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Petrol/oil lubricated flywheel side bearing

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Petrol/oil lubricated flywheel side bearing

Postby Knowledge » Sat Jan 01, 2022 9:19 pm

What are the pros and cons of converting the flywheel side bearing to petrol/oil lubrication?

I rarely find any grease in my flywheel side mag flange when I strip my engines after many miles of use. However, the bearing is usually ok and it seems quite happy running with the oil supplied by the petrol.

I know that series 1 engines had flywheel side bearings that were lubricated by the oil in the petrol. I also recall Charlie Edmonds modifying engines to be lubricated by this method when he was launching the Super Monza. I have also seen on FB that Terry Carpenter (Kettering Massive) has modified a mag flange to use this style of lubrication.

Let’s have your thoughts please, and how do you do it (e.g. a spacer to replace the inner oil seal, a groove to direct the oil into the bearing,......)?
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Re: Petrol/oil lubricated flywheel side bearing

Postby bike grim » Sun Jan 02, 2022 1:57 pm

The fancy Casa mag flanges are like this aren’t they?
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Re: Petrol/oil lubricated flywheel side bearing

Postby Knowledge » Sun Jan 02, 2022 3:11 pm

That’s interesting. I have a mate with a SST265T in a yet-to-be-assembled state. I will ask him to have a look and send a photo.

I did get a pm from a contributor to this forum who suggested that the bearing will run cooler and there will be less drag, which sounds fair enough. He also suggests that most other two strokes now use this method of bearing lubrication. Thinking about it, P range Vespas have flywheel side bearings lubricated by petroil mix. Hmmm, there must be something in this.

Meanwhile, keep the opinions and info coming.
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Re: Petrol/oil lubricated flywheel side bearing

Postby ULC Soulagent » Sun Jan 02, 2022 7:00 pm

As far as I know all the club members that run Super Monza’s have the S1 mag housing for using the grove and it must run 4% oil.
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Re: Petrol/oil lubricated flywheel side bearing

Postby dscscotty » Mon Jan 03, 2022 11:43 pm

This is my usual method for lubrication of mag bearing. It's not a new concept. ;)
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Re: Petrol/oil lubricated flywheel side bearing

Postby Warkton Tornado No.1 » Tue Jan 04, 2022 12:27 am

I’ve used petroil to lubricate the mag side bearing but it’s been in conjunction with the addition of a ‘breather’ from the offside of it though to the transfer port to create pressure, thus drawing the petroil mist through.

Whether or not it is a worthwhile modification depends upon how you judge primary compression. I believe that HPC is the wrong way to go the standard it is already too high. That’s my opinion, of course, but modern two stroke engines do not tend to pursue the HPC route either.
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Re: Petrol/oil lubricated flywheel side bearing

Postby vegansydney » Thu Jan 06, 2022 10:06 pm

dscscotty wrote:This is my usual method for lubrication of mag bearing. It's not a new concept. ;)


Interesting! So, could I fit a GP-tapered crank to an early Series 1 engine and retain the original 'channeled' mag housing? Or are you using a Casa 'Cooler' Performance multi-piece mag housing? If yes, would it be as easy a fitting the S1 oil seal (25-46-7) and an NU2205 bearing or is it slightly more complicated?

Just thinking out loud as I have a Framebreather project I've been procrastinating on for some time as I'm uncertain on which way to go with the engine.
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Re: Petrol/oil lubricated flywheel side bearing

Postby Warkton Tornado No.1 » Fri Jan 14, 2022 2:08 pm

vegansydney wrote:
dscscotty wrote:This is my usual method for lubrication of mag bearing. It's not a new concept. ;)


Interesting! So, could I fit a GP-tapered crank to an early Series 1 engine and retain the original 'channeled' mag housing? Or are you using a Casa 'Cooler' Performance multi-piece mag housing? If yes, would it be as easy a fitting the S1 oil seal (25-46-7) and an NU2205 bearing or is it slightly more complicated?

Just thinking out loud as I have a Framebreather project I've been procrastinating on for some time as I'm uncertain on which way to go with the engine.


I’ve only ever used OEM SIII magneto housings but can confirm that the NU2205 bearing works so it’s likely the NU205 would also cope.

Dependent upon personal preferences as to whether the roller type bearing is necessary, there are also deep groove ball bearings that will work. Arguably, they work as well, if not better, despite less load capability, functioning successfully in very powerful race engines. If you can think about the way that the crankshaft is likely to flex & accept that as a natural occurrence, then deep groove or specific ‘magneto’ bearings can make a lot of sense in trying not to resist the flex in any way. A roller bearing of the NU type will naturally resist flex.

If a deep groove ball bearing is utilised, the journal on the crank should be modified to be a looser fit in the bearing.
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Re: Petrol/oil lubricated flywheel side bearing

Postby Knowledge » Sat Jan 15, 2022 11:36 pm

Warkton Tornado No.1 wrote:If a deep groove ball bearing is utilised, the journal on the crank should be modified to be a looser fit in the bearing.


I was thinking about this WT1. If I remove the inner track of the NU bearing from the crank and put a roller bearing in the mag housing, I could relieve the steel on the crank (where the NU bearing sleeve was situated) with something like emery cloth, rather than actually machining it in the lathe. Slowly does it with lots of test-fits until the inside of the bearing just slips over the crank.

Is that along the lines you were thinking WT1?
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Re: Petrol/oil lubricated flywheel side bearing

Postby Warkton Tornado No.1 » Sun Jan 16, 2022 8:34 pm

Knowledge wrote:
Warkton Tornado No.1 wrote:If a deep groove ball bearing is utilised, the journal on the crank should be modified to be a looser fit in the bearing.


