ET: Engine (Twin) Starting a twin

[Sakura]

My Rapide has always been a pig to start. I've been working on bikes for 55 years and owned dozens of British bikes. Usual starting technique for everything is a bit of a tickle and a good kick. Unless something is seriously wrong it's usually first or second kick. Not so with my Rapide!
I've finally found the technique - close both chokes, no throttle, no tickle, don't even turn on the juice if it's been on in the last few days, ease over the two close compressions and give it a good kick. First or second kick and catch it on the throttle. It's not too rich, spits back if I open the chokes too quickly, new Amals, standard settings. I can't explain it, never known any bike to start like it. Even the slightest tickle and it doesn't want to know. Anybody got a reason for it?

 

[nkt267]

My Rapide has always been a pig to start. I've been working on bikes for 55 years and owned dozens of British bikes. Usual starting technique for everything is a bit of a tickle and a good kick. Unless something is seriously wrong it's usually first or second kick. Not so with my Rapide!
I've finally found the technique - close both chokes, no throttle, no tickle, don't even turn on the juice if it's been on in the last few days, ease over the two close compressions and give it a good kick. First or second kick and catch it on the throttle. It's not too rich, spits back if I open the chokes too quickly, new Amals, standard settings. I can't explain it, never known any bike to start like it. Even the slightest tickle and it doesn't want to know. Anybody got a reason for it?

No, but my comet is like that and the Rapide likes a good tickling

 

[passenger0_0]

My Rapide starts best with chokes only and no throttle so not all that different to yours. Maybe you could check the float level on both carbs if you need to have the fuel turned off as well?
I have a mantra - 'just because it's new doesn't make it right.'

 

[Sakura]

Checked the float levels when I installed the carbs. Just fractionally below the top of the mixing chamber bottom cap using an adaptor and clear plastic pipe.

 

[passenger0_0]

Checked the float levels when I installed the carbs. Just fractionally below the top of the mixing chamber bottom cap using an adaptor and clear plastic pipe.

That sounds about right for the height. I never tickle mine as this seems to flood the engine. If your new starting technique works and the bike runs fine then maybe this is simply the 'new normal' for your bike?

 

[Sakura]

That sounds about right for the height. I never tickle mine as this seems to flood the engine. If your new starting technique works and the bike runs fine then maybe this is simply the 'new normal' for your bike?

Interesting that yours doesn't like being tickled. Most of the old road tests describe a similar starting technique, with just the lightest of flooding, so it's obviously a Vincent trait. My query is why do they seem to want to start on a fairly lean mixture but need choke to run and start? It defies any explanation that I can think of.

 

[macvette]

My Rapide has always been a pig to start. I've been working on bikes for 55 years and owned dozens of British bikes. Usual starting technique for everything is a bit of a tickle and a good kick. Unless something is seriously wrong it's usually first or second kick. Not so with my Rapide!
I've finally found the technique - close both chokes, no throttle, no tickle, don't even turn on the juice if it's been on in the last few days, ease over the two close compressions and give it a good kick. First or second kick and catch it on the throttle. It's not too rich, spits back if I open the chokes too quickly, new Amals, standard settings. I can't explain it, never known any bike to start like it. Even the slightest tickle and it doesn't want to know. Anybody got a reason for it?

Odd isn't it my D is the opposite. Tickle the front carb, no choke, over compression with lifter, one or two kicks and off it goes. Just started it yesterday after winter lay up, three kicks. It has monoblocks and has never needed the chokes and doesn't run rich.

 

[vibrac]

You can't tickle a Mikuni and no matter how many times I read it I can never remember which way is Choke on the lever it's counter intuitive so I never touch it or I may loose my way but the cooking comet started fine now I have gone up a size on the 2020 as it's an old race engine so I am hoping 32 mm will be as good

 

[passenger0_0]

Interesting that yours doesn't like being tickled. Most of the old road tests describe a similar starting technique, with just the lightest of flooding, so it's obviously a Vincent trait. My query is why do they seem to want to start on a fairly lean mixture but need choke to run and start? It defies any explanation that I can think of.

I'm not sure but have put this behaviour down to the fact that petrol IC engines need to run above stoichiometric (slightly rich) to avoid overheating issues but this is harder to ignite at very low kicking speed with a magneto. Not ticking the carbs ensures you're closer to stoichiometric during the starting phase but you need to have it richer with the chokes to keep it going. Mine also spits back once it starts if I back off the chokes too early or open the throttle too much.

I could guess that Series D machines have coil ignition so obviously won't experience this same starting issue/technique. ( I'm probably going to get corrected here......)

 

[Bill Thomas]

My Rapide has always been a pig to start. I've been working on bikes for 55 years and owned dozens of British bikes. Usual starting technique for everything is a bit of a tickle and a good kick. Unless something is seriously wrong it's usually first or second kick. Not so with my Rapide!
I've finally found the technique - close both chokes, no throttle, no tickle, don't even turn on the juice if it's been on in the last few days, ease over the two close compressions and give it a good kick. First or second kick and catch it on the throttle. It's not too rich, spits back if I open the chokes too quickly, new Amals, standard settings. I can't explain it, never known any bike to start like it. Even the slightest tickle and it doesn't want to know. Anybody got a reason for it?

I thought it was just me and getting old, For you, Greg has told us about drilling out the pilots on new carb's, It's on the Forum Somewhere.
I still think it's this so called Petrol.
If I have my twins as rich as they need, They mess the plugs up after a few miles, Mine are all race engines.
Brother Ron's Comet is like yours.
We need proper chokes !, My special with big Dellorto's, Needs choke after a short stop by the sea, ie cold.
They all start fine from hot, After getting petrol.
The Comet is super, Mk2 Con' any time, But also with any carb, Mk1 Con' or USA race carb'
The ex L/ning is the begger, Mk1, When it was on T.T.s It was fine, But messed the plugs after a few miles.
Now running Champion plugs, N5 or N9y, Can't use NGK anymore.
Just ordered a pair of Mk2 s, I wanted 1 for the new Comet, But he had a pair, So I might put them on the L/ning, I am sure that would fix it.
With proper chokes, They work better than a tickle, You can give it what it wants/needs.
Good Luck, Bill.