Kawi2strokes.com Forum

Lets say the crank is close 90 degrees from the crank wheel on one side, and wide at the other side at the opposite 90 degrees. Using a flat taper blunted chisel, on the close side, tap that side to "wedge open, spread the flywheels so both sides match", check, etc.

Now, .005 is a very wide variation, Hurley and I used to have contests on whom could come closer to .000 true.

The Kawasaki crankshaft rebuilding manual, used BH factory certified rebuild stations and techs, says to align the flywheels by using a lead hammer to "whack" the high flywheel into alignment with the opposite side when. I do it differently, I built a fixture to hold a crank in my press, and press the "high" flywheel into true. Just 50 years of being one of those factory certified crankshaft rebuild techs.

I’ve been working on the crank a little here and there. I have it at .003 , both needles moving at the same time/same amount. If we say the needles are at 12:00 o’clock, then the high spot is with the crank pin at 3:00 o’clock, low spot is 9:00 o’clock… this allows me to either squeeze the spread part or spread the squeezed part.

I’ve put the wide spot in a vise, hit it with my brass hammer etc…I “think” I got .001 improvement thay way ….The thing I’m having a problem visualizing is this… the crank pin is a press fit, with shoulders in the middle no less…(wider where the big end bearing goes)
For the crank to move in a way that would solve a pinch or a spread ….something would have to give. It’s easy to see how the crank halves move around the pin if smacked, it’s just a pivot.

So what is it that moves or gives when we use the wedges or a vise
To try and get rid of the pinch and spread? I’d hope the pin wouldn’t have enough clearance for the crank halves to wobble on it exactly.

I had made a jig of sorts for this crank to put it together and it worked fairly well…I could improve on it.
I am using my craftsman lathe as a truing stand . it’s not a great lathe but makes a very nice crank jig..looks very much like the $900 fixtures online.

I’m having a blast with this really.

I took a class a while back on aligning things like motors/pumps/gearboxes etc and we had some test rigs set up and I was able to get my setups to .001, which is what the instructor said we needed out of it. So I would like to get this crank to .001 at least. Im spending a little time on it here and there in between all the other projects in my shop. Hope to get the old S2 done this spring as well.

Anyway I really appreciate the info and replies !

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1972 S2 350, 1972 F9 350 Bighorn, 1975 KX400, 1981 YZ465, 1980 XT500 (Built for MX) , 1987 KD80, 1995 MZ Skorpion, TTR 125, 1994 KDX200 , 1978 Mobylette, 1985 KX350R-F91m (Frankenstein) and a Doodle Bug

Everyone and his dog talks about getting cranks down to .001 and less, but in the real World the Bearings run more than that. Discuss!

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"One day, your life will flash before your eyes. Make sure it's worth watching." : anon.

We are moving the flywheel on the crank pin. Spreading moves the pin in the wheel sideways. Out of round, the wheel radically on the pin.

Using the index finger on both hands, stuck straight up, next to each other,

Fingers closer at the tips, from the hands, if we "wedge" them open farther at their tips, to past equal, then let them return, we straighten the wedge.

If we have the fingers straight and equal, but one tip offset from the other, the wheels are not true, and we have to move them on the pins to straight.

Not all pins insert into flywheels dead straight, some can insert a touch canted offset, to fix, we align. No jig will be totally straight align for every pin press in.

Yes, I know, rudimentary, but effective.

Crankshaft alignment is extremely important to rods tracking straight, quite different than the "fit running side clearances" of a ball bearing running inline with other ball bearings.

Case in point, the old Honda single crank 800cc V5 was so "touchy" on crank set in the cases, race mechanics in now, MotoGP, were forbidden to split engine cases, in fear of actually binding it in the cases when reassembled. Honda had ONE tech, at the race department in Japan, that set all the cranks in the cases. NOBODY else was allowed to do so. If there was a question/problem with the crank, the crank/case set was replaced as a preassembled unit only. It was well known that if a crank wasn't set correctly in the cases, up to 20 horsepower could be lost from ball bearing side binding.

All that was with the same C3 (EMG) bearing looseness we have on our cranks, so, straight, true, aligned and set in place is essential for proper engine operation.

Got it!!!
.001 on each, moving the same. Apparently I
Was envisioning the spread wrong….with the needles at the high point, I was thinking I had to squeeze the opposite side to bring the shafts down as it sat in the fixture . I made it worse this way so I flipped my method around.

Since the centers are fixed, pinching the opposite side would INCREASE the needles deflection. Got it to move the way I wanted so I kept going in that direction, having to true the halves a couple times in between.

Now I can start getting the cases together !

Thanks again for the very informative replies!!!

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1972 S2 350, 1972 F9 350 Bighorn, 1975 KX400, 1981 YZ465, 1980 XT500 (Built for MX) , 1987 KD80, 1995 MZ Skorpion, TTR 125, 1994 KDX200 , 1978 Mobylette, 1985 KX350R-F91m (Frankenstein) and a Doodle Bug

Learning by teaching by doing is always good.

Also, finding any single cylinder pressed together crank to learn from is always a help.

Now, as you get the cases together, nuts snug, with plastic hammer, tap crank LIGHTLY back and forth in the cases. Then, torque the case nuts. This sets all the outer races of the main bearings sitting with the same end to end clearances. This is the important part of what the Honda tech did. Reduces any side loading of the ball main bearings, drag, and makes correct power, no binding tension.