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[Jakub]

Recently became owner of 1959 Constellation. PO fitted Keihin clone carb named 30 PWR. The first time I drove bike was pretty sluggish so I raised needle two up, became eight stroking so needle went one down. Somehow it rides. Compere to my other old bikes which are 350 and 500 respectively its faster, compare to my modern bike it’s slower. But my gut feeling tells me that twin 700cc should be more lively.
According to GPS top speed was 110 Roman Catholic or 70 Church of England.
Surprisingly the speedo indicated speed was also 70. Usually with this old machines speedometers are horribly inaccurate.

Anyhow, would it be sensible to go for twin carb setup?

If I go with host shop it’s about 650 GBP plus additional hassle of getting shipment to Europe. So it’s little more than few nuts and bolts. Is the expenditure worthy?
Also I do have Amal current reproduction on my other bike. Let’s say the quality isn’t that much satisfying.

[Marko]

Have you checked your ignition timing? 70mph (110km) top speed is not right. I have no experience with the Keihin clone carbs (PWK?). When you say "replica Amal" do you mean Amal or Wassell? You could always fit the single carb manifold & a new Monobloc or Concentric if you wanted to save some money instead of the 2 carb setup. There were 2 different single carb manifolds available ( 1 1/16" & 1 3/16"), the larger for the Constellation. My Connie is fitted with a single 389 Monobloc & runs fine.
Anyway, before messing with the carb just make sure the basics are correct: valve clearances, ignition timing. Valve clearances by the book are "0" - zero both, or 0 on the inlet with .005" on the exhaust for racing or whatever the manual describes. I've found .002" on the inlet and .004" on the exhaust satisfactory & have been using these settings for a few years without problem.
Good luck & let us know how you get on

[Adrian]

The Keihin PWK (clone) was used successfully on RE Bullets by the former US importer. It's use on twins is possible too, there's a UK firm which sells conversion kits for a range of British classic bikes. Getting the carb set up right is just as important with any make, but for the PWK you might find this is helpful, there are several twin cylinder bikes whose settings should be "pretty close". Pattern PWK jets can be had for beer money.

https://brillbikeparts.co.uk/images/jets.gif

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[Jakub]

Thanks for answer, I have pre-Monobloc (I think it’s 276 model). From these guys.
http://burlen.co.uk/news/cat/news_amal/
Purchased about 15 years ago but judging by pictures the manufacturing protocol hasn’t changed.

My main complaint is huge tolerance in between carb body and throttle slide. It’s OK for higher revs but setting idle is diabolical. Sometimes it works sometime it doesn’t.

From PO I have received old Amal carb, could be original but not for Constellation I think. The manifold is 1 3/16 and carb 1 1/8. I think it's monobloc 389. Anyhow I am going to try it later on. But firstly need slightly better weather outside and secondly PO was messing with manifold. It’s in the machine shop right now waiting for new studs to be made.

[Jakub]

Thanks Adrian. You are right about Keihin clone parts. Actually I have ordered and already received few main jets to try. I’ve paid 10 GBP for three jets including delivery.

But in the long term I would be more happy with something more appropriate. Then again the covers for air box doesn’t have “ears” which I understand were installed with twin carb.

[Marko]

Single Monobloc 389 for Connie: 1 3/16" bore, 300 main jet, 30 pilot, 106 needle jet, 3.5 slide

[Adrian]

I think our hosts also still have TT carbs for the early Constellations. You could buy a large number of PWKs for the same price.

A.