BSA C15 "F"Type engine Build X 2.


OK I have the engine from the Blue C15T now stripped out for its rebuild, this is the F type engine, with side points, but only a timing side main bearing bush.


So I thought, as the engine for the "Scott" bike also has one of these I would duplicate the rebuild and build both of the engines up together and to the same specification.


I now have my own timing-side bearing conversion, and have bought an Alpha one for the C15T engine.

On unpacking the Alpha unit I now find that they share the same Needle roller bearing.


OK,I will start the build of these two engines on Monday and Take pictures has I go. and also any problems I find along the way will be explained.


Both engines are sporting 69mm Triumph pistons, but using the steel barrels.


OK here is the picture of the modifications to the clutch side crankcase half.



As you can see, I have ground down the lip on the engine oil seal flange, so that it wont foul the primary chain with the small engine sprocket fitted. 18 tooth.

I have sourced a thinner oil seal that can now Be fitted as well has the oil seal that is left in the main bearing. this main bearing was the rubber sealed type with the inside seal removed from the bearing. this in theory gives a second seal now you are using the thinner one on the outside.



Oil seal number is E2802-VG 40-52-5. 5mm wide.


These are the thinner oil seals, and you can see the number of them,along with the numbers for the needle roller kick-start quadrant bearings.


Another modification I did on the gearbox mainshaft top gear bush, was machine the end of this bush down to 20mm, and machine the sprocket cover out to take the 60804RS bearing.(32mm).

not only does this make a better seal but it also takes some of the pressure off of the top gear and the gearbox main-shaft from the rear chain snatch.





I am now working on a different system to try for this conversion by running the bearing on the gearbox main-shaft its self and not the sleeve....


Will it work?  ...I don't know until I have tried it...

 So watch this space...I may machine a Dural plate to take that bearing if it works...


SAMOX / NBK 1905317 Rubber Sealed Max Type Deep Groove Bearing 19.05x31x7mm
Click for more information free shipping for any order in the United Kingdom

SAMOX / NBK 1905317 Rubber Sealed Max Type Deep Groove Bearing 19.05x31x7mm

SAMOX Max Type Rubber Sealed Deep Groove Ball Bearings: These types are manufactured with rubber seals inserted into the outer raceway and in contact with the inner race providing protection against the ingress of moisture, dust and other foreign matter and serve to retain the pre-filled grease in the bearing.

MAX Type bearings have no cage and a filling slot for the balls. MAX stands for Maximum Balls possible in the bearing which is achieved by using the filling slot to insert the balls, the balls are effectively next to each other.

They generally have a 35% more load capacity than caged bearings. MAX bearings do not spin as smoothly as the cage bearings and should in general be used for suspension pivots or problem areas where standard bearings wear out prematurely.

Static Load capacities are limits well before deformation of the bearing and are conservative.

Always install bearings by pressing on the outer race only into a housing with a fixture that is a close match to its diameter, never knock bearings into their housings with a hammer - premature bearing failure will occur from knocking bearings into housings. With max type bearings in application like suspension pivots try to position the filling slot at 90 degrees to the loading direction where practical.

 Seals can be easily removed for applications that only require 1 seal.
Benefits: Prevents moisture and dirt getting into the bearing, lubricated for life, maximum load capacity

So Watch this space...


While we are on the subjects of modifications, another that is relevant if you are converting the rear sprockets to take 520 chain is this 2mm wide spacer to space out the gearbox sprocket so the chain does not modify your crankcases.


2mm washer.......


One of the forced modifications to the blue bike engine, was to make an oversize inner camshaft bush as the old one was floating on air,with a 1mm gap all round.

Below you can see the new bush I had to machine up, the bush probably sticks to the camshaft from lack of lubrication, and then turns in the crankcase using that as a bearing surface.

Not good and this is not the first case I have heard of this happening.





This is both barrels so to speak? 69 mm Triumph jobs,for the first two engines smaller for the third, as I am trying something new.






