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[PeteF]

P, I fear you will get some flak for your last post. Drilling a jet out? Terribly inaccurate! Awful practice!
I'm with you though, if it works it works.

[Tim NZ]

The poor bloke is having trouble even getting the bike to start and run, and you offer suggestions on drilling out jets?


Size variables of 0.0005" and smaller are the base line here; drilling jets is jumping out of the frying pan and into the fire.


I definitely side with PeteF...

[Bikerterje]

Thank's Tim NZ for very informative answer. I have also asked Our host for help and advice in choosing jets, I Guess they wil respond as soon as they can.

To day I started the motor and it ran fine With the choke engaged. As soon as it is hot enough, take a log time, it allows me to disangage the choke an it runs very Nice at idle. As soon as I try to open the throttle thow it spits back and chokes. This is without the tape blinding at the bellmouth. With the tape on it is possible to run the bike but just barely. As you wrote I believe I will have to change the slide as well as the jets.

For the time beeing I will have to keep the bellmouth tape and hope for the best. I will most certanly not drill out any jet. PS! Mnifold is New so no leaks there.

[Bikerterje]

Just ordered the Amal MK1 kit. This seems to be the answer to my needs and I hope this will fix the problem. Recommended by our host. Will keep you updated when it's here.

Thank's again for all answers.

[Thack]

Dammit, that's a shame. In my opinion the Mk1 Concentric is probably one of the worst carbs ever made. You can buy a proper Mikuni for only fifty quid more and get a top class carb.



Anyway, sorry! You probably didn't want to read that after ordering one, but I can't resist warning others who might read this thread in the future.



The good thing is, it's an easy fix. You know it's correctly jetted and will work OK.

[sofiaspin]

Totally disagree with Thack comment - pity there is no explanation behind the comment, anyway, with 6 x Mk 1 Amals under my belt and another about to go on an Electra X, don't worry , best choice, they are excellent, and hope your bike is sorted.

[PeteF]

I, however, agree with Thack (just to keep things balanced)
All Amals are outdated to some extent.
Mikuni are a much better instrument and there's not a lot wrong with Mikarb (Mikuni copy) I know a few people who, having changed to Amal, have reverted to Mikarb and been happier.

[sofiaspin]

I am not saying Micarb is bad - just that it is not right to say, ergo, Amal is not good. The Amal is for the period, and suit the bike, which is why our hosts presumably supply them. I have not had any issues, and as long as they are set up properly, perform perfectly, and look right.

[Bullet Whisperer]

I swear by the Amal MK II's and Monoblocs and swear at the MK I's.

[Thack]

sofiaspin: I've never found a Mk1 Concentric that "performs perfectly".



They all have an insoluble problem of a flat spot just off idle, which can be reduced by setting the idle mixture and throttle slide too rich, but not eliminated. They have fixed emulsion tubes and primary air jets so your tuning options are limited. When tested in the late 70s on a test rig, alongside all the other bike carbs at that time, they came out bottom for mixture control and consistency.



The cold start system is truly appalling. The choke slide has a powerfully progressive effect with throttle position, rendering the bike undriveable when it's in use, and let's be honest: the tickler system is so crude as to be laughable. Yes, it works for a cold start, but at the cost of fuel dribbling down the outside of the carb.



They also suffer from excessive slide wear (compared to Mikunis, et al), but these days that is rarely a problem as bikes mostly do very low mileages.