Bottom end rebuild questions

[JZ05220r]

Just curious what you guys recommend to do to make sure the crank is centered. My plan was to predetermine how much room is on each side with a feeler gauge and then drop it in, bottoming out on my gauge. Also wasn’t sure if the crank puller works on both ends of the crank. I might grab one if needed in case I run into issues heating and freezing. I saw that it only works on one end from an older post and not sure if Tusk updated their adapters. Also when I heat the cases for the bearings and once again for the crank, what is a good temp and time in the oven? Also when I put the cases together, one side will be fresh out of the oven and mating with a room temp case with a coating of case sealer. Will there be a curing problemoranything? If I can think of any more questions I’ll add to this. Just want to make sure I’m doing things right. Thank you!

[Chuck78]

Using a heat gun around the area of the bearings after it's lightly heated in the oven could be a better option, so you can localize the heat to the areas of interest, while the rest if the case halves act like a bit less of a heat sink, while not needing to worry about having the cases too hot to be within the case sealer's specified workable temperature range.

I'll be trying this approach at some point soon on my spare KDX engine.

[Molly's 70]

I always use a press to install the bearings & crank. After I get the case half's buttoned up, I use a soft mallet to center the crank. Just soft
taps is all it takes.

[JZ05220r]

Using a heat gun around the area of the bearings after it's lightly heated in the oven could be a better option, so you can localize the heat to the areas of interest, while the rest if the case halves act like a bit less of a heat sink, while not needing to worry about having the cases too hot to be within the case sealer's specified workable temperature range.

I'll be trying this approach at some point soon on my spare KDX engine.

Thanks for the suggestion! Would be nice to hear how that goes. I’m not going to be finished with this before winter.

[JZ05220r]

I always use a press to install the bearings & crank. After I get the case half's buttoned up, I use a soft mallet to center the crank. Just soft
taps is all it takes.

That makes it sound very simple. I have a press but just worry about messing up the crank with a press

[Chuck78]

I always use a press to install the bearings & crank. After I get the case halves buttoned up, I use a soft mallet to center the crank. Just soft
taps is all it takes.

That makes it sound very simple. I have a press but just worry about messing up the crank with a press

That's exactly why I'm going with the heat / freeze methods I mentioned, but just as much for the delicate handling of the bearings, but also to not knock the crank out of true whatsoever. I plan to have Boyko Racing or Tom Morgan Racing rebuild my crank(s) with Wossner forged rods, and professionally balance the cranks. I hear it makes a significant difference after having a press pin crankshaft professional do a proper balancing job on it.

[JZ05220r]

I always use a press to install the bearings & crank. After I get the case halves buttoned up, I use a soft mallet to center the crank. Just soft
taps is all it takes.

That makes it sound very simple. I have a press but just worry about messing up the crank with a press

That's exactly why I'm going with the heat / freeze methods I mentioned, but just as much for the delicate handling of the bearings, but also to not knock the crank out of true whatsoever. I plan to have Boyko Racing or Tom Morgan Racing rebuild my crank(s) with Wossner forged rods, and professionally balance the cranks. I hear it makes a significant difference after having a press pin crankshaft professional do a proper balancing job on it.

I’ve got my eyes on the new Vintco crankshaft.

[SS109]

Having the crank centered isn't really critical. Just make sure you have at least the minimum side clearance to the case on each side and you're good to go.

[Chuck78]

That makes it sound very simple. I have a press but just worry about messing up the crank with a press

That's exactly why I'm going with the heat / freeze methods I mentioned, but just as much for the delicate handling of the bearings, but also to not knock the crank out of true whatsoever. I plan to have Boyko Racing or Tom Morgan Racing rebuild my crank(s) with Wossner forged rods, and professionally balance the cranks. I hear it makes a significant difference after having a press pin crankshaft professional do a proper balancing job on it.

I’ve got my eyes on the new Vintco crankshaft.

Vintco is making a replacement '89-'06 KDX200/220 crankshaft? I believe a lot of their stuff is made by Wossner, right?

[kdxdazz]

Having the crank centered isn't really critical. Just make sure you have at least the minimum side clearance to the case on each side and you're good to go.

Strongly disagree, the crank has to be pulled to take the side load off the bearings, this is a critical step especially using heat and freeze method as when everything normalises there is so much side load on the bearings it can feel a bit stiff to rotate

My method is either use a crank puller to pull or case splitter to push, apply tension then I use my plastic welder to heat the cases where the bearings sit, you will eventually here a sharp pop sound which indicates side load has been taking off

[JZ05220r]

With the heat/freeze method and a pre determined shim prior to dropping the crank in to account for the centering of the crank I would think that there would be no issue with side load. I asked Jeff fredette, and this is the method he uses.

[JZ05220r]

That's exactly why I'm going with the heat / freeze methods I mentioned, but just as much for the delicate handling of the bearings, but also to not knock the crank out of true whatsoever. I plan to have Boyko Racing or Tom Morgan Racing rebuild my crank(s) with Wossner forged rods, and professionally balance the cranks. I hear it makes a significant difference after having a press pin crankshaft professional do a proper balancing job on it.

I’ve got my eyes on the new Vintco crankshaft.

Vintco is making a replacement '89-'06 KDX200/220 crankshaft? I believe a lot of their stuff is made by Wossner, right?

Yes, they are affiliated with Wossner.

[SS109]

With the heat/freeze method and a pre determined shim prior to dropping the crank in to account for the centering of the crank I would think that there would be no issue with side load. I asked Jeff fredette, and this is the method he uses.

