Crankshaft and front pulley question

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Ian D
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Crankshaft and front pulley question

Postby Ian D » Sun Jun 14, 2015 5:35 pm

Hello again Folks
I am continuing with my Cub rebuild (when time allows) and have a couple of questions today please.
I am rebuilding my engine following a re-bore and having sleeves fitted along-with new valve guides and valves. I have the valves, crankshaft and camshaft back in and the pistons in too. I have camshaft end float which fell exactly in the range as per the shop manual (0.003"-0.012") I have 0.009" so quite happy there.

However, with a full set of new crankshaft main bearings fitted - I have no crankshaft end float - (shop manual says between 0.004"-0.008") the crankshaft turned freely before dropping the pistons in and turns fine with all connecting rods connected. Following speaking to someone - they suggested I take off the centre main bearing cap and slide the centre main bearings out (which have the thrust washers on) and carefully run a fine file over the thrust faces to give it some end float?? This I am not keen of doing really as I appreciate the thrust faces are smooth (and flat) and I do not want to damage the upper bearing taking it out with the crankshaft in place. Will it take any hurt with no end float is my first question? and secondly; if the answer is yes; what is the best way to take a tiny bit off the thrust walls?

My next question concerns the fitting of the front crankshaft pulley - I have a new one due to the old one being scored where the seal made contact. I understand the pulleys are what we call "interferance fit" What is the best way to fit these? I am thinking heat it up a bit in warm/hot water but I am very wary of getting it too hot and damaging/melting the oil seal? It may be better to press it on using the thread in the end of the cranshaft is it? Any advice would be greatly appreciated

Best wishes
Ian
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Re: Crankshaft and front pulley question

Postby ricky racer » Sun Jun 14, 2015 6:03 pm

Ian,
Did you have the crankshaft reground due to wear? If so, I assume you've installed thr appropriate sized main bearings. If that has been the case, check the radius on the crank journals and make sure they are in spec. Myself, I'd be reluctant to alter the bearings since my guess they aren't the problem. Have you checked the bearing clearances with plasti-gage?

Regarding the front pulley, I agree with heating it up but no more than 180-200 degrees F, around 90 degrees C. Apply an anti-seize compound to the bore and shaft and pull it on using a length of threaded rod, steel plate with a hole for the threaded rod to pass through and a nut. Grease the seal journal prior to assembly.

Others will be along with other thoughts regarding the crankshaft end play.
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Re: Crankshaft and front pulley question

Postby Bob McCarty » Sun Jun 14, 2015 8:14 pm

Ian, I have watched Raymond Durban install a dozen front pulleys without heat. He inserts the all thread, greases the crank and inside of the pulley, stacks several greased washers on the pulley and then uses a closed end wrench to drive it on. Make sure there are no burrs on either the crank or pulley. Too late for your use now, but there is a thin shell called a "speedi sleeve" that often comes with the seal. It covers the scored section of the shaft and presents a smooth surface for the new seal to ride on. I'm sure you have them there, but they may have a different name.

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Re: Crankshaft and front pulley question

Postby Dale Finch » Sun Jun 14, 2015 10:20 pm


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Re: Crankshaft and front pulley question

Postby Gary Dotson » Mon Jun 15, 2015 6:54 am

On the crankshaft end play issue, try loosening the bolts on the center main cap, using a soft hammer (dead blow) whack the crank forward & back a few times, then re-measure. That usually centers the cap and corrects the problem. Yes, you must have a small amount of end play, although not very much is required.

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Re: Crankshaft and front pulley question

Postby Smokeycub » Mon Jun 15, 2015 7:29 am

Gary Dotson wrote:On the crankshaft end play issue, try loosening the bolts on the center main cap, using a soft hammer (dead blow) whack the crank forward & back a few times, then re-measure. That usually centers the cap and corrects the problem. Yes, you must have a small amount of end play, although not very much is required.

:Dito:
If that doesn't take care of it then be sure the main caps are oriented correctly. I've found rod caps installed backwards resulting in uneven wear on the bearings. I would also inspect the kerf of the center journal on the crank, if it was machined maybe they didn't get it quite right.
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Re: Crankshaft and front pulley question

Postby Ian D » Tue Jun 16, 2015 3:42 am

Thanks folks, all advice taken on board and greatly appreciated.
Regarding my crankshaft; it hasn't been re-ground, its still standard, standard size bearings removed and replaced but I will try the options suggested to try and get a little bit end float. I agree with not filing the thrust washer faces, not good practice at all.
Thanks for the pulley fitting avice too.
Regards
Ian


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