I am trying to restore an old 1986 KX 125 for a friend (dont ask me why). I have completely rebuilt the motor and individually each component is good. It starts right up and once warm is very responsive. Once i get on it and try and ride it there is no power    

The plug looks good and it runs smooth just no pull. It has a new clutch, piston, carb bearings and seals. I have tested the crankcase for leaks and it tested fine.

The ignition OHM's out to specs and has a good spark on the tester but could it be going weak at rpm?

    
  

Give me a cam and valves anytime!!!!!

imo it is just the fact that it is a 125 they hardly pull they are not that powerfull... try fanning the clutch to get the rpms up and if u dont feel the power just except the fact that it is a little 125 lol........

my friend had that year back when it was new and it had no power band.if it did it was somewhere between 10,500 and 11,000 RPM.Nothing before and nothing after!

Take a good look at the kips valve. Did you align the marks on the sub-port valves/governer rod correctly?  I used to have an '87 years ago and the guides that the ends of the sub-port valves sat in were so worn & sloppy that the rod would strip the teeth off the valves almost as fast as I could replace them. Also, check the ignition timing.

The book I have says to pull the KIPS rod all the way to the left and align the marks on the valves with the rod marks.  The book refers to the LEFT as the stator side of the motor.  The problem is there is NO possible way to align the marks with the rod all the way to the left.  They will align if I pull the rod all the way to the right (clutch side).  Could this be a misprint?

As far as powerband, there is none.  I cannot even get thr rpm up if I feather the clutch.  Its like Im always in 4th gear even when taking off.

jnybbad1l40 said:

Both of those things lead to the rotating drums of the PV system being in backwards.  Put them in the other holes and see if it lines up.

This was a common problem with that PV system.

-Steve

The PV drum that is supposed to be on the right, clutch side, per the book has a groove on top.  I have this one on the clutch side.  

Does anyone have a manual that they can double check the procedure for me???

No manual, but looking at the parts fiche on buykawasaki.com it looks like you're right, the grooved one is on the right. If you're sure the kips is set up right and the ignition timing is correct, I'd look for an aspiration problem. Is the carb clean? Reeds good? Any exhaust restrictions? I had an FMF pipe for a KDX sitting around once so I put it on. The bike started fine but wouldn't rev out . Turns out a mouse made a nest in it.

jnybbad1l40 said:

I have a couple manuals on this and I don't think it's a misprint. My manuals say slide it to the left which I understand to mean push the rod all the way into the motor, which would be to the left (if your visualizing the motor in the bike). The actuating mechanism pulls the rod to the right when you riding the bike. I have done this on my KX500 many times and you can line those marks up.

It does sound like a power valve problem that you have.

Yeah it sounds like its the problem.  The issue is if you push the rod all the way into the motor (to the left) the marks disappear into the cylinder.  There is no way to line them up???

If I remember correctly:

1. Remove circular valves.

2. Slide governer rod all the way in.

3. Drop circular valves straight down in, aligning marks or chamfered teeth on valves with marks on rod.

jnybbad1l40 said:

You do have to take the cylinder off the motor to accomplish this task. Then the rod should be visible.

Old_Man_Time said:

Yes.....cylinder off the motor and head off the cylinder.

Am I looking for these marks under the cylinder?  With the head off and the caps off the KIPS drums I can see the marks on the rod and the drums, but only when the rod is pulled to the right.  If I push the rod to the left the marks on the rod go into the head where you cannot see them.  This is very confusing!!

With the valves out, you should be able to see the marks on the rod through the holes where the valves go (Through the top of the cylinder with the head removed). Then with one valve in your hand, find the mark (or chamfered tooth)on the valve and slide the valve straight down in there. Repeat for the second valve.

Let me add some information my manual brings out about the 85-87 exhaust valves.

a. The exhaust valves are different. The right hand exhaust valve has a groove cut into the top of the valve's shaft. The left hand exhaust valve does not have a groove.

1. The top of each exhaust valve has a punch mark for the alignment with the valve rod.

2. The valve operating rod has 2 grooves for alignment with the valve operating rod.

3. The left and right hand valve guides are identical.

4. Install left and right exhaust into their correct port

5. Turn each exhaust valve until the punch marks faces forward.

6. Lift both exhaust valves slightly and install the valve operating rod. The teeth on the valve operating rod point to the back of the cylinder. Push the valve operating rod all the way to the left, while at the same time aligning each exhaust valve punch mark with the respective groove on the valve operating rod. If the marks do not line up when the valve operating rod is pushed all the way to the left, remove the valve operating rod and reinstall it.

(My note on the point of pushing the rod all the way to the left. If you are able to push it farther to the left than the completely assembled rod would physically allow it to move then you have pushed it too far to the left.
To find out how far it can mechanically push to the left in a fully assembled valve rod:
Leave the valve rod in the cylinder without the valves. Install the right hand cylinder plug and gasket. Tighten the plug securely. Install the circlip, collar, circlip on the right end of the rod. Now push it all the way to the left. Note how far to the left it actually travels. It cannot go any farther to the left than the circlip, collar, circlip will allow it. That is what they mean by all the way to the left)

Once you know the actual physical limits of pushing it to the left you should be able to line up all the marks and finish the job.

I hope this helps.

Thanks for the info.  Ill check one more time.  I found another weird thing while troubleshooting it today.  I was playing with the timing and found that it runs WAY better if I advance the timing about 10mm past the timing marks... I know your not supposed to go 7mm or more past the outer mark but it seems to need more.  I get no ping and it starts and runs crisp.  It is like the marks are in the wrong place.  I wonder if the bike has a startor from a different bike??  Maybe not thr whole problem but deffinately didnt help.