6 replies to this topic

[Bluemini]

Just put my drop gears on and they felt ok when I turned them, as soon as I put the end cover on tho they felt like they were binding. I checked the clearence and this is ok, and they only bind for quarter of a turn ever 2nd full turn of the primary gear. I had a look on IME and there was a post on there saying that these simptoms could be down to the first motion shaft nose bearing not being on quite straight. Has anyone else had this problem??? I've got 2 days to figure out what it is!

[dklawson]

I have not seen this problem but have a suggestion.

I assume when you tigthened the end cover you did so with the gaskets "dry". If you didn't, get some new gaskets and clean off everything. Fit the end cover with the dry gaskets, make sure it's all torqued down. Put a paint mark on the primary gear so you know where the tight spot is. Now remove the end cover (leaving all the gears in place on the block) and temporarily fit a sheet of paper in the gap in addition to the gaskets. Tighten it up again. Re-check for the tight spot. IF the binding goes away, your clearance measurements may be off a bit and you need thinner thrust washers. A sheet of regular bond paper is usually about 0.003" thick. IF the binding is still there I would pursue that first motion shaft bearing idea.

[Guess-Works.com]

nice idea dklawson... I was also thinking, the idler only rotates about 2/3rds the speed of the primary, and the roller in the idler bearings will go round about 1/2 that speed, which, gives a complete bearing turn for three primary turns, hence a illfitting or worn idler bearing could give that symptom.

[Dan]

Has the first motion bearing race in the flywheel housing been changed to the one that came with the bearing on the gear? A lot of people don't change this outer race 'because they think it'll be hard to get out, which it can be but the bearing is matched to its races and they should be fitted as a set.

[Bluemini]

Well, I spent a couple of hours at the engineers tonight trying all different things, but we recon its down to the fact that the bronze bushes in the primary gear have been machined on a lathe instead of being line honed. Whoever did the machining on it hasn't got it quite centered properly, so the primary is turning on a slightly off centre axis, only by a fraction tho. If this is the case, then it will be ok, because it has always been like it and I drove it like that as did the guy who owned it before me for a long time.
Besides, the bushes are very expensive too :/

[dklawson]

MiniSpares offers a "floating bush" for the inside of the primary gear. They aren't too expensive. You could install the fixed one and have it bored to size then fit the floating bush and get rid of the problem. by the way, you can line bore the two bearings on a lathe, you just have to be very careful setting the part up and indicate it so it is running true.

[Dan]

I have a set of spare bushes lying around if you want 'em mate.