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Discussion Starter · #1 ·
hi all, i recently got my SL350 going after 30 years parked, and found in the process, an amount of rubber inside the crankcase near the oilpump. after searching the forum yesterday i found a post where someone had found a small piece of rubber in the same spot and it was concluded that it was off the camchain tensioner roller. i have part dismantled the engine enough to see that the roller has lost the complete shoulder section of both sides but the central raised section is okay. i have no idea why it would have disintegrated like that, maybe the years in storage, but my question is, could one be fabricated from nylon stock. turned to spec on a lathe. i know this part is very common to over 100 different Honda models and should be readily accessible, but i like manufacturing things like this and thought it could be a good option. love to hear your thoughts.
Gary.
 

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Discussion Starter · #4 ·
thanks for the link, thats exactly what i was going to do. maintenance has always been carried out regularly, being used for racing it didn’t do a lot of hours per year, but the time running certainly was a lot harder than your average bike. i think that time itself is the main culprit, with a motor that hasn’t turned for 30 years, the rubber roller deteriorating and then when it is turned, the shoulders of the roller crumbled away.
 

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...my question is, could one be fabricated from nylon stock. turned to spec on a lathe. i know this part is very common to over 100 different Honda models and should be readily accessible, but i like manufacturing things like this and thought it could be a good option. love to hear your thoughts.
Gary.
Well, yes. Yes one could. :D

Here are the dimensions I used. This is the lower roller. I did not make a top roller. At the time, I did not have an unused specimen for sizing. The dimensions listed are approximations. Use at your own risk!
Personally, I do not anticipate any problems. It is MUCH closer to spec than nearly any of the used rubber rollers in use. ;) That said, I just assembled the engine it is being used in several days ago and it may be a month or two before I get to the point of even trying to start it. During assembly however, it fit nicely and offered no suggestion of being a problem. As mentioned in the previous thread, this is an idea that's been around, been used and even been marketed for many years.

Cam-Chain-Roller.jpg

WP-20190116-001.jpg

When actually assembling the wheel into the bracket, I encountered a clearance issue but I don't recall exactly what it was. Something related to the (raised) hub section surrounding the bronze bushing. You'll have to play it by ear. The "inch size" bronze bushing was an expedient part as well. It is ever so slightly sloppy on the metric axle pin. I think you'll agree though that it is not "sloppy" to the point of being an issue. It is merely not quite as tight as one would expect new parts to go together. As well, the nature of the application (keeping the chain spread) is such that critical "play" should not be a factor. This is especially apparent when considering the play that exists in regard to those old, used rubber rollers working perfectly okay in thousands of these engines today.

A stick of 6/6 nylon 12 inches long cost +/- $20 I think. The bushing was a couple bucks at the local hardware store. Counting applicable waste and especially if several were turned simultaneously in one set-up, you could easily make 8-10 from a $20 stick. Realistically it's probably more like 5-6. But, how many does one man need? :grin: I'm not into the whole burden of making critical parts for someone else's engine! ;) These parts (new rubber ones) ARE still available if you look long enough. They are not terribly more expensive than the materials you'll have invested in making your own. As you mention though, there is that attraction of "making things." :D

When I made mine, and posted the process here, there was some discussion about not using ball bearings. Very simply, I neither consider it critical enough to necessitate ball bearings, nor am I particularly fond of the idea of introducing hardened steel balls into an engine in an unproven part. ;) Most pointedly though. The bronze bushing is at least as useful as the original steel sleeve and a fraction of the cost of ball bearings! The OD of an off-the-shelf ball bearing unit is also MUCH larger than the bushing and adds more weight.

If you've never worked with nylon it cuts well, but dimensions will be difficult to get EXACT as measured in the lathe. The material has a small degree of what I call "springback." Luckily hundred-thousandths of an inch are not critical to this application! In regard to boring the axle hole, it is actually a plus as a 3/4 drill will result in an ever so slightly smaller than 3/4 inch hole. This allows for a very good press-fit of the bushing! ;) I simply pressed it in with the bench vise using a disc of nylon cut from the same stick to protect the roller.

While you're at the store, pick up a couple 1/2-3/4 OD rubber stoppers ("corks"). If your roller is that bad, and especially if you were not super careful during disassembly, you probably need the little 1/2 round rubber spacers that cushion the axle pin for this roller. They are quite easily replicated (even if you don't have one for a model) from these commonly available rubber stoppers. Turn them roughly to applicable sized cylinders on a disc or band sander, cut the bottoms off and the shoulders for the axel and slice to the necessary thickness. Viola! Brand new obsolete 45 year-old disposable Honda parts. What's not to love? :cool:

It was a fun project. Engineering on the fly can be that way. It can also be very, very cruel. :D Good luck and let me know if there is anything I can do to help.
 

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Discussion Starter · #6 ·
thanks for all the details oupa, i have made one using the original wheel centre, pressed it into the nylon blank and then turned the new wheel to spec with it mounted on a mandrel. have to wait now for a gasket set from china, and a coil set from the states and i should be back in business. the first time i rebuilt the motor i remember those half round rubbers dropping into the crankcase during the rebuild, and whenever i touch them now i get nervous.
 
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