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1998 KX125 Project...What The He** Am I Doing?!?!?!

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Ok, so new guy here. Had a few quads in my days, rode many a dirt bike in my younger years but never owned one. Always been a car guy (I bleed Ford Blue) and thought I find a cheap bike to have some fun with.

 

Found this 1998 Kawasaki KX 125 for cheap and thought it be perfect to spend a couple bux on and have some fun.

 

I rode the bike before bringing it home. I needed to be push started, but it DID RUN and it has a title, so I knew there was at least SOME value in this bike. Granted, it didnt run very well and bogged down and yadda yadda yadda. Fine, ill take it. So home it went.

 

On the way home it dawned on me that even though i can fix and rebuild most any Ford V8 on the planet, that doesn't really make me super qualified to troubleshoot this ol 2-stroke. But, im not completely incapable of figuring things out and internal combustion driven stuff is generally fun, so screw it.

 

Somewhere in the first hour of taking the plastics off and getting into the top end (keeping in mind that a "top end rebuild" is basically foreign to me) I decided that im gonna go full on Meth Head on this bike and completely tear it down. Check the whole thing out and see if I can get myself familiar with the bike. So thats whats happening now.

 

 

Easter Sunday, the CL deal is done and the bike is home.

 
 

Went all out on this super custom orange bike stand and here she is in all her old and neglected glory. But on a positive note, theres a SICK lil fanny trail pack. So theres that.

 
So I got to this point and thought to myself, hmmm...this doesn't seem right at all. Car pistons shouldnt look like this, so im guessing this piston shouldn't either. Haha
Insert artsy photo here...
 
Look Dad, its just like a real piston, only smaller
After being defeated by the final bolt, the swing arm bolt, for about 24 hours, I got it out and the frame is stripped.

 

 

 

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Now what? The parts that my infinite wisdom (which i have gained over the last couple weeks) determined I needed are here and are as follows:

Chain - O-ring sealed - current chain appeared to be quite stretched and in bad shape

Front Sprocket - Looked pretty bad which im guessing was due to the pretty bad chain

Carb Vent Hose Kit - Carb hoses (Holy crap theres a LOT of hoses on this lil guy) are very hard and feel quite brittle

Top End Gasket Kit - Just seemed logical

New Piston (kit - ring, pin, clips, needle bearing) - I showed the current piece...YIKES. I should mention that I checked the cylinder and it looked very clean and measured out to factory spec. The ring is SHOT and all sorts of worn.

Fork Seals and Wipers - Front forks felt ok...but what do i know... but where leaking just a lil bit

Dual Stage Air Filter - Old filter was black and appears to have had a mouse or two living in there at one time or another

Bolt Track pack - There were more than zero odd bolts in this machine, so this seemed like a simple purchase to get some original hardware back

 

So thats what I have to work with.

 

I started to blast the frame, but this powdercoat is STRONG. After about 5 mins i had gotten a 2" portion of the frame clean and realized that I just didn't care enough to keep going. The frame is in good shape. The bottom is missing paint and the sides by the pegs are as well. I am really at a loss as to what to do with this frame.

Do i strip it? Touch it up? Clean it, scuff it, prime it and repaint it? Strip it with some stripper and then blast it and clear the bare frame?

 

I honestly dont know what to do with it and that is a bummer because its holding up the project. So chime in...AND....GO.

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Now what? The parts that my infinite wisdom (which i have gained over the last couple weeks) determined I needed are here and are as follows:

Chain - O-ring sealed - current chain appeared to be quite stretched and in bad shape

Front Sprocket - Looked pretty bad which im guessing was due to the pretty bad chain

Carb Vent Hose Kit - Carb hoses (Holy crap theres a LOT of hoses on this lil guy) are very hard and feel quite brittle

Top End Gasket Kit - Just seemed logical

New Piston (kit - ring, pin, clips, needle bearing) - I showed the current piece...YIKES. I should mention that I checked the cylinder and it looked very clean and measured out to factory spec. The ring is SHOT and all sorts of worn.