I have spent the last ten days preparing the parts to reassemble these two engines and also the converted "Dizzy" motor that I now have a set of competition flywheels for.

I have also prepared the end-flow later engine parts for building.

I feel doing each job in batches is more sensible for me. by having the tools at hand to perform a task on one engine! why not do the same job on the other engines in line.

So one of the major tasks was to remove the sludge-trap plugs on each of the sets of flywheels, to clean them out.

These little plugs are so difficult to remove? and this is why most of them get left!!

Well I started on one of the new arrival cranks (one of five) and to my amazement the plug was not that difficult to remove with the tool I had made out of a old square wood chisel, that I could fit a spanner onto. And this flywheel had been looked after has there was only a small amount of sloppy residue inside. This was flushed and then blown through with the airline. Then oil forced through with an oil can to make sure the galleries were clear.

One down four to go.

The next one was the crank from the blue bike.

Well after an hour trying to remove the plug, and using heat ,and a centre punch in the end, I managed to loosen the plug. But because this was distorted more than normal, it was acting like a cam on the edge of the recess, and took another thirty minuets to remove.

The cavity was full of hardened engine debris. and I had to resort to using a battery drill to remove it.

this was again flushed through and then blown. But I could not get oil to the big-end!

 I left the cavity full of a mixture of WD40 and thinners overnight to see what happened.

But the cavity was still full after two days and I could just not blow anything through to the big-end.

 A decision was made to press the flywheels apart, has I was getting nowhere with the situation.

This meant me making up tooling to do this operation on the hydraulic press.



Well now you can see why there was a lack of oil getting to the big end.


This was full of the same solid sludge as the filled cavity.

No wonder this engine was noisy and very oily. the big end must have been only getting oil from the splash feed from the full sump. If we had run the motor more and not stopped the bike in the IOM trial it would have gone "Bang".

Amazingly the  "Alpha" big end and con rod are OK. we must have just caught it at the right time

although the rest of the bronze bearings in the motor have suffered.

Flywheels now back together and trued.

The other three sets of flywheels were again full of sludge but have cleaned out OK and  I have got oil running through the big ends.

The "Competition" crank had a vast amount of white metal particles in its trap. I hate to think what the timing side bearings were like in the motors this was previously in.



So there you have it Clean out your Sludge-Trap before the little blighter's give you grief no matter how difficult it is to remove the plug.

I am thinking about making new plugs using the heads of large Allen bolts!

A tip from Chris,

 If you can't budge the trap plugs, drill a hole in it sharpen an old 1/2" drive socket extension to a point and knock it into the drilled hole then put an impact driver gun onto the extension, and pulse rattle it out, Never failed he says.


On with the builds.

OK I have fitted the new Alpha timing side bearing into the engine from the Blue bike.

also the new bigger camshaft bush, just waiting for the reamer to arrive to dress this out to the right size.



I have pulled the crank into position using the new puller I made using Ruperts book for instructions.



All threads have been tapped out and the joint faces resurfaced.


4th Nov 2015.


I will update the build of the first engine with detail here, as this is now fitted back into the "Blue" C15T and is ready to start.Update when started.

This engine was fitted with a Alpha timing side bearing conversion,

 the barrel was returned to an original steel item and bored out to take the 69 mm Triumph piston, the cylinder head was reconditioned with bronze valve guides being fitted. and the broken fins repaired.

I also fitted a new Mikuni carb as the one fitted before gave a good feel to the bike whether this will be the case with the higher compression piston and bigger bore, we will see.




The Ex Bryan Hyatt BSA C15T.



I am now building the other two engines up to this specification,so I will give details as I go along with these.




Well it has been a while but now I have my new "Engine Room" shed up and running I have made more progress with these builds now I have every thing to hand, and without having to carry them back and forth to the workshop, and my stores are at hand too.

I should have built this little engine workshop years ago. 