I was thinking about this WT1. If I remove the inner track of the NU bearing from the crank and put a roller bearing in the mag housing, I could relieve the steel on the crank (where the NU bearing sleeve was situated) with something like emery cloth, rather than actually machining it in the lathe. Slowly does it with lots of test-fits until the inside of the bearing just slips over the crank.

Is that along the lines you were thinking WT1?


By ‘roller bearing’ presumably you mean a deep groove ball bearing? Sorry if that appears pedantic, but I only intend to clarify the description precisely so we are not @ cross purposes :D

If that is what you mean, then the modification you describe is the way to do it ;)
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Re: Petrol/oil lubricated flywheel side bearing

Postby Knowledge » Sun Jan 16, 2022 9:16 pm

I intend to use a ball bearing, not a roller bearing.

I have been looking at deep groove ball bearings today and decided against them as they looked like the design would restrict the ease with which the petroil can access the balls. After all, the drive side bearing is not a deep groove bearing.

Does that sound sensible?

I have started stripping the mag flange today with the intention of undertaking this conversion.
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Re: Petrol/oil lubricated flywheel side bearing

Postby Warkton Tornado No.1 » Tue Jan 18, 2022 5:02 pm

Knowledge wrote:I intend to use a ball bearing, not a roller bearing.

I have been looking at deep groove ball bearings today and decided against them as they looked like the design would restrict the ease with which the petroil can access the balls. After all, the drive side bearing is not a deep groove bearing.

Does that sound sensible?

I have started stripping the mag flange today with the intention of undertaking this conversion.


The drive side bearing is classified as a ‘deep groove ball bearing’ but the description is only thus to communicate that the rolling elements (balls) are retained by the ‘deep groove’

I have mentioned ‘magneto bearings’ in previous replies but they are only a variance on deep groove ball bearings & considering their likely decreasing popularity not necessarily an economic option. However, I am aware of their use on occasion in highly tuned Lambretta engines.

The oil mist lubrication that petroil offers is apparently adequate for many two stroke engines that utilise a bottom end exactly as we are discussing, other than their drive side bearings would also rely upon the petroil mix for lubrication. The chance are that a top tuner somewhere has also modified the drive side bearing arrangement in that manner in an attempt to decrease primary compression…..

My thoughts are that the most stressed bearings within the whole piston/crankshaft assembly are the needle/roller bearings within the conrod & they appear to cope with the scant oil mist that they get (if the oil is good enough as I know some will be thinking) but any improvements that can be made should be applied. In the case of petroil lubrication to the crankshaft support bearings, a drilling from the transfer through to the ‘dark side’ of any bearing is essential.
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Re: Petrol/oil lubricated flywheel side bearing

Postby dscscotty » Tue Jan 18, 2022 9:29 pm

Knowledge if you intend to use a non nu type bearing its advisable to relieve the inner track of the bearing and not the crank, if to much is taken from the crank its wasted, the clearance required is minimal, the bearing should only just slide over then loctited if there is to much clearance the crank shaft can wear very quickly.
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Re: Petrol/oil lubricated flywheel side bearing

Postby Knowledge » Tue Jan 18, 2022 10:13 pm

Thank Darren.

The intention was to go very easy on relieving the crank. I acknowledge what you are saying about the wasting the crank, but if I go slowly, slowly on the crank and later decide against the Petroil lubricated mag-side bearing, I should be able to revert to NU by securing the inner track with some Loctite.

I am also wary of being able to relieve the inside of the inner track of the 62205 bearing properly. If I was to put it in the lathe (and it is a bit of an[i]if[i]) I wonder if I could remove such a small amount of material. That is why I thinking of using emery cloth on the outside of the crank as I should be able to achieve a consistent parallel reduction.

If someone has got a reliable technique for relieving the inside of a bearing, please post below.

The engine is out of the frame now and will be dismantled tomorrow if I get the time.
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Re: Petrol/oil lubricated flywheel side bearing

Postby Warkton Tornado No.1 » Wed Jan 19, 2022 3:11 am

The crankshaft journal is probably more easily modified to remain concentric by finding tubing or an old oversize bearing bore (though an Imperial 1” is 25.4 maximum) in conjunction with grinding paste.

I take the point made about avoiding modifying the crankshaft journal as it is best to permanently modify a cheaper (sacrificial) bearing instead.

I wonder if a die grinder/Dremel type tool mounted on the lathe cross-slide with a sturdy enough mount could be a method :?:
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Re: Petrol/oil lubricated flywheel side bearing

Postby dscscotty » Wed Jan 19, 2022 8:45 am

I can only advise its upto you to decide what to do, what I can tell you is that the current BSSO group 4e Championship winning lambretta, group 6 winning lambretta, the only lambretta to win a UK Endurance race and the 2a
nd placed lambretta in the LCGB BSM championship for 3 years were done this way, so tried n tested.
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Re: Petrol/oil lubricated flywheel side bearing

Postby Knowledge » Wed Jan 19, 2022 9:23 am

Darren,

Which Loctite do you recommend for securing the bearing to the crank journal?

After all, this thing has got to come apart again one day.
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Re: Petrol/oil lubricated flywheel side bearing

Postby dscscotty » Wed Jan 19, 2022 10:28 am

In reality your probably better running an NU2205 type with collar on a road engine, it'll save you a lot of chew, this also allows a margin of error if the crank is slightly out off alignment, also negates the use of spacers etc. Generally to really do the job 270 loctite, the advantage with race engines is we strip and check regularly so often have a good indication of any issue before they arise.
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