BSA C15 "F"Type engine Build X 2.


OK I have the engine from the Blue C15T now striped 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 mainshaft from the rear chain snatch.




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.




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!

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 Bryn 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 with out carrying 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 270 Triumph piston top end fitted. and Boyer Bransden trials ignition,like the Mk 1 "Otter".




 So you see I am keeping busy.


More Later.........