Transmission Output Shaft Stripped

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Colorado Mike
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Post by Colorado Mike »

My kid's KX was split and re-assembled by the previous owner. They guy did an almost perfect job. I say almost, because he managed to get a small crack in the case between the shifter shaft and the CS . :blink: The nice thing is we don't have to change the oil so often, it just kinda comes out on it's own. :supz:

If you do this on your own, just be real careful. The money you save will be less than half of what a new case costs.
Mike

Life's tough, it's even tougher if you're stupid.
'04 KDX220
TD3
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Post by TD3 »

What was the hardest bit on re-assy.
Keeping "everything" aligned is the hardest part. The shift drum and fork rods have way too much side to side movement. You have to try and keep them straight when pressing the case together. When the case comes together there is no way of holding them.
Do you need the press to get the crank back on the bearings?
Yes, both inner and outer bearing races are a press fit. This makes the whole job a royal pain. I used a couple large C clamps and a DIY case holder to help press them together. I also left the crank outside in the cold for the night and used a hair dryer on the case halves. This does help lessen the interference fit during assembly.
How did you cope without the special tool to keep the two crank plates aligned?
I inserted a couple narrow blocks of aluminium between the plates. (I never said I did it correctly :mrgreen: ) Once assembled, I measured the run out on the ends of the crank. I checked the plates with feeler gauges by turning the crank slowly and checking the gap between the plate and case.

Like I said, this lower end is a pain to split and reassemble. I'll pay someone to do it next time. I hope this helps you.
chris_psmith
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Post by chris_psmith »

Well I have just got the motor back together and thought I would post the experience in case it is of use to anyone (bit wordy but you don't have to read it):

Crank Case Splitting

Before starting you will need some special tools:
1.Fly Wheel Puller – Only cheap and not worth trying to find another way around it (£7.50 from e-bay).
2.Crank Case Splitter – Can be made with a length of box section, two long M6 bolts and one M8 with nut. Put two holes in the bar the same distance as two bolt holes on opposite sides of the flywheel cover and a hole in the centre to take the M8. Use two spacers on the M6 bolts to ensure that they form a tight frame and are fully home in the case threads (i.e. clamp the bar down against two spacers to make everything rigid, if you don't it is very easy to put a side load on the case and possibly split it when you try and force the case apart – I used two long nose sockets for spacers). Pass the M8 through the bar with the nut underneath, and then tighten the nut forcing the M8 against the crank end.
3.Fly Wheel holding tool – Can be made using the same piece of box section as the case splitter but fitted with two M8 bolts and nuts. Drill two holes in the bar at the same distance as the two holes in the flywheel, fasten the two bolts to the bar and double check that the length of bolt left sticking out can not come into contact with the electrical windings visible behind the flywheel.
4.Bearing puller – You will need this to get the crank bearing off the shaft, it needs to be able to get between the bearing and the crank so needs a thin wedge shape to work.
5.Bearing heating tool – lots of ways to do this, I used a slug of aluminium machined down to fit inside the bearing (enough undersized so that it doesn't get stuck in when you heat it), and a handle to hold it without getting burnt.
6.Cylinder nut torque tool – 12mm ring spanner with a socket welded to it so you can use the torque wrench.