Exactly.

Having the crank centered isn't really critical. Just make sure you have at least the minimum side clearance to the case on each side and you're good to go.

Strongly disagree, the crank has to be pulled to take the side load off the bearings, this is a critical step especially using heat and freeze method as when everything normalises there is so much side load on the bearings it can feel a bit stiff to rotate

My method is either use a crank puller to pull or case splitter to push, apply tension then I use my plastic welder to heat the cases where the bearings sit, you will eventually here a sharp pop sound which indicates side load has been taking off

There isn't any real side load on anything as long as you have the proper side clearance as there isn't really much room either way to begin with. Been building engines for a long time now and never had any issues with any bearings failing. The piston floats independently from the rod itself so no real side loading can occur and is partly why it is designed that way.

[kdxdazz]

With the heat/freeze method and a pre determined shim prior to dropping the crank in to account for the centering of the crank I would think that there would be no issue with side load. I asked Jeff fredette, and this is the method he uses.

Exactly.

Having the crank centered isn't really critical. Just make sure you have at least the minimum side clearance to the case on each side and you're good to go.

Strongly disagree, the crank has to be pulled to take the side load off the bearings, this is a critical step especially using heat and freeze method as when everything normalises there is so much side load on the bearings it can feel a bit stiff to rotate

My method is either use a crank puller to pull or case splitter to push, apply tension then I use my plastic welder to heat the cases where the bearings sit, you will eventually here a sharp pop sound which indicates side load has been taking off

There isn't any real side load on anything as long as you have the proper side clearance as there isn't really much room either way to begin with. Been building engines for a long time now and never had any issues with any bearings failing. The piston floats independently from the rod itself so no real side loading can occur and is partly why it is designed that way.

Piston floating has nothing to do with side load on crank bearings, the fact that you think that is very telling
Of course side loading is an issue which is the reason the service manual has a whole page dedicated to side loading and releasing it

[SS109]

With the heat/freeze method and a pre determined shim prior to dropping the crank in to account for the centering of the crank I would think that there would be no issue with side load. I asked Jeff fredette, and this is the method he uses.

Exactly.

Strongly disagree, the crank has to be pulled to take the side load off the bearings, this is a critical step especially using heat and freeze method as when everything normalises there is so much side load on the bearings it can feel a bit stiff to rotate

My method is either use a crank puller to pull or case splitter to push, apply tension then I use my plastic welder to heat the cases where the bearings sit, you will eventually here a sharp pop sound which indicates side load has been taking off

There isn't any real side load on anything as long as you have the proper side clearance as there isn't really much room either way to begin with. Been building engines for a long time now and never had any issues with any bearings failing. The piston floats independently from the rod itself so no real side loading can occur and is partly why it is designed that way.

Piston floating has nothing to do with side load on crank bearings, the fact that you think that is very telling
Of course side loading is an issue which is the reason the service manual has a whole page dedicated to side loading and releasing it

I think you and I are talking about two different things as far as side loading and the crank being centered. You're talking specifically on the crank bearings themselves, yes? I'm talking about side loading that some believe could be induced by the crank not being centered due to the rod.

As to what you're saying, the service manual does not dedicate a whole page to this (95+ Service Manual, Page 7-9, slight blurb and rest of page is blank). It briefly tells you what to check for and how to correct it. The method said to "center" the crank is by tapping it with a mallet. This doesn't do anything other than move the crank, and possibly bearings, over to one side or the other. It doesn't address side loading of the bearing(s) themselves but of the crank being up against the case half. This is why I said to just make sure you have some side clearance between the crank and case halves and all is well.

[kdxdazz]

maybe we are talking about different things but the term side loading refers to pressure put on the side of the bearings,obviously this cannot occur on the big end needle bearing or floating piston so can only refer to crank bearings.
when the case halves are assembled using the heat and freeze method the crank will be somewhat stiff to turn becuase of this side loading and needs to be released, yes the service manual states to tap with a soft mallet and use a wedge to stop the crank being knocked out of true. the crank is not up against any case halves when assembled even when off centre, at least that was the case with the 3 kdx engines i have built, the crank when off centre is pushed up against the inner race of the bearing
when the the crank is installed in the first case half and the other case off is put on with the preheated bearing by the time you get this on and the bolts in the inner race temperature will have normalised and grabbed the crank then when you torque up the bolts the side load pressure is now created
to answer the OP's question about temperature i use 80 degree celsius temperature, this is both for the case to drop the bearings in and the inner race of the bearing to drop the crank in, in the past i have frozen the bearing or crank but i now think this is somewhat incorrect because of the amount of moisture created

[KDXGarage]

kdxdazz, please try to use a little tact. Statements like "the fact that you think that is very telling" don't really add much to helping the original poster's concern. Thank you.

[Chuck78]

I would definitely tend to agree with the need to relieve the side loading on the bearings, and also that it's quite critical to wedge the crank to keep it from going out of true. Granted I'm certain that both of you have built far more 2-stroke engines than myself, but myself, I do tend to be very analytical and overly attentive to all mechanical details and proper repairs.
More tact is definitely a good thing in this type of forum environment.

Centering the crank is not a terribly critical & precise step, although it should be reasonably centered to keep the clutch basket and crank primary gears aligned, as well as the flywheel rotor vs stators and case.

[kdxdazz]

kdxdazz, please try to use a little tact. Statements like "the fact that you think that is very telling" don't really add much to helping the original poster's concern. Thank you.

My apologies

[KDXGarage]

Thanks, man. We are all lime green brothers here. :-)