Crankshaft split overhaul assembly

Gary: 50 ton press? You got a gauge on that?
Rich: I think MikesXS crankpins are solid, but I've seen some hollow pins. Know nothing about them.

Well a 50 ton frame with a 40 ton ram and gauge. From what I gleaned here and elsewhere; You don't need 50 tons but you DO need a stiff frame so you can push the pin a predictable amount. Get a flexy 12 or 20 ton HF press all wound up and the frame spring will cause the pin to overshoot and you end up going back and forth on clearances.

My one day a week post office job has become a 5 day 9 -10 hour a day slog, really interfering with my leisure plans.

Found this, thought it may be interesting:

From: Cycle Guide Sept 1974

TX650A ride evaluation

Last year the TX650 had a small lever on the handlebars which was hooked to the starter motor and also operated an exhaust valve lifter (which acted like a compression release). Pulling this lever would activate the starter and lifter simultaneously. But the starter cranked the engine over so violently that it often jerked the crankshaft flywheels out of alignment. Once this happened, the already-heavy engine vibrations would become heavier.

The TX650A doesn't have the valve lifter this year, and it uses a starter motor that transmits less torque to the crankshaft so the crank stays in alignment. But it sometimes takes three or four pushes of the starter button before the starter gears engage. The spring in the Bendix starting unit is too strong and won't always allow the starter gears to mesh. The resultant clunking and whirring sounds are terrible.

In my 70-74 Factory book it has the instructions to do a crank tear down and rebuild. It shows tools like Motomasher used in the Garage thread linked to earlier.
It sounds easier than it is.
As I said I did two.
A larger press with a stronger frame = less flex. A lighter frame will flex until it goes past the pressure to move the parts. Then when the parts move it does so in irregular increments. A stronger frame won't flex ands the movement is much more predictable.
On the truing a large lead hammer, 3 to 5 lbs. works well. The heavier the better for the coarse work. The smaller once you get close to fine tune.
Leo

It seems that cranks twisting and walking apart has been with us for a while......

yup, luckily, i found a guy in the province over from us that loves them, and did the split and trued it for 180.00 cdn. I supplied n.o.s. rods. had a friend of mine tig the outer pins. left the center.

XSLeo said:

In my 70-74 Factory book it has the instructions to do a crank tear down and rebuild...

Click to expand...

Okay, so we'll put that in here. I extracted the relevant pages (58-62), and put them into an album:

Crankshaft Specifications and Servicing

Pages 58 and 62 have been annotated in red to show the proper V-block positioning that's been bugging me for years.
On the Crank Service page 58, there's a bit of text that says "mount the crank in live centers", but for old/used cranks with possible rotor shaft end damage from creative rotor pullers, that may not work well.

The album also has some crank specifications that were cut/clip/pasted into usable pages.


Edit: More crankshaft threads of interest.

http://www.xs650.com/threads/another-crank-rebuild-question.54046/

Video of Applebee doing an XS650 crank balance.

Just a trivial update.

One crank inspection involves "rocking" the conrod, and measuring the deflection.


That's nice, but what does that translate to as the conrod's big end "axial" clearance?

Using these dimensions for the 447 connecting rods:


Assuming that:
The conrod big end ID is straight/square/true,
The big end roller bearings are straight/square/true,
The crankpin OD is straight/square/true,
And the "rocking" measurement is done at the outer edge of the small end,
Then it calculates out that the conrod's axial clearance to the crankpin is about 1/14th of the "rocking" value.

The new and service limit values of the "rocking" measurement runs from 0.8mm to 2.0mm.


Using the 1:14 ratio, we get these axial clearances:

0.8mm (0.032") --> 0.057mm (0.0022") (about 0.002")
1.0mm (0.040") --> 0.071mm (0.0028") (about 0.003")
2.0mm (0.080") --> 0.143mm (0.0056") (about 0.006")

For reassembly you can use shims to stop the parts moving so you don't overshoot due to the press frame springing. Measure the length of the rod pin and subtract it from the target cheek-to-cheek width. Divide that by 2 to find the necessary shim thickness. I'll add a couple thousandths because even with the shims it can still overshoot a bit. Put the shim in the bottom of the rod pin hole then press in the pin until it bottoms out on the shim. Put the rod and trust washers on the pin then put another shim on top of the pin and press on the other cheek. If all was done well, then the rod side clearance should be spot-on.

Loctite bearing mount 620 is a simple and effective way to add strength to the joints without welding. The brochure says that it will "double" the strength of a press fit. I did a test that shows that it isn't just advertising fluff.

I cleaned up a pin and pressed it in dry. It took 4-1/2 tons to separate it (that is typical for a stock crank).

I reassembled it with Loctite 620 and let it set overnight. It took 8 tons to separate it.

I cleaned the Loctite off and tried it again dry. Again it took 4-1/2 tons.

I pressed it in again then gave it to a buddy to TIG weld. The plan was to press it apart [yes, welded cranks can be pressed apart] and see how it compares to the Loctite. Unfortunately, I never got it back.

Can somebody explain what happens to create wobble in the end of a formerly good crank?

Mrriggs a shame you didn't get the crank back to find out how much it took to separate, I've recently had a welded crank come apart, I was taking it up to around 9.5 to 10 thousand revs though

It not uniformly good any more..

Since there's a "bent crank" thread on the front page, it's prolly a good time to revive this thread.
Consider it revived.

did anyone se the tool I made to put cranks bac together after rephassing them, its at the very end of the tytronics install video