Dummy bearings, AV7/10 crank fitting??'s

I've been reading the rebuilding manual and there are a few points I'm unclear about. One the use of the dummy bearings. I assume these are over/under sized so they slide fit on the crank and into the case. I'm also assuming that the bearings are supposed to "bottom out" in the case halves, and the resulting space between the bearing and the crank is to be made up with shim washers. My final question is about the seals, the springs go inside right?

Are my assumptions correct? I don't want to make an ass out of me and umptions. Any other tips tricks? I got plenty of time on this build, I'm tryingto gather al the stuff I need to put in my mental toolbox right now

thanks

crackstar

Re: Dummy bearings, AV7/10 crank fitting??'s

Err.. I have no idea what a dummy bearing is. But the bearings can only go on one way, with the chamfered side toward the inside of the crank. There are no endplay shims to worry about on these so just drop it in the case. Make sure the bearings sit all the way down on the crank otherwise the case will not sit together. It's all pretty easy, oven the bearings, freeze the crank, drops right on. Get a tube that slides around the crank and catches the inner race and rap it with a hammer to make sure it's seated. Done.

Re: Dummy bearings, AV7/10 crank fitting??'s

I was referring to this page, and about the setting of endplay? on the crank in the cases

Re: Dummy bearings, AV7/10 crank fitting??'s

Ahh, they are talking about using a set of spacers that are the same size as the bearings to check the end float on the crank. Every case is a little different and so is the cranks. So you don't want the crank moving back and forth too much, but some play is good, so you put the dummy bearings in, slide it in the cases, and then measure with a dial and block how much the crank moves back and forth. Then you calculate the shims you need to put behind the bearings in the case to give it the play that you want. Although in practice, I've never seen a moby with those shims, and they all pretty much are the same so you can just drop em together and go. 103s have those shims though.

Re: Dummy bearings, AV7/10 crank fitting??'s

Don't worry about it, just skip to the final assembly.

Re: Dummy bearings, AV7/10 crank fitting??'s

See, I would rather not half ass it, with my polini cases and doppler crank, I have noticed a quite a bit of difference in the depth of the holes for the bearings in the case and the actual thickness of the bearings. I f I were to drop one side on and have that bearing bottom out in the case the crank may be off center, in reference to the con-rod, when I place the other case half on. Thats all Im checking into..

but is it everyone who builds these just drops the halves on/together, no blow ups or ruined bearings/parts/kits with this method?s

Re: Dummy bearings, AV7/10 crank fitting??'s

hot and cold is your best friend for AV7 rebuilds. Freeze the crank (the longer the better really), and heat the bearings at about 350. CAUTION: If youre using the FAGS, they have a plastic bearing race as opposed to the ZKLS which use a metal bearing race. I learned the hard way that the FAGS melt... thats why i only get ZKLS now, you can heat them as much as you want.

Once you have your crank cold and your bearings hot, your bearings will literally drop right to the bottom of the crank, no coersion necessary.

Once you have the bearings on, do it all over again except now putting the full cranky assy in the freezer, and the case halves in the oven. Still havent mastered this step of the process yet, but its not so bad. I lube the crankshaft up a bit with 2 stroke oil, dunno if that helps at all. Then once i get the crank seated in a case halve, i kinda just tap it with a rubber mallet to help everything get seated. Once again, i dunno if that helps at all but it sounds about right.

Re: Dummy bearings, AV7/10 crank fitting??'s

i didnt read your post above. i know what you mean.. i just rebuilt a bottom end and one of the bearings was a smiiiiiiiiiiiidge... and im talking a SMIDGE... not deep enough in its recess. so, like you said, the con rod was just barely noticably off center. i didnt like that at all cause i was putting the malossi 62 on it and, like you, didnt want to fuck things up. i tried 2 or 3 more times to get the bearing in there deeper but no luck. so eventually i just bolted it all together and hoped for the best. ive put 150 or so miles on it since then with no trouble.

still, as soon as i rebuild another bottom end im putting my kit on that instead, just in case. that is, if it comes out better than this one.

Re: Dummy bearings, AV7/10 crank fitting??'s

super easy.

heat the bearings and drop em on or not, and hammer them onto the crank. then heat the case and drop one side of the crank with bearings attached in. heat the other case side drop the other side in. if it doesn't go all the way heat again till eveything slide in smoothly and moves freely.

Re: Dummy bearings, AV7/10 crank fitting??'s

There is no need to heat the bearings and freeze the crank (seriously, do you think the metal in the crank will contract a noticeable amount? I don't). Just place the bearings on the crank and get a bit of tubing just big enough to fit around the crank arm and not big enough to make contact with the inner metal part of the bearing and hammer on. No need for heat, just a couple taps of a hammer.

As for assembling the crank, getting the oil seals in there is a bit tricky without the proper tool, so I can't tell ya an easy way for that, but all you need to do is heat up the case half with a torch, gas burner, anything, to get it so hot that you see the air rippling from the heat of the case, once it is that hot, just slide the proper end of the crank arm though the opening and it should just slide right in with minimal effort. Repeat with the other half. I've yet to have an issue with this method. In fact I'm about to take half my av10 case off the crank by heating it up on my gas stoves burner till the half literally just falls off the crank. I've got to make a new gasket!

Re: Dummy bearings, AV7/10 crank fitting??'s

no, i dont think they will contract a _noticable_ amount. but just cause i cant observe the size change doesnt mean it isnt happening. how do i know its happening? because when i heat them and freeze the crank, they drop right on. why hammer shit if you can just let physics do the work for you?

Re: Dummy bearings, AV7/10 crank fitting??'s

dude, seriously, heat is the way to do this. A press fit is usually 5 thousands over. Which means the inner is larger than the outer by a small amount. The steel will change that much if you heat it by 3-400 hundred degrees. Why hit things with hammers if you don't have to.

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