Late Single valve events

Previously David Cooper wrote:

It looks partly like valve clearances.

From your numbers - if BDC is zero degrees, IOBTDC should be at 150 degrees later and ICBDC is 435 so the peak cam lift is at 292.5. Your number 1 engine is at 289.5, so 3 deg late. Number 2 is at 301 so is 8 deg late. And number 3 is 300.5 so is 8 deg late so should be bright forwards 2/3 of a tooth.

Similarly, EOBBDC should be 642 and ECATDC at 935 so the peak should be at 788.5 deg. Your number 1 is at 789 = correct, and number 2 is at 791.5 so 3 deg late. But number 3 is at 796.5 so is 8 degrees too late so sould come forward one tooth.

There are 3 keyways to allow 1/3 tooth changes = 3 degrees.

Thanks David for your very lucid reply, I would have said so sooner, but I can read postings at work but not reply to them!

Firstly, I see where you are coming from re. clearances, obviously tight clearances will increase duration , advance opening, etc, but as the standard setting is "nil, free to turn without perceptible up and down movement", and there is no access to the cam/tappet gap with the timing case on (and the cams therefore supported), and none to the rocker/valve gap, and nowhere else I can see to insert a feeler gauge, increasing the clearances would be a bit hit and miss.

Engine No.1 which is essentially correct, is an original factory assembled engine as built, I ran it for over 60.000 miles but never had more than 60mph out of it, No.2 came out of a canal and presumably ran until it was dumped (siezed) but is otherwise as per factory, when I stripped it there were no signs at all that it had ever been apart, and No.3 came to me already rebuilt through a swap, there are no signs of wear in it at all, but the timing marks look true.I shall do as you suggest but I think 1 degree early on the inlet should be close enough, to begin with, so I shall just advance both camwheels 1 tooth in the first instance and see where that gets me.

Mike Pemberton told me years ago that in his opinion the 350s in particular were not accurately timed at the factory, as the workers were on piecework and the ride-to-work buyers would not care about top end, I always assumed that my (No.1) engine was one of these so to find that it was one of the more accurate ones was a bit disheartening given its always mediocre performance. I was hoping that when the bike goes back on the road after its incredibly protracted rebuild that it would be a bit faster.

We shall see!

Thanks again,

Cheers,

Niall

Previously niall_topping wrote:

Previously David Cooper wrote:

It looks partly like valve clearances.

From your numbers - if BDC is zero degrees, IOBTDC should be at 150 degrees later and ICBDC is 435 so the peak cam lift is at 292.5. Your number 1 engine is at 289.5, so 3 deg late. Number 2 is at 301 so is 8 deg late. And number 3 is 300.5 so is 8 deg late so should be bright forwards 2/3 of a tooth.

Similarly, EOBBDC should be 642 and ECATDC at 935 so the peak should be at 788.5 deg. Your number 1 is at 789 = correct, and number 2 is at 791.5 so 3 deg late. But number 3 is at 796.5 so is 8 degrees too late so sould come forward one tooth.

There are 3 keyways to allow 1/3 tooth changes = 3 degrees.

Thanks David for your very lucid reply, I would have said so sooner, but I can read postings at work but not reply to them!

Firstly, I see where you are coming from re. clearances, obviously tight clearances will increase duration , advance opening, etc, but as the standard setting is "nil, free to turn without perceptible up and down movement", and there is no access to the cam/tappet gap with the timing case on (and the cams therefore supported), and none to the rocker/valve gap, and nowhere else I can see to insert a feeler gauge, increasing the clearances would be a bit hit and miss.

Engine No.1 which is essentially correct, is an original factory assembled engine as built, I ran it for over 60.000 miles but never had more than 60mph out of it, No.2 came out of a canal and presumably ran until it was dumped (siezed) but is otherwise as per factory, when I stripped it there were no signs at all that it had ever been apart, and No.3 came to me already rebuilt through a swap, there are no signs of wear in it at all, but the timing marks look true.I shall do as you suggest but I think 1 degree early on the inlet should be close enough, to begin with, so I shall just advance both camwheels 1 tooth in the first instance and see where that gets me.

Mike Pemberton told me years ago that in his opinion the 350s in particular were not accurately timed at the factory, as the workers were on piecework and the ride-to-work buyers would not care about top end, I always assumed that my (No.1) engine was one of these so to find that it was one of the more accurate ones was a bit disheartening given its always mediocre performance. I was hoping that when the bike goes back on the road after its incredibly protracted rebuild that it would be a bit faster.

We shall see!

Thanks again,

Cheers,

Niall

Been thinking about this, and got out my copy of the late, great, Phil Irving's 'Tuning for Speed', often look at it, but its been a long time since I actually READ it. Having done so, whilst re-timing, had the cams out,clocked them, and as I now suspected, some previous owner had ground .025" off the base circles to increase the lift, whover did it made a real good job and to a casual observer they look bog standard.

Went through the bike by the book, and having done so it started third kick and sounds better than it ever did before. Still don't really understand why it wouldn't run before though. Unfortunately I can't take it out until I've got it tested, inspected and got a log book as I've never had one for this frame. Had to get it running as my local station weon't MoT a bike unless it runs, although I can't remember ever having to start a bike for the test....

Better get on, lots to do,

Thanks again.