[jez]

Thanks to partial lifting of English lockdown, and perfect weather, I swapped the Nuovo Falcone for the  535. Old fuel didn't help but finally she started  so of to get petrol. Within half a mile the engine was racing, and this got ever worse. Took off the carb and cleaned the slide. Reset the throttle stop [That's odd] and she ran fine.
Half a mile later the engine was racing again.
It transpired that the engine vibration was causing  the throttle stop to rotate clockwise.......
Cheapo design, Amal having dispensed with the locking spring. Put a ding in the threads and reset. Fine but an afternoon wasted.

[Richard230]

More stink'n Spam.   

[jez]

Since this post refers directly to the Hitchcocks amal carb fitted to my 535 I fail to see how it's spam.

[Richard230]

Since this post refers directly to the Hitchcocks amal carb fitted to my 535 I fail to see how it's spam.

It looks like the spam was removed by the moderators. 

[Adrian II]

There have been some spam attacks on this forum lately, but if you're only an occasional visitor you will have missed the spam posts as well as their subsequent removal by the admins. This does not however remove member's posts complaining about the now deleted spam posts, which is why Richard230's post now APPEARS to be complaining about your legitimate post!

Collateral damage?

A.

[Bilgemaster]

Thanks to partial lifting of English lockdown, and perfect weather, I swapped the Nuovo Falcone for the  535. Old fuel didn't help but finally she started  so of to get petrol. Within half a mile the engine was racing, and this got ever worse. Took off the carb and cleaned the slide. Reset the throttle stop [That's odd] and she ran fine.
Half a mile later the engine was racing again.
It transpired that the engine vibration was causing  the throttle stop to rotate clockwise.......
Cheapo design, Amal having dispensed with the locking spring. Put a ding in the threads and reset. Fine but an afternoon wasted.

That's a clever fix, jez. Thanks for the tip for possible future reference. That was one of the new and improved and harder-wearing "Premier" ones I presume? I also wonder if the older model's sprung throttle stop screws are forward-compatible with the new model for those like me who may have an old worn out Amal or three just laying around in the parts bin. Apparently Amal will also sell you just the little spring too: http://amalcarb.co.uk/throttle-stop-screw-spring.html . Though whether this may fit the newer style Premier ones isn't really clear.

Just for a gag I've sent the following inquiry/enquiry to Amal via their contact page at http://amalcarb.co.uk/contacts/ :

"Some users of your new harder-wearing Premier Series of Concentric have described how engine vibration can cause its now unsprung throttle stop screw to change position, thereby either increasing or decreasing engine speed. Would the throttle stop screw spring described at http://amalcarb.co.uk/throttle-stop-screw-spring.html fit the Premium models and perhaps cure this? Alternatively, are the older style sprung throttle stop screws compatible with the new Premier models?"

I'll keep you all posted on any responses I may receive.

[Richard230]

There have been some spam attacks on this forum lately, but if you're only an occasional visitor you will have missed the spam posts as well as their subsequent removal by the admins. This does not however remove member's posts complaining about the now deleted spam posts, which is why Richard230's post now APPEARS to be complaining about your legitimate post!

Collateral damage?

A.

And unfortunately, the forum system does not allow someone to remove or modify their post after a relatively short time period. So I am no longer able to alter the message to remove the confusion that resulted from my complaint about the spam which is now gone.    Spammers suck. 

[jez]

It is a Hitchcocks supplied carb so I would have thought a Burlen one rather than a copy, and thanks for explaining. The carburation is as good as it gets but there is wear on the slide after perhaps no more than 3000 miles. Mikunis wear a lot better, in part due to being rubber mounted. The Hitchcocks Mikuni kit costs less than their Amal kit but doesn't use the original air filter housing. If one were to use a track cam rather than Hitchcocks smooth and progressive road cam I think a bigger carb would be in order but there is absolutely no room for a bigger than 32 mk1 Amal. I don't know if a mk2 or Mikuni would fit at 34mm. The body size of carbs tends to go up at that point. On Paul Henshaw's channel one owner said that switching to a 32 Amal knocked a few mph off top speed. Henshaw himself has said that ideally he'd prefer a mk2 34 concentric.  If the SR and XT500 forums are anything to go by there would be several different Mikuni jetting specs that would work; if only one had the time to discover them......

[Adrian II]

May I make a suggestion?

The Dell'Orto PHF. 30, 32, 34 or 36mm? Choice of anodized or chrome brass slides. Same casting used for the body on all of these, and good spares coverage in the UK.

There's even a Malossi one piece carb rubber to fit with mounting hole centers at the right 58mm spacing for late iron barrel 500 Bullets. It has a tapered bore narrowing down to 30mm at the flange but can be bored to suit the larger sizes.

I have PHF36s on my AVL500 Hybrid and my Not A Fury.

A.

A.

[Bilgemaster]

As mentioned in a previous post, I reached out to the good folks at Amal about that idle screw issue, and here is their response along with my original inquiry/enquiry as promised:

Dear Mr Connelly,

The Monobloc Throttle Stops are also a 2BA thread and can be used. The stop would need shortening slightly. I've just tried this to prove it can be done and you'll need to find a shorter spring as the Monobloc spring becomes coil bound before it starts to move the throttle valve. I shortened the screw to approximately 36mm.

Kind Regards
Phil Beresford
Customer Services Advisor

Burlen Limited - The SU, AMAL & ZENITH Carburetter Companies
Spitfire House, Castle Road, Salisbury, Wiltshire. SP1 3SA
Tel: +44 (0)1722 412500
Fax: +44 (0)1722 334221 
Email: customer.services@burlen.co.uk 
Website: http://www.burlen.co.uk


-----Original Message-----

From: AMAL Carb co [mailto:info@burlen.co.uk]

Sent: 15 July 2020 13:24
To: Sales Department <info@burlen.co.uk>
Subject: Throttle Stop Screw Spring for Premier Series Concentrics

Name: William Connelly
E-mail: [xxx]
Telephone: [xxx]

Dear Amal:

Some users of your new harder-wearing Premier Series of Concentric have described how engine vibration can cause its now unsprung throttle stop screw to change position, thereby either increasing or decreasing engine speed. Would the throttle stop screw spring described at http://amalcarb.co.uk/throttle-stop-screw-spring.html fit the Premium models and perhaps cure this? Alternatively, are the older style sprung throttle stop screws compatible with the new Premier models?

With Regards,
Bill Connelly
Woodbridge, Virginia USA

[ace.cafe]

34mm matches the port entry.
32mm gives a little more speed over the jet for atomization, improves low/midrange, but does slightly cut the top end.
I think if the rpm limit is kept to 5500 rpm, the 32mm would be fine. If you want 6500 rpm and have the cams and valve springs for it, a 34mm is better. We actually squeaked out couple more hp at the top end with a 36mm EFI throttle body and a 36mm port entry, and a 36mm carb might also do.