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Ok well I'm about to start rebuild my bottom end and it looks like I'm going to need a case splitter, fly wheel puller and a crank puller. Just wondering if i in fact NEED all of these or I can do the job without buying these tools. Im rebuilding a 2006 kx450f. thanks

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Ok well I'm about to start rebuild my bottom end and it looks like I'm going to need a case splitter, fly wheel puller and a crank puller. Just wondering if i in fact NEED all of these or I can do the job without buying these tools. Im rebuilding a 2006 kx450f. thanks

That depends. If you've never done a bottom end before and you're not very mechanically inclined, but the correct tools, it will make it much easier. If you're mechanically inclined, you only need the flywheel puller. I use dry ice, an oven and a small press for main bearings and cranks.

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That depends. If you've never done a bottom end before and you're not very mechanically inclined, but the correct tools, it will make it much easier. If you're mechanically inclined, you only need the flywheel puller. I use dry ice, an oven and a small press for main bearings and cranks.

I have not done a bottom before but I am mechanically inclined. So what would I use to split the cases and pull the crank into the case?

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I have not done a bottom before but I am mechanically inclined. So what would I use to split the cases and pull the crank into the case?

your mechanical skills... the cases will come apart with patience, a soft touch and maybe even a little heat. putting your bearings in the freezer for 1/2 hour and heating your cases in an oven will help greatly with bearing install, repeat this with the crank (put it in the freezer) and heat the cases with newly installed bearing again, the crank should slide right in... as was mentioned by GMO the only really necessary tool is the flywheel puller.to make the job easier i would recommend a heat gun and impact gun (for loosening/tightening clutch, drive gear, and flywheel nuts)... oh and a manual would do you good too

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Alright thanks for the advice. I just ordered the fly wheel puller so when I get that I'm gonna go ahead and tackle it. Any other advice on tearing into the bottom is much appreciated. Tips/tricks i heard it was kind of a pain in the butt. Thanks again

Edited by Chrisj0806

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not really a pain, just requires patience...if theres anything i would recommend it is to keep the motor mounted in the frame until you loosen flywheel, drive, and clutch fasteners (it alot easier getting them loose while the engine is held in the frame). drain all fluids, then take off the seat, subframe+airbox, muffler, kick-start, etc...

take some pictures and start to disassemble cabling, wiring etc (the pictures will be useful in identifying routing on reassembly) then take off the clutch side engine cover and flywheel cover. start at the flywheel nut. if you dont have an air impact gun, or a gear jammer, put the bike in gear and stick a suitable piece of wood between the sprocket and swingarm to prevent the bike from "free-wheeling" when trying to loosen the fasteners.

use 6 point wrenches as they will lessen the chance of you rounding off the fasteners. use IMPACT rather than your muscle, what i mean is: take up the slack in the drive line and use a suitably large hammer with momentum (NOT force) to tap the end of the wrench counterclockwise to "break-loose" the fastener. once loose, leave them on for now and move to the clutch side and use the same technique on the drive gear (on crank shaft) and THEN disassemble the clutch pack and inner hub nut. BE CAREFUL on the clutch inner hub nut! use a socket and suitable extension and make sure it doesnt slip off and bend/break the aluminum thread towers... finally move to the drive sprocket nut and break that loose.

once the hardware is all loose begin to dismantle the carb, head, cylinder, etc...

again take pictures!!! for reference. once thats all off, go back to the flywheel and take off the nut. use the "plug" supplied with the puller to protect the oil passage on the end of the crank shaft. use the puller to get the flywheel off (this can sometimes require quite a bit of force). once the flywheel is off, remove the timing chain and circlip (that retains the timing chain drive sprocket) and place them in a clean spot in the order of their disassembly.

move to the clutch side and remove the basket and drive gear (take note (pictures) if there are any timing marks on the drive gear and make sure they line back up on reassembly).

remove any necessary componentry from the bottom end while its still in the chassis and THEN remove the whole engine and place it on a bench. keep the engine facing flywheel side up (you can make a rig out of wood (2x4 rectangular box) to keep the engine up right and not leaning on the shafts etc...

remove all fasteners and double check that ALL fasteners and componentry really HAVE been removed. take a rubber malet and work at a 45 degree angle all around the case to break the seal. put that plug you got with the puller back on the crank. this parts a little tricky... get someone to hold the motor up by the LEFT side case only an inch off the table. take your rubber mallet and tap evenly between the crank and drive shaft to separate the right case from the left case. when done right the right case with all internals will simply drop down and out of the left case....

sorry about the vagueness of the explanation on some parts. i would highly recommend consult someone whos had this bike if you dont have a manual. (ive only done one bottom end on a kawasaki... ironically it was a 2006 kxf450 but that was a LONG time ago, so i may be missing something that is specific to the kawi...)

