Converting a B50 to wet sump. (aka Boris Johnson)

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Converting a B50 to wet sump. (aka Boris Johnson)

Post by Momus »

Has anyone here had first hand experience converting a B50 from dry to wet sump?
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Re: Converting a B50 to wet sump.

Post by minetymenace »

<135 to the form Momus.
Would you update your profile and let everyone know rough;y where you are please?

To have a wet sump, the oil level would have to ve below the crank/flywheels and of sufficiently large volume to keep cool, unless you had a cooler in which case you might as well have an oil tank. One of the great things about the B50 is the frame, and as its internal volume is large enough for a tank. Some would say that the design tries to revert to a wet sump anyway, but joking apart, it kind of begs the question: Why would you want to?
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Re: Converting a B50 to wet sump.

Post by Jack Gifford »

Having had lots of experience with dry-sump oiling (competition V8 & 4-cyl), I can tell you one reason I would prefer wet-sump, although it would probably be less of a concern for a bike engine. Since a dry-sump system must be designed with the scavenge rate sized greater than the pressure-side rate, the scavenge pump will always be injecting a significant amount of air into the scavenged oil. In the interest of delivering all-liquid oil to the pressure pump, de-aeration of the scavenged oil is a huge concern, and never 100% effective (my 4-cyl, designed for 10,000 RPM, needs a centrifugal air/oil separator stage in addition to the usual labyrinth-baffled tank return). If it weren't for the additional space required under the engine, I would instead use a very deep oil pan (oil level well below crank & rods)- all the benefits of a dry-sump system, but without the aeration concern (and without the complexity and cost).
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Re: Converting a B50 to wet sump.

Post by BSA_WM20 »

BSA gave up making wet sumps around 1936 from memory which the release of the new B group.
They did this for very good reasons
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Re: Converting a B50 to wet sump.

Post by Momus »

minetymenace wrote: Sun Apr 05, 2020 9:50 pm <135 to the form Momus.
Would you update your profile and let everyone know rough;y where you are please?

To have a wet sump, the oil level would have to ve below the crank/flywheels and of sufficiently large volume to keep cool, unless you had a cooler in which case you might as well have an oil tank. One of the great things about the B50 is the frame, and as its internal volume is large enough for a tank. Some would say that the design tries to revert to a wet sump anyway, but joking apart, it kind of begs the question: Why would you want to?
I'm in southern Australia at the moment with a bit of time on my hands.

I have a couple of old Beezer B50MX engines, one in a frame as a complete bike and another spare that I am making a Clews Stroker style frame for.

My main interest is simplifying the engine installation.
There is a small pick up sump and it seems pretty straight forward to enlarge that so it holds a litre or so without compromising the ground clearance too much.
Last edited by Momus on Mon Apr 06, 2020 9:57 pm, edited 1 time in total.
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Re: Converting a B50 to wet sump.

Post by Momus »

BSA_WM20 wrote: Mon Apr 06, 2020 11:17 am BSA gave up making wet sumps around 1936 from memory which the release of the new B group.
They did this for very good reasons
Jack, pretty much most of my reasons.

I've done a few car dry sump conversions as well and am looking for simplicity. I won't need much oil A litre extra should be enough.
Last edited by Momus on Mon Apr 06, 2020 7:25 pm, edited 1 time in total.
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Re: Converting a B50 to wet sump.

Post by Momus »

BSA_WM20 wrote: Mon Apr 06, 2020 11:17 am BSA gave up making wet sumps around 1936 from memory which the release of the new B group.
They did this for very good reasons
What do you imagine their reasoning was?
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Re: Converting a B50 to wet sump.

Post by Jack Gifford »

Momus wrote: Mon Apr 06, 2020 7:17 pm ... Jack, pretty much most of my reasons...
Go for it! Make the [deeper] sump from light alloy with plenty of fins- which will get more air contact than a tank hidden out of the air stream. Thermally insulating it from the engine cases would be desirable- but challenging.
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Re: Converting a B50 to wet sump.

Post by minetymenace »

How about a sketch of the plan?
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Re: Converting a B50 to wet sump.

