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Old 10-04-2007, 04:43 AM   #21
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On some engines, if a valve is wide open when the piston comes to the top, you can bend a valve.
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Old 10-04-2007, 07:43 AM   #22
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High speed bearings? it's only 10k RPM.

Try here: ebay Bearing Brothers
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Old 10-04-2007, 08:50 AM   #23
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Originally Posted by guyl
As it so happen, I just did a bearing change on my Saito 100.
Bought bearings from Mention high speed bearings when ordering. Front bearing was $9.15 rear bearing was
$28.72 I elected to buy a cageless bearimng for the rear. Because
the original is caged and the race started to breakup...thats is when I
heard that awful noise. You need a PRESS otherwise you are just
fcuk arnoud and taking chances of damaging the crankcase. The timing
gear is very loose fit and easy to screw up your timing. Therefore
fill it up with thick grease so it will not move. Piston has to be at TDC
and timing gear DOT at the bottom 6 oclock position.
Just ran it this afternoon on my Funtana a bit tight yet as there
was some surface corrosion on crank that had to be removed.
Hope this help.

Guy L.
First please be careful when ordering your bearings. Do not upgrade the bearings to a higher precision as there may not be enough clearance to allow for the higher temperatures of an internal combustion engine. We use precision bearings when we rebuild machining spindles at work and if they run hotter than you can hold your hand on the housing there will be a problem. The bearings that come in these engines are radial thrust only they are not even angular contact simply a standard ball bearing in most cases. Sometimes there will be needle bearings and they are standard fit. Instead of spending money for a higher precision bearing spend the money on a quality bearing instead.

Setting the timing on a Saito is easy with the little tool you can order or make. It fits through the lifter hole into a hole in the cam locking the cam at the correct position. Easy to make if you have brass tubing on hand. The bags K&S of assorted off cuts are perfect for this. Since the cam housing is off anyways roll the cam until you see the small hole in the cam itself. Find the size tubing the just fits in the hole. If you have to polish it down a bit to fit chuck it up in a drill or drill press and use a file and sandpaper to bring just the end down to size. You will have to do the same and make a slip fit of a larger piece of tubing for the lifter hole. The brass tubing slides closely one over the other so you can use small pieces to fill in between the small diameter and the large diameter ending up with a plunger much like the one they sell. Assemble with a dab of thin CA and it will hold everything together. Insert your home made plunger through the proper lifter hole and lock the cam in place and install the housing. Done and you have the tool the next time you need it.

Originally Posted by AJCoholic
Guy L,
I am sorry to disagree but for working on 99.9% of model engines you definitely do NOT want to use a press. The crankcase must be warmed up enough to allow the slightly interference fit bearings to easily slide out. If you press them out or in, you can damage the bearing and/or the crankcase.

This is no my opinion by the way, its the way things have been done for years- and is the accepted practice.

Precision bearings (and small bearings in general) should never be pressed into an interference fit.

Andrew is correct because rebuilding at home most of us will be using what ever hand tools and equipment we have on hand, Heating the case even a few hundred degrees knowing the thermal expansion of aluminum is greater than the steel the bearings are made of allow for easier removal and replacement of the bearings. Making sure they are removed and replaced as straight and square as possible to the bearing cavity is most important as the aluminum is softer and more easily damaged. Even a very minor score or galling of the bearing pocket can result in a tight or out of location bearing and a short bearing life. Cleanliness most definitely is number one.

As to using a press, if done properly there is no problem. At the factory they do not use heat to assemble our small engines but they do use properly fitting arbors. I usually make mine up as needed but still heat the crankcase a bit to aid installation. The arbors aid in keeping everything square and allow me to position the bearing easily. If you put the front bearing in first then put the rear bearing on the crankshaft the front bearing will act as a guide and by pressing on the center of the back of the crankshaft you can easily align and position the rear bearing. To use this method the crankcase must be heated to allow easy installation of the bearing. This is because you are applying pressure to the inside race through the bearings to the outer race and you do not want the force to be any greater than would occur with the pull of the prop. DO NOT STRIKE THE CRANK WITH ANY THING NOT EVEN A SOFT MALLOT TO SEAT THE BEARING THIS COULD CAUSE A BERNELLING OF THE RACES AS THE BEARINGS THEMSELVES ARE SLIGHTLY HARDER. THESE MICROSCOPIC IMPERFECTIONS WILL CAUSE PREMATURE BEARING FAILURE.

The proper arbor to press bearings in acts on the inner or outer race that the interference fit relates to. For instance pressing a bearing on a shaft the arbor should be hollow and press only on the inner race. Pressing a bearing in a pocket the arbor will have a guide pin that slips though the hole in the bearing for alignment purposes but will only press on the outer race. The outside diameter of the arbor should be slightly smaller than the diameter of the pocket so there will be no damage to the pocket if the bearing is to be pressed below the surface of the pocket.

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Old 10-04-2007, 08:26 PM   #24
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Originally Posted by Tyler2
Its is the Saito .82.
With the help of one of the guys at my club i got the engine apart and just need to get the bearings.

If the timing is off what will happen? Will it just not start?

I guarantee the information to set the timing is in the .82 manual. Its not more than a paragraph because basically they just tell you where the punch mark on the cam is supposed to be when the piston is at TDC or BDC.

If the timing is off even one tooth, it will make the engine very unhappy. It may still run depending upon which way its off, but it is not accpetable. Luckily it is very easy to hold the piston in the right spot, and lower the cam housing & cam onto the crank at the proper position.

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Old 10-05-2007, 02:36 PM   #25
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There's been a lot of commenting on how to change the bearings here, and lots on timing issues etc.
There have been a couple of links to bearing suppliers.
Here's an outfit that specializes in bears for us RC type of folks. There's also some good reading on types of bearings, their classes, and install hints.

Try checking this site out:

Bill O.
London, Ont.
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Old 10-06-2007, 12:20 PM   #26
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I got the bearings and crank shaft in today. It feels smooth when i turn it but it doesn't spin freely. I thought they would spin freely. Is this normal or should they spin freely?

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Old 10-06-2007, 01:29 PM   #27
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The bearings may have oil or greaee in them, enough to prevent them spinning freely. If you wish to find out, clean the bearings with aerosol brake cleaning fluid. This will remove oil and grease and dry very quickly. Remember to oil them up again.

Ed S
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Old 10-06-2007, 06:24 PM   #28
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Got it all puat back together and tested it on the bench. I was a little worried at first because there did not seem to be much compression but after running it a bit the compression got better. It purred like a kitten. It was much quitter than before and seemed to still have good power.

Thanks for all of the response. They really made it easy.

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