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Anybody have a clever trick for getting bushings out when there is no access to the far side? I have heard that a Dremel is the second best tool for any job, so I'm hoping there is a better way. I have access to a mill if the recommendation is to bore it out oversize.



Thanks!
-Jim

Just an idea - could you tap a thread in it, so a bolt can be used to get a purchase?

Jordan

I like that idea... I'll need to look through my taps to see if i have one that is about the right size. I could use a long bolt to make a "slide hammer dent puller" style tool to remove it. Originally I was thinking of using a large screw extractor, but I was concerned that it would just push the relatively soft bronze outward into the walls. The tap and pull method sounds better!

Tapping the hole and using an adapter and slide hammer works every time. Best method in my opinion.

Nigel Lacey

That's how I got mine out, a 1/2"-20 tap worked fine so I'm sure a 13mm would work also. If you need to you're more than welcome to stop by and do it here. I've all the equipment to do the head work too, so you could also cut your valve seats and do the valve faces if you haven't done that yet...


Bill

It reminds me of removing the pilot bsushing in the end of a crankshaft where the flywheel bolts on. In which case you could thread the tap in, once it bottomed you could continue to turn it in and it would pull the bushing out as the threads tried to go in with no place to go the only thing to give is the bushing. Of course, a big block chevy crank shaft is probably a little tougher than the little Ducs engine case.

Mike

My 250 NC crank was running well out of line and i suspect may have worn the bush and crank end, does anyone know what what would be acceptable sizes for both?

I'm up against the same problem. The workshop manual specifies the bushing ID tolerance as 12mm to 12.027mm, but gives no info on the crank end. I'm thinking that it would be 12mm, but I don't have my crank here to check. It would be nice to know or come up with an acceptable tolerance in case the crank end needs to be ground down and an undersized bushing fitted. If the surface of the crank end is in good shape then it may not need to be reground even if it is worn. Here's my thinking: a non-concentric crank end is wearing evenly over the entire diameter against one spot on the bushing and therefore the bushing is the only thing wearing unevenly... plus the bushing is a softer material and will sacrifice itself.

Anyhow, I'm thinking that since the wear limit on the bushing is only about .001" that the diameters should be an exact fit (both are the same diameter) to start and they will "break in" in a short period. The interface between the two is relatively small and shouldn't cause much friction during the "break in". My bushing looked slightly eccentric, so I'm going to machine the bushing pocket slightly over-sized and aligned, then fit a custom bushing. I'm planning to mount the timing cover to the end mill bed in a way that allows me to temporarily assemble on the case half to find the crank center. Then I can remove the case half and bore the pocket out on center.
-Jim

If your crankshaft is pressed together slightly out of alignment, the error will get amplified out at the end, causing a wobble- that may account for your eccentric bushing- the crankshaft end may be OK. Before doing a complicated setup to 'blueprint' the bushing location, you could bolt you crankshaft into the cases and put an indicator on the end to check for radial run out. Or, put the timing cover with a new bushing onto the crankshaft/crankcase assembly, but without the dowel pins or bolts in the cover- spin the crankshaft while holding the cover and feel if the cover is moving in relation to the crankcases- you can feel incredibly small movements with just your fingers.
Rick

I seem to remember that there was 4 thou clearance on mine , so i can expect my big end to go bang!!, I could not make any sense of the data in my books, I bet Nigel knows what it should be,-----NIGEL!!!!. A new bush is on my Chrissy list, but what is the min size for the crank?.