Post by BSA_WM20 »

Momus wrote: Mon Apr 06, 2020 7:18 pm
BSA_WM20 wrote: Mon Apr 06, 2020 11:17 am BSA gave up making wet sumps around 1936 from memory which the release of the new B group.
They did this for very good reasons
What do you imagine their reasoning was?
Viscous drag for starters both on start up and while running.
Remember your car has an external flywheel behind the crank & a smaller one on the front.
Thus the sump oil level is below the lowest point of the conrod and the oil is not beaten to death by the big ends.
Over oiling of the bore from the splash generated by the afore mentioned end cap tossing oil every where .
Oil overheating as it was carried in a sump chamber in front of the engine but still part of the crankcase .
Excessive frothing preventing the oil sludging out the contaminants .
Reduced oil leaks.
Should you find yourself at a BSA event where there are Empire stars with both the obsolete Q engine and the new M engine, see if the owners will allow you have a few kicks.
Now the Q an the M are both 82mm x 94mm and they have the same box with the same kickstart pinion and same length kick start pedals.
The wet sump Q is a leg breaker to turn over while the M is soooooo much easier.
Sit behind them ( hard to do on a B50 even with trials gearing ) and watch the pipes . Every time the Q riders opens up or closes down a nice period puff or two of healthy smoke will emit from the exhaust pipe . You will not see the B engine doing the same thing ( well not as pronounced any way )
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Re: Converting a B50 to wet sump.

Post by koncretekid »

So enlarge the sump, hook up the outlet from the sump pump thru an oil cooler, back into the inlet pipe, and take out the driven gear from the pump so the oil goes directly into the crankshaft. You could try that, but I would experiment with a B25 motor or a B44 first, as they aren't as pricey as the B50 motor. You might want to incorporate a check valve (although there already is one) to make sure you get oil at start-up, at least for the B25.
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Re: Converting a B50 to wet sump.

Post by kommando »

A true wet sump has one pump pulling directly from the sump and into the crank hopefully via a filter, in my IMHO all the suggestions so far are for a dry sump where the sump is extended in depth. Still using the twin oil pumps with the feedside drawing from an oil tank and a return side drawing from the top of an extended sump so not wet sump. I fail to see the point of the mods when you can just fit a bigger or supplementary oil tank if you need the extra capacity as per the B44GP with its OIF and mini oil tank. At least it will be away from the rocks sump guard or no sump guard.
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Re: Converting a B50 to wet sump.

Post by koncretekid »

kommando wrote: Tue Apr 07, 2020 4:31 pm A true wet sump has one pump pulling directly from the sump and into the crank hopefully via a filter, in my IMHO all the suggestions so far are for a dry sump where the sump is extended in depth.
My suggestion was to use the scavenge side of the pump as the main pump, which could pump thru a filter (as well as a cooler) and directly back to inlet side of the supply side of the pump. Would it not then just reenter the outlet port of the pump into the crankshaft if the driven gear (or both gears if you like) is/were removed from the normal supply side of the pump?

Not to argue with you as to the necessity of doing this.

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Re: Converting a B50 to wet sump.

Post by minetymenace »

When running full chat, the crank acts like a pump, is that going to be a problem in this setup? Thinking with such little resistance between the crank and sump, will you get too much oil?
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Re: Converting a B50 to wet sump.

Post by Momus »

minetymenace wrote: Tue Apr 07, 2020 10:08 am How about a sketch of the plan?
Externally, imagine an aluminium box that mounts in place of the pickup cover below the engine. It would be about 60 mm deep, 100 across and about 200 long.

Internally the pickup would be extended and the pressure side oil would go via the relief valve to the crank and top end. The second stage would be independent and push oil through a filter, and if needed, a cooler.
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Re: Converting a B50 to wet sump.

Post by Momus »

minetymenace wrote: Tue Apr 07, 2020 9:36 pm When running full chat, the crank acts like a pump, is that going to be a problem in this setup? Thinking with such little resistance between the crank and sump, will you get too much oil?
There may well be windage problems to overcome. The static oil level will be about 50 mm below the bottom of the crank which as you know has a scraper.

I expect the venting side of things will be a process.

Not sure what you mean by the crank is a pump.
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Re: Converting a B50 to wet sump.

