Spun bearings
 

I am messing with an Echo cs-650evl. One of the bearings has spun. It is no longer a super tight fit in the case. My cs-510 evl needs a heat gun to expand the case and allow the bearing to fit in the recesses. This one is much looser. Not sloppy but there is a slight clearance, no galling.

I was thinking....buy new bearings. Second take an electric pencil and put a gillion little peene marks inside the bearing recesses. After that use some of that super duper high temp gasket goop to secure the bearing?

I would really like to use it. Any sugestions?

Scot

RE: Spun bearings
 

Assemble it and use JB Weld between the case and the bearing.

The crank will hold it inline.

RE: Spun bearings
 

Locktite makes a product for gluing bearings in. don't have the number off the top of my head.

RE: Spun bearings
 

Scot,

I use Loctite 620 Retaining Compound for my prop hubs and bearings when I have an issue like yours. Depending on how bad the bearing surface is spun you may need to look at Loctite 603 which is for press fits in parts that have a .005 gap. This product also is oil tolerant which you may need to consider. Not a lot of oil in there but you have gaps and oil can break down the sealant.

Tim

RE: Spun bearings
 

I have used the same 620 Retaining Compound in air cooled and automotive engines and had very satisfactory results. It is designed for the application you have and I recommend its use.

RE: Spun bearings
 

OK, Locktite 620. There is proabably a thousandth play in the seat. Would it be a good idea to use the electric pencil/engraver to give the locktite some "tooth" , center the bearing and restore the press fit?. It is polished bright with a coined finish right now. Should I use my dremil to skuff the finish of the bearing? It has covers right now that I will remove later. That would keep the grit out.

For once I have documented every step of this conversion with photos. I'll post them to my website and share it when the project is done.

Thanks for the help,

Scot

Amended, "There is proabably a thousandth play in the seat." It is more like .006 per side. I measured it with a dial indicator. I spent a while learning about "retaining compounds" Great stuff, I did not know they existed. It loks like I should keep the block warm for a couple of days before I mess with it to get maximum strength.

RE: Spun bearings
 

I would probably "knurl" the bore somewhat as you suggest. Just be careful that whatever material you raise cannot flake off when you install the bearing, and subsequently get into the bearing.

AV8TOR

RE: Spun bearings
 

Thanks,

I'll do that . If this attempt fails I'll go ahead and make some press fit bushings and glue them in with the 620. I have access to liquid nitrogen. I can make the bushings a couple thousand over the dimension I bore the block halves to. Then heat the halves with a heat gun and drop in the bushings. I can then machine the bushings to the original dimension.

RE: Spun bearings
 

Making bushings for the bad bearing surfaces sounds good. However, how would you indicate the case in to assure concentricity and horizontal alignment of the crankshaft? The only reference surface you could use is no longer a perfect line bore to the case and would, I am sure, cause more problems than it is worth. Not being critical just concerned.

RE: Spun bearings
 

I will try the glue first in any case.

As far as concintricity, I was taking on fath that the crank case halve part lines were 90-degrees to the crank bearings.

RE: Spun bearings
 

Never trust the casting lines as reference points. Everything has to be indicated from some machined and known plane. Problem for us doing this is we don't have prints to use. We would be able to pick-up a plane or line and work from there. Oh well, good luck and keep us posted. I am sure the loctite will work anyway.

RE: Spun bearings
 

I am out of airspeed and ideas. The loctite seems to have worked. Unfortunately the crank, where it fits the bearing is worn. It makes the prop hub about 0.020" off center as I spin the crank. I was thinking of grinding the crank between centers to true it up where the bearing fits. Unfortunately can not find a bearing that would work. I would think that there would be "repair bearings" that were under/over sized. I can not find any. It looks like my project is destined for the scrap pile.

I bought two saws on EBAY. They were advertised for parts or repair. Both were worthless junk. This CS-660 is absolutely trashed. The guy washed it off in a solvent tank to make it look better. A CS-510 I got for the crank is siezed solid and looks like it was submerged in water. A junk carb was loosely installed. I have not taken it apart to see if the crank is useable, the bearings on the con rod are probably ruined. Beware of EBAY crooks!

My final idea on how to save it is to grind or turn the crank to remove the damged area. Then make a sleeve and shrink fit it over. Then finally grind it between centers to restore original dimension. Is this workable or a waste of time?

RE: Spun bearings
 

First I would file a complaint with eBay for the sale of faulty goods. I wouldn't spend the time trying to fix the crank. Sounds bent to me. The amount of run-out you are saying is excessive. I have never seen a crank worn where you say yours is in all the engines I have done.

RE: Spun bearings
 

I think I learned a lesson and paid $40 to do so, plus what I have in bearings and fancy glue. I won't be buying old saws without checking them out carefully. You can't do that on EBAY. It seems pretty dangerious to buy such items sight unseen. There is not much left to send back anyway. I am dissappointed at not getting a 65cc engine out of it and spending so much time. It would have been a very nice job. I'm getting pretty good at prop hubs and paring down crankcases. :)

I did send the guy a scaving E-mail. His rating is 99.9%. My wife sells on Ebay. She tells me I can't give him a bad rating without giving him a chance to make good. Maybe he will do so? He did answer a question on the item and described it as,

" the saw is actually in pretty good shape- I'm not sure why it was retired- but there is still plenty of good usable parts on the unit"

He has a real company, I guess I can hope..

Next day,

He did good! My money was refunded. I guess my synicisim was unfounded. Conistering his attitude and quick action I put him on the "good guys" list.

Maybe I am a gluttion for punishment? I found another crankcase and crank on EBAY. I bought it today. This seller guarentees it to be good. I figure I have made all the conversion parts so I might as well finish the project.