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Tonight we re-assembled the cases on our '04 KDX220. RB rebuilt the crank with a new Hot Rods rod & bearings. Installed new main bearings and seals. Taking no chances after an OEM piston failure (yes, all the warnings are true, and some of us don't find this forum until AFTER she blows!).

First - froze the bearings in Acetone and dry ice, warmed the case halves in the oven, and they dropped right in place. Just as advertised - no drama. Bearins spin nice and free.
Second - froze the crank overnight in the family fridge. Tested fit on unheated, installed bearings - slid right in the right side.
Third - stuck the crank back into the freezer while we gooped up the halves (Yamabond 4).
Fourth - dropped the crank easily into the right side, then lowered the left side over it. Got to about 3/8" case separation, then tapped it home with a soft wood block and hammer (just on the frame mounting bolt holes).
Fifth - torqued all bolts to spec in alternating pattern.

Now, trans shafts spin freely. But crankshaft takes a lot more effort to turn than I expected. I can turn it, but it takes some effort. Once at bottom of stroke, I need to help with a finger twist on the crank end to bring it back to TDC, but once there, can rock it back and forth just pushing/pulling on the rod small end.

Question (already): is this normal - just needs to be broken in? Or did I screw something up? Crank appears to be tighter against the right case than the left, so I don't think I forced anything together against its will.

I don't want to over worry it, but hate to keep going if I have a problem.

Thanks!

I just did crank seals and used the Tusk crank puller to put the left side back on. That tool works great! I would guess that you have too much side load on the left crank bearing. I also did the freezer and heat thing to put the crank in but you just don't have enough time to get the left cover on while the crank is cold.

You could try swatting the crank back and forth but mine goes back together VERY tight so it may take more than that.

I could be wrong but it sounds like to me you are just experiencing what all engines do when they get to BDC. It will always be harder to get it coming back up as the crank isn't really spinning. Try pushing down on the rod hard enough that the inertia of the crank while rotate itself past BDC and see if the resistance is the same then. Also, did you lube the bearing (crank and rod) at all? Dry bearings will have more resistance than lubed ones, obviously. Just something to check. If the resistance changes during the rotation then something is wrong. Normally that means the crank isn't indexed (trued) correctly.

Thanks for the responses. The resistance is constant through all 360 degrees, and I don't feel any interference, for example no rattle or clicks. RB Designs assembled the crank, so I'm confident it is true. I did not lubricate the bearings before assembly - was debating heating the cases, and didn't want more oil smoke in the kitchen if we went the route!

BTW - I read a previous thread where the hot case, cold crank method was discussed. I couldn't figure out how to get the gasket goop on the cases doing this, unless applying it before heating (baking it, and risking a bad seal). Otherwise, the cases would cool while I'm smearing it on, defeating the purpose? Decided against.

I did a test assembly of the cases without the crank, to make sure I had everything in place and that the sides would pull in tightly. I needed to tap it the last ~1/4" even without the crank. I was sure it was just resistance from the two dowels that prevented me from pushing the halves together with my hands. I don't think I encountered a lot more resistance than that with the crank in place - possibly a little more. The crank had been out of the freezer only seconds at that point - literally maybe 10 seconds.

My conclusions at this point: 1. the bearings are new/dry, and therefore stiff. All will be fine after break in; and 2. the crankshaft in the freezer overnight method worked pretty slick.

If everything blows up on the first ride, well, then I'll adjust my self confidence settings

I've had cranks feel a little tight after assembly, and usually I can free them up by just whacking both ends with a hammer (wood in between) - sometimes thats all it takes to get the ass'y to seat properly and spin easily.

kawagumby wrote:I've had cranks feel a little tight after assembly, and usually I can free them up by just whacking both ends with a hammer (wood in between) - sometimes thats all it takes to get the ass'y to seat properly and spin easily.

Yep. Also look with the jug removed and make sure the clearance is the same on either side of the crank lobes.

Don't try the heat freeze method for the final assembly. You NEED a crank puller for that final step. THE CASE BOLTS WILL NOT CUT IT!

Slick_Nick wrote:Don't try the heat freeze method for the final assembly. You NEED a crank puller for that final step. THE CASE BOLTS WILL NOT CUT IT!

I've done it without a crank puller about half a dozen times in the past couple years. No problems.

Julien D wrote:

Slick_Nick wrote:Don't try the heat freeze method for the final assembly. You NEED a crank puller for that final step. THE CASE BOLTS WILL NOT CUT IT!

I've done it without a crank puller about half a dozen times in the past couple years. No problems.

The last time I did it I used the case bolts and it worked. This time I froze the crank to drop it into the right case and then I used a crank puller for the left side. Once you try a crank puller you won't want to do it any other way. I was trying to get everything lined up and by the time I did the cases were back together. I kinda thought I missed something it worked that good.

Yeah, It's a nice to have. Not a necessity though.

Update: crank lobes were not centered in the case opening. Gave the right (primary) end a few good whacks with a hammer and soft (pine) wood block between. This centered the lobes, and freed the crank up nicely to where it would easily spin round and round by just making like a piston on the rod end.

Lessons learned? I can see why the crank puller might be handy - If I had one, I'd still freeze the crank, then I'd use the puller. That said - the frozen crank slipped so easily through the bearings, even the second one - I'd do it again without the puller. But next time I'll lift slightly after dropping it in the right side bearing, before sliding the left side on and tapping it down. But, I'm REALLY hoping there is no next time!

Note - I did NOT pull the cases together with the case bolts. I did tap on the frame mount holes to push down onto the two dowels. But since I needed to do the same during my dry run without the crankshaft, I'm pretty sure the bearing was not holding the cases apart.

I really, really appreciate all the quick responses and help!

Awesome! I'm glad you got it sorted out.

Slick_Nick wrote:Don't try the heat freeze method for the final assembly. You NEED a crank puller for that final step. THE CASE BOLTS WILL NOT CUT IT!

bullshit

Although a crank puller likely makes the final case assembly easier, the case bolts will totally pull things back together. I've done it three times. That said, I may well invest in a crank puller next time, as getting the case halves close enough for the bolts to start working was a little iffy.

Just use a little longer bolts to get it started, that way there's no risk of pulling the threads

The benefit of the crank puller is that it pulls the crank into the bearing, not push the bearing onto the crank. I have done it both ways and I found the crank puller to be MUCH quicker and when the cases were together the crank spun just like it should. No swatting or reallinging to be done.

It can be done with the case bolts but if you plan on doing more than one case splitting lob than the $50 bucks for the crank puller is a good investment. A few of the guys I ride with and my self have been buying different tools to get the big jobs done and we swap tools as needed. Makes having the right tool a little bit cheaper.