[stinkwheel]

I've been working on my distributor so I thought i'd do a video of taking it apart and a bit on how it works with regard to the points and auto-advance.

The plan was to re-shim it today but it turns out there's so much play, the shims I have aren't going to do the job. I'll try to do another video of reassembling and explaining what's going on the the shims once my new shims arrive.

https://youtu.be/PFZRPBTGKfM

[Karl Childers]

Great video, thanks for sharing!

[AzCal Retred]

Thanks - great vid! First vid I've ever seen on this. I'll be putting your intel to use in the next week or two. 

[Raymond]

Great video, thanks for sharing!

+1

[tooseevee]

I've been working on my distributor so I thought i'd do a video of taking it apart and a bit on how it works with regard to the points and auto-advance.

The plan was to re-shim it today but it turns out there's so much play, the shims I have aren't going to do the job. I'll try to do another video of reassembling and explaining what's going on the the shims once my new shims arrive.

https://youtu.be/PFZRPBTGKfM

        ++1   Excellent video. You are a credit to the forums.

         PS: Has everyone watched the avatar long enough to see.....? 

[Super45]

Have you done a subsequent video with the reassembly?

I'm in a similar position with play in the distributor shaft and wondered where you were fitting the shims if needed after new bushes?

Thanks

[stinkwheel]

On its way. I'm waiting for a couple more shims, turns out I didn't order enough of the right thicknesses. I also want to do a bit of maths to check I'm allowing for differential expansion when the alloy heats up, don't want it tightening up on a long run.

[stinkwheel]

Just so you can get the ball rolling. I found the hitchcocks shims were limited in how much play they can take out because they fit over the taper between the pinnion and the main body of the shaft. Stack up a few and you stop the pinnion engaging with the taper.

I ordered some larger steel shims which measured 18mm ID x 25mm OD. These sit neatly in the recess of the casting and have enough overlap with the base of the pinnion to space it out nicely (there is almost no thrust load on this shaft anyway). I just didn't order enough of the correct thickness to do my video.

Thermal expansion is a potential issue, you don't want it binding up tight when it gets hot, the aluminium casing will expand way more rapidly than the steel shaft...

Google says the thermal expansion coefficient of aluminium is up to 0.024mm/metre/degree.

I wouldn't expect the distributor housing to ever get hotter than 100 degrees. So say a maximum increase of 80 degrees celcius.

1 metre of aluminium would expand by 1.92mm when heated by 80 degrees. So to get the thermal expansion, we need to multiply the length of the distributor housing in metres by 1.92.

The expansion in the steel shaft is negligeable (less than 0.01mm).

So Minimum end-float on the shaft = length of the housing in metres x 1.92.

[Raymond]

So if I've understood, as long as it feels ever-so-slightly loose, you're good to go?

[Super45]

Just so you can get the ball rolling. I found the hitchcocks shims were limited in how much play they can take out because they fit over the taper between the pinnion and the main body of the shaft. Stack up a few and you stop the pinnion engaging with the taper.

I ordered some larger steel shims which measured 18mm ID x 25mm OD. These sit neatly in the recess of the casting and have enough overlap with the base of the pinnion to space it out nicely (there is almost no thrust load on this shaft anyway). I just didn't order enough of the correct thickness to do my video.

Thermal expansion is a potential issue, you don't want it binding up tight when it gets hot, the aluminium casing will expand way more rapidly than the steel shaft...

Google says the thermal expansion coefficient of aluminium is up to 0.024mm/metre/degree.

I wouldn't expect the distributor housing to ever get hotter than 100 degrees. So say a maximum increase of 80 degrees celcius.

1 metre of aluminium would expand by 1.92mm when heated by 80 degrees. So to get the thermal expansion, we need to multiply the length of the distributor housing in metres by 1.92.

The expansion in the steel shaft is negligeable (less than 0.01mm).

So Minimum end-float on the shaft = length of the housing in metres x 1.92.

So for thicko's in the back of the room , are we talking behind the timing cog end in the small recess by the 3 retaining screws? 

This is my bike's amount of play and I'm not 100% sure but there may be some 360 degree play as well as fore and aft.

https://www.youtube.com/shorts/aSikMmkPmmI

[stinkwheel]

Yes, you have a lot of play there. There's an awful lot of wear on your bushings which is causing that side-to-side play you demonstrated second, there should be pretty much no play in that direction and it'll definitely be affecting the ignition timing. Those bushes are going to need to be replaced.

If it was me, I'd change those bushings as a first step then see what it looks like as that might take up a fair bit of the end float too. The end float is less of a worry until it gets to the point where the auto-advance can foul the back of the contact breaker backing plate (which yours almost certainly can).

