Posts
20
Joined
12/15/2015
Location
AU
Edited Date/Time
12/29/2015 6:48am
Hi All,
I've just got hold of a cheap KX 250 2000 model and the motor is completely seized/locked
The guy I brought it off already pulled the head off it and realised its a bigger Job for him then he thought
Anyway just a few questions
1, crank bearings, what's the go? My dad and I rebuilt a YZ 125 and we just heated the case up and put a punch through oil seal hole and knocked the bearing out,
By the looks of the KX the seal is on both sides and if I heat the bearing to knock it out I'll melt the seal,
Any tips or info for replacing the big end bearings and seal and also what else to look out for?
I've read a few threads on here regarding poor cylinder coating, clutch etc in the KX
2. Also I'm thinking of throwing a hot rods bottom end kit and wiseco top end in it? Thoughts on this one?
3. And for the gaskets, any recommendations on gasket glue?
Kinda new to rebuilding motors so learning as we go. These forums are so good!! Thanks everyone
Lodgie
I've just got hold of a cheap KX 250 2000 model and the motor is completely seized/locked
The guy I brought it off already pulled the head off it and realised its a bigger Job for him then he thought
Anyway just a few questions
1, crank bearings, what's the go? My dad and I rebuilt a YZ 125 and we just heated the case up and put a punch through oil seal hole and knocked the bearing out,
By the looks of the KX the seal is on both sides and if I heat the bearing to knock it out I'll melt the seal,
Any tips or info for replacing the big end bearings and seal and also what else to look out for?
I've read a few threads on here regarding poor cylinder coating, clutch etc in the KX
2. Also I'm thinking of throwing a hot rods bottom end kit and wiseco top end in it? Thoughts on this one?
3. And for the gaskets, any recommendations on gasket glue?
Kinda new to rebuilding motors so learning as we go. These forums are so good!! Thanks everyone
Lodgie
Here is the damage from the crank inside the casing
Also here's the KX it's in pretty good condition
1 - If you're going to replace the main bearings, you're crazy not to replace the main seals. It's cheap insurance. So if you're going to replace them, who cares if they get ruined? But generally you can use a seal tool or a screwdriver to pop them out. I would 100% replace them though. Like I said, it's cheap insurance.
2 - Hot Rods crank kits are all about the person doing the rebuild of the crank. I'm a fan of OEM but I don't know if they're available. I've never used a Wiseco crank either, so my experience is limited.
3 - Why do you want to use gasket glue in your assembly? I'm assuming you're planning on buying a gasket and seal kit for the entire motor? If so, simply install the gaskets and tighten up the motor. If you need to hold a gasket in place for alignment, a tiny bit of grease will do the trick.
Good luck and enjoy the process. It's a lot of fun.
Shane
Cheers for the reply mate,
Sorry yeah I am replacing the seals they come with the kit, what's the best way to get the bearings out and in on the case? To get them out do you recommend heating the case and punching them out?
Then to put them in freeze the bearings, heat the case up and drop the seal in then the bearing? Probably a stupid question but just thought I'd ask hahaha
I thought they use gasket glue on the gaskets for the crankcase gasket?
Thanks man
Lodgie
Then to put it in I freeze the bearing inside a zip lock bag and then I usually can just drop them in with a few taps with a rubber mallet (small head, really useful. Good for helping bearings along but not big enough where you can damage anything). The main thing is to make sure they go in straight. If they don't, or perhaps get stuck, lightly tap it out the other way and try again (maybe refreeze it). You don't want to put too much force on the inner race so be gentle.
And with the gaskets, you don't normally need to use anything with them. I have taken bikes apart with gasket maker and a paper gasket but I think the reason was because they were re-using the paper gasket and it wasn't sealing properly.
If you need tools, Rocky Mountain has heaps of good stuff. Usually you need a flywheel puller, case splitter and a rubber mallet comes in handy. A blind bearing puller also might be required to get some transmission or water pump bearings out too. You want to be very sure the transmission is in good shape because splitting the cases is a pain. Clutch and water pumps usually can be done without much hassle but still a good idea to replace bearings if the bike looks quite worn on the inside.
The Shop
To reinstall, freeze the bearing and tap it in as was suggested. As for the main seals, if I recall correctly they install from the outside. So they can go in once the bearing are seated. You shouldn't have to pull the main bearings to replace the main seals. It's been a long time since I've had that motor apart though.
Some bikes utilize an adhesive gasket for the center cases, but it's not super common. There's typically a paper gasket. And in that case, simply install the gasket and tighten. Like I mentioned, if you need to hold the gasket in place use just a tiny bit of grease. You don't need it everywhere. Just a spot or two.
Kickerman had some solid advice in his post. And don't underestimate the value of having the tools for the job. A little investment goes a long way. I can't tell you how many tools I've bought simply to do the job right a single time. The time that and frustration I saved by having the proper tool more than offset the cost. And besides, what guy doesn't like buying tools?
Shane
The KX does not use a center case gasket, you will need to get some sealer such as Threebond #1184. Clean the cases really good before assembly and make sure they are dry and no oily residue on the mating surfaces before you apply the sealer. Also go light on the sealer when you apply it, cut the tip of the tube so it only has a very small hole in it and take your time, keep in mind anytime you tighten up the cases or anything that you use sealer on, if you can see it squishing out on the outside it is likely squishing out in the inside also.
Take your time and have fun with it.
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