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i've just completed a bottom end rebuild on my 09, the adivce above is very sound, but i'll add a few more bits as well, be sure to keep track of where everythings come from, and whe actually splitting the cases be sure nothing fall's off the gearbox shaft's, on these bikes there's no circlips holding the gear's, dogs and shims in place, the crank will be easy to remove, it will just slide out of the bearings, removing the bearing not so much, you will need a 32mm socket and a hammer, the prevent damage to the cases i recomend getting a butane torch and heat the cases (do not heat it to much or it may permanently warp the cases), i suggest heating only untill it is uncomfortable to touch by hand) just be aware that the heat will quickly tranfer into the bearing casuing the bearing to expand too, if this happens wait for it to cool down completly before trying again, you have two options for removing the clutch side main bearing, you can completly remove the gearbox, i however got a friend to help me and hold both gearbox shaft's and the selector fork shaft's into the cases as i drove the bearing out of the case, when driving the bearing out of the case, relocate the socket onto the inner race of the old bearing after each hit, and use just enough effort to get the bearing to move a little, dont use exsesive force (not you cannot drive the bearing back in by hitting the inner race, this will side load the bearing and damage it), , to install the new bearings place them in the freezer for an hour or so, and heat the cases and they should slide in with minimal effort, if it does need a tap to locate it, use a SOFT FACED HAMMER ONLY i use a nylon faced hammer, and be sure the bearing's aren't going in crooked.

when putting the cases back together make sure the joining surface between the two cases is perfectly clean, there is no gasket here and i suggest not using any sealer as it will mess with the tolerances with the gearbox shaft's and crank, be sure all dowel's are in place, and take your time for reassembly.

good luck :smirk:

kxenginerebuild5-1.jpg

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+1 on the use of heat to remove the bearings. i use a heat gun which typically is not enough heat to cause damage to the cases, then use a socket as mentioned above and MOMENTUM to drive out the bearing NOT force... the best way i can explain this is to kinda let the hammer "drop" on to the socket as opposed to pounding on the socket...

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not really a pain, just requires patience...if theres anything i would recommend it is to keep the motor mounted in the frame until you loosen flywheel, drive, and clutch fasteners (it alot easier getting them loose while the engine is held in the frame). drain all fluids, then take off the seat, subframe+airbox, muffler, kick-start, etc...

take some pictures and start to disassemble cabling, wiring etc (the pictures will be useful in identifying routing on reassembly) then take off the clutch side engine cover and flywheel cover. start at the flywheel nut. if you dont have an air impact gun, or a gear jammer, put the bike in gear and stick a suitable piece of wood between the sprocket and swingarm to prevent the bike from "free-wheeling" when trying to loosen the fasteners.

use 6 point wrenches as they will lessen the chance of you rounding off the fasteners. use IMPACT rather than your muscle, what i mean is: take up the slack in the drive line and use a suitably large hammer with momentum (NOT force) to tap the end of the wrench counterclockwise to "break-loose" the fastener. once loose, leave them on for now and move to the clutch side and use the same technique on the drive gear (on crank shaft) and THEN disassemble the clutch pack and inner hub nut. BE CAREFUL on the clutch inner hub nut! use a socket and suitable extension and make sure it doesnt slip off and bend/break the aluminum thread towers... finally move to the drive sprocket nut and break that loose.

once the hardware is all loose begin to dismantle the carb, head, cylinder, etc...

again take pictures!!! for reference. once thats all off, go back to the flywheel and take off the nut. use the "plug" supplied with the puller to protect the oil passage on the end of the crank shaft. use the puller to get the flywheel off (this can sometimes require quite a bit of force). once the flywheel is off, remove the timing chain and circlip (that retains the timing chain drive sprocket) and place them in a clean spot in the order of their disassembly.

move to the clutch side and remove the basket and drive gear (take note (pictures) if there are any timing marks on the drive gear and make sure they line back up on reassembly).

remove any necessary componentry from the bottom end while its still in the chassis and THEN remove the whole engine and place it on a bench. keep the engine facing flywheel side up (you can make a rig out of wood (2x4 rectangular box) to keep the engine up right and not leaning on the shafts etc...

remove all fasteners and double check that ALL fasteners and componentry really HAVE been removed. take a rubber malet and work at a 45 degree angle all around the case to break the seal. put that plug you got with the puller back on the crank. this parts a little tricky... get someone to hold the motor up by the LEFT side case only an inch off the table. take your rubber mallet and tap evenly between the crank and drive shaft to separate the right case from the left case. when done right the right case with all internals will simply drop down and out of the left case....

sorry about the vagueness of the explanation on some parts. i would highly recommend consult someone whos had this bike if you dont have a manual. (ive only done one bottom end on a kawasaki... ironically it was a 2006 kxf450 but that was a LONG time ago, so i may be missing something that is specific to the kawi...)

