Bottom end rebuild questions

[JZ05220r]

I’m thinking of ditching the idea of throwing the cases in the oven and instead using an appropriately sized socket to transfer heat to the inner races of the crank bearings. I’m unsure of what temp to heat them to. Looks like you can feel the inner race expand based on the change in rotational resistance while heating the races.I watched a video that Ken O’ Connor racing did assembling a blaster bottom end and he heated the his to 250F. This was without any crank seals, as the blaster engine seals can be installed from the outer cases.

[KDXGarage]

Have you got a solid rod that you could use? I would think a solid rod would retain heat longer. From what I have read, people seem to have used low 200's. The slug method does avoid heating the seals.

[Chuck78]

Have you got a solid rod that you could use? I would think a solid rod would retain heat longer. From what I have read, people seem to have used low 200's. The slug method does avoid heating the seals.

Thanks for the reminder of this method! I'll definitely be trying that. I've got a few old blower motor shafts from large HVAC units (my occupation) at my disposal, and can turn them down in my lathe to the frank bearing i.d.
I've been moderately concerned about heating the seals up too much on a bottom end reassembly. This "hot slug" method should do the trick!
An infrared laser thermometer is an irreplaceable tool if concerned about heating parts too hot. I find high strength threadlocker loses it's bond at around 275° F, which is very useful in working on engines and suspension.

James, if all else fails and you aren't in a big hurry, I could send you a rough cut "slug" of solid steel rod whenever I make onefor myself.

[kdxdazz]

I used the hot slug method on my last build, socket is not ideal, you really want solid aluminium, what I did is preheat the slug to 100 Celsius and drop in, then I used my plastic welder to continue heating the slug, aluminium has high thermal conductivity but bearings which are 50100 steel have low thermal conductivity and takes a little bit of time to evenly absorb the heat, with the hot slug method you can continue heating with no risk of burning the seal

Now here is a tip to learn from my mistakes and I did want to make a video about this, the kdx crank has a very sharp lip but I can't remember which end, that lip is best to be carefully deburred, on my 2nd build the sharp lip grabbed the seal on install and turned it inside out. When using the heat method that seal becomes incredibly soft and pliable, as such in my third build I removed that lip then gave the seal a blast with freeze spray before dropping the crank in

[JZ05220r]

Have you got a solid rod that you could use? I would think a solid rod would retain heat longer. From what I have read, people seem to have used low 200's. The slug method does avoid heating the seals.

Thanks for the reminder of this method! I'll definitely be trying that. I've got a few old blower motor shafts from large HVAC units (my occupation) at my disposal, and can turn them down in my lathe to the frank bearing i.d.
I've been moderately concerned about heating the seals up too much on a bottom end reassembly. This "hot slug" method should do the trick!
An infrared laser thermometer is an irreplaceable tool if concerned about heating parts too hot. I find high strength threadlocker loses it's bond at around 275° F, which is very useful in working on engines and suspension.

James, if all else fails and you aren't in a big hurry, I could send you a rough cut "slug" of solid steel rod whenever I make onefor myself.

Thanks for the offer. This will be my winter project so if you beat me to it, I would be happy to take one and take care of any shipping charge.

[JZ05220r]

Have you got a solid rod that you could use? I would think a solid rod would retain heat longer. From what I have read, people seem to have used low 200's. The slug method does avoid heating the seals.

I do not. I’ll have to weigh my options when the time comes. Doing a lot of mental planning before I start the process

[JZ05220r]

I used the hot slug method on my last build, socket is not ideal, you really want solid aluminium, what I did is preheat the slug to 100 Celsius and drop in, then I used my plastic welder to continue heating the slug, aluminium has high thermal conductivity but bearings which are 50100 steel have low thermal conductivity and takes a little bit of time to evenly absorb the heat, with the hot slug method you can continue heating with no risk of burning the seal

Now here is a tip to learn from my mistakes and I did want to make a video about this, the kdx crank has a very sharp lip but I can't remember which end, that lip is best to be carefully deburred, on my 2nd build the sharp lip grabbed the seal on install and turned it inside out. When using the heat method that seal becomes incredibly soft and pliable, as such in my third build I removed that lip then gave the seal a blast with freeze spray before dropping the crank in

Thank you, are you referring to the “hot slug” method or oven? I’d think you were referring to the oven method based on the fact that you said the seal was real soft. Also, was it obvious when the seal lip was turned inside out?

[kdxdazz]

I used the hot slug method on my last build, socket is not ideal, you really want solid aluminium, what I did is preheat the slug to 100 Celsius and drop in, then I used my plastic welder to continue heating the slug, aluminium has high thermal conductivity but bearings which are 50100 steel have low thermal conductivity and takes a little bit of time to evenly absorb the heat, with the hot slug method you can continue heating with no risk of burning the seal

Now here is a tip to learn from my mistakes and I did want to make a video about this, the kdx crank has a very sharp lip but I can't remember which end, that lip is best to be carefully deburred, on my 2nd build the sharp lip grabbed the seal on install and turned it inside out. When using the heat method that seal becomes incredibly soft and pliable, as such in my third build I removed that lip then gave the seal a blast with freeze spray before dropping the crank in

Thank you, are you referring to the “hot slug” method or oven? I’d think you were referring to the oven method based on the fact that you said the seal was real soft. Also, was it obvious when the seal lip was turned inside out?

Yes correction, should have said the seal issue was not the hot slug method, I haven't used the oven, I always use my plastic welder
The seal wasn't obvious at first but when I did a crankcase pressure test it leaked like a sieve , after spraying soapy water I saw the seal turned inside out

[pumpguy]

Mention was made above about high strength Loctite loosing its bond around 275*F.

This very much depends on the grade of high strength Loctite being used. I use high strength Loctite in my pump work and some parts require assembly with high strength Loctite. I have found that very high temperature is sometimes required for disassembly.

Loctite informs me that grade 262 has the lowest bond loss temperature. Other grades with higher numbers loose their bond at higher temperatures; some as high as 400*F. or even higher.

[JZ05220r]

Gotcha. I’m starting to feel more comfortable, with using heat (oven or maybe hot slug method) on the right side case for crank (less/no seals to worry about on the right side ex:shift shaft seal, countershaft seal), then using a puller on the left side.

[Molly's 70]

This guy has some good video's.

[Chuck78]

This guy has some good videos.

Great vid, thanks for posting!

[JZ05220r]

This guy has some good video's.

Very well put together video, thanks. Sounds like alittle I’m putting a bit too much thought into this.