Quick question on an old kx 80
 

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RE: Quick question on an old kx 80
 

you might consider checking / regrinding the valves.. could be carbon build up that is allowing the compression to realease...

Id also check the spark and if its weak, change out the points??(How old is this bike??)

Thats my two cents...

RE: Quick question on an old kx 80
 

Its a two stroke--it has no valves. It may have a power valve but thats a whole different animal--just alters the height &/or volume depending on style of the exhaust port.

Sounds low. 80cc two stroke + old = top end job minimum. But they are super easy & cheap if not a coated bore. Course all the usual--carb plugged? getting spark? questions apply too.

RE: Quick question on an old kx 80
 

First thing is to replace the plug! Two stroke foul plugs all the time. If the plug is fouled it will not start!! I don't know how long its been sitting but I bet the carb needs to be cleaned out. 30 psi is low.. you might be able to get it to start but it wont have much power. A new piston and rings is not that expensive I would say around 100 bucks or so...good luck!! Hope this helps..

RE: Quick question on an old kx 80
 

I was thinking more along the lines of the exhaust valves, I know my CR125R was prone to carbon build up on the exhaust ports.

This might help:


Compression Testing

A compression tester is a useful diagnostic tool, and readily available from Sears or auto parts stores. Buy the threaded type and make sure the kit comes with an adapter that matches the spark plug threads of your engine. Performing a compression test is simple. Start by removing the spark plug, thread in the adapter, and hold the throttle wide open and the kill button on. This will prevent any spark and enable the engine to draw in maximum airflow. Then kick-start the engine several times until the needle on the pressure gauge peaks. The pressure reading depends on two main factors; the compression ratio and the altitude at which the engine is being tested. The compression ratio will also depend on if the engine is equipped with exhaust valves and their condition. When the exhaust valves are in the closed position the compression ratio will be greater than if the valves are carbon-seized in the open position. The difference may yield a pressure reading 25 psi. The quality of compression testers varies greatly. The main thing that a compression tester can identify is a change in condition. Whenever you rebuild the top end, take a compression pressure reading and mark it down. When the pressure changes 20% check the condition of the piston and rings. Pistons usually last twice as long as rings.

Its part of a much more indepth discussion on top end rebulilds as KLXer is describing...

http://www.off-road.gr/News-article-...de-thread.html

I think that if its not carbon buildup holding the exhaust valves / ports open, and the spark is good, then its probably the top end needing some attention as KLXer says.

RE: Quick question on an old kx 80
 

Dude, you need to read up on two strokes...;):D No offense.
There are no valves in a two stroke motor. Only ports. A whole different beast from our KLX motors. This might help:
http://en.wikipedia.org/wiki/Two_stroke

And yes, 30 psi is too low. Time for a top end.

RE: Quick question on an old kx 80
 

It should be at least 100 psi just to get it started, correct psi would be around 180 approx. No point putting a new plug in it, as Jason said new top end is required

RE: Quick question on an old kx 80
 

No offense taken, I was not using the right verbiage and its good that its corrected so that readers don't get confused.

Thanks ;)

RE: Quick question on an old kx 80
 

Back in 1989, I bought a 1985 Suzuki LT 250R Quadracer, I couldn't get the thing started when I went to buy it, but I guess I didn't care about stuff like that at the time. Any way when I got it home I had my wife pull start me with the truck and it finally started after about 100 yards. Well the next time I went to start it I got nothing. So I decided to tear off the jug, that's the only thing I like about 2 strokes, well besides the power, no nasty valves to work on or a timing chain or cam, anyway I pulled off the cylinder and low and behold there was a hole the size of a pencil lead in the top of the piston, well I ordered a $40.00 Weisco piston and rings set, installed in less than a half hour and the quad started up the second kick every time after that. Then I blew out the rear end and traded it in on a 88 Honda Accord. So if the compression is that low either the rings are stuck or you got a hole in the piston.

Now speaking of this quad, I shared this story with some of you over a year ago, but with so many new (noobs) here I thought I would tell it again. As all of you know, back in the day, there was no 4 stroke that compared to the power band of a 2 smoke. So when I got this quad It only took me a minute to decide that no one else that I cared about would ever be able to ride this thing. I mean it was fast. Anyway one day my then wife and then sister-in-law walked up to me with this look I will never forget, sort of like a kid asking something even though they already knew the answer. Previously they had bugged me to ride it and I always said no, explaining that it is just too dangerous. By the way we didn't even own a helmet in those days. Anyway they once again asked if they could ride it and I gave them the same speech about how fast two strokes were and that I didn't want them to get hurt. This time they had an answer for me, and I swear to God they uttered the words I will never forget, and since we are all still friends I bring up when I see them. And I'll put it in quotations. They both at the same time said, are you ready for this....... "Can’t you just take off the two stroke part so we can ride it" Yea I'll get right on it. So I had to explain the difference between two and four stroke motors, but I think they just thought I was being a jerk, and so they walked off. Oh well they are both still alive today. OK that story earns one smiley. :DThis next story, (oh by the way sorry for thread jacking) deserves a triple set of Smileys.

One day when my first wife and I were first married and living in Longview Wa I came home from work and saw that there were plastic bags on all of the phones. She was in the kitchen making dinner. I looked around the whole house and yep all of the phones had plastic bags on them. We sat down to eat and somehow I had to bring this up in a normal conversation, so I say.."hey honey is there something wrong with the phones?” And again I'm not making this up, she says...."Oh I was listening to the radio today and the guy said that the phone company is cleaning and blowing out the phone lines and to keep dust out of your house you should cover them with plastic bags”........I just sat there and thought to myself.....WOW! I know we're both young (too young to have gotten married now looking back)I mean she was under 18 and I was 19, but what the heck? I laughed about it then, but dude are people out there really that dense? :D:D:D

RE: Quick question on an old kx 80
 

On my 79 YZ80 (first bike), somehow I sucked a small pebble in through the air filter, through the carb, through the reed valve, and it jammed itself firmly in between the piston and the cylinder wall with a nice deep gouge (in the cyl wall). I popped off the top-end, had the cylinder machined at my dealer, and they gave me an oversize piston and ring set... The machining didn't take out the entire gouge, but it was smooth enough that she really pulled hard after that... Must have been a YZ110 by the time I was done. Ahh, the good ole days. :)