KX60 need help assembling motor

[Baker1]

Hello. I pulled the motor from my daughter's KX60, pulled the head, and discovered that the big end bearing was toast. So I split the cases. The cylinder is okay.

Parts ordered and en route - piston and rings and pin and clip; complete crank assy; crank bearings and seals; all other oil seals (shift shaft, output, kick starter, water pump); gaskets. By the way - www.mrcycles.com had better prices on OEM parts than I could find on aftermarket parts anywhere! Very good prices!

I did not remove the clutch or starter assy or tranny from the right side case.

I have 6 questions:

1 - I don't have a press; what's the best way to get the main bearings on the crank and then seated properly in the cases? Seat bearings in cases first, and then tap the cases together over the crank? Or put bearings on the crank first, and then make cases together over the whole assy?

2 - Does the hot bearing onto cold crank or cold bearing into hot case trick work? What oven temp to use to avoid oil seal damage?

3 - what assembly lube to use in a 2-stroke lower end? Just oil, or???

4 - what tricks to use to get the tranny shafts properly seated in their bearings at the same time as getting the cases together around the crank? Any tricks here, or just tapping and loving?

5 - I was very careful to watch the tranny shafts as the cases finally came apart. No shims or washers anywhere on the left side of the shafts or in the left case. Is that normal?

6 - Just for fun, I twisted the shiftdrum around some to watch the gears changing. It was fun. Then I realized that I had no idea which way was neutral or which way to turn to get it. That was funny also, in an idiot sort of way. :coocoo: So I just hunted around until I found neutral again. Am I okay here, or did i bugger some special alignment between shift forks and drum and neutral?

Okay that's it! I have yamalube4 for case glue and 2-stroke oil for rings-piston-cyclinder lube.

Any tips you might want to throw my way would be very appreciated!

:cool:

 

[Baker1]

anybody?

 

[Ol'89r]

I have 6 questions:

1 - I don't have a press; what's the best way to get the main bearings on the crank and then seated properly in the cases? Seat bearings in cases first, and then tap the cases together over the crank? Or put bearings on the crank first, and then make cases together over the whole assy?

Baker. I normally install the bearings on the crank first. You can use a deep socket to drive them on and seat them. Be sure that the socket fits the inner race not the outer race. Driving against the outer race will damage the bearing. Heat the bearing slightly to expand it.

2 - Does the hot bearing onto cold crank or cold bearing into hot case trick work? What oven temp to use to avoid oil seal damage?

If you don't have a torch, go to your local hardware and get a plumbers propane/butane torch. Heat the case evenly until you can sizzle a drop of water or spit on the case. Then, drop the crank with the main bearing installed into the case. Heat the other case and put the two cases together. Install your seals after the cases cool off. You can heat the cases in the oven but, your wife will want to know why her chocolate chip cookies taste like Yamalube. :ohmy:

3 - what assembly lube to use in a 2-stroke lower end? Just oil, or???

I use whatever two stroke oil is going to used as pre-mix.

4 - what tricks to use to get the tranny shafts properly seated in their bearings at the same time as getting the cases together around the crank? Any tricks here, or just tapping and loving?

Just tap the cases evenly with a soft mallet and spin the shafts with your fingers to make sure they don't bind.

5 - I was very careful to watch the tranny shafts as the cases finally came apart. No shims or washers anywhere on the left side of the shafts or in the left case. Is that normal?

If I remember correctly, that's normal. I would be a good idea to purchase a service manual to make sure.

6 - Just for fun, I twisted the shiftdrum around some to watch the gears changing. It was fun. Then I realized that I had no idea which way was neutral or which way to turn to get it. That was funny also, in an idiot sort of way. :coocoo: So I just hunted around until I found neutral again. Am I okay here, or did i bugger some special alignment between shift forks and drum and neutral?

That's ok. The gearbox doesn't care what gear it is in when you put the cases together.

 

[Baker1]

Hey Thanks 89r! I appreciate the tips!

 

[Baker1]

Some quick notes for people who followed this thread:
Disassembly:

Be sure to break the main nut loose on the right side of the crank before removing the magneto drum. That nut is dang tight. The slot on the right end of the rank is a water pump drive mating surface. It is not a suitable backup for breaking the main nut loose. The magneto would provide a better backup, you just need a good way to grab it.

I had already removed the magneto with a puller, and since my crank was toast, I just locked it up with a pair of vice grips to break that nut.

The cases were very difficult to split without a case splitter. If I ever do this again, i will drive the engine to the local shop and pay them 20 bucks to split the cases for me. Splitting was by far the hardest part of the job.

Reassembly:

1 - I split the cases, installed new seals and new crank, and reassembled the motor all without rmoving the clutch or kick-starter gears or any transmission components. On my KX60, there were no shim or spacer washers on interior tranny shafts, and only one gear on the clutch-side shaft would come off.

2 - I installed the new main bearings on the new crank by putting the crank in the freezer for 1 hour, and the main beaings in a 175°F oven for 20 minutes. Wearing light leather gloves, I pulled everything out onto the counter, and immediately dropped a bearing onto the right side of the crank. Clink - it stopped 1/32" shy of being totally seated. I immediately dropped the other bearing on the left side. Clink, it only seated halfway. I put the crank in the parts washer because water/ice was condensing all over it.

3 - I made a press out of two blocks of wood and 4 long bolts. Drill the blocks while clamped together for perfect symmetry. Drill a centered big hole for the crank ends and 4 small holes for the bolts. Sandwich the crank between the boards, and tighten the bolts evenly to squish the bearings. It worked easily.

4 - Install the crank into the right-side case first. Be sure to install the right side main oil seal before installing the crank into the right side case. That oil seal only installs from the "inside". To install, freeze the crank assy again, then lightly heat the crank area of the right-side case with a propane torch. My frozen crank seated all the way home when I dropped it into the lightly heated case. Then back into the parts washer until the crank warmed up.

5 - I used a q-tip to spread yamabond 4 onto the right side case rim. It made a nice smooth layer. Trimmed the q-tip once when it started to shed fibers.

6 - Before mating cases, make sure that the one loose tranny gear and the two case retainer pins and the crankcase vent hose are in place.

7 - I pulled all old oil seals from the left side case. Then lowered case into place on the crank. I had no problems at all with tranny shafts, shift drum ,or shift shaft lining up with their holes. I did not change the smaller bearing sets inside the left case.

8 - use the case bolts to start evenly pulling the cases together. I ended up focusing primarily on the bolts around the crank, because that was the only resistance I encountered. When the gap between the cases was about 3/8", I heated the main beaing area of the left case slightly with a propane torch. Everything went home quickly after that.

I then installed the 3 new oil seals on the left side: main, output, and shift shaft.

Everything turned smoothly by hand, but felt pretty dang tight.

I did a quick break-in as follows: 10-minute idle, 30 minute cool-down, repeat once.

Motor runs fine, plenty of power. I used new piston, pin, small-end bearing, and rings in the old cylinder.

I repacked the muffler.

The bike is kind of smoky, so I may tweak the needle clip.

That's it.

4 -