Morini 350 Bearing Query

[simonnorthroad]

More familiar with 500 motors so excuse the ignorance, but according to the Morini parts book the 350 LH crank main-bearing is a standard 6306? C3 presumably?

The Morini parts-book I have, lists the gearbox engine sprocket-bearing as a 6204 (47mm OD) , but on my late engine the bearing is DEFINITELY a 6205 (52mm OD) presumably a later strengthening mod by the factory? hence my asking about the correct main-bearing for a late-ish 350 engine!

Anyone got a list of all 350 engine bearings and seals. It seems obvious, but I've done a search on here but found nowt.
Simon

[George 350]

Hi Simon,

I've only ever stripped earlier motors, so cannot answer for late/Cagiva era bikes, but on mine, all the bearings are standard off the shelf items.
As for sizes, whatever was published in the parts lists was correct on mine and other pre 1980 motors.
Regarding C3, there will be some that say it is very important, while others ( me included) have simply fitted 'standard clearance' bearings without issue. My bike? my Sport is now at around 98000 miles, some 28000 since it was last apart.

Hope this helps,
George

[MickeyMoto]

I buy bearings after dismantling and buy the same as installed. Yes the engine bearings were C3, Morini must have specified them for a reason.

[3potjohn]

According to my notes…..
Bearings
6306 main left
6202 camshaft x2
6304 gearbox sprocket side ( 20 52 15)
6204
6203 x2
All are C3
Seals
Camshaft 15 24 7 3
Main 80 30 40 5
G box 80 20 30 7

[70sbikes]

Charlie from Antietam Classic Cycle posted this photo elsewhere and I saved it as a reference...



This is the complete set for earlier 3 1/2's that had a ball bearing instead of a plain bearing on the right side. A roller bearing with a removable inner works best as a replacement for those...

[simonnorthroad]

Thank you all. V helpful.

As i say, the gearbox 'sprocket-shaft' bearing that came out of my crankcases differs to the parts-book I have

[simonnorthroad]

Charlie from Antietam Classic Cycle posted this photo elsewhere and I saved it as a reference...



This is the complete set for earlier 3 1/2's that had a ball bearing instead of a plain bearing on the right side. A roller bearing with a removable inner works best as a replacement for those...

NJ206 I THINK is a bearing used in 500s

[MickeyMoto]

The Club parts manual show both the plain and roller main bearing engines and the bearing types.

[mbmm350s]

Hi Simon
Is this an X engine or a A engine?
MRC parts book only covers up to 1980

For example
Kanguro X2 parts book has 24.01.08 6304 i.e 20x52x15 for gearbox sprocket side bearing.
Dart 350 has the same 6304 part 24.01.08 in parts book
These agree with Johns notes from a late K motor i.e not 6205 but 6304 but these are dimensionally the same size.
Main bearing all were 6306.

Fit class should be marked on bearing if you know they are original.
Old bearings had hard to see and hence to read circular rings to indicate fit class.
Unusual bearings may have been fitted to rectify a spun bearing in the housing.

Mark

[70sbikes]

NJ206 I THINK is a bearing used in 500s

NU206 ECJ C3 is the bearing with the removable inner. You press the inner onto the crank, and the outer into the casing.

[Trevor-3_1/2]

WARNING
Hi, I had to replace the bearing behind the clutch & while the engine was in bits I thought I would replace all the bearings, including replacing the timing side ball type bearing with a roller type like that pictured. It made assembly easier. However after about 800 miles the outer race had started to move in the casing. I stripped the engine again & used the appropriate Loctite to retain the outer part of the bearing. Once again with less than 1000 miles there was the oil behind the alternator & the outer had moved again - Doh!
I decided to go back to the standard ball type main bearing & have several thousand happy miles without issue.
This is my personal experience & it does seem that other people have done this conversion without issue. However I have since heard of other failures doing this modification & Benjy showed me photos of the roller bearing failing in a catastrophic way within very few miles of being fitted.
I did the conversion in the belief that it was 'betterment' but it just caused me hassle.
Two halves to every story; so make your own choice.
I hope this input helps you Trevor

[70sbikes]

Hi Trevor.

I did see your posts about the bearing issue, and decided to "suck it and see". My bike has done 1803 kilometres (1120 miles) with no problems so far. I remember when I installed the outer I had to use a 10 ton press, and it did make a loud "squeek" as it went into place (this was with a heated case and a frozen outer).

However, I am curious about the things that alerted you to the imminent bearing failure (for my own future reference). Did the engine start to make odd noises? You mentioned oil behind the alternator, how obvious was this leak? I just went out into the garage, had a look behind the flywheel, and it looked pretty dry. I also started the bike, and that side of the motor is very quiet...

Finally, what method did you use to install the ball bearing (i.e. bearing installed in the case first, or bearing installed on the crank first)? When I separated the cases, I had to use a crankcase puller, and the bearing stayed stubbornly on the crank. This was somewhat disconcerting, as the YouTube videos showed the cases separating quite easily.

I appreciate your post. If the bearing does fail, I'm quite prepared to strip the motor again, and it's not something I'm going to stress over...

Cheers

Trevor