Crank bearings

[Mad Dog]

I am freshening up a 95 project motor.
The motor sounded tight but when I split the cases, the crank easily pulled away from the right side bearing. Bearing stayed in case. The bearing feels smooth and rolls nicely.
The bearing has obviously been heated prior. The crank will push into the bearing without heat or a press.

Is there an issue here?


Rob's response on the other site was to check the specs on the journal, which I will have Q & E check.

Just a note there is no apparent galling or movement of bearing on crank.

Another Q, is it possible for the bearing to have been heated so hot it didn't retain it's specs?

[dannygraves]

my motor was the same way, it was snug, but no real work to separate the crank and bearings. I just chose to run it and haven't had any problems.
But, thet being said, I've also been keeping an eye out for a crank so that I can swap that out next time I split the cases.

[Rosco-Peeko]

I think the best bet is to have the journals spec'ed out. If they are good, replace the crank bearings. Look for any burnishing on the journals. Are they OEM bearings? What are the markings on them? My old stuff like I said was "slip-fit" the bike shook like Elvis. After 15 minutes my hands were numb.

[AlisoBob]

Ive used Loctite 638 for this.....




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A maximum strength retaining compound for use where high dynamic forces or cyclic loading is expected. Locks cylindrical assemblies up to .010" diameter clearance. Fixtures in 5 minutes.

Related Products

Primer T 7471 (Acetone)


Retaining Compound 638 Maximum Strength

A maximum strength retaining compound for use where high dynamic forces or cyclic loading is expected. Locks cylindrical assemblies up to .010" diameter clearance. Fixtures in 5 minutes.

Related Products

Primer T 7471 (Acetone)

Rosco tried it, it think he had mixed results...

It's worked well for me....

Technical Data Sheet
LOCTITE® 638
May-2004
PRODUCT DESCRIPTION
LOCTITE® 638 provides the following product characteristics:
Technology Acrylic
Chemical Type Urethane methacrylate
Appearance (uncured) Green liquidLMS
Fluorescence Positive under UV lightLMS
Components One component - requires no mixing
Viscosity High
Cure Anaerobic
Secondary Cure Activator
Application Retaining
Strength High
LOCTITE® 638 is designed for the bonding of cylindrical fitting
parts, particularly where bond gaps can approach 0.25 mm
(0.01 in.) and where maximum strength at room temperature is
required. The product cures when confined in the absence of
air between close fitting metal surfaces and prevents loosening
and leakage from shock and vibration. Typical applications
include locking bushings and sleeves into housings and on
shafts.

Cure Speed vs. Activator
Where cure speed is unacceptably long, or large gaps are
present, applying activator to the surface will improve cure
speed. The graph below shows shear strength developed with
time using Activator 7471 and 7649 on Zinc Dichromate steel
pins and collars and tested according to ISO 10123.
1min 5min10min 30min 1h 3h 6h 24h 72h



For Assembly
1. For best results, clean all surfaces (external and internal)
with a Loctite cleaning solvent and allow to dry.
2. If the material is an inactive metal or the cure speed is to
slow, spray with Activator 7471 or 7649 and allow to dry.
3. For Slip Fitted Assemblies, apply adhesive around the
leading edge of the pin and the inside of the collar and
use a rotating motion during assembly to ensure good
coverage.
4. For Press Fitted Assemblies, apply adhesive thoroughly
to both bond surfaces and assemble at high press on
rates.
5. For Shrink Fitted Assemblies the adhesive should be
coated onto the pin, the collar should then be heated to
create sufficient clearance for free assembly.
6. Parts should not be disturbed until sufficient handling
strength is achieved.

For Disassembly
1. Apply localized heat to the assembly to approximately 250
°C. Disassemble while hot.

[Rosco-Peeko]

That stuff sets FAST! It seemed like it held for a while then starting vibing again when I tried it.

[conrod]

That’s interesting, my main bearings have been out and in quite a bit over the years, 94 cases, I think a few times they may have spun and have taken a lot of metal out of the cases with the bearing. If for example it is beyond loctite, can they have hot metal spraying in the cases and machined to size again, or are new cases more economic, anyone been down that road?



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[conrod]

Oh yeah, I meant to add regards the crank going into the bearing easy, I would expect the large mass of the crank to expand more than the small mass of the bearing inner core, so the bearing should get snug and tight when the engine is run and the crankshaft expands.




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