Back at the Mount Equinox Hillclimb in 2017, on the first run of the weekend, I melted the #2 piston in the Quantum Two. Now I am finally getting around to rebuilding the engine with a new piston. As part of that, I am cleaning and inspecting all the parts that I remove from the car.
Recently, SAAB guru Tom Donney of the SAAB Heritage Museum USA and Tom Donney Motors posted a video about some crank pulley issues he’s coming across on the SAAB two-stroke. As a consequence of this video, I took a much closer look at my pulley than I otherwise would have.
THERE IS A CRACK!
Honestly, I was a bit surprised to find a crack in the pulley as I didn’t think it had many miles on it, but really I don’t know for sure.
So I went digging in my parts collection looking for another pulley. While I have a few on the shelf, none are for a 750. The diameter of the sealing surface (where the crack is) is smaller on the 750 than on the 850. It is a simple task to replace the current 750 front cover (the thing that keeps all the grease in the distributor drive area) with one from an 850 so I can use one of the pulleys I have.
The 850 pulley should be stronger too, because it has more material around the center hole. So that’s a good thing.
Now it is time to take a look at the pulley I want to use, i.e. the cleanest one on the shelf. It is a brand new one (aftermarket) that came with a rebuilt crank we had done a while back.
Thanks to Mr. Donney’s video, I knew to look for a couple of issues with this brand new pulley.
- The casting didn’t have enough relief (wasn’t deep enough) in the center to allow the tensioning cup to install fully and properly tighten down the harmonic balancer weight.
- The sealing surface where it goes in the front cover is unfinished (with a rough surface) and will wear out the oil/grease seal in short order.
So, onto the lathe it went!
Here is Tom’s video that helped me so much in identifying the problems I had and the solutions I needed to put into effect. Thank you Tom!
