SOS- need help with my rebuild


11 replies to this topic
  • cowboyona426

Posted November 06, 2010 - 03:52 PM

#1

Working on the 426 today, get the trans reinstalled and the crank slid in the right engine case. Apply sealant, get the left case into place and the crank is very, very difficult to turn. I could also hear some light rubbing on the right case before I put the case halves together. So much for riding it tomorrow I guess:lol: Any help would be appreciated, I really need to get this thing going.

  • grayracer513

Posted November 06, 2010 - 04:35 PM

#2

OK, so the main bearings are OEM, with the edge groove cut on one side for the bearing retainer plates, right? And the screws in the retainer plates are all the way in? And you think that the crank is rubbing something? Shouldn't be. Odd though it may sound, install the two gears on the right crank axle and torque the nut down, then put a drop of oil in each bearing and see what happens.

  • cowboyona426

Posted November 06, 2010 - 05:02 PM

#3

Main bearings are OEM. Retainer screws are tightened down. Without any screws in the cases everything is fine. If I put one screw in each end of the cases and tighten them down the crank binds.
Since I'm asking questions anyway, how easy should it be to shift the trans? The shift drum will turn but its kind of stubborn. And since I havent ever been this deep in an engine before I'm not sure how to test it.
Unrelated to the above, but what does the flywheel retaining nut look like? Sifting through the random bolts that were removed prior to me buying the bike I couldn't find one that seemed right.

  • grayracer513

Posted November 06, 2010 - 10:21 PM

#4

The trans doesn't "dry shift" well, really. It's friction at the fork pins in the drum and such. Then there's the matter of getting the gears rotated into alignment as you shift. As long as it works, it should be OK.

The flywheel nut is a 17mm nut, 10mm thread, with a washer under it.

  • Birdy426

Posted November 07, 2010 - 08:07 AM

#5

Put some machinist's blueing on the bearing retainer plates and screw heads, slap it together and spin the crank.Look at where the blueing is gone to find out what the crank is rubbing on. (You can use nail polish, model paint, etc as well, just don't put it on thick as that can give a false indication) When the bearing retainer screws are installed, they get punched on the edge (half on the screw head, half on the retainer plate) with a centerpunch as a locking feature. It sounds like there may a burr left in the countersink of the bearing retainer or screw head that is holding the screw head a few thousandths out from "flush". If that's the case, clean the burr up with a file and you should be set.

  • cowboyona426

Posted November 08, 2010 - 07:59 AM

#6

Anyone else have any suggestions? Hoping to get back to it tonight. I was too disgruntled to mess with it yesterday.
As for staking in the retainer screws, the manual I have says that is optional. Should I go ahead and do it, or should I just put a drop of blue locktite on them?
Additional info that may help- getting the case halves to go together was a real PITA, getting them apart is fairly easy. I have the trans/crank slid into the right case half, the manual says to install them in the left case half. Any chance it will make a difference if I do it that way?
Any ideas on what is causing the crank to bind up? One crank bearing is an OEM replacement, the other one I left alone because it was in good shape. The bearing is installed correctly (machined groove for the retainers toward the middle of the engine) and was dropped into the case after heating the case half and freezing the bearing (worked great, thanks Grayracer). Any chance the bearing could be slightly crooked in the cases causing the binding? And just for clarity, the crank is very hard to turn with even 2 bolts installed in the cases, to the point of being virtually locked up. Remove the bolts and it spins just like it should.

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  • grayracer513

Posted November 08, 2010 - 09:45 AM

#7

If you did not seat the bearing you installed with a hammer and driver/punch, that could be the problem. Heat the case up again and go around the outer race to be sure it's all the way at the bottom.

The retainer plate screws should be installed with red Loc-Tite and, IMO, staked.

When you remove the screws, do the cases open up at the joint? Have you tried torquing down the primary gear?

  • cowboyona426

Posted November 08, 2010 - 10:17 AM

#8

If you did not seat the bearing you installed with a hammer and driver/punch, that could be the problem. Heat the case up again and go around the outer race to be sure it's all the way at the bottom.


I will do that, maybe this evening.

The retainer plate screws should be installed with red Loc-Tite and, IMO, staked.



I didn't see any evidence of red lock-tite on the screws but I'm 90% certain this motor has been opened up before. Many of the screws/bolts in the bearing retainers were loose :p I don't have any red on hand, I guess I'll have to pick some up.

When you remove the screws, do the cases open up at the joint? Have you tried torquing down the primary gear?


I can't remember exactly. I believe the case halves were together but there may have been a very small gap in between. I have not tried torquing the primary gear down yet.

  • grayracer513

Posted November 08, 2010 - 10:30 AM

#9

Be sure the bearing is seated, and if the crank binds again, try torquing up the drive gear. You might also check the side clearance at the rod as a way of checking that the crank is pressed together all the way. One other thing that you might try is punching down the INNER race of the left side main bearing in on the crank axle to see if that relieves the strain.

  • cowboyona426

Posted November 08, 2010 - 11:15 AM

#10

Now I know why the case sealant comes in such a big tube... I'm going to end up pulling this thing apart a bunch of times I'm afraid :p

  • Birdy426

Posted November 08, 2010 - 10:36 PM

#11

As for staking in the retainer screws, the manual I have says that is optional. Should I go ahead and do it, or should I just put a drop of blue locktite on them?


I think you misunderstood...when Yamaha originally built the motor, the screws were staked as a locking method. The staking can leave burrs on both the countersink in the retainer and screw head. As you mentioned rubbing on the right case half, it's possible that the screw head is raised up on a burr and causing the rubbing/binding. I, too, use red locktite AND a center punch.

Let us know what you find.

  • cowboyona426

Posted November 09, 2010 - 07:20 AM

#12

I think you misunderstood...when Yamaha originally built the motor, the screws were staked as a locking method.


I'll have to look in the manual again, but I was almost sure that it said staking the screws was optional. I'll be doing it anyway, after noticing that many of the screws/bolts for the bearing retainers were loose in this engine before I ever put a wrench to them.





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