Well it did seize !

[72degrees]

Those who followed my 'Forgotten Error' tale of the speed hill climb special may recall that on its first competitive outing at Loton Park I thought it seized. Then later I decided (as it ran again after rolling back down to the paddock) that the 'brick wall' effect was just massively rich main jets as this engine had a weird reground cam in it.

Well, the time has come to rebuild it again but with an L5 profile cam supplied by a regular on here. On removing the front cylinder in preparation for parting the cases I discovered two things.

1) As I lifted the cylinder a gugeon pin circlip fell out!
2) The piston bears witness to a fairly significant 'picking up' event. See photo.

These could be connected I suppose. I've put many a Morini piston on and never had a circlip pop out before. These are not OEM pistons of course and the clips were if anything too easy to fit having long 'ears'. I guess I didn't get it snug in its groove though.

I may take a swiss file to it in the traditional 'Tuning For Speed' manner, or I may end up swapping over the complete 375 top end (not just the very nice Kanguro heads). I treated that to new pistons on the last rebuild and the bores didn't seem very worn.

Otherwise, the strip down is proceeding well, except for getting the crank timing pinion off. Couldn't find the special tool (thick washer) I used last time so have ordered a couple of suitable ones from ACCU. I suspect I may have used a drop of Loctite on it, so may have to resort to heat and shock 'n unlock as well as a two legged puller.

The plan is to leave the crank and rods undisturbed in the drive side case. The state of the oil isn't too sludgy and no hint of corrosion anywhere. With luck, I will end up with a motor with reground crank and new rods, all new bearings (including timing side roller conversion), L5 alike cam, 375 pistons and Kanguro heads with lightened rockers. I won't go base gasket free this time as it will be for road use only and the compression is high enough to stress my hip without seeking the ultimate. That leaves the gearbox - see other post.

piston.jpg (487.53 KiB) Viewed 2785 times

[72degrees]

The crank timing pinion succumbed after a good heat and shock 'n unlock cycle once armed with a perfectly fitting 28mm ID x 5 mm thick washer behind the circlip and a 30 to go behind that over the timing belt splines (supplied very quickly by ACCU). A heavy duty two leg puller soon had it off.
Struggled with parting the cases until "d'oh the rear base gasket (alloy) is still in place on the cylinder studs" - the front had come off with the cylinder. The gear change shaft was also reluctant to pass through the case and seal and in the end the mechanism popped off the selector drum and came out with the case. Perhaps some corrosion on the shaft. Easy enough to address.

See other post re. gear bushes. Just waiting for a CNC quote.

If ICBA I will rig up some kind of pointer on the pinion end of the cam and a reference mark to quickly get some idea if the timing on the new L5 ground cam is significantly different to the reground jobby that I put in last time. The two engines were certainly very different to ride (fitted in the same machine for running in) . The original 375 has a very marked difference in how it eagerly picks up even when you just rev it on the stand and needs much bigger main jets (with same exhaust and 'air filters') than the mystery cam 350. Perhaps I got the timing all out by a tad, though the crank pinion had been clearly marked for 'vernier' position , the new B belt was towards the tight side.

From October 2018:

"The cam in the 375 is definitely an L5 and possibly a (II):

IO 35 IC 60 EO 61 EC 34

The mystery cam in the FE still is!:
IO 28 IC 60 EO 53 EC nearly 40!

All a bit 'ish', given a timing disc stuck to the alternator rotor nut with blu tack and a bit of wire screwed to the crankcase as a pointer."

I shall get a degree disc on the crank when the cases are back together before I do more rebuilding but may still be left with a riddle wrapped in a mystery inside an enigma.