Hello everyone,

I'm new to the forum here, and I was wondering if someone could help me out. First of all I will say that I'm actually looking for connecting rod berings to fit my '83 Yamaha XZ550 motorcycle. Unfortunately those bearings are no longer available, but I have been told that the connecting rod bearings from a 1988 Mazda 323 would fit (engine was not specified). A few months ago I bought some Clevite bearings from summit racing that were supposed to fit... they did not. Thinking I had gotten the wrong part, I tried again from another distributor, strike two.

At this point I was a little aggravated, It seemed as though I had just wasted more time, and money while still making no further progress on my project. The next thing I did was try to see if I could find the Mazda's con-rod and crank dimensions so I could compare them to my motorcycle's parts. Using the measurements in this manual, it seemed as though the Mazda bearings (from both the SOHC, and DOHC Turbo) would fit with little to no machining. As I already mentioned, all the bearings I have gotten do not fit/match the dimensions listed on pages 1026, 1029, and 1030 of that manual.

With all of that in mind, I have a few questions. Is the manual I'm using incorrect, or are the parts I'm getting incorrect? If the latter, where can I get the correct parts? Any help is appreciated. I really hope someone can help me sort this out, a set of custom bearings/an expensive bill from the machine shop is not an option I'm looking forward to.

Thanks, Rory

 

Is the issue with the bearings to large radially? the clearance is too small for the journal? If that is the only issue I'd mic the journal, and the inside diameter of the bearing, subtract the clearance, take it to a machine shop to have it scraped to that dimension.

 

The bearings have several flaws. First is the lack of a lubrication hole in the bearing. This is illustrated in the manual, although I wouldn't mind drilling one if I could sort the other issues. Second is the fact that these bearings are around 16mm wide, while the manual says they should be 22mm (which would fit my rods perfectly). Lastly, the bearings ID is slightly larger than it should be to fit the crank properly, as is the bearings OD to fit the con-rod's bore. Both the crank OD and con-rod big end ID fit within the range of measurements listed in the manual. That said, the bearing's thickness is just right. This means that when the bearings are installed, the bearing halves are forced in a way that makes them pinch the crank where both halves meet. This makes the connecting rod unable to spin freely, but because the bearing's thickness is correct, a plasti-guage will still give me the proper oil clearance number.

Basically, to get the bearings I have to work I would need to build up the crank pin's OD (or get under sized bearings, and bore them out/file down the crank), bore out the connecting rods, drill oil holes, and then I would still end up with bearings that are only 16mm wide when they should be 22mm. I think at that point I would be better off searching for different bearings. Does anyone mind comparing measurements of parts they have with those in the manual I linked?

Thanks again,

Rory