Yes, the shims are fitting in the recess on the end of the housing which fits in the timing chest, on the right hand side of the bike, under the cog (pinion is a fancy term for the smaller of two meshed gears).

You don't actually need to remove those three screws to do all of this, the bushes can be drifted out and new ones fitted with the aluminium distributor housing on the bike. I took it off because a) it's easier to do on the bench and b) It's easier to show it on a video.

For the benefit those at the back of the room . When you get new bronze bushings, they are often made very slightly thicker than you want them. Fitting them in the housing isn't usually too much of an issue because -as mentioned above- aluminium expands quite a lot when heated, so if you heat up the housing, a tight fitting bush will usually press in quite easily.

The inside diameter needs a little more fiddling. It's often slightly undersize AND it can contract a little as it's pushed into the housing meaning it's too tight for the shaft to fit inside and/or move freely. There are a few ways of sorting this out. (in order of "correctness").

1) Ream it out with a correctly sized reaming tool in a pillar drill or (preferrably) a mill.

2) Hone the inside with a small brake caliper honing tool.

3) (what I do) Hone the inside with an improvised flap-wheel made using a piece of aluminium tube with a slot cut in the end and a piece of emery tape or folded wet and dry paper stuck in the slot so it's liong enough to rub on the insides of the bushing when inserted. Put it in an electric drill and wizz it in the bushing a little at a time until the shaft is a good fit. So it slides in and out and rotates easily but has no real sideways play.

Remember to clean off any abrasive residues thoroughly afterwards.

[cyrusb]

The reamer would be the better choice with brass. Or even a knife/dull drill bit. Abrasives embed themselves in the soft brass so you are basically charging a lap.
 Nice fix on the threaded holes.

[Super45]

Yes, you have a lot of play there. There's an awful lot of wear on your bushings which is causing that side-to-side play you demonstrated second, there should be pretty much no play in that direction and it'll definitely be affecting the ignition timing. Those bushes are going to need to be replaced.

If it was me, I'd change those bushings as a first step then see what it looks like as that might take up a fair bit of the end float too. The end float is less of a worry until it gets to the point where the auto-advance can foul the back of the contact breaker backing plate (which yours almost certainly can).

Yes, the shims are fitting in the recess on the end of the housing which fits in the timing chest, on the right hand side of the bike, under the cog (pinion is a fancy term for the smaller of two meshed gears).

You don't actually need to remove those three screws to do all of this, the bushes can be drifted out and new ones fitted with the aluminium distributor housing on the bike. I took it off because a) it's easier to do on the bench and b) It's easier to show it on a video.

For the benefit those at the back of the room . When you get new bronze bushings, they are often made very slightly thicker than you want them. Fitting them in the housing isn't usually too much of an issue because -as mentioned above- aluminium expands quite a lot when heated, so if you heat up the housing, a tight fitting bush will usually press in quite easily.

The inside diameter needs a little more fiddling. It's often slightly undersize AND it can contract a little as it's pushed into the housing meaning it's too tight for the shaft to fit inside and/or move freely. There are a few ways of sorting this out. (in order of "correctness").

1) Ream it out with a correctly sized reaming tool in a pillar drill or (preferrably) a mill.

2) Hone the inside with a small brake caliper honing tool.

3) (what I do) Hone the inside with an improvised flap-wheel made using a piece of aluminium tube with a slot cut in the end and a piece of emery tape or folded wet and dry paper stuck in the slot so it's liong enough to rub on the insides of the bushing when inserted. Put it in an electric drill and wizz it in the bushing a little at a time until the shaft is a good fit. So it slides in and out and rotates easily but has no real sideways play.

Remember to clean off any abrasive residues thoroughly afterwards.

Perfect thanks, TBH it may be easier to do off the bike from my perspective or replace the whole unit with a later bearing fitted unit not quite sure yet which way I'll go, either way I need to relearn how to time the bike up correctly it seems!

[stinkwheel]

If you can get a bearing one, that would be better. I'm just being awkward/cheap sticking with the bushing one. With the amount of play on your bushings, there could also be wear on the shaft. If there is, you're fast approaching the point where you may as well just replace the whole thing.

[Super45]

If you can get a bearing one, that would be better. I'm just being awkward/cheap sticking with the bushing one. With the amount of play on your bushings, there could also be wear on the shaft. If there is, you're fast approaching the point where you may as well just replace the whole thing.

That's what I'm pondering, £67 off eBay for a new one, although the seller I've spoken too doesn't know if its bush or bearing dizzy.

Either way I'm looking forward to your follow up videos and the refit.