Rebuilding a bottom end

[ThumperTDC]

I have finally got some time to work on my YZ125 I have been rebuilding for some time now. I just got the cases put back together, but I have seemed to run into a lil problem.

I goto tighten the case bolts, I get them all hand tight and the crank will spin just fine. I got to barely tighten them with my ratchet and it binds up. I am barely giving each bolt a 1/4 turn. As soon as I back them off it will spin fine. My manual says to tighten them to 10 ft/lbs. I am almost posative that I am not tightening them that tight, but I dont have my torque wqrench here to double check.

I am thinking that something is binding a bit, but I am not 100% sure. Any help/advice is more than welcome. Could it be that the shop who rebuilt my crank didnt get it pressed all the way back together and this could be why it is binding?

I have rebuilt 4 strokes several time, but this is my first attempt at a 2 stroke, and I am kind of doing it blind so to speak, since I got the entire engine in a box all tore down.

[drman]

Will it still rotate? It could be the new bearings and seals--they will a good amount of drag until the bike is ran for a bit. Do you hear any noises?

[CRF731]

What do you mean by "binds up" Is it jammed where it will not turn at all or does it still turn and just seem kind of tight?

[YZGreg]

Also how much yamabond are you putting in the case halves maybe not enough or not letting it dry long enough?

[ThumperTDC]

It will still rotate when I tighten it down, but I really have to push down on the rod to get it to move. As soon as I loosen the bolts it will move easier, but not as easy as it did before I joined the two cases.

I tore it back apart and noticed some of the sealer...........(I used hondabond..........same stuff) was inside the crankcase. I will let it sit then remove all of it, then try to do a better job with the sealer so it doesnt run into the inside when I put it together.

Alex,
I dont hear any noise, when it tight there is definately something putting some serious drag on something cause it was taking alot of force to get it to rotate.

[CRF731]

HMMMmm SInce you have it apart again. I'd double check the crank bearings and seals to make sure they are seated properly and all the way into the cases where they should be. If you have a manual it should give you the specifications for the gaps on either side of the rod bearing where the crank is pressed together. I'd check that as well or maybe take it back to the shop that changed the bearing and rod for you to get them to double check it. Hope that helps.

[Oring]

Could be that bearings are not quite on far enough!
On a side note the best thing I have found for putting on bearings is the Freezer and the Oven!
Man they make it so easy!
Also couldn,t get a bearing out the other day. One of the fitters at work welded a T piece bar onto the bearing with a piece of steel tube to act as a slide hammer. To easy! Didn't damage the case and came out second wack! Bless his Sole!
easy when you know how!

[yamracer58]

dont worry, thats normal.
i just got done rebuilding the bottom end on my yz 125.
the bearings just havent been worn in yet. put the bike back together and just kick it over a few times.
eventually they will rotate.

[dirtdemon4life]

I know the bearings on my friends bike were a bit stiff after rebuilt...It took some effort to turn it over without the piston or anything on.

[cr2504life]

I have heard that you might have gently tap the cases with a rubber mallet to get the crank centered. Not sure if there is any truth to this. I think it is normal for the crank to be pretty tight.

[ossagp]

Never heard of tapping the cases, but many do tap the crank to center it. How far off are your flywheels from center?

Now Tony,,obviously you didnt read the thread on this. (FFR and I picked on eachother good naturedly to cover just about everything).

Personally I don't like to put them back in any kind of bind, but many do that and don't report any negatives. I just cant think of a reason to put anything back that does bind. Wearing in is not something it is suposed to do to loosen up. A few heat cycles will eventually seat the bearings where the forces want to leave it. Just kind of depends if that is where you want it left I guess.