62T Bottom end assembly question

[Watty]

I recently had to replace the lower half of my crank cases with a spare that I had lying around. It's in good condition, but is the older grey instead of black (62t btw).

I notice once I have aligned all the bearing stop pins, and put the two halves together, the crank spins very nicely. Once I actually torque all of the case bolts, the crank becomes harder to spin. I can hang onto the rods, and get it spinning up and down in constant motion like the pistons would when the engine is running.

I'm wondering if this is normal, as I have never really noticed it before thats all. All my bearing pins are aligned (well, the ones that actually stick out!) so I'm wondering if this has anything to do with the bottom half I'm using being a little tighter. They are identical parts numbers as well.

I've already had it apart once to check things out, and everythinkg is fine visibly.

Cheers.

 

[Keith]

Are the case halves a matched set? If so what did you torque the case bolts to? The service manual says 20ft.lbs.

 

[Keith]

Ok I re-read your post and it sounds like you are using a set of unmatched cases. That may be why when you torqued the bolts down it was harder to spin the crank. If that is the case I would not run the motor because I believe that your crankshaft will suffer a premature failure due to too much pressure on the crankshaft bearings.

 

[wildman326]

Um. Yeah. Don't run it if it is harder to turn when you torque it down.

Something is jacked up.

 

[Watty]

When you say unmatched, I'm not sure what you mean?

So from what you're saying, if I happen to do damage to the top half of the crank case, I should throw the bottom one away as well as they are not matched?

The new bottom half that I am using is stamped exactly the same as the one that is trashed, and I find it odd that these would be cast in pairs in the factory (top and bottom) to match each other.

The torque is as per the settings in the manual, and I'm using a Hotrods crank. This could have been the case with the other bottom half, but I never really took much notice.

 

[ski4]

i have heard a lot of talk that they should only be used as a matched set, in the same breath i have read a lot of people say they have gotten away with what you are doing with no trouble. sbt claims ther is no truth to the case matching ideas and they do it all the time???????????????

are you sure you didn't pinch a bearing or anything with the locator pins or anything

 

[sflsurfrider]

i doubt that you have a problem with mismatched yami cases.

mismatched simply means a set that did NOT come from the factory as a 'set'.

it could just be the seals causing the resisance. if youre unsure, split the cases, remove the seals then re-sandwich the crank and torque the case bolts to spec. if it spins freely then, it was just crank seal resistance which is normal.

make sure to use grease on the lips of the seals when re-assembling.

and install the crank with the cases upside-down so gravity holds the crank in place while aligning the pins.

why arent all of your pins in place? if one is just sticking out a LITTLE, and isnt in the hole, itll cause problems.

 

[Watty]

Yeah, thats what I find strange. It's EXACTLY the same bottom half. I've had the cases aprt to check, and then put them back together as I was worries about, but it does the same thing. For example, when I ratchet up the bolts to pull the cases together flush, it spins really freely. Once I apply the correct torque, thats when it gets a bit tighter.

I would imagine there would be some kind of resistance there as from what I've heard, the cases are a poof-teenth smaller than the crank bearing size for a nice sandwich fit. Can anyone confirm?

 

[Watty]

And yeah, the crank seal resitance sounds right to be honest, as I can't think of anything else that may make it a little tighter. As I said, I can put a pin through the rods and pump the engine in succession, although only just.

 

[sflsurfrider]

have you tried it w/o the seals?

 

[Watty]

No, I haven't to be honest. That would be the logical progression I guess!

Thanks.....I'm gonna need beer......stat.

 

[Keith]

Try it without the seals. I have spun them in my hands out of the crankcase and again when in the crankcase and not noticed any difference after it was torqued down. I may be off here but I hate to see you waste a crank. Mabye Mr. Magoo can chime in here.:bigeyes:

 

[sflsurfrider]

the crank should spin 100% freely w/o the seals.

 

[douglee25]

SFL is correct. The crank should spin 100% freely. Any resistance is going to burn up a bearing. Have you tried throwing the old bottom case back on and turning the crank for a baseline feel? Maybe you'd have something to compare it to.

Doug

 

[SUPERTUNE]

When cases are manufactured they are linebored as a matched set, so technically you should always use as a matched pair!! All newer black painted 62T cases have a serial # on the top and bottom of case at the back by the rear crank seal to keep them paired up. I will never use a mis-matched set for any Hi-Perf application or for that matter any motor I'll put together... I know that a few have done it before but not all Yamaha cases will interchange!!
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