Fork Seals and Wipers - Front forks felt ok...but what do i know... but where leaking just a lil bit

Dual Stage Air Filter - Old filter was black and appears to have had a mouse or two living in there at one time or another

Bolt Track pack - There were more than zero odd bolts in this machine, so this seemed like a simple purchase to get some original hardware back

 

So thats what I have to work with.

 

I started to blast the frame, but this powdercoat is STRONG. After about 5 mins i had gotten a 2" portion of the frame clean and realized that I just didn't care enough to keep going. The frame is in good shape. The bottom is missing paint and the sides by the pegs are as well. I am really at a loss as to what to do with this frame.

Do i strip it? Touch it up? Clean it, scuff it, prime it and repaint it? Strip it with some stripper and then blast it and clear the bare frame?

 

I honestly dont know what to do with it and that is a bummer because its holding up the project. So chime in...AND....GO.

It looks to me like a decent bike, I've bought worse.

If you can rebuild a V8 you'll have an easy time with a 2 stroke. A service manual and an afternoon would rebuild the whole engine.

If it were me I'd touch up the paint on the frame, or in the case of my brothers KX 125 we painted it black and touch it up every winter. It looks good, hides flaws well, and is easy to touch up. The factory powdercoat is tough to remove as you now know.

I noticed you didn't mention a rear sprocket, replace them as a set and you'll get more mileage out of them that way. I usually run a steel chain and sprocket on my 150, keep it clean and adjusted and can get 30-40 hours out of it. Sometimes the o-ring or x-ring chains are too wide for the 125's and rub the case, they also have more drag which may or may not matter.

You didn't mention it but I assume you are getting the cylinder recoated? Make sure you either order the piston from the coating company, or send it with your cylinder for sizing. Is the crank good? Might be worth looking in to that before you put it back together.

KX's are good bikes that are very reliable with proper maintenance. The project looks good, looking forward to seeing the progress.

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Is that metal pieces scattered all over that head ? Also check linkage and swingarm bearings and bushes while you have it all stripped down.

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A more sturdy milk crate or proper stand will serve you well.

Seen thos buckets give up the goast in the middle of the night and let the bike fall over.  Lever end on the hood of your car?  Leaking gas out onto the floor?  Not good.

But, guess you dont really need it when the bike is in such small parts right now :)

 

Touch up paint on the frame.

Get that into your meth brain and go forward.

You are a gear head and it will all fall into place.....unless you dwell on the frame paint.

Dwell on the mechanics of it and rip er up.  Little frame scuffing is least of your issues. 

 

That cylinder head looks suspect.  Like something dinged around in there for a bit.  Make sure the bottom end bearings are good...maybe flush out the case.

 

But yea, keep buying parts for it and put it back together and ride it.  That is what you bought it for....something to wrench on and mess with and rip around....

 

Coo

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It looks to me like a decent bike, I've bought worse.

If you can rebuild a V8 you'll have an easy time with a 2 stroke. A service manual and an afternoon would rebuild the whole engine.

If it were me I'd touch up the paint on the frame, or in the case of my brothers KX 125 we painted it black and touch it up every winter. It looks good, hides flaws well, and is easy to touch up. The factory powdercoat is tough to remove as you now know.

I noticed you didn't mention a rear sprocket, replace them as a set and you'll get more mileage out of them that way. I usually run a steel chain and sprocket on my 150, keep it clean and adjusted and can get 30-40 hours out of it. Sometimes the o-ring or x-ring chains are too wide for the 125's and rub the case, they also have more drag which may or may not matter.

You didn't mention it but I assume you are getting the cylinder recoated? Make sure you either order the piston from the coating company, or send it with your cylinder for sizing. Is the crank good? Might be worth looking in to that before you put it back together.

KX's are good bikes that are very reliable with proper maintenance. The project looks good, looking forward to seeing the progress.

To address the rear sprocket. The previous owner...who got the bike in some random craigslist bartering swap deal...put a new petcock on and a new TAG rear sprocket on it.

