Engine Builders - How do you handle this/ bearings?
Post Reply    Forum -> Not-So-Modern
Author Message
Joined: 26 Jan 2019
Posts: 878
Location: california
Sun Nov 17, 2019 11:02 pm quote
Folks - Looking for some insights from the experienced.

VBB cases.
New crank - Pinasco.
Chose the following method for assembly.
1. Install clutch side bearing
2. Slide fly side bearing (one piece) on to the crank
3. Pull crank in - flush with bearing
4. Put small side (fly) case on

I was surprised to see that the bearing on fly side is ~2.5mm exposed in to case (see pic below).

Interested to hear how other's address this.
- Put bearing in fly side of case first? (leaves 2.5mm gap from bearing face to crank web if I do)
- Use shims to move bearing further off crank web - and closer to flush fit with case?
- Leave it - that's how its supposed to be
- Some other approach?

Given the factory maintenance books I have seen say you are supposed to fit the bearing to the crank first - it would suggest that this exposed bearing on the fly side is the norm?

Opinions and experience appreciated.
- CM

bearing is proud of case by about 2.5mm - top arrow

Honda elite
Joined: 19 Jun 2007
Posts: 768
Location: California
Mon Nov 18, 2019 10:11 am quote
I think sime66 was working this out on his build page 3. For our case seems like a shim under clutch seal to move crank towards flywheel? Clutch maintains crank is home to that side.
2015 GTS300, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 4300
Location: San Diego, CA
Mon Nov 18, 2019 11:05 am quote
Looks like the wrong bearing width
1984 PX(177)EFL
Joined: 14 Apr 2017
Posts: 222
Location: Cornwall UK
Mon Nov 18, 2019 11:55 am quote
hibbert wrote:
I think sime66 was working this out on his build page 3
Although I have just done these bearings myself, I'm not sure I can add anything, but I'll share what I do.

The crucial point for me (the bit Hibbert is referring to on my build thread) was making sure the main clutch-side bearing allowed the crank web to sit perfectly over the inlet pad; this was particularly important because I wanted the pad opening to be as wide as possible, so there was no room for error. That sets, fixed, the clutch-side bearing and the crank, which is pulled tight onto the bearing.
The 'P' fly-side bearing is in two parts; the inner race fits onto the crank, allowing a 1mm gap between it and the crank itself; you can buy a spacer, but guess what I made one.
The other half of the flyside bearing does sit very slightly proud of the inner face of the casings to keep the oil channel clear. In the image below you can just see that, and all I did was to make sure I could poke something thro'.
So, with the clutch-side bearing and crank fixed and non-negotiable, the fly-side bearing inner race located relative to the crank precisely (1mm), and the outer half fixed just enough to keep the oilway open, as long as the casings close, and nothing is rubbing, having already ensured the pad opening is covered as first step, it's job done, move on to the next task.....

Your casings or bearing might be different, but that's P/PX casings. Yours looks like it all wants to move towards the flywheel, but I think your inlet pad and crank web alignment would dictate what you can do; that has to be right.

CM Fly Bearing.jpg

Crank Web Centred on Inlet Pad.jpg

Joined: 26 Jan 2019
Posts: 878
Location: california
Mon Nov 18, 2019 2:21 pm quote
Gents - thank you for the shared experience.
John - double checked - bearings are the proper ones. Thanks tho.
Sime - I took the same approach you did.
Inlet to crank web relation is controlling factor.
This meant the crank is flush with clutch bearing, which is flush with case.
That left me with the 2.5mm gap on the fly side.

You are the second or third to bring up the gaping for oil on the fly side.
I agree - the gap does allow the oil hole to feed oil to the back side of bearing - it likely receives some from the front as well as the crank has a shoulder that separates the bearing from the web about 1mm.
Starting to believe this gap is how they designed the motor from factory.

So... clutch side will be as close to case as I can - maximizing inlet to crank overlap on center. Believe I will add a one of my nice shims to push the fly side bearing 1mm further in to the case and away from the crank on fly side - it will still poke out 1.5mm proud from case.

Am surprised that this is not an oft discussed topic - could not find a previous thread.

Thanks gents!
- CM
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1676
Location: London UK
Mon Nov 18, 2019 7:04 pm quote
One more thing about the bigger gap on the flyside, is that as the main bearing wears, the crankshaft moves to that side when the clutch is pulled. Can be quite a lot of movement after 50,000 miles on the same bearings. On P engines this is often too tight and the crank rubs on the casing by the time the bearing is properly worn.

I think you'll be fine. Where are the pictures of this finished exhaust port?
Team Scooter Trash for Petfinder Foundation   vespa scooterwest scooter west Motorsport Scooters   Cool Ass scooter seat cover
Post Reply    Forum -> Not-So-Modern
[ Time: 0.1504s ][ Queries: 26 (0.0399s) ][ Debug on ]