Although I have today been out and bought a long, flexible magnet thingy and waved it thoroughly under and around the flywheels with no result at all... Good news is that Brian Parsons says that the piston, rings and bore are OK.
Friendly chap with huge kickstart foot required!
- Thread starter Phil Baker
- Start date
Continuing what would in today's terms would doubtless be called 'my journey' only I ain't goin' no journey on the Comet............. I have now not only turned the top link the right way up (not too hard) but also turned the bottom link up the right way and THAT meant inventing a whole new raft of bad words. Incidentally, as I make furniture as a hobby I have sash cramps knocking about and they were great for compressing the springs for refitting to the girdraulics.
The valve timing is still driving me nuts! I've just bent a pushrod so that's it until Russ sends a new one..... Can't get the timing anywhere near - if I get the inlet valve opening at approx 41 degrees before TDC it doesn't close anywhere near the right time. Exhaust is all over the place. How can that be????
I've ordered a new pushrod from Russ in Wales and it should come tomorrow or Friday.
My cams are Mk 1 - compared with one that Stumpy has with a Mk 1 exhaust and Mk 2 inlet with an invoice to point the way. So the figures in the book should be right: inlet opening 44 degrees BTDC or 41 degrees, dpending upon the book.....
Anyway, I think that the cams, the shaft, and the cam gearwheel itself have been pressed out and refitted out of line with the original settings and my thought was, before bending the pushrod in the endeavour, to put the cam pinion in with the cam tight up against the inlet cam follower as if it is about to open the inlet valve (verified by a dial gauge), with the piston at 41 degrees before top dead centre. The only problem I have with that is that I don't know where the breather pinion 'B' should be because there is nothing for it to line up with - does it matter? - although, thinking whilst writing, I could then rotate the engine and match it in with the book setting B tooth leaving to B tooth leaving the alloy large idler. Is there a particular time at which the engine should breathe? Anybody got a view on that, please?
The valve timing is still driving me nuts! I've just bent a pushrod so that's it until Russ sends a new one..... Can't get the timing anywhere near - if I get the inlet valve opening at approx 41 degrees before TDC it doesn't close anywhere near the right time. Exhaust is all over the place. How can that be????
I've ordered a new pushrod from Russ in Wales and it should come tomorrow or Friday.
My cams are Mk 1 - compared with one that Stumpy has with a Mk 1 exhaust and Mk 2 inlet with an invoice to point the way. So the figures in the book should be right: inlet opening 44 degrees BTDC or 41 degrees, dpending upon the book.....
Anyway, I think that the cams, the shaft, and the cam gearwheel itself have been pressed out and refitted out of line with the original settings and my thought was, before bending the pushrod in the endeavour, to put the cam pinion in with the cam tight up against the inlet cam follower as if it is about to open the inlet valve (verified by a dial gauge), with the piston at 41 degrees before top dead centre. The only problem I have with that is that I don't know where the breather pinion 'B' should be because there is nothing for it to line up with - does it matter? - although, thinking whilst writing, I could then rotate the engine and match it in with the book setting B tooth leaving to B tooth leaving the alloy large idler. Is there a particular time at which the engine should breathe? Anybody got a view on that, please?
Hello Phil, Are you sure you had the pushrods seated in the cups ?A quick way to get the valve timing set is to have the valves rocking on the wrong stroke TDC ie Both valves open,just a bit The same. Then see if you can get it better. Don't trust any markings, Cheers Bill.
Phil,
You can get your engine real close by removing the pushrod adjusters, removing the Large Idler, camshaft and breather and putting the crank at TDC. Next, replace the large idler with the straight line centered on the crank and 1/2 time pinion (you probably will have to find the correct slot for the keyway to align), now line up the "B"'s on the breather and slide it home, the slot edges should be equidistant from 12 and 3 o'clock on a vertical line through the crank, idler and breather. Next, point the indexing slot in the camshaft as close as you can to straight down and slide it home. Now, set the magneto (fully advanced) to release a piece of cellophane (cigarette wrapper is perfect) between the points at 15/32" before TDC .. 7/16" is OK, 1/2" will work too, but may ping/pink.. Button it all up and you should be good to go.
Cheers, John
For the breather you can do the check with a clean plastic tube attached to the breather pipe. With the rear cylinder at TDC you should not be able to blow in the pipe. As you turn the engine with the dergree wheel in place the you should be able to blow in the pipe at 70 ATDC. The breather will remain open until 30 degrees ABDC (rear cylinder still). If it is way off, pull the breather and move a tooth and repeat. This was the advice that Neville Higgins gave in MPH 608 at page 23. This will work for the Comet also. You can be a few degrees off.
John's advice on timing is good. Timing can drive a seasoned mechanic crazy sometimes, so do not get down. If you have lost track of the marks you can easily check the work you have done without them if you are using two dial indicators. When both valves are open equally, namely, intake and exhaust are at the same height, the degree wheel should indicate 4 degrees BTC. If it is in the area, plus or minus 4 degrees, it will run. I have set up engines this way when there are no marks on the gear wheels or I am unsure of the marks.
David
No, Bill, I definitely didn't get the exhaust pushrod in the cup! I have tried the 'rocking at 4 degrees before wrong TDC but Stumpy's dial gauges are each calibrated differently and both spin like nutters so not managed that yet! Phil
Thankyou to all
OK, lots of useful stuff there, thanks everyone. I'll incarcerate myself in the garage again later, hammer the pushrod straight (or completely flat if I get carried away with the hammer - don't worry, I'll put the new one in when it arrives and before I attempt to start - start, what does that mean? - the Comet) and have another go!
Phil
OK, lots of useful stuff there, thanks everyone. I'll incarcerate myself in the garage again later, hammer the pushrod straight (or completely flat if I get carried away with the hammer - don't worry, I'll put the new one in when it arrives and before I attempt to start - start, what does that mean? - the Comet) and have another go!
Phil
Hello Phil, Don't feel bad, We have all done the same,You can do it by eye, Leave the adjusters out, Push rods in and with the large idler out, Watch the top of the push rods on overlap as you turn the camwheel back and forward, Try and get them the same lift. Good Luck Bill.
Phil,
Fancy bending a pushrod!! You amateur!! Did you just bend it a bit, or did you get it to a full question mark shape like I did?
H
ps sometimes you can see the follower cups using a little LED torch shone down the pushrod tubes - but the front exhaust always causes me problems - just don't rush things.
Fancy bending a pushrod!! You amateur!! Did you just bend it a bit, or did you get it to a full question mark shape like I did?
H
ps sometimes you can see the follower cups using a little LED torch shone down the pushrod tubes - but the front exhaust always causes me problems - just don't rush things.
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Sorry, Howard - meant to click on 'like this post' but finger trouble overtook me - much the same as when I reformed the pushrod into a vaguely questioning shape!!!
Phil
Phil