Also the bike has fresh brakes front and rear.

 

I had no clue that the O-ring chain could be too wide, I just chose this chain because logic lead me to thinking that a sealed o-ring type would just naturally mean it is "better" Is this a brand-to-brand difference on width's of the chains or will i most likely need to swap this chain out for a standard steel one?

 

I had not planned on getting the cylinder recoated. I have full knowledge that 2-stroke cylinders have a coating, but im clueless as to why or what the process is for the recoating and when it should be done. I took measurements of my cylinder before ordering a new stock sized Pro X piston and ring. Once i got them i checked the ring gap in the cylinder and it is right on. So I was planning on just going with it. Do i NEED to get this replated?

 

Is that metal pieces scattered all over that head ? Also check linkage and swingarm bearings and bushes while you have it all stripped down.

Those are nice little dings and chips in the piston. After full inspection once this thing was completely tore down, I have come to the conclusion that it had to be an electrode that broke off and pinged around in there. I inspected the reeds which looked brand new and appear to be the boyeson reeds as they dont look like the stock ones in the picture. I drained the lower unit (hmmm...is that proper MX lingo or am in talking boats now? haha) and that came out fine. Did a pretty solid visual inspection with the head off and using the connecting rod to rotate the crank while shining my super bright led down in and its looks SPOTLESS down there. No slack in the big end bearing either. All moved like glass.

What you saw in the picture is actually the piston, but the cylinder head matched all those marks. I have since smoothed the head of its nicks and dings.

 

Swingarm has now been checked. That swingarm bolt was a NITEMARE, but its out with no damage. One of the bushings was rusted to it. All the other parts of that linkage appear to be fine...i guess...No grooves or anything in the bolt and the bearings all move free, so i was just planning on greasin er up and going with it.

 

A more sturdy milk crate or proper stand will serve you well.

Seen thos buckets give up the goast in the middle of the night and let the bike fall over.  Lever end on the hood of your car?  Leaking gas out onto the floor?  Not good.

But, guess you dont really need it when the bike is in such small parts right now :)

 

Touch up paint on the frame.

Get that into your meth brain and go forward.

You are a gear head and it will all fall into place.....unless you dwell on the frame paint.

Dwell on the mechanics of it and rip er up.  Little frame scuffing is least of your issues. 

 

That cylinder head looks suspect.  Like something dinged around in there for a bit.  Make sure the bottom end bearings are good...maybe flush out the case.

 

But yea, keep buying parts for it and put it back together and ride it.  That is what you bought it for....something to wrench on and mess with and rip around....

 

Coo

So yeah, the bucket gave way and i got a gouge down my wrist about 7" long. Lesson learned...i mean, not that i didn't know from the beginning that the bucket was a bad idea, but hard headed guy like myself needs to bleed to truly learn. Haha. I have a real stand now.

 

So thats that for now. I going to start reassembling the engine tonight unless I get word from here that I NEED to replate the cylinder.

 

Oh, my spokes are fairly loose on the back, so I have to address that as well. But I've been through wheel lacing on my road bikes (pedal bikes) so i feel like I should be able to handle the spokes ok.

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You NEED to replate the cylinder if there are any gouges. If it looks good and is within spec, you should at least hone the cylinder.

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You NEED to replate the cylinder if there are any gouges. If it looks good and is within spec, you should at least hone the cylinder.

The cylinder actually looks great. I spent a lot of time double and triple checking spec and the actual cylinder walls themselves. 

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Oh man, look at that.

I give the guy good solid advice....but it was to late?!

 

:(

 

But a gash on the arm from it falling over is better than a puddle of gas that the fumes ignight in the middle of the night and burn your house down...or worse.

 

As I often have kid's bikes here for the weekend, or longer, we used to put the 85cc machines on buckets.  Went to work one day and there was a kid's YZ85 fallen over onto another kid's TTR125 type bike.  Tore a whole in the seat.  Felt bad for him.  Felt good for me that is wasn't worse.

