Topic: Crank Won't Turn

[Rocketman]

Hoping someone has run across this before.  Here is the scenario:

I am building a motor for my CB550.  Before buttoning up the bottom end I used plastigage and had .0015 to .0025 clearance with 15 ft lbs of torque.  I double checked the Service manual and it specks up to 18 ft lbs which is what I used.  Imagine my suprise when I found the crank nearly locked up.  It took 2 hands and great effort to move it.  So I pulled the bottom end back apart and plastigaged it again.  I used 18 ft lbs and found the clearance running between .001 to .0015.  So, it does get tighter when the torque on the bolts is increased.  I then reassembled it and ran it up to 15 ft lbs and it was free and felt fine, then increased it to 18 ft lbs and it is nearly frozen. 

I made the classic mistake of not keeping my parts separated between the two engines I tore down.  I am not sure which engine the crank came out of.  The bearings that came out of this engine were 13317/Green.  With new Green bearings on 2 of the journals the clearance was between .002 and .003.  In an effort to tighten it up I put 13315/Black bearings in it.  My next step is to put the crank in a lathe and see if there is any run out.  I'll also put a machinst straight edge on the cases and check them.  I have a full set of green bearings on order and will see what that does.

Give it to me straight guys, I can take it.

[bwaller]

For fun check the case letters (rear of bottom case) and journal numbers to see what brgs. the service manual suggests. I know these are production codes but it can be a place to start. Did you try a second crank to see if it tightened up too?

[754]

There. Can be variances in the thickness of your sealer.... Maybe put. Another coat on...might work..

[lordmoonpie]

Do you have a standard gearbox in the bottom end? I had this exact same problem and it turned out to be a clearance problem in the nova CR box. I removed the end shim and it worked fine ever after. If it's a standard box, worth checking it's assembled right...

[trueblue]

Torque does affect tunnel sizes, the tunnels will be set at a certain torque.  If you go over this you will get an oval tunnel .  If it was me I would pull it down to torque X, check it for round with an internal micrometer.  Then pull it down a bit tighter and tighter, and the point it starts to deform and go oval, I would call that the torque your engine was designed to run.  When it deforms you will get a larger measurement across the journal than you will from top to bottom.

[bwaller]

For your info, these bearings have been NLA from my source in the US but Honda Canada still list them. (at this point) I just bought another set, paid more for them  but at least were available quickly.

[MRieck]

Did you mismatch the case halves?

[Bill/BentON Racing]

I'd wait and try the green bearings! Bet they work, it's what was in there...and since you didn't change anything they'll probably take the 18lbs. Bill

[Rocketman]

Had the crank in a lathe last night and the runout was .0015 in the middle.  Also put a machinist straight edge on the cases and they look good.  It really is looking like the bearings at this point.  Will check the codes to see if I can figure out what was in the engine when it was built.  New bearings are on order from CMSNL, should have them in about a week.  I am confident the case halves did not get mixed.  If the new bearings do not solve the issue I'll round up an internal mic and check for roundness.  Thanks for all the suggestions, last thing I need is to toast a crank flat out in top gear! 

Just ordered a Fowler 1.4" to 6" dial bore gauge to check the bearing tunnel.  The price was right at $103.16.  Any excuse to buy a new tool.   

[Bill/BentON Racing]

Someone on here, don't remember who tried the same thing on a 750.... went to blk..to tighten up like you did...same problem. Put the greens back in ,worked fine. Green was most common, if you couldn't measure, use codes etc then green was the place to start. Bill

[754]

The question really is... How thick is the case half sealant.. And how do you. Consistenly control it..
 Spray product. Would be nice but requires .masking.

[Rocketman]

Installed the new Green bearings last night and my problem is resolved!  First checked the clearance with plastigage and was at or a little less than .002.  Then lubed up the crank and bolted the cases together and at 18 ft lbs the crank is free and smooth.  Cleaned it all up, sealed the cases, and bolted it all back together for what I hope to be a long time.  I am using chip brushes from Harbor Freight to apply the sealer, lets me put down a thin consistent coat.

Thanks to all for their advice and suggestions.  Guess the learning is you can get to little crank bearing clearance.

[bwaller]

Good news.

[Bill/BentON Racing]

Invoice in the mail! Haha great news, love those greens, can't measure or when in doubt.go green!