I can vouch for this. I missed a bolt under the oil pump cover and it cost me a set of cases. Also, be very careful when reassembling the oil pump to not break the drive. It's small and fragile. As the other gentleman said, take lots of pictures, follow the manual, and bag all the parts individually and label them with a sharpie. Makes it much easier when it comes time to reassemble if you know which bolts go to what. Good luck with the rebuild and don't hesitate to ask a lot of questions on here. There is a ton of experience available to you.

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Great posts. Thanks guys. I got to split mine, as soon as I get the time.

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Great posts. Thanks guys. I got to split mine, as soon as I get the time.

I´m interested in the shape of your engine Numroe, it has a serious amount of hours on the bottom end and has never been apart right?

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i've just completed a bottom end rebuild on my 09, the adivce above is very sound, but i'll add a few more bits as well, be sure to keep track of where everythings come from, and whe actually splitting the cases be sure nothing fall's off the gearbox shaft's, on these bikes there's no circlips holding the gear's, dogs and shims in place, the crank will be easy to remove, it will just slide out of the bearings, removing the bearing not so much, you will need a 32mm socket and a hammer, the prevent damage to the cases i recomend getting a butane torch and heat the cases (do not heat it to much or it may permanently warp the cases), i suggest heating only untill it is uncomfortable to touch by hand) just be aware that the heat will quickly tranfer into the bearing casuing the bearing to expand too, if this happens wait for it to cool down completly before trying again, you have two options for removing the clutch side main bearing, you can completly remove the gearbox, i however got a friend to help me and hold both gearbox shaft's and the selector fork shaft's into the cases as i drove the bearing out of the case, when driving the bearing out of the case, relocate the socket onto the inner race of the old bearing after each hit, and use just enough effort to get the bearing to move a little, dont use exsesive force (not you cannot drive the bearing back in by hitting the inner race, this will side load the bearing and damage it), , to install the new bearings place them in the freezer for an hour or so, and heat the cases and they should slide in with minimal effort, if it does need a tap to locate it, use a SOFT FACED HAMMER ONLY i use a nylon faced hammer, and be sure the bearing's aren't going in crooked.

when putting the cases back together make sure the joining surface between the two cases is perfectly clean, there is no gasket here and i suggest not using any sealer as it will mess with the tolerances with the gearbox shaft's and crank, be sure all dowel's are in place, and take your time for reassembly.

good luck :smirk:

kxenginerebuild5-1.jpg

Really? No sealant between the cases? Have you done this before with no leaks? I would thnk you would have to use some type of sealant there. Off to read my manual...

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Really? No sealant between the cases? Have you done this before with no leaks? I would thnk you would have to use some type of sealant there. Off to read my manual...

yes this can be done, but the matting surfaces have to be PERFECTLY clean without ANY scratches and not warped of course. i remember that we DID use a sealant in our rebuild but ive heard of engines that have been put together without it. Ttoks perhaps can elaborate

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I´m interested in the shape of your engine Numroe, it has a serious amount of hours on the bottom end and has never been apart right?

Correct. Original bottom end. 315 hrs. I'm keen to see it and measure it too. But I'd not be surprised if it generally looks fine. But there are no abnormal noises. On the last top end change, the crank and big end felt fine. Big end run out fine.

I want to change it before my rod breaks on a panic rev. I'll order the parts in the next few days, from the US. So I hope I'm n a position to do it in about 3 weeks from now.

About to go put another 2 hours on it now. Sand track. Again! :smirk: No jumps. Based on fuel usage per hour, I'd guess I load the engine about half as much as real pros, and I'm at mid revs most of the time. I ride more gently since my crash in Sept where I hurt my shoulder. Now I cannot hold on real tight. Been good for my skills actually.

Real an article by an Aus factory mechanic, and he said that his team roughly found/believed that bottom end life was halved for every 1000 rpm increase in average rpm. Based on that, if I ride my 450F at 3000 rpm lower than I ride a 250F, then I should get 8 times the life of my 450 bottom end. Having said that, I still love riding a 250F.

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Correct. Original bottom end. 315 hrs. I'm keen to see it and measure it too. But I'd not be surprised if it generally looks fine. But there are no abnormal noises. On the last top end change, the crank and big end felt fine. Big end run out fine.