Now lean them against a wall or a strong milk crate or proper stand.

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The cylinder actually looks great. I spent a lot of time double and triple checking spec and the actual cylinder walls themselves.

I thought I read in your original post that the cylinder was measuring out of spec, I misread the post. If it looks good and measures good then there is no need to replate. Sorry for the confusion.

As far as the chains go, most all of the sealed chains are pretty wide. You might get lucky and it will work, but the clearances get pretty tight with those chains. With how fast they are spinning it doesn't take long to grind a case.

What did you decide to do with the frame?

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The cylinder actually looks great. I spent a lot of time double and triple checking spec and the actual cylinder walls themselves.

do you still see cross hatching?

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Is that metal pieces scattered all over that head ? Also check linkage and swingarm bearings and bushes while you have it all stripped down.

I cant see any pictures of the bike/

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I thought I read here NOT to hone the cylinder if it is plated...

umm yeah you can. use some wd40 and a scotchbrite pad. You don't want to use a ball on nikasil because it'll catch on the ports and screw things up.
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I thought I read in your original post that the cylinder was measuring out of spec, I misread the post. If it looks good and measures good then there is no need to replate. Sorry for the confusion.

As far as the chains go, most all of the sealed chains are pretty wide. You might get lucky and it will work, but the clearances get pretty tight with those chains. With how fast they are spinning it doesn't take long to grind a case.

What did you decide to do with the frame?

 

Frame is going to be repainted. I finished prepping it for primer and paint last night. Will prime tonight and get a first coat on. Finish it tomorrow and clear the hell out of it. I will also be putting clear vinyl over the common wear areas to make them hold up longer.

 

I have also stripped the swingarm. I just have a few little areas i need to hit again, but then the swingarm is ready for paint as well...well, not paint. I decided im going to hit the freshly cleaned aluminum with 2 coats of lightly tinted clear and then 3 or 4 coats clear, just to give it a little bit of a darker 'smoked' look.

 

No clue where all the pics went, I set up my "garage" on here and added all the pics and shared them from there, but now everything is gone.

 

Heres all the pics of the bike thus far...

https://drive.google.com/folderview?id=0B-rKIfopyTGOMWdTbGxUUGRVQ0U&usp=drive_web

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Bike looks good, nice car BTW

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umm yeah you can. use some wd40 and a scotchbrite pad. You don't want to use a ball on nikasil because it'll catch on the ports and screw things up.

So you can use the kind that has the flat stones on a plated cylinder?

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All the damage iunder the head looks like crank bearing cage.  You should take the bottom end to someone that knows what to look for before you put a new piston in there.  Carnks are cheap, do a bottom and top end to get the motor right, then worry about all the other chassis stuff later.

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All the damage iunder the head looks like crank bearing cage.  You should take the bottom end to someone that knows what to look for before you put a new piston in there.  Carnks are cheap, do a bottom and top end to get the motor right, then worry about all the other chassis stuff later.

I hear ya on the lower bearings. Thing is, I can't possibly imagine how the bottom end could move so perfectly smooth when spinning crank using connecting rod. Plus, there are literally zero signs of damage to any other internal part except for the top of the piston and the top of the cylinder head.

 

I even went as far as to put a stethoscope on the bottom case to listen for any grinding or catching from a shot bearing, and it sounded clean and smooth.

 

If it needs a bottom end, then it needs a bottom end. But I really have no interest in putting much more money into this bike because I am about $100 away from the number where I MUST quit spending. That is why I went as far to visually (and audibly) inspect the bottom end components.

 

Plus, there this dang crazy deal with me wanting to just get out and ride that dang thing, since ive yet to do that. But i dont really want to throw away a new piston because i wanted to ride a week sooner. But i dont really want to spend another $300-$400 on something it MIGHT need.

 

I dunno. I guess if it needs a bottom end, then I have a VERY CLEAN '98 KX 125 with title for sale, only needs the bottom end done. Lulz 

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