Post by Momus »

BSA_WM20 wrote: Tue Apr 07, 2020 10:47 am
Momus wrote: Mon Apr 06, 2020 7:18 pm
BSA_WM20 wrote: Mon Apr 06, 2020 11:17 am BSA gave up making wet sumps around 1936 from memory which the release of the new B group.
They did this for very good reasons
What do you imagine their reasoning was?
Viscous drag for starters both on start up and while running.
Remember your car has an external flywheel behind the crank & a smaller one on the front.
Thus the sump oil level is below the lowest point of the conrod and the oil is not beaten to death by the big ends.
Over oiling of the bore from the splash generated by the afore mentioned end cap tossing oil every where .
Oil overheating as it was carried in a sump chamber in front of the engine but still part of the crankcase .
Excessive frothing preventing the oil sludging out the contaminants .
Reduced oil leaks.
Should you find yourself at a BSA event where there are Empire stars with both the obsolete Q engine and the new M engine, see if the owners will allow you have a few kicks.
Now the Q an the M are both 82mm x 94mm and they have the same box with the same kickstart pinion and same length kick start pedals.
The wet sump Q is a leg breaker to turn over while the M is soooooo much easier.
Sit behind them ( hard to do on a B50 even with trials gearing ) and watch the pipes . Every time the Q riders opens up or closes down a nice period puff or two of healthy smoke will emit from the exhaust pipe . You will not see the B engine doing the same thing ( well not as pronounced any way )
I'm with you on the oil drag.Are you saying the early engines had the crank running semi submerged?
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Re: Converting a B50 to wet sump.

Post by Momus »

kommando wrote: Tue Apr 07, 2020 4:31 pm A true wet sump has one pump pulling directly from the sump and into the crank hopefully via a filter, in my IMHO all the suggestions so far are for a dry sump where the sump is extended in depth. Still using the twin oil pumps with the feedside drawing from an oil tank and a return side drawing from the top of an extended sump so not wet sump. I fail to see the point of the mods when you can just fit a bigger or supplementary oil tank if you need the extra capacity as per the B44GP with its OIF and mini oil tank. At least it will be away from the rocks sump guard or no sump guard.
Kommando, I'm trying to eliminate the oil in the frame to simplify the engine install and frame construction and reduce the oil carried. We only need a litre or so and storing it at the bottom of the engine, and picking it up and sending it directly to where needed makes it a wet sump design, like most bikes.
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Re: Converting a B50 to wet sump.

Post by minetymenace »

Momus wrote:Not sure what you mean by the crank is a pump.
When the crank is spinning fast it will act like a centrifugal pump, the oil being thrown out to the big end will draw oil up through the system.
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Re: Converting a B50 to wet sump.

Post by mlb50 »

I'm struggling to see how this idea is going to simply engine installation.
I suggest try making up a stiff cardboard replica of the sump and see how that fits under the motor, what clearances etc''. For a dirt bike I think this is going to be more of hinderance than a benefit.
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Re: Converting a B50 to wet sump.

Post by Momus »

minetymenace wrote: Tue Apr 07, 2020 11:31 pm
Momus wrote:Not sure what you mean by the crank is a pump.
When the crank is spinning fast it will act like a centrifugal pump, the oil being thrown out to the big end will draw oil up through the system.
Still not sure about the thought there.

The BSA oil pump feeds oil to the big end via a drilling in the main bearing journal. That journal drilling is on a radius and as it spins it will centrifuge oil away. The pump has to overcome that centrifugal force before oil can go to the big end. In that sense it is a restriction, not a pump? The situation is a bit more complicated granted as the big end is on a larger radius.
Nose fed cranks, like H*nda have used on their cranks since the mid 60's, can act like a draw pump. They only run about 3 to 5 psi. Judging by the Beezer's relief valve tension it is pumping at a fair old pressure
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Re: Converting a B50 to wet sump.

Post by Momus »

mlb50 wrote: Wed Apr 08, 2020 1:07 am I'm struggling to see how this idea is going to simply engine installation.
I suggest try making up a stiff cardboard replica of the sump and see how that fits under the motor, what clearances etc''. For a dirt bike I think this is going to be more of hinderance than a benefit.
Mlb50 it will ease the installation by eliminating the oil tank/oil in frame and associated plumbing and messy external conjivery- filler, breather, drainage provision etc. It will also have a range of minor but useful weight, center of gravity and frame layout advantages.
The ground clearance is going to be compromised, no question. My idea will put the bottom of the sump about 2" lower. I can live with that. I have down pipe 2 strokes with a lot less that have been raced for years without damage.
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Re: Converting a B50 to wet sump.

Post by minetymenace »

Are you thinking of using a different frame or the original frame but dry?
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Re: Converting a B50 to wet sump.

Post by Momus »

minetymenace wrote: Wed Apr 08, 2020 7:58 am Are you thinking of using a different frame or the original frame but dry?
I'm making a new frame along the lines of a Clews Stroka.

