who offered to do all that work to ask a few questions...this is the second time his story changed for a different bike. Neddles to say, I won't be asking him to do the work.

If I were to bore it, how far should I go? If I mill the head, how far should I go to keep running pump gas? What else should I do/change while it's all apart? I'm going to do the clutch mods you recomended in the past, replace the belt, rollers, spring etc.

 

The stuff on the plug is aluminum. You've had a meltdown for some reason. It could be from wear. It is 6 years old now.
I have no reason for the fan fins breaking.
Compression should be 120. Your cylinder is fine, just needs to be bored. I'll presume that it's all stock. If that's the case, you'll want a .5 over piston. Yes, Suzuki pistons! Wiseco when the bore goes to 1.5 over.
You can shave the head .030 to bump up the compression and get the motor to run more efficient.
Better check out the carb (cleaning it). I'm wondering what jets are in it.

 

I saw the pistons labeled as .5 OS and 1.0 OS. If I go with a .5 piston, how much should the cylinder be bored? I assume 0.5mm over stock with a tolerance of +/- .01mm?

Shaving the head .030 will still allow for pump gas right? 92 I assume?

If I need a new chain, should I get the after market setup I've seen people talk about (can't remember where I saw it or what it's called) rather than the OEM one?

I've also seen you suggest that the OEM clutch spring gets weak when hot, do you recomend another after market spring? I will do the clutch mods you also suggested for this primarily stock engine, replace all 6 rollers in the front (I'm sure they're trash) and lighten the clutch shoes to 180 grams, and replace the belt. Does the manual describe clutch maintenance and intervals for it?

Do you do porting and what does it cost? And my last stupid question for now is the KFX and LT80 are the same except for the plastics right? I want to make sure I get the right parts, but I'm pretty sure they are the same.
Thanks for all your help.

 

You take the new piston and cylinder to a shop that bores. they bore the cylinder to the new piston. Piston to wall~ .0025 clearance.
89/90 octane should be plenty.

Chain/sprockets:: Order a 1988 LT80 12 tooth front and 26 tooth rear from Suzuki. They are 428 size. You should get a 13 tooth front (aftermarket), There's a good chance that you'll want one.
Then you can run 428 or 40 chain. I run #40 chain from a tractor supply or go-kart shop. Get 1/2 and master links. The machine will push with one finger with #40 chain.

Clutch:: For what your doing, the stock springs will work just fine. The belt is prolly fine too. The more they wear, the better they get.

Maintenence is cleaning and checking the rollers for flat spots (front). Lightly sand the rear shoes (in lil circular motions) to remove the glaze and check the bearings (rear).

The KFX and LT80's are the same. There has only been a few changes (like the 1988 428 gearing) but nothing that your dealing with.

Your very welcome.

 

I have a cd rom with the oem manual. all the stuff you need and more. pm me your address and I will send ya one.