I want to change it before my rod breaks on a panic rev. I'll order the parts in the next few days, from the US. So I hope I'm n a position to do it in about 3 weeks from now.

About to go put another 2 hours on it now. Sand track. Again! :smirk: No jumps. Based on fuel usage per hour, I'd guess I load the engine about half as much as real pros, and I'm at mid revs most of the time. I ride more gently since my crash in Sept where I hurt my shoulder. Now I cannot hold on real tight. Been good for my skills actually.

Real an article by an Aus factory mechanic, and he said that his team roughly found/believed that bottom end life was halved for every 1000 rpm increase in average rpm. Based on that, if I ride my 450F at 3000 rpm lower than I ride a 250F, then I should get 8 times the life of my 450 bottom end. Having said that, I still love riding a 250F.

interesting take on the matter, but it is true. the more the bike revs (and sustains load) wear increases EXPONENTIALLY... this is why it is hard to recommend an hourly interval for people who ask WHEN to do top ends, because it depends on how hard they are on the bikes

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Really? No sealant between the cases? Have you done this before with no leaks? I would thnk you would have to use some type of sealant there. Off to read my manual...

correct no sealant, i've been on 3 rides on mine now since rebuild with no problems at all, slight oil leak from the cam cap cover because i forgot to put sealant on that, but none between the cases, as i said get the cases perfectly spotlessly clean, i used a soft scotch bright pad to clean mine.

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Real an article by an Aus factory mechanic, and he said that his team roughly found/believed that bottom end life was halved for every 1000 rpm increase in average rpm. Based on that, if I ride my 450F at 3000 rpm lower than I ride a 250F, then I should get 8 times the life of my 450 bottom end. Having said that, I still love riding a 250F.

I´m looking forward to pics and reports on the engine splitting. Does it still shift fine?

On the topic of lower end life, I´m not entirely sure that generalisation can be made. I´m sure the wear increases on the same engine if it is revved higher and under a greater load than before. But a 250f is not the same engine, and it´s made to rev higher from the drawing board. The rod and main bearings are under LESS load when the RPM climbs (at full throttle). My personal belief is that an engine will last the longest if the RPM´s are kept in a "normal" range, where the engine makes it´s best power.

If the engine is lugged and held wide open out of every corner in low RPM´s the rod is under the greatest stress.

Dean Wilson is not easy on his engines let me tell ya :smirk:

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I´m looking forward to pics and reports on the engine splitting. Does it still shift fine?

On the topic of lower end life, I´m not entirely sure that generalisation can be made. ...

If the engine is lugged and held wide open out of every corner in low RPM´s the rod is under the greatest stress.

My 06 shifts fine. Have be firm with the lever, like every KX450F or KX250F I've ridden. Ease of shifting depends on type of oil I use. I'm gentle on shifting. I rarely shift it under high load, or down shift twice without a little delay for the engine to catch up.

I agree totally that there is a correct RPM range where the motor is least stressed. No laboring. No over revving. I've read in a few places that rod load increase is proportional to RPMs squared. They can fatigue by laboring at low revs, but they tend to break at high revs.

I try not to lug it. The thing about my engine, is that I can ride a 2nd gear corner in 3rd and it wont hesitate to build revs. So I can low rev load it, but it's only for a second or two. Unlike the nice 2010 KX250F where you think "oops, this will take too long, motor wont like this" so downshift.

Thinking about what I wrote earlier I was wrong to suggest a 450 crank+rod can typically go 8 times a 250 crank+rod, but double or triple the life seems reasonable. That mechanic remark about halving bottom end life per 1000 RPM increase was referring to the same engine, when ridden by a rider who is riding in the high revs most of the time.

Edited by numroe

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Ease of shifting depends on type of oil I use.

Numroe

Don't want to start an oil war (We have had enough of those on TT).just wondering what oil you think shifts the best or easiest?

Thank you in advance

Ernie

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Ernie, I get best shifting using Shell Rimula-X diesel oil. It's the Aussie nearest equiv to Rotella. Seems like luck that I get best clutch feel/progression with it too. It's cheap and 15w40 viscosity. My engine has done maybe 200 hrs on that stuff.

It's also done about 60 hrs on Delo 400, but I went back to Shell for the ease of shifting. I've also tried synth bike oils from Shell, Silkolene and Motul, but the diesel oil feels better to me. Recently I've been using an Australian made diesel oil that is 15w50 for the extra wear protection in summer. Penrite HPR 15, which feels ok. But Rimula X still a bit better. It's pretty easy to feel shifting and clutch grab.

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