Chain Milling Away Selector Box

[Duccout]

I have a problem with the 350 which I am hoping someone may have encountered...... The chain is milling away the boss which holds the small bush at the back of the selector box. I thought that it was due to the 530 chain and sprockets and would stop when I changed to 428 size, but it has not and it has probably milled away about 2mm of the alloy and the bush on one side.

The sprocket is located by the gearbox bearing and the selector box by the crankcase, so what is happening? Has anyone else come across this?


Cheers,

Colin

[LaceyDucati]

Colin

Most modern 428 chains used are "Heavy duty" and have wider side plates which makes the situation worse. Later Mototrans models usually have the boss and bush reduced to allow the 530 chain to clear. All I would say is they all do it to some extent and it will stop once it's found it's way. I quite often shorten the housing back a bit to tidy it up. Chains vary in width, so maybe be selective with chain choice and leaving the 0.5mm "thrower" washer out behind the output bearing (if you are using a sealed bearing) will also help.

Regards Nigel

[Duccout]

Thanks Nigel,

That has reassured me a bit. I will clean up the boss a little with the Dremel.

Cheers,

Colin

[blethermaskite]

Colin, yes I have come across this issue a number of times, there's not much room in there, so chain alignment is a contributing factor make sure your sprockets are dead in line with each order,
Cheers,
George

[themoudie]

Aye Colin,

Happens on the 450 MKIII as well, as George suggests, get the chain alignment as good as you can and don't run with a slack chain or over-worn sprockets. I will post an image, for reassurance!

Good health, Bill

[Duccout]

I think that Nigel hit the nail on the head when he pointed to chain width. In the past I always used Reynolds chains which were much narrower.




Colin

[Duccout]

Looking at the chain today I can see that it is the spring link that is the main culprit, which is not very good for chain safety, and I wonder if this problem is a reason for Ducati Singles breaking their chains? Anyway, I will see if I can fit the spring link on the other way around, with the spring on the back.



Colin

[Andy Higham]

I have fitted one of the Sports Motorcycles selector boxes as everything inside mine was sh***ed. I can now fit my finger between sprocket and selector box, so plenty room.
https://sportsvalve.com/ducati-single-4 ... ector-box/

Less than a week from ordering to delivered

[Duccout]

Hi Andy,

Let us know how it performs.



Colin

[themoudie]

Having dived into the final drive, 500 miles after fitting a new front and rear sprocket and chain, to see what the wear patterns were, after previous comments here about possible chain misalignment and not posting as earlier promised in January 2023, chain abrasion of the selector box and swingarm pivot tube on my '74 450MKIII, for which I apologise, I thought an update was in order.

I have always had some abrasion of the selector box inner case boss, which appeared to cease when using an IWIS RZ1 428 chain and has now re-appeared when using an RK 428 HSB chain.

With 4 different manufacturers chain to hand, I had a wee measuring session with a micrometer, of the overall pin width of the chain and the overall pin width of the chains split link. I do not have a sample of a Reynolds chain from which to take measurements. It should also be noted that the last sprocket/chain set 17:42/IWIS 428RZ1, 121 pins, lasted 8,000 miles, with regular ~1,000 mile cleaning and re-oiling in a 50:50 chainsaw chain oil/EP90 transmission oil bath. The new sprocket/chain set was 17:41/RK 428 HSB, 120 pins. This is going to be changed to a 17:41/IWIS 428RZ1, 120 pins set.

IWIS 428RZ1 chain link pin length = 16.74mm Split link pin length = 18.32mm

CZ MotoX 428-7Y chain link pin length = 17.73mm Split link pin length = 19.60mm

RK 428 HSB chain link pin length = 18.75mm Split link pin length = 20.33mm

DID 428 HD chain link pin length = 18.83 Split link pin length = 20.38mm

So, no wonder that the CZ and Japanese chains gouge the selector box boss! It would appear that the split link pins are the culprits. Whether, this causes any increase in chain failure, I don't know, but having your split pin link acting as a milling head on a steel/bronze/aluminium alloy, boss/shaft, can't do it any good.

Another area of abrasion that I have always had is on the swingarm pivot tube and the underside of the reinforcing web on the 450's swingarm. I have used JB epoxy weld to fill up the grooves, but after ~100K miles, I think something else will be require afore I wear through the steel. Having changed from 530 chain to 428 chain doesn't appear to have increased the wear. But, increasing the length of the rear shocks from Hagon 300mm between centre units, to NJB 310mm between centre units, appears to have made a reduction in the wear rate. I've also lost a couple of stone from my 92 Kg days, to a current 80 Kg, so that should help a bit as well!

Images below for clarification.

Good health to you all and keep wearing them out, BillR