Disassembly
Strip the engine down, all straight forward enough if you follow the manual (Head off / Barrel off / Right hand cover off). A note of caution, when you take the right cover off it is easy to loose track of some of the washers as they may come off stuck to the cover or stay on the engine, falling off later when you are not looking – small washer over the kick start shaft and washer behind the clutch bush, also watch out for the white plastic tube that is on the gear shifter, had me a bit confused when I spotted it lying on the bench.
Take time to photograph everything and make lots of sketches as the manual is not as clear as the notes you will be able to make.
The first difficult bit is how you remove the fly wheel nut, the clutch centre nut and the crank main drive nut. The best way I found (with hindsight) was to remove the four bolts from the clutch, remove the square clutch plate and replace it with four washers, then bolt the clutch assembly back down. This will give you the ability to lock the engine with the fly wheel holding tool described above. Hold the crank main drive nut with a 22mm socket and release the flywheel nut (17mm from memory), then insert the flywheel holding tool and release the crank drive nut, then the clutch centre nut, then remove the four clutch bolts and clutch assembly.
Insert the fly-wheel puller (left hand thread into the flywheel) and pop the wheel off.
Remove the screws that hold the winding and sensor in place – take extra time to make sure you have a screwdriver that fits the heads correctly, if you strip the heads it will be a big job to get them out!
Remove the shift shaft and the circlip on the transmission output shaft cog, remove the cog and washer.
Attach the case splitter and carefully tighten the nut to put force on the case/crank, when it gets tight, tap round the case with a soft hammer / mallet, then tighten again, keep doing this and it should start to come apart. I ended up tapping the case on the housing that sticks out at the front whilst holding the splitter frame as this is the only place you get any force in the direction you are trying to split (but I was very careful!). Make sure the case gap stays equal throughout the process to ensure nothing gets snagged, may need to tap the trans output shaft to keep the back end straight.
When the case is apart, massive relief! Pull the two shift rod shafts up and then lift out the two gear sets, lift the red plate off the changer drum (as you can be sure it will fall off and get lost later), check where the case bushes are (should be two bushes in the right hand cover and two bushes in the crank cases), it was at this point I also noticed the one of the woodruff keys had fallen off the crank, so check you have removed the woodruff keys from either end of the crank shaft.
Remove the bearing from the crank using the puller and some heat from a propane torch, don't be tempted to start hammering at the gap between the crank and bearing as from this point in you have to take lots of care to make sure you don't disturb the crank alignment.
It was at this stage that I had an issue; I hadn't taken the crank drive nut off! The only way round this was to take it to work and get it removed with an impact driver, they pushed the crank out of the case half for me while I was their so I can't help on how to do that part of the job.
The remaining crank bearing stayed in the case, this was easy to remove with some gentle heat and some pressure on the back of it to pop it out.

Assembly
Assembly is simply the reverse of disassembly, well not actually! Oil the con rod bearings then put the crank in a freezer for as long as possible, I would say at least over night. Put any new bearings and seals in the freezer for at least a couple of hours.
Apply a gentle heat to the case halves where the seals / bearing go and carefully push in the seals and bearings into the cases. Add some high temp. grease to the bearings. (I tapped the new bearings in using the old bearing as a bush).
Re-assemble the gear train and all other parts that came out of the case, ensure you put the red disk back on the shifter and the two bushes in the case, put a thin coating of semi-hardening gasket sealant on one case half, check and double check you have everything in place, then check again, make sure the shifter is in place and working, put high temperature grease on all seal surfaces and the mating shaft ends. Have a few mental run-throughs of how you will assemble the cases; make sure you have supports to hold the case flat, a soft hammer, sockets to match the case bolts (8mm) etc. Time is the most important thing in the assembly.
When you are ready, heat the aluminium bearing tool until its nice and hot, then hold it inside the bearing to transfer the heat (making sure you don’t touch the new oil seals), keep doing this until the two crank bearings and the trans output bearing are nice and hot (I may have been too cautious with this, but the thought of waving a propane flame on my nice new bearings and seals didn't appeal too me).
When you are happy they are hot enough, remove the crank from the freezer and drop it into the case half (do make sure you have it the right way round, you will be dropping the thin end that takes the flywheel and the arrow on the piston top should face forward (I lost sleep over this one dreaming that I had re-assembled the crank cases with the crank back to front). Then put the other case half on and tap lightly around it too take up the position and get all the shift shafts / drive trains etc stared in their holes (this wasn't too hard), keep tapping the case until the gap has closed down to engagement of the case bushes. Insert the crank case bolts and carefully (but quickly) gradually tighten the bolts down to keep the gap constant as you tighten them down. This wasn't difficult, just tense, and required minimal force on the crank.
I believe you can get away without the Kawasaki tool to keep the alignment of the crank so long as you are careful and don’t put too much force on the crank, this was the single biggest concern I had throughout the build, but there seems to be enough people around that have done this now without engine failure later to suggest it is OK, heating and freezing removes a lot of the force that would be needed to do it the way Kawasaki describe in the manual using the special tool.
When the cases are back together it is just simple spannering to rebuild the engine. Remember to re-assemble the clutch with the washers instead of the square plate to allow you to tighten the three nuts described earlier.
When it comes to tightening down the cylinder you will need a ring spanner with a socket welded to it (as described already on this forum - thanks it worked a treat), you will also need two torque wrenches to work out the equivalent torque value, as the spanner extension will change the torque value, set one wrench to the correct value and adjust the one with the tool fitted so they both click at about the same time.

I hope that is of help to someone, I have quite enjoyed the strip and build, would have preferred not to have the time pressure of being booked in for a race the next weekend, but that’s life. If it explodes I will be sure to let you know not to try this. I have photos I can post if anyone is interested. :supz:
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m0rie
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Post by m0rie »

Chris - Thanks for all the useful info.
1989 KDX 200
2007 TTR-50E
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