The whole point of a “mechanical build” was to prove the chassis parts, and consolidate the reuse of so many 40 year old semi-worn parts.
To get to this point, I have had to buy many more replacement parts than I had anticipated, but there is still a large number of older parts on the bike.
One of these came to light soon after I started the running in period.
After only 50 miles, I became aware of a rattle noise from the right hand side engine casing.
it sounded very much like “normal” clutch basket rattle, but louder… and ominously, it did not go away when the clutch lever was pulled in, as clutch rattle normally does.
I was so tempted to ignore it, but that never has good consequences, so I drained the oil and coolant, removed the RHS engine cover, and dismantled the clutch.
Oh Woe!
The centre bush of the clutch basket has fractured and fell out when I removed the basket from the mainshaft.
No worries, I was going to replace the clutch basket with it’s heavily worn tangs anyway, but the kits supplied to re-rivet onto the primary drive don’t include the centre bush, just the alloy basket itself.
After spending some time on various search engines, it seems that the centre bush is not a replaceable part.
Another primary drive, clutch basket assembly is required.
A dive into the parts box revealed only an old RD400 item, 02K0-1, as a suitable replacement, and a quick line up showed that it would fit, and that the primary gear teeth would engage, however, its basket tangs were also quite worn, and the backlash number is 67, which paired with the 91 of my primary drive pinion makes 158, or slightly too tight.
New 4L0/4L1 clutch assemblies are no longer available, but 31K assemblies from later YPVS bikes are, and look to be slightly more robust.
They are however expensive, at circa £400.
The Yamaha Banshee engine shares many parts with the YPVS, and the clutch basket/primary drive assembly is one of them. The big world market for Banshee parts is in the USA, and eventually, I found Partzilla.com, who list the part at a much more palatable $167, which will of course be Plus postage from the U.S. and almost certainly, Import tax and duties on entry to the UK.
Notwithstanding extra costs, I loaded up my Partzilla shopping basket with additional parts which are inexpensive in the USA, and excessively pricey in the UK, and hit the buy button.
So what could have caused such a catastrophic failure?
Perhaps it is simply a matter of time and wear. The part is 40 years old and has completed over 50,000 miles.
Maybe, it was shaken to bits, when I tugged on the end of the mainshaft, I could feel it “clicking” as I waggled it up and down, (and side to side).
The bearing is definitely worn, and I would estimate the lateral play as being approximately half a millimetre.
To be safe, I should replace it, and so, it’s time to remove the engine from the frame once again, and to replace the bearing, I’ll need to split the cases.
While it’s out, I will also replace some other worn parts which I have identified, while we are awaiting parts to ship from the USA.
I ordered the parts from Partzilla on August 30th 2021.
On 1st September I received an email informing me that one of the parts I had ordered, a small bolt, would be out of stock until October 30th, whereupon my order would be sent.
An email to Partzilla on the same day resulted in that part being removed from the order and refunded.
The order was on it’s way via UPS on Thursday 2nd September, and arrived at my door on the 8th.
I had to pay “import levies”, which is presumably VAT, and a handling charge to UPS before they would hand over the parcel. The order value (converted to Pounds Sterling), was £254, and the Payment to UPS totalled £55, of which £44 was import levies, and £11 was the processing fee.
I am not impressed with the packing skills of Partzilla. The parts were loose in the box with only a cursory scrap of crumpled brown paper providing any kind of padding.
there was a neat set of parallel cut-outs on the outside of the box where the clutch basket had tried to escape, and the primary gears had penetrated to the outside world.
Fortunately, the damage was limited to a small chip on the edge of one tooth which was dressed out with a file and some wet’n’dry.