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Tossing and Turning

When I first measured the runout on the crank @ 0.0065 in (0.165 mm) the first thing I feared was the clutch being tossed around. With a little work I was able to get the fixed half of the clutch trued, well as much as I could to compensate this huge runout. At an inch from the end (approx. 6 in from the crankcase), the runout measured 0.010 in (0.254 mm). With the fixed half repositioned 180 deg, the runout had more than doubled.

Specialty tools required for truing

Long Range Dial Indicator ~ $65

Finding the high side of the PTO stub

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Applying Graisse Blanche to true the fixed half on the pto stub

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Finding the high side of the fixed half

> It was then turned for the picture

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Alignment marks used to offset the fixed half with the pto stub @ TDC

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Indexing the fixed half with TDC

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Measuring runout on indexed fixed half @ TDC 0.010 (0.254 mm)
High spot at ~ 3 o'clock

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Truing the fixed half with the pto stub will allow the clutch to turn straighter, but will it necessarily get rid of some tossing and rocking effect ?

I'm thinking if the crank is tossing itself out of balance in one direction, maybe the fixed half being out could possibly do a better job of correcting than when it's trued. So I would need to find some way to determine how good of a job I have really done, and if it would run better in a different position. Is there an instrument (or rig) that I could I use to measure this ?
 

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Trouble. You need spec or better for it to be vibration free. Unfortunately that crank needs to come out & be trued before attempting clutch lapping or truing. If you ran it for extended heat cycles the bearings will have to be checked closely. Pull one of the motor plate bolts & mount your indicator there if possible to double check your numbers. Some magnetic base shafts (metric) screw right in. You may as well check phasing.
 

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Clean the crankshaft stub with 600 wet or dry then the inside of the pulley and recheck as above with the dial gauge mounted on the cases. You need to rotate the crank evenly not using the recoil. Better to put a short bolt in the PTO end and slowly turn it with socket wrench.
 

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You guys are making it sound like this is a simple task. The crank should be checked prior to installing in crankcase. The tapered stub end has to be checked for concentricity. The stub tapered surfaces can be off and the rest of the crankshaft straight. I believe the engine must be fully assembled to make final checks. You always have to attach measurement tools directly to the engine. The engine should also be held solidly and in a position for easy access. When we were working on multi-cylinder motorcycle engines we built framework to allow attaching engine to a standard engine stand. I did the same thing for working on these engines. It is really nice to be able to rotate these engines 360 degrees when assembling and checking tolerances. If you do not have access to metal fabrication, you can build the framework from wood since these engine only weigh around 100 lbs.

You can now see why these engines can be a ticking time bomb when the owner or shop rebuilds this engine from the ground up in a long afternoon. Yes you can throw all new parts into a crankcase and mono-block in a afternoon but you are rolling the dice to the rebuild longevity.\

Daag

Sorry to highjack your topic. The pics and info are excellent.

One more comment. When you are checking runout you should mark where the crank throws are in relationship to the readings attained from the dial indicator. This will reduce head scratching when trying to analyze your readings.
 

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That was no highjacking, from any of you. All your comments are precisely the help I've been looking for, and this is not a series to hold back on. The more technical the merrier. I did inadvertently open the door to the bottom nightmare sooner than I wanted to, and I was stumped on how to move forward.

Tonight I took a breather and went through one of Maize's resurrection threads, and I even tried asking him how far he was going to dive into the bottom end just to save me from doing so. But it didn't sound right to ask him, so I'm here now, and no use turning back. I also don't need to go through a complete rebuild to cover the core subject, and hopefully our threads can complement each other. Also now that I have the engine running, I can finally get a closer look at the electrical.

The dial indicator setup may look questionable, but to me it looks easy and interesting for its purpose. I will demonstrate all this over the week-end, but for now I can tell you it was far more precise than I had expected.
 

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Tomorrow will be a nice sunny day and my personal consultant is back, so it's not looking so grim as 1 in the morning. Besides, I wasn't ready to get into the electrical and fuel pumps.