The converted "D" type engine now has its bottom end finished with just the clutch and engine sprocket to fit and the Eletrex World ignition. this engine is then destined to be fitted into the long time waiting "Scott Ellis replica bike.


The original engine for the Scott bike with my timing side bearing conversion has also now got a gearbox cluster sorted, as I am fitting the first gear pair from my B25 gears, and I have replaced these with a pair of wide ratio B40 WD new gears. this is for the engine that is going into the New Foster "Otter" build.

The Scott engine is going into the John Draper Replica C15T  and is having the other 270cc approx 69mm Triumph piston top end fitted. and Boyer Bransden trials ignition,like the Mk 1 "Otter".




 So you see I am keeping busy.




I now have another SS80 engine I am converting to "F" type too.

 It started as an experiment to see if we could fit a later Victor gear-set into a early set of cases.

I have now worked out that it is a matter of machining a depth of 1mm  deeper on the seat the lay-shaft bush sits into.

 and then refitting a modified bush back in lower,

Picture of this operation later.




Here is the photo of the machining now done on the gearbox.

 I set the cases up on the Bridgeport milling machine,

And has you can see  made the layshaft bush recess 1mm in depth lower, then the modified bush was then re pressed in so as to be just flush of the original surface, the layshaft "Victor"cluster was then dropped in without the trust washer because the bronze bush does that job.

 The cases are now ready to fit together as soon as the gear-change quadrant I forgot to get for this engine arrives.




I had a set of cases to use, but these had been fitted with thread inserts, and one of the barrel studs was stripped, and had received the same treatment (Heli coiled) and needed a one off stud making.

So I decided to buy another set of crank-cases, and did, and to my amazement although I did have a inkling  looking at the photos, but they came with a solid new bronze timing side bush fitted, and the crank I had fitted perfectly into this.

 So the build was on. and I ended up buying two complete Victor gear clusters,

Because one had the lot cam-plate selectors shafts etc.

And the cases had the rest, only thing and it should be here Monday is a New cam-plate spring.

Then I pieced together the rest, I had just bought a set of cam-followers and was tying with turning a bush to use a "G"type Camshaft I had.

 But then thought why not fit a old-type cam,as I don't need the points drive on this motor, as the other experiment is to fit an ignition system from a pit bike ??? yes a pit bike, with better advance curve than the units usually fitted. Will it work? well it has been done before. so we will see.

So after missing three camshafts, I finally got the best deal anyway and the cam is as new.

Moving to the other side of the motor.I needed the lot. the NEW ignition unit has arrived and was expensive £19.99.

I needed a clutch,I had some of the parts to make another up, but not the centre unit,so decided to buy another, missed three again, but then ended up with a very good deal everything, a B25 clutch complete as new, and including the washer lock-tab and nut. Woooow.

Sprockets a bit   more tricky, Talon are out of stock of 18 tooth engine, but Amanda from Trialsbits as told me they are now in the process of manufacture.

I have had to have a 13 tooth gearbox sprocket from her for the same reason.

A New primary chain came with the crankcases.

And one of my own adjusters will be used.

Timing cover not saying until after the weekend..............

So moving up the engine.I decided to use the shaved B25 barrel piston and spacer but I need to realine the liner which has moved around. this needs removing and then refitting with Locktite.

 Cylinder head, well should I repair the broken fins and one of the main head steady bolt threads or buy another?

The other thing I need was the valves and springs etc.

 Then found a head on eBay with NO broken fins except for the little one next to the plug hole that is always missing................. What were BSA thinking. first time the plug was changed, and you did have to do that a lot at the time. the fin broke of when the plug spanner slipped.

And the head had valves and springs every thing except the collets. and Amanda has sent me some of those and they arrived the same time as the head, same post man.

One new, and one very good valves but both inlet.

 Now where did I put that spare exhaust valve.

So that is where I am today. and it is too cold to  venture into the shed, so I will clean the had up in the conservatory this afternoon


 More later and photos.


More on the Victor gear conversion on the Next engine page down to this...



More Later.........