E: Engine Lame duck Comet

[Black Flash]

Just a quick update,
My friend found out that the bearing in his magneto was worn or not correctly shimmer, so he could move the atd left to right about a mm.
I sent him my spare magneto and a new atd.
he changed the magneto and tried my ATD and his using his old springs again... No change in speed.

He has now done about 2000 miles on the new piston but he cannot achieve more than 70 MPH maximum.
he will use the bike nevertheless to visit the classic TT.
when he returns we will take the timing side to pieces again, check each and every part again.
The head scratching just carries on

Bernd

 

[Bill Thomas]

You don't have to get too involved, Rocker caps off, Plug out, Both valves rocking, On the non firing stroke, Tappets Same height, Look down the Plug hole, To see T.D.C. Move the engine back and forwards by turning back wheel with it in forth gear, to see T.D.C. by eye.
I have been told of pinion slipped on the camshaft, But not had it myself. Cheers Bill.

 

[chankly bore]

Just a quick update,
My friend found out that the bearing in his magneto was worn or not correctly shimmer, so he could move the atd left to right about a mm.
I sent him my spare magneto and a new atd.
he changed the magneto and tried my ATD and his using his old springs again... No change in speed.

He has now done about 2000 miles on the new piston but he cannot achieve more than 70 MPH maximum.
he will use the bike nevertheless to visit the classic TT.
when he returns we will take the timing side to pieces again, check each and every part again.
The head scratching just carries on

Bernd

Worth checking as to WHY the magneto bearing failed. There have been bad pinions in the past that "grew". Magneto must be timed at about 35 degrees B.T.D.C. fully advanced but with the pinion resting back against the small idler. The magneto pinion should have about .008" backlash. Also, since one end of the magneto is worn, check that the cam ring is not sloppy in its housing at t'other end of gubbins.

 

[Howard]

I assume he's turning the magneto pinion backwards to take up all backlash, before tightening the ATD on the shaft.

 

[Black Flash]

I spoke to Dieter again,
he will use the bike as it is to put more miles onto the new piston.
when he returns from the TT he will register his shadow again and take a look at the innerds of his timing side etc.

So surely nothing going on the next week's.

Anyway thank you for your feedback. I wish you all a good time and safe riding.
Bernie

 

[Black Flash]

Just an update for those that are interested.
I visited my friend dieter last weekend.
We used two digital clocks and guess what, with the timings marks being all correct the equal lift appeared at 13 degrees, not at 4 as they should.
The closest we could get to were 5 degrees and the bike now behaves as it should.
This reminds me of the words Frank Griffin once told me :never assume anything, control everything!
He can now quickly achieve 80 mph upright. We also installed this new Bth thing and while the sparks looks very thin the bike starts first kick every time now.
Altogether the bike works as it should now.

The racket out of the straight through silencer is fantastic, if you like that kind of noise.
The neighbours always wave to him... With a fist.
Bernd

 

[vibrac]

You must have good eyes to see the BTH spark I never can but it burns holes through fag papers!

 

[Martyn Goodwin]

Just an update for those that are interested.
I visited my friend dieter last weekend.
We used two digital clocks and guess what, with the timings marks being all correct the equal lift appeared at 13 degrees, not at 4 as they should.
The closest we could get to were 5 degrees and the bike now behaves as it should.
This reminds me of the words Frank Griffin once told me :never assume anything, control everything!
He can now quickly achieve 80 mph upright. We also installed this new Bth thing and while the sparks looks very thin the bike starts first kick every time now.
Altogether the bike works as it should now.

The racket out of the straight through silencer is fantastic, if you like that kind of noise.
The neighbours always wave to him... With a fist.
Bernd

Now put a 50 tooth on the back and you will be even more impressed with the performance- plus it is less load on the motor!

Give it a try - you will NOT want to go back to the 48!

Martyn

 

[Martyn Goodwin]

I find the Comet Gearbox, Change is quick enough, Just the space between the gears, The down change is as quick as anything, To me.
I wonder how many people have been put off the Comet, Because of it ?.
I would love to get my new 560cc built, To see if the extra power would help with the gears.
I now know I have been silly trying to do it myself, It would have been quicker and cheaper to get a top man to make the Flywheels.
We live and learn !. Cheers Bill.

I came to the same conclusion. IF there is a next time I will simply buy a Terry Prince crank assembly - its complete with crank and con rod as well!