2000 yz 80

[Georgiaboy1286]

Hello everyone the name is Paul and I'm a New to the works of dirt bikes.
So my problem is I was given a fairly decent Yamaha yz80 with what was believed to be a seized engine. For fixing a 4 Wheeler for my buddy. Upon taking out the engine everything looked fine I can even turn over the engine with a wrench fairly easy. So I guess my question is of its seized should I be able to turn it over and secondly I think threes problem is in the kick starter. The gear seems to be catchicasng part of the engine case. Thanks for the help

 

[_JOE_]

Sometimes an engine will seize then free back up once it cools. I'd pop the cylinder off and have a look. If all looks well then reassemble with a fresh piston kit. To check the kickstart assembly you'll have to pull the clutch and right side engine cover. You'll need some gaskets for this. Check the water pump bearings and replace the seals while you're there. Look at the clutch plates, the fibers should have grooves in them, if they're smooth they're probably toast. Look for damage to all the gears and cases. It should be apparent if there was any contact with the cases. Take pictures and upload them here.

 

[Georgiaboy1286]

Well I just got done with all of that. I have no clue about clutches or anything like that. But I did look over every thing. all the gears look good but there is a spot on the case where the kick start gear was catching it. Im assuming that the last person just didn't put it in right. I wild the spring up an extra spin and the kick starter its working fine now. But can't get the damn thing to fire. It will turn over tho. Like I said I'm new to this thing so this is probably gonna be a stupid question lol. I put everything back together and installed the engine back on the bike all but the fly wheel or stator. Whatever you all call it. Does this need to be pressed back on or just run a nut on it and tighten. And does it have to be on the bike in order for it to fire

 

[_JOE_]

Yes, you need the flywheel on to get spark. No pressing involved, just torque the nut. Make sure the key is in the crank and the flywheel is aligned.

 

[Georgiaboy1286]

Fly wheel back on nothing is sticking now. But no matter how fast slow or how many times I kick I cannot get this thing to start it sounds like it has good compression. Do these bikes need back pressure? Should I put the pipe back on. Or would that be a waste of time?

 

[_JOE_]

How was the cylinder? New piston?

 

[Georgiaboy1286]

Cylinder looks great. Piston not so much... There are some small grovea. Also at one point the kick start got so easy that I could polish out down with my hand. Is this right? No compression? Also I contacted the guy who owned it before my buddy he said that the water pump went out. So could there be small pieces of the water pump on the bottom end. And there also some dark purplish coloring on the crank and the arm. Is this a sign of over heating? All don't under stand why I can't get out to fire.

 

[Georgiaboy1286]

Cylinder looks great. Piston not so much... There are some small grovea. Also at one point the kick start got so easy that I could push it down with my hand. Is this right? No compression? Also I contacted the guy who owned it before my buddy he said that the water pump went out. So could there be small pieces of the water pump in the bottom end. And there's also some dark purplish coloring on the crank and the arm. Is this a sign of over heating? I still don't under stand why I can't get it to fire.

 

[_JOE_]

You need to the cylinder inspected by someone with some experience. If it was overheated to the point of causing discoloration of the crank you'll need a complete lower end as well. The water pump is a very simple design with few parts. The chance of it cuasing debris is slim. It's also impossible for that debris to get into the crankcase.

 

[Georgiaboy1286]

Hey yes I'm back.... So I've ripped my engine back apart and I'm gonna replace the crank arm and piston what numbers on the piston do I go by to figure out what size it is

 

[Georgiaboy1286]

Also as I stated before I don't know much about dirt bikes. How do I tell If the bike has power bands

 

[Georgiaboy1286]

Scratch that last question. That prob.just made me sound like a ****ing idiot. lmao.... I figured it
out out. I think.

 

[_JOE_]

Lol. If you DIDN'T figure it out, all engines have "powerbands". In most cases you're better off buying a complete crankshaft assembly than you are buying a rod kit and paying a COMPETENT technician to swap it out. I'd check into it and see what a new crank assembly would cost vs a rod replacement. As far as the bore size, you need to have that measured by a COMPETENT technician to see if your bore is standard size. They should also check for oval or tapered wear when they do that. These engines aren't very tolerant of being put back together half-assed. Take your time and spend the money to do it right or don't bother. Good luck! Hope you can get her back together without too much hassle.....

 

[Georgiaboy1286]

Yea I googled it right after I posted.... One thread said something about the wider the power band the more hamsters that will fit so that's Why bikes with wider power bands are faster lmao... I was like great I'm officially a dumbass. But I found a crank assembly gaskets seals and bearings on Ebay 125.00 bucks and a piston kit for 130.00 buck Both wiseco is this a good price in your opinion. I'm afraid that the "COMPETENT" technician might screw me cuz I talked to him and got him to pull the flywheel off and while I was there he priced some things for me and it seemed a little higher than what I was finding

 

[_JOE_]

Things are tough for the small shops these days. You can buy the parts at about the same price he pays. He's gotta make something. What year is the yz?

 

[Georgiaboy1286]

2000