I want it small and low.
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Re: Converting a B50 to wet sump.

Post by kommando »

Momus wrote: Wed Apr 08, 2020 7:26 am
minetymenace wrote: Tue Apr 07, 2020 11:31 pm
Momus wrote:Not sure what you mean by the crank is a pump.
When the crank is spinning fast it will act like a centrifugal pump, the oil being thrown out to the big end will draw oil up through the system.
Still not sure about the thought there.

The BSA oil pump feeds oil to the big end via a drilling in the main bearing journal. That journal drilling is on a radius and as it spins it will centrifuge oil away. The pump has to overcome that centrifugal force before oil can go to the big end. In that sense it is a restriction, not a pump? The situation is a bit more complicated granted as the big end is on a larger radius.
Nose fed cranks, like H*nda have used on their cranks since the mid 60's, can act like a draw pump. They only run about 3 to 5 psi. Judging by the Beezer's relief valve tension it is pumping at a fair old pressure
The C15 and B40 pre G cases fed the crank via the main bearing bush and so had to push against centripetal force to feed the crank, however the B50 crank is end fed, the pump does not push against the centripetal force but with it. As the big end bearing is a needle roller bearing there is no back pressure so eventually at higher revs the centripetal force will be higher than the pump but that is not an issue as the pump is still supplying oil and the supply increases with revs but linearly not exponentially like the centripetal forces. Due to the needle roller have no restriction the psi like the H*nda will only be 3 to 5 psi at an oil pressure gauge. The BSA relief valve is only worked when a shell bearing is used as in the B25, no need for it on a B44 or B50, I delete it.
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Re: Converting a B50 to wet sump.

Post by minetymenace »

Hey kommando, this might start a war, but that's what happens when you are locked in solitary confinement. I dithered about whether to use "centripetal" or "centrifugal", because the latter doesn't exist and is only an apparent force, but I though I wouldn't be pedantic and everyone would know what I meant, so the vernacular won and I used "centrifugal"..............but BUT BUT as centripetal forces act towards the centre, would you like to reconsider editing your post concerning the pump working with or against the said force? <201 >44 :ban

Sorry, its been a long day :oops:
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Re: Converting a B50 to wet sump.

Post by Momus »

kommando wrote: Wed Apr 08, 2020 11:38 am
Momus wrote: Wed Apr 08, 2020 7:26 am
minetymenace wrote: Tue Apr 07, 2020 11:31 pm

When the crank is spinning fast it will act like a centrifugal pump, the oil being thrown out to the big end will draw oil up through the system.
Still not sure about the thought there.

The BSA oil pump feeds oil to the big end via a drilling in the main bearing journal. That journal drilling is on a radius and as it spins it will centrifuge oil away. The pump has to overcome that centrifugal force before oil can go to the big end. In that sense it is a restriction, not a pump? The situation is a bit more complicated granted as the big end is on a larger radius.
Nose fed cranks, like H*nda have used on their cranks since the mid 60's, can act like a draw pump. They only run about 3 to 5 psi. Judging by the Beezer's relief valve tension it is pumping at a fair old pressure
The C15 and B40 pre G cases fed the crank via the main bearing bush and so had to push against centripetal force to feed the crank, however the B50 crank is end fed, the pump does not push against the centripetal force but with it. As the big end bearing is a needle roller bearing there is no back pressure so eventually at higher revs the centripetal force will be higher than the pump but that is not an issue as the pump is still supplying oil and the supply increases with revs but linearly not exponentially like the centripetal forces. Due to the needle roller have no restriction the psi like the H*nda will only be 3 to 5 psi at an oil pressure gauge. The BSA relief valve is only worked when a shell bearing is used as in the B25, no need for it on a B44 or B50, I delete it.
You have sorted me out re the B50 crank oil feed Kommando. Thanks. I have bare B50 center cases and am using a B40 crank as my lube reference. So, minetymenace was correct re the potential pump, and I am pleased as that will simplify the job some more.

I use centrifugal rather than centripetal as l do weight versus mass. 🤔
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Re: Converting a B50 to wet sump.

Post by Jack Gifford »

kommando wrote: Wed Apr 08, 2020 11:38 am ... the big end bearing is a needle roller bearing there is no back pressure...
No pressure? Don't side clearances of the rod's big end determine the pressure?
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Re: Converting a B50 to wet sump.

Post by kommando »

Compared to a shell bearing the clearance is much larger, only cold oil will register much pressure. If there was back pressure then the wider B25 gears would need to be fitted, but they are not.
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Re: Converting a B50 to wet sump.

