Overthinking a Rebuild and a Few Questions
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'81 P200E, '80 P200E, '64 V90 and 3 Ciaos
Joined: 27 Mar 2014
Posts: 136
Location: Tucson, AZ
Mon Dec 31, 2018 3:01 pm quote
Been having a bit of a "ship of Theseus" exercise in starting into the rebuild of my '64 V9A. The scoot is hardly original anymore, but it's apparent that a large portion of the bits that comprise it have been collaborating to move riders around for a good long time. The engine was torn down to clean and sort parts and to address some case damage. The crankcase has been repaired and it's about ready to receive parts. My challenge lies in which parts to re-use and which parts to replace.

What's the general consideration when rebuilding a vintage bike? Save all that you can and replace only what you can't save? I understand the impetus behind "it's only original once" and the intrinsic value of maintaining the bike as-produced less the new luster replaced with a patina cultivated through time and use (or lack of).

In my case, this scoot is in some respects a survivor and will never be a restoration. It has been personalized and altered over time to suit the tastes of a cavalcade of owners. This machine tells an interesting story through it's bits and it seems proper to keep as much of it around as possible. The exterior stuff is easy enough, but mechanicals that give me pause. They're integral parts of the story, but they work in the background and won't present themselves to the casual observer.

Some bits have been pretty easy. I was going to rebuild the cush drive in order to preserve the primary gears, but the primary basket was a bit too bashed up to reuse. So, replacement primary gears were the way forward.

Some other items are less easy to decide. The gear blocks for the shift stirrup are badly rutted and the batwing was bent to hell. I was able to remove the stirrup without too much fuss and un-mangle the batwing. I have a new FA Italia assembly, but it seems wrong somehow when I know I can replace the O-ring, gear blocks and the taper pin to return it to service. I need to reconcile this.

Being a 1st-series machine, certain parts are going to be hard to replace. The keyway on the Christmas tree shows a bit of wear on the clutch shaft and a touch of erosion by the key slot, but it otherwise serviceable. The drive gears are in less usable condition and I question their authenticity...no recognizable manufacturer stamp and after cleaning, they have a straw-coloration to them, which suggests flame hardening. Never have found that on any of the later Vespas I've worked on, but this one is a bit older. OE or not, I'd consider reusing them if first gear's drive dogs weren't so hammered. I'm left seeking alternate parts from another story and a sense of disappointment.

As stated on the tin, I'm overthinking this when I could be focusing on riding it again. With that all spelled out, there are a few easy questions which I pose to the group:

1) I'm seeking good replacement gear cables. The originals are far too hosed to refurbish. Recommendations?

2) I'm looking to replace the haggard flywheel side engine bearing. Are all of the N204 bearings using polyamide cages these days, or is it possible to get a metal caged bearing anymore? Should it have a 6204 bearing instead?

3) Is there a noticeable performance difference between a bushing crank and a needle bearing crank on a stock V90? The original crank was drilled for a bearing when the cylinder was overbored for a V9B piston. This was poorly executed as the top end rod width is a fair bit narrower on the bushing crank; the bearing had all sorts of room to walk on the piston pin and wasn't fully supported by the rod.
I procured a Mazzuchelli crank for early V9As since I couldn't find an original part, an OE first over piston and an original bore that cleaned up to 1st over. Since all these bits are unavoidable new additions and revert the engine to it's as-intended state rather than preserving the character it had gained, is it worth considering just using a later crank and rod to reduce internal friction and improve the rev range?
50 N
Joined: 20 Dec 2015
Posts: 264
Location: North Aberdeenshire
Mon Dec 31, 2018 3:28 pm quote
I'm all for preservation on earlier and rare models where possible but consumables need replaced as they wear out. Not so easy on earlier bikes I know.

And then comes the resto-mod angle, which for me at least, is a more realistic way of looking at things unless you have a 15 Grand plus VS1 or something like that.

It's a V90, they were always rubbish, I've had a few. Later ones were slightly less rubbish.V100's surprisingly quite a bit better but still rubbish.

Guygrr is running an interesting thread on another forum at the moment, can't remember if he is on here but assume so, about fitting a 4 speed box in an early case. Way too much work for me but fair play to the lad.
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