Well it did seize !
Posted: 29 Oct 2023 16:25
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.
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.