I will make another segment to look into the runout, which is something I was taught just recently on DooTalk (segmenting that is). First I will need to make sure the stub is clean, then get a more reliable setup for the long rang dial indicator. The position of the throws will be marked, and we will see if we can gain insight into the crank before deciding on a teardown. Testing for concentricity will be difficult with the crank in place, but I do have an old crank lying around to work out a good setup. I may even have access to a spare case. So who knows how far this will go.
 

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You guys are making it sound like this is a simple task. The crank should be checked prior to installing in crankcase. The tapered stub end has to be checked for concentricity. The stub tapered surfaces can be off and the rest of the crankshaft straight. I believe the engine must be fully assembled to make final checks. You always have to attach measurement tools directly to the engine. The engine should also be held solidly and in a position for easy access. When we were working on multi-cylinder motorcycle engines we built framework to allow attaching engine to a standard engine stand. I did the same thing for working on these engines. It is really nice to be able to rotate these engines 360 degrees when assembling and checking tolerances. If you do not have access to metal fabrication, you can build the framework from wood since these engine only weigh around 100 lbs.

You can now see why these engines can be a ticking time bomb when the owner or shop rebuilds this engine from the ground up in a long afternoon. Yes you can throw all new parts into a crankcase and mono-block in a afternoon but you are rolling the dice to the rebuild longevity.\

Daag

Sorry to highjack your topic. The pics and info are excellent.

One more comment. When you are checking runout you should mark where the crank throws are in relationship to the readings attained from the dial indicator. This will reduce head scratching when trying to analyze your readings.
I love this stuff. I should have been building 1Ks along time ago.

I am glad to see I am not the only who has built a stand to put engines on to check runout before, during and after assembly.

I even made a tool that screws lightly on the MAG side and PTO to rotate the engine easily.

The stand I have now is for Series III engines, but I will be making one for this engine.

When I put together engines, I check and adjust my own runouts. I have a lead hammer and lead anvil for adjusting side to side. I have a modified set of bolt cutters for adjusting the inward deflection, and a homemade lever for the outward deflection. Ski-Doo says .0118" is acceptable. To me that is INSANE!! and to me could be part of the reason for untimely failures.

When I get my crank from Ski-Doo, I will refuse to put this crank in with more than .001" runout and will spend hours if I have to try to obtain .000" runnout. When I torque the flywheel bolt down I have made a tool that bolts to the flywheel to hold it in place to torque the nut down.

Then install the MAG and flywheel. Once the flywheel is on, check on the PTO end and then clean the flywheel plate off and check that as well.

Once that is done, I will will put the crank in the cases, torque it down and check both ends again. Then put the pistons on and install the cylinders and check it again. Then put the head on it and torque it down and check it again.

Sorry....didn't mean to turn this into a 'what I do' thread. I tend to just post the stuff that "normal" people do when assembling engines. When I am backing my engine builds for my customer's, I want to know E V E R Y detail and measurement of an engine. I don't want to leave any doubt about measurements.

Perhaps on my current build I will post everything I do when assembling an engine. It is usually a weekend process with adjusting runout on the crank.
 

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Tomorrow will be a nice sunny day and my personal consultant is back, so it's not looking so grim as 1 in the morning. Besides, I wasn't ready to get into the electrical and fuel pumps.

I will make another segment to look into the runout, which is something I was taught just recently on DooTalk (segmenting that is). First I will need to make sure the stub is clean, then get a more reliable setup for the long rang dial indicator. The position of the throws will be marked, and we will see if we can gain insight into the crank before deciding on a teardown. Testing for concentricity will be difficult with the crank in place, but I do have an old crank lying around to work out a good setup. I may even have access to a spare case. So who knows how far this will go.
Concentricity can be checked in a preliminary manner while still in the engine by just taking readings of the stub at different locations (3 or 4) while rotating crank and comparing both to each other along with crank throw position. They usually check good but you never know if there is significant wear on the crankshaft stub. Just some thoughts.
 
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