Mid-Shaft Alignment/ shimming

L

Loganight

Location
Riverside, CA
Hey everyone, I’ve been doing some research on aligning the mid-shaft and haven’t really found what I was looking for. When I was pulling everything from my 96 SJ, my mid-shaft had shims. I marked them accordingly to save for Installation but didn’t think much of it. When it came time for installation, I aligned my pump using the CF tool and proceeded to put on my rebuilt @JetManiac mid-shaft to which my questions came.
If it is supposed to be shimmed, is it for the offset of a slightly slanted bulkhead? (Only thing I could think of) and if so, How would you even check the alignment for the midshaft?

If anyone has some insight it’d be much appreciated!
 
brapperdoodle

brapperdoodle

Location
Asheville, NC
I’ve thought about this many, many times. I’m a sucker for over complicating things and I can tell you with confidence, leave it alone haha. Unfortunately I can’t tell you why Yamaha used bulkhead shims but unless you’re facing some really bad alignment, you shouldn’t need them. Just align the pump and shaft using the CF tool and let it fly. This is one of those things that is easy to overthink. When you do align, mark your shaft and rotate it 180 degrees when checking alignment… you’ll find that the shaft is never completely straight. You’ll just split the difference of the “bend” and shim accordingly. I’ve aligned many driveshaft and our sports “best pumps” have had the most bent shafts I’ve seen. Even after they claim to be 100% accurate and made as 1 piece. The best and straightest shafts I’ve seen come from a member here, Sasquachcrap! His shafts are recut OEM and he straightens them to the best of his ability and does a fantastic job. Hope this helps, don’t drink the Kool-Aid
 
L

Loganight

Location
Riverside, CA
brapperdoodle said:
I’ve thought about this many, many times. I’m a sucker for over complicating things and I can tell you with confidence, leave it alone haha. Unfortunately I can’t tell you why Yamaha used bulkhead shims but unless you’re facing some really bad alignment, you shouldn’t need them. Just align the pump and shaft using the CF tool and let it fly. This is one of those things that is easy to overthink. When you do align, mark your shaft and rotate it 180 degrees when checking alignment… you’ll find that the shaft is never completely straight. You’ll just split the difference of the “bend” and shim accordingly. I’ve aligned many driveshaft and our sports “best pumps” have had the most bent shafts I’ve seen. Even after they claim to be 100% accurate and made as 1 piece. The best and straightest shafts I’ve seen come from a member here, Sasquachcrap! His shafts are recut OEM and he straightens them to the best of his ability and does a fantastic job. Hope this helps, don’t drink the Kool-Aid
Click to expand...
Thanks for the reply! So you’re saying I should just get rid of all the mid-shaft shims? or just run the stock ones? (im guessing they’re the stock ones, I don’t think the owner before me was too mechanically savvy lol”
 
JetManiac

JetManiac

Stoked
Site Supporter
Vendor Account
Location
orlando
Loganight said:
Hey everyone, I’ve been doing some research on aligning the mid-shaft and haven’t really found what I was looking for. When I was pulling everything from my 96 SJ, my mid-shaft had shims. I marked them accordingly to save for Installation but didn’t think much of it. When it came time for installation, I aligned my pump using the CF tool and proceeded to put on my rebuilt @JetManiac mid-shaft to which my questions came.
If it is supposed to be shimmed, is it for the offset of a slightly slanted bulkhead? (Only thing I could think of) and if so, How would you even check the alignment for the midshaft?

If anyone has some insight it’d be much appreciated!
Click to expand...
Yes, if it was shimmed from Yamaha, then bulkhead was off some. I would reuse them in the factory locations again. We like a bead of silicone around outside edge of housing to help make sure no airleaks there and to keep water/corrosion away from the aluminum to rubber vulcanized junction there.
But agree with @brapperdoodle that not critical for housing to be shimmed unless bulkhead is way off. Seen a few blasters that were off over the years but most yami oe hulls are close enough w/o shims.
 
brapperdoodle

brapperdoodle

Location
Asheville, NC
Loganight said:
Thanks for the reply! So you’re saying I should just get rid of all the mid-shaft shims? or just run the stock ones? (im guessing they’re the stock ones, I don’t think the owner before me was too mechanically savvy lol”
Click to expand...

I’d say run them where they are if it appears to be factory, but even if you took them out you’re gonna be fine. Aligning the pump to the best of your ability is the important part. But as Jetmaniac said, sealing the midshaft housing against the bulkhead is another important step. Also know that the spline engagement on the shaft to midshaft is important as well, although if you’re using stock Superjet parts, this will likely not be an issue. When you get into AM hulls with custom length drivetrains, this aspect becomes critical in addition to the other items I mentioned above.
 
john zigler

john zigler

Vendor Account
Location
wisconsin
Many times we use shims on the Midshaft housing. Infact I just did a video on this. (Have not posted it yet).

Typically you can tell is shims are needed. I use the CF alignment tool, once the shaft is perfectly centered. "IF" you feel any binding when sliding the bushing over the shaft and into the plate, try a shim under the tool plate. I usually find it needs a shim on the top most mount bolt. You want the bushing to slide in like butter, NO binding whatsoever.

Sometimes I will remove the tool plate from the hull, and then slide it, with the bushing over the shaft and measure all three bolt mount holes to the bulkhead. (Hope this mase sense). This too will show if the shaft angle is square to the bulkhead.

I will say, I am really good at overdoing everything...... sometimes way too picky, but IMO doing things super picky will help parts last longer.
 
L

Loganight

Location
Riverside, CA
T
john zigler said:
Many times we use shims on the Midshaft housing. Infact I just did a video on this. (Have not posted it yet).

Typically you can tell is shims are needed. I use the CF alignment tool, once the shaft is perfectly centered. "IF" you feel any binding when sliding the bushing over the shaft and into the plate, try a shim under the tool plate. I usually find it needs a shim on the top most mount bolt. You want the bushing to slide in like butter, NO binding whatsoever.

Sometimes I will remove the tool plate from the hull, and then slide it, with the bushing over the shaft and measure all three bolt mount holes to the bulkhead. (Hope this mase sense). This too will show if the shaft angle is square to the bulkhead.

I will say, I am really good at overdoing everything...... sometimes way too picky, but IMO doing things super picky will help parts last longer.
Click to expand...
hat made perfect sense. Thankyou I will give all that a try when I get to my ski next. Video also helped out a lot!
 
kevbo

kevbo

Location
dfw
The idea is simply to make sure nothing is pulled into a bind when the bolts are tightened. Using shims is one way to fill gaps. Most of my pump change mods get the pump and carrier potted with thick epoxy. Everything fits perfectly after that.
 
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