all choked up

Mart UK · Oct 17, 2021

Fuel on, choke on, press button, hold throttle at around 1,500 - 2,000 revs, and turn choke off straight away. After 30 secs, I can release the throttle, close the garage and get back to the bike without stalling. Ride off. The first mile is 30mph speed limit, then 3 miles at 40mph limit. At the junction it idles nicely and I am happy to start using a bit more of the throttle. Be interesting to see how this changes as we head towards winter.

Not sure what I'd gain by removing the choke (enrichener, Amal)?

Fast Eddie · Oct 18, 2021

Mart UK said:
Fuel on, choke on, press button, hold throttle at around 1,500 - 2,000 revs, and turn choke off straight away. After 30 secs, I can release the throttle, close the garage and get back to the bike without stalling. Ride off. The first mile is 30mph speed limit, then 3 miles at 40mph limit. At the junction it idles nicely and I am happy to start using a bit more of the throttle. Be interesting to see how this changes as we head towards winter.

Not sure what I'd gain by removing the choke (enrichener, Amal)?

If it runs that good you’d be daft to change owt.

Leave it be and enjoy !

marshg246 · Oct 18, 2021

Mart UK said:
Fuel on, choke on, press button, hold throttle at around 1,500 - 2,000 revs, and turn choke off straight away. After 30 secs, I can release the throttle, close the garage and get back to the bike without stalling. Ride off. The first mile is 30mph speed limit, then 3 miles at 40mph limit. At the junction it idles nicely and I am happy to start using a bit more of the throttle. Be interesting to see how this changes as we head towards winter.

Not sure what I'd gain by removing the choke (enrichener, Amal)?

*IF* you're talking about Amal concentric carbs and *IF* you mean you're starting it with the throttle open somewhat, then of course you need the chokes since you need them to offset the excess air you're letting in by having the throttle open. *IF* you're talking about Mikuni or Amal MK2 carbs, then of course you must leave the enricher installed - removing it would mean that you are always enriched!

With a Tri-Spark ignition and two properly setup Amal Premier Concentric carbs that have no chokes installed: I tickle, kick without touching the throttle, walk to the other side of the bike, climb on, and go gently at first (have to kick with my right leg on the right side of the bike due to hip problems). Exactly the same on my 850 and my 650 Bonneville - also on my Trident with thee carbs.

BTW, with the air screws set correctly (correct air/fuel mixture) it is possible to not have enough mixture at idle. Amal Premier carbs are fine with #17 pilot jets as far as mixture goes, but something Fast Eddie said a while ago caused me to experiment. My 750 Roadster and 650 Bonneville both idled OK with #17 pilot jets but opening the throttle was iffy when cold. I switched to #19 and that went away. When the jet gets bigger you still have to get the mixture right but having more correct mixture is better especially when cold.

Mart UK · Oct 18, 2021

marshg246 said:
*IF* you're talking about Amal concentric carbs and *IF* you mean you're starting it with the throttle open somewhat, then of course you need the chokes since you need them to offset the excess air you're letting in by having the throttle open. *IF* you're talking about Mikuni or Amal MK2 carbs, then of course you must leave the enricher installed - removing it would mean that you are always enriched!

With a Tri-Spark ignition and two properly setup Amal Premier Concentric carbs that have no chokes installed: I tickle, kick without touching the throttle, walk to the other side of the bike, climb on, and go gently at first (have to kick with my right leg on the right side of the bike due to hip problems). Exactly the same on my 850 and my 650 Bonneville - also on my Trident with thee carbs.

BTW, with the air screws set correctly (correct air/fuel mixture) it is possible to not have enough mixture at idle. Amal Premier carbs are fine with #17 pilot jets as far as mixture goes, but something Fast Eddie said a while ago caused me to experiment. My 750 Roadster and 650 Bonneville both idled OK with #17 pilot jets but opening the throttle was iffy when cold. I switched to #19 and that went away. When the jet gets bigger you still have to get the mixture right but having more correct mixture is better especially when cold.

No throttle when I hit the starter. Though I do need a bit of throttle to start, no choke, when the bike is warm. It is a single 34 mk2 Amal on a Mk3 850. I find a 22 pilot jet works best once warmed up. I tried 20 and 25 jets and it was difficult to get the idle and initial pick up smooth.

A bit like emission controlled EFI until it warms up though. It hunts a little at steady throttle and throttle response a bit on/off, but that soon goes away and it's lovely once it's warm. I set idle at about 1200rpm. Pilot air screw just over 1.5 turns out.

When I first got the bike, I did think I would go to twin carbs. But I find I'm happy riding below 6,000 revs (mostly 2500 to 4500) and it pulls nicely. So I'll stay with the single for now. But it is too tight for space with the standard rubber flange mount. I may try the shorter Amal version, once it is back in stock.

Just as well I haven't taken the choke off it, I didn't know!

phippsy · Oct 18, 2021

marshg246 said:
*IF* you're talking about Amal concentric carbs and *IF* you mean you're starting it with the throttle open somewhat, then of course you need the chokes since you need them to offset the excess air you're letting in by having the throttle open. *IF* you're talking about Mikuni or Amal MK2 carbs, then of course you must leave the enricher installed - removing it would mean that you are always enriched!

With a Tri-Spark ignition and two properly setup Amal Premier Concentric carbs that have no chokes installed: I tickle, kick without touching the throttle, walk to the other side of the bike, climb on, and go gently at first (have to kick with my right leg on the right side of the bike due to hip problems). Exactly the same on my 850 and my 650 Bonneville - also on my Trident with thee carbs.

BTW, with the air screws set correctly (correct air/fuel mixture) it is possible to not have enough mixture at idle. Amal Premier carbs are fine with #17 pilot jets as far as mixture goes, but something Fast Eddie said a while ago caused me to experiment. My 750 Roadster and 650 Bonneville both idled OK with #17 pilot jets but opening the throttle was iffy when cold. I switched to #19 and that went away. When the jet gets bigger you still have to get the mixture right but having more correct mixture is better especially when cold.

Mine stars ok like yours until the needle drops below 5 degree centigrade,it will start but then stop , that’s why I am thinking of chokes , what are the lowest temperatures yours will start ,as I have been out in minus degrees on mine.

marshg246 · Oct 18, 2021

Can't say today as I don't ride in the cold. As I build and fix bikes all year long, I do start them for timing and such, but it rarely gets below about 30F here and even in Jan/Feb there are usually some 50F days to test.

From 1968-1970 I only had a Triumph 500 and I rode to college no matter the weather including well below 0F and I had no chokes. The cold oil was a bigger problem than the carbs in starting. The bike sat outside at all times - no garage, no shed.

Try this. Once warm, blip the throttle. If it stumbles at all turn your air screws in a tiny bit and try again until it does not stumble. Then when it's cold see if your issue is gone. If not, turn them in a "TINY" bit more. (only once). If you have Premier carbs and you have #17 pilot jets and you still have a problem, switch to #19 pilot jets.

Also, if you don't have a EI with idle stabilization, consider installing a Tri-Spark or other that does.

phippsy · Oct 18, 2021

Cheers Got a tri spark, so will give it a go , if it stops raining here ,poor girl sits outside.

all choked up

Mart UK

Fast Eddie

marshg246

Mart UK

phippsy

marshg246

phippsy

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