Post by minetymenace »

Weren't the Ducati singles wet sump?
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Re: Converting a B50 to wet sump.

Post by Momus »

Jack Gifford wrote: Thu Apr 09, 2020 6:39 am
kommando wrote: Wed Apr 08, 2020 11:38 am ... the big end bearing is a needle roller bearing there is no back pressure...
No pressure? Don't side clearances of the rod's big end determine the pressure?
Nope. Common misconceptions wth fluid film bearings too. The radial clearance creates the aperture - imagine a concentric ring 2.00" diamet 001" in wide for a typical journal/rod bearing with .002" clearance. The side clearance would usually be at least double that so an easy path out.
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Re: Converting a B50 to wet sump.

Post by Momus »

Well it looks like I am on my own converting this old beast to wet sump.

I have mocked the under engine mods up and made a dummy sump extension from timber. It extends about 45 mm below the bottom of the tin cover, so no ground clearance issues and holds about 1.2 litres of oil with some ullage space and almost 50 mm from oil level to the bottom of the crank. I will mill the finished sump from solid 5083 or 6061, use an O ring in a groove to seal and weld a bottom cover on.
I only have one B50 oil pump and that is in my complete bike which I don't want to disturb so the pump mods can wait until I source another.
Internal oil drainage should not be disturbed as it all heads in the same direction standard and as per modern 4 stroke single practice I will fit a miniature filter element- from a YZ450F- and a wrap around the head stock oil cooler from an XR400- proven bits that I use on a couple of other builds.
I have just finished turning the steering head tube for the new frame and have all the tubing-4130- I bought a couple of years ago is ready for the saw, bender notcher and Tig. I'm bolting the hollw dummy engine to the frame jig now and should have tube fit roughed out by the end of Easter.
I'm obviously not a marque purist and in the interests of budget, convenience, design and expediency will use components to hand for the main running gear parts while still maintaining a Pre75 character. H*nda or S*zuki fork, Y*maha conical front hub, not sure on the rear wheel and so on.
Engine wise it will come out a bit over 600cc. I have a Nicasil 92 mm bore, a 3 speed box and update clutch and various other stuff. We are doing a head with revised porting, valves etc.
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Re: Converting a B50 to wet sump.

Post by koncretekid »

You will not be on your own, as we will be watching and will continue to comment. 92mm x 90mm = 599cc per my calculations.
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Re: Converting a B50 to wet sump.

Post by minetymenace »

Go for it Momus, please start a topic in project bikes (or I can move this topic there). Post lots of pictures, while we might "tut" and frown a bit, but we will all be interested.
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Re: Converting a B50 to wet sump.

Post by Momus »

minetymenace wrote: Sat Apr 11, 2020 6:58 pm Go for it Momus, please start a topic in project bikes (or I can move this topic there). Post lots of pictures, while we might "tut" and frown a bit, but we will all be interested.
Yes, Project Bikes will be there at place. I will try to get some photos happening over the next day or so.
I'm setting up the dummy engine in the frame jig and again scratching my head about that huge engine off set. Nothing at all can be done to reduce it.
If you love it, lube it.
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Re: Converting a B50 to wet sump.

Post by beat »

Momus wrote: Fri Apr 10, 2020 7:18 pm I have a Nicasil 92 mm bore,
where from :?:

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Momus
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Re: Converting a B50 to wet sump.

Post by Momus »

beat wrote: Sun Apr 12, 2020 7:47 pm
Momus wrote: Fri Apr 10, 2020 7:18 pm I have a Nicasil 92 mm bore,
where from :?:

beat <201
BSA Unit Singles.
If you love it, lube it.
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Re: Converting a B50 to wet sump.

Post by beat »

thanks Momus, - and what crank are you using ?

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Re: Converting a B50 to wet sump.

Post by Momus »

beat wrote: Mon Apr 13, 2020 8:44 pm thanks Momus, - and what crank are you using ?

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I think I'll make one, with a bit extra stroke and a proper taper for the CDI rotor.

That was supposed to happen last year but I couldn't get my hands on a sample to measure.
If you love it, lube it.
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Re: Converting a B50 to wet sump.

Post by beat »

Momus wrote: Mon Apr 13, 2020 11:16 pm with a bit extra stroke
what do you think is the max stroke getting out of the B50 cases and this Nikasil 92 barrel ?

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