E: Engine Big bore Comet

[mercurycrest]

I am pretty certain its a big bore engine it certainly feels like it but I cant think of an easy way to check without stripping it, any non messy ideas? angled rods through the plug hole are inconclusive

Unscrew the spark plug, crank the engine until the piston is in its upper position, then fill up the hole with oil . Then crank the engine another half turn until the piston is down. Then pour more oil in the hole until it is full again. This amount is the displacement of the cylinder.

 

[Nulli Secundus]

Has anybody actually identified the hard starting issue or are we all just guessing, what with longer kick starters, changing ignition timing.........sounds like a bunch of experts at the race track.

Just making anyone experiencing a little difficulty in kick starting a bike with an AMC gearbox aware that there are longer kickstart levers available. No need to be rude about it Greg.

 

[Nulli Secundus]

How does the PR kicker compare in length to the RGM kicker?
Just curious as I need a kickstart for a hi compression 920, might be worthwhile getting the AN item, even if it requires a mortgage.

Glen

Just need Clive to measure his RGM Kickstart lever. I have already said how long the PR one is.

 

[Monkeypants]

Has anybody actually identified the hard starting issue or are we all just guessing, what with longer kick starters, changing ignition timing.........sounds like a bunch of experts at the race track.

In the first post Clive stated-

"It starts immediately on the rollers,"

So that ruled out hard starting.

It just needs to to roll over with some oomph.

Getting the optimum kicker length makes a big difference
I made 3 for the 1360 before finding the sweet spot for length.
Too long can be a problem as well.

Glen

 

[Bill Thomas]

Nulli, Am I right in thinking with a Commando, You just kick it over ?,
Because it's a Twin, There is no valve lifter ?.
I remember the very good production Racer, Jim Poole, Just kicking ?, And i know He had BIG Pistons.
So maybe with your longer kicker, It's possible to do it closer to TDC ?.

 

[Nulli Secundus]

Nulli, Am I right in thinking with a Commando, You just kick it over ?,
Because it's a Twin, There is no valve lifter ?.
I remember the very good production Racer, Jim Poole, Just kicking ?, And i know He had BIG Pistons.
So maybe with your longer kicker, It's possible to do it closer to TDC ?.

You are correct Bill, there is no valve lifter on the Commando. With the Norton I rightly, or wrongly, apply pressure on the kickstart and as soon as I feel the piston is about to go over compression I go for it. The longer lever helps with this.

I am sure depending upon your build and leg strength, many people could just go for it.

 

[Black Flash]

Hello Nulli,

as you just said, go over tdc on a Commando and give it a kick works great, I had a 750 SS myself.
Now the Commando is a parallel twin that fires every rotation of the crank. A single only fires every second rotation, that is exactly why i suggested to ease the piston over tdc, the slowly press down the kickstart 3/4 of its way, let it return and give it a good kick.
Kickstarting my single with is pretty much the same with the Norton box and a really high compression, like Bob's 636cc engines, i very rarely succeed in starting the bike if I kick it just after passing tdc.

Cheers
Bernd

 

[Peter Holmes]

Has anyone suggested converting the engine to 500cc and fitting a Burman gearbox with a Honda clutch, if still using a magneto of any sort, Lucas, old BTH or new BTH, swap it out for a distributor and coil, Type 29 Amal carbs also work really well, I can almost tell my bike to start using mental telepathy, nothing so complicated as just over compression required.

 

[Black Flash]

Peter,
I honestly admire you! I can vividly remember German rallies where folks were exhausted and had to get out of their motorcycle gear full of sweat as their Vincent wouldn't start.
Those were happy days.
Now if you have ever ridden a 600CC TPV or one of Bob's bored and stroked Comets along the twisties, I am sure you wll be convinced about these bikes too. They are not as good as an original bike pottering along, but once you twist the grip, the grin certainly sets in!

 

[Bill Thomas]

Any of you Lads been properly timed for top speed with a BIG engine ?.
I got 99.8 mph at the end of a flying 1/4 mile, With my Blue Road Comet, Flash spec' engine,
No fairing !. 36mm Dellorto Carb'.