Saving Old Seagulls

No it's a very different cylinder that's from a Century 100, inlet on wrong side, might have bridged exhaust & transfer.

I would guess that with the casting level of quality and mass production it's no wonder that there are plenty of internal stresses that are realeased by the action of rust weakening thin and thick webs.

We have talked about Century cylinders before viewtopic.php?f=2&t=3264

I still think that the only option is to remove the head, remove the rust with a hammer and electrical screwdriver (can take a few hours)
get out as much as you can, then keep looking for non salt use engine block as a spare, because any salt use block will have a finite life.

I agree that the century block has a design fault, with the exhaust stub pocket. It holds water after use. As Charles L says, drill the stub and install a water outlet.http://www.saving-old-seagulls.co.uk/i_ ... icexh2.jpg

If after you have cleaned out the water passages and you have a few cracks, it is not the end. I repaired my Century race engine block with epoxy. It is still going strong after winning most of the events in the UK . I used a Dremel to key the cracks with a small tungsten burr, then just filled with epoxy.

I wonder if pumping rust remover round the water passages is a waste of time and money, take the head off if the bolts sheer of then drill out and re-thread. This is the only way that you will get a reliable engine, that will give you many hours of trouble free use.

H-A

Horsley-Anarak wrote: I wonder if pumping rust remover round the water passages is a waste of time and money, take the head off if the bolts sheer of then drill out and re-thread. This is the only way that you will get a reliable engine, that will give you many hours of trouble free use.

H-A

Big true after all. I like doing experiments though..!

Ive got to aske Stelios - you avatar ... aare you being attachdk by jellyfish or have you just farted?

Both I suspect. The jellyfish then legged it smartish.

Hehehe, no we were making fun when freediving, it was an early try to make rings by air underwater.

Charles uk wrote:No it's a very different cylinder that's from a Century 100, inlet on wrong side, might have bridged exhaust & transfer.

It is three port and I will weld the crack up and put it all back together. I will leave it down south on the Donnelly and thrash it whenever a transom shows up to see what happens. (I have been tempted to get an aux bracket for my boat.....maybe this is the time).

My question for you is what is a right and wrong side and why would SG change sides?

1/2 time in the sack?

B

Try as I might I don't know what SG changing sides and 1/2 time is all about...

charlesp wrote:Try as I might I don't know what SG changing sides and 1/2 time is all about...

For goodness sake............SG is SeaGull? I converse with lots of people globally............SG is is the short form for British Seagull in the relevant conversations?

1/2time and change sides in the sack is what you do being polite in sharing a wet spot during a Saturday night pick up on Sunday morning?

Now that is clear, what about the block side difference etc?

B

News about my experiment. I put the block on a larger tank and I use as electrode a metal tape doing rounds around the block. It look to be working much better as the floating rust is more than before. The problem is that after one day and a half I have to rasp the electrode because something stuck on it and cuts of the current. The solution gets green under the rust so I suspect that there might be copper (from the gasket) mixed with the rust of the block.

I've no idea why they changed sides, perhaps "wrong" was not the right word "other" might have been better.

That inlet stubb was for the Villiers 1/2" carb, the one on the other side is for the Amal twin jet (about 15mm) & the Amal 416 carb (16mm).

There is little doubt that the LLS/CPC cylinder runs slightly better with 2 x 1/2" Villiers carbs, which gives the equivalent area of 1 x 18 mm carb, it might be that they felt the Century 100 was a little asmatic & could benefit from a bigger carb & by putting it on the other side it would mark a clear change to the improved version.

But please bear in mind this is only an educated guess as the other Charles's extensive researches have not revealed as yet, any definative answers.

All

I have a theory on the carb side swaps, (which no doubt be contested)

In a preferred 2 stroke design the exhaust flow is perpendicular to crankshaft axis. This allows for the thrusting interface of the piston/bore to be positioned opposite the exhaust. Piston/bore thrust is taken on a relatively clear bore surface opposite the heat of the exhaust & the large cutouts of the moving port gates. Induction is achieved thru reed valves case mounted & directed in a straight flow toward the transfer ducts between the crank webs. This layout not sensitive the the crank swirl direction.

The seagull is consistent with basic pre-war designs in that;
* the exhaust flow is parallel to the crank shaft axis, so the side thrust is perpendicular to the exhaust flow
* induction to the case is by sideport, so the bore side are not very continuous

In the case of a silver century or 102 the crankcase sideport is positioned on the thrusting interface of the piston/bore, a poor thrusting layout. The benefit of this design is the intake charge takes advantage of the crank swirl direction.
In the case of a century 100 the crankcase sideport is positioned opposite the thrusting interface of the piston/bore, a good thrusting layout. The detriment of this design is the intake charge opposes the crank swirl direction.

While each design has advantages, each has disadvantages. Neither is ideal.

RexNZ