Comet Inspection/Repair after 10,000miles

[b'knighted]

How easily should the Half Time Pinion removal be? Right now it requires tapping into place and a puller to remove. Even without the key. Is this unusual? Should this fit be a sliding fit?
View attachment 12478

Page 114 of Richardsons book shows figure 55 - the half time pinion and dynamo pinion extractor. I think there was a dimensioned drawing in KTB. If an extractor is required it suggests that it is meant to be a tightish fit. At its simplest it would be a plate drilled to allow three screws to attach it to the tapped holes in the pinion and a central hole to allow a bolt, through a nut under the plate, to push on the end of the shaft. This would save tapping the plate.

 

[vibrac]

How easily should the Half Time Pinion removal be? Right now it requires tapping into place and a puller to remove. Even without the key. Is this unusual? Should this fit be a sliding fit?
View attachment 12478

I think the main thing is for the HT pinion to rotate freely on the shaft I made up a temporary key that pushes in from the front with a 'handle' to push in and pull out . When you are happy with the choice of keyway then fit the correct (new) key and secure with E80- you will probably need an extractor next time to remove it if its fitted correctly

 

[Bill Thomas]

I would say Snug ! Rather than tight, I have never found one that needs a puller, I have drilled three holes in my Exhaust spanner and three bolts to gently wind in, Putting any bit of metal between the side of the spanner and the end of the mainshaft, Maybe another spanner or screw driver etc, Once it has moved a bit it becomes loose ? Cheers Bill.

 

[Peter Holmes]

Hello Peter, No, the top of the pushrods will be sticking out the top of both of the rockers, This is the overlap method, Not the opening and closing points, Cheers Bill.

Bill, I understood that the pushrods came through the threaded part of the rocker arm (without the adjusters in situ) my query was do you just let the rocker arms flop to their settle position with gravity or do you somehow lift the rockers gently so the forked end is kissing the valve stem collar thereby ensuring that both rockers are in the optimum position for timing to commence.

 

[Bill Thomas]

Hello Peter, You are not looking at the rockers, It's the top of the pushrods you are watching, It shoud be T.D.C. on the NON firing stroke, One pushrod is going up and the other is going down, Just leave the rockers to flop !, You want the pushrods with the same lift, If you want a fast bike , Do as Vibrac says a few deg' befor T.D.C.. It a good test at the side of the road, Just take the adjuster caps off, Don't touch the adjusters, Spark plugs out, Put it on the rear stand, Put it in 4th gear, Move the rear wheel by hand untill you get to the overlap, Both valves open the same amount and it should be T.D.C. Or very close, Cheers Bill.

 

[davidd]

How easily should the Half Time Pinion removal be? Right now it requires tapping into place and a puller to remove. Even without the key. Is this unusual? Should this fit be a sliding fit?
View attachment 12478

I think that sounds right. I think that I am lazy enough that I just slip the gear on far enough to engage the idler gear and then tap in the key lightly just enough to prevent shifting. They come off easier and you only need to sink them home when you are sure of the selected position.

David

 

[craig]

I did not get parts due to snow yesterday, so I took pieces I had and did some timing training for me. I positioned the 1/2 time pinion about half on, key about half in, new steel pinion, clearances about right. dial gage on only exhaust valve. I then proceeded to time , pulling the HTP and key off/out as needed and found that considerable care must be taken.....as I kept checking TDC and finding it moved a couple times.....maybe I bumped the timing degree wheel pulling HTP.
I would like to get the .050 lift at closing/opening about right and have the 4,5,6 degree BTDC crossover be in a reasonable range, but it aint happening for me yet.
I am now doubting the previous posted graph of valve timing and my .169 lift at crossover/equal lift point. So I would like to confirm this Megacycle cam 554x1 with someone else please.
I added a couple friction washers to hold cam in place while repositioning HTP

 

[Martyn Goodwin]

I did not get parts due to snow yesterday, so I took pieces I had and did some timing training for me. I positioned the 1/2 time pinion about half on, key about half in, new steel pinion, clearances about right. dial gage on only exhaust valve. I then proceeded to time , pulling the HTP and key off/out as needed and found that considerable care must be taken.....as I kept checking TDC and finding it moved a couple times.....maybe I bumped the timing degree wheel pulling HTP.
I would like to get the .050 lift at closing/opening about right and have the 4,5,6 degree BTDC crossover be in a reasonable range, but it aint happening for me yet.
I am now doubting the previous posted graph of valve timing and my .169 lift at crossover/equal lift point. So I would like to confirm this Megacycle cam 554x1 with someone else please.
I added a couple friction washers to hold cam in place while repositioning HTP
View attachment 12485

I do not think you can trust "published" graphs as no 2 cams are EXACTLY alike. You actually need to graph your own cam so you really know what you are dealing with. When I did this on my Comet I removed both the drive side cover and the timing side cover. I mounted the degree wheel onto the centre of the ESA between PD5 and PD8 then tightened up the ESA bolt, first making sure the degree wheel was correctly indicating TDC. Then use your dial gauge mounted directly onto the valve stems (not the pushrods).

To proceed I suggest you do one valve at a time. To make life a bit easier remove the "tappet" adjustor from the valve you are not measuring so as to reduce the spring forces as you rotate the motor. Of course you also want the spark plug out.

With a note pad at hand and a suitable spanner - a socket with a "T" handle worked for me - Start rotating the motor. After each 5 degrees make a note of the crank position and the lift. Once you have completed TWO full revolutions then switch to the other valve and do the same.

Now using the data, plot the graph of your camshaft - something like Excel on your computer works well for this.

Why remove both covers? Well now you know your Cam, you can start working on the cam pinion and half time pinion position to get the "action" you want without disturbing the degree wheel - I suggest you try for equal lift at 4 BTDC. Always keep in mind that Phil Irving maintained that the most important part of cam timing was the CLOSE point of the inlet valve and for a Mk1 cam that should be between 60 - 64 ABDC.

While at it be sure to set your timed breather so it closes at or just before BDC

 

[davidd]

This is the last MK1 I did a few months ago. I think equal lift was 0.149".

I assume that you are finding TDC with a piston stop. If not you will be dealing with some amount of TDC duration, even if it is small. I also do the measuring off the valve stem. I degree the cams on a bench engine with no con rod or piston, so I have to start at equal lift as I do not have TDC. Once it is degreed I install it based on the data.

David

 

[Martyn Goodwin]

This is the last MK1 I did a few months ago. I think equal lift was 0.149".

I assume that you are finding TDC with a piston stop. If not you will be dealing with some amount of TDC duration, even if it is small. I also do the measuring off the valve stem. I degree the cams on a bench engine with no con rod or piston, so I have to start at equal lift as I do not have TDC. Once it is degreed I install it based on the data.

View attachment 12486
David

On my Mk 1 cam I got equal lift at 0.070" - see partial plot below