my new amal concentric premier - bike v hard to start

[nablats]

spitting on kicking over so i referred to this - taken from vintagebike mag article - MY COMMENTS IN CAPS & IN BRACKETS
1- There is a new anodized aluminum slide. The cutaways match the earlier pot metal
slide. - (MY 928 HAS THE NUMBERS 0603? IS THIS A 3 1/2 LIKE IT SHOULD BE FOR A SINGLE CARB HEAD?)
2 - The pressed in pilot jet is replaced with a new screw in jet. This jet allows easy changing, or cleaning. (JUST BLAST IT WITH CARB CLEANER?)
3- Because of some dimensional changes from the original white plastic float they should be used with an aluminum float needle. (MINE IS OK)
4- Also these dimension changes require the top of the float be aligned with the top edge of the bowl. (PREVIOUS LEVEL WAS 2mm BELOW??)

[DAVE BRADY]

Hi,

Even though it is new it is best to make sure it is clean.  If you have not touched the timing the spitting could indicate a fuel problem hence, give it a clean.
Start by removing the jet and use some carb cleaner and then make sure the mixture screw is set at about 1 1/4 turn out and start from there.


Dave.

[nablats]

Cheers, actually from new the carb had a lot of swarf in it, had to take the head off and lap the valves in again to get some compression.
I have an ultrasonic cleaner, so a good blast in there should do it. I wasnt sure if this new jet needed something like an old g string to clear it.

[DAVE BRADY]

Hi,

Also, an air line if you have one to blast through all the tiny drillings. Squirt some carb cleaner on the inlet side and you should it coming out in the inlet tract.

Dave.

[nablats]

Thanks again - did you make any sense of item #4? I have no idea what that means.
I have cleaned/blasted and ultrasonicked the heck out of it, not a squeak out of it.
I am beginning to think lack of compression again

[cdsdorset]

Item 4 refers to the float level. The float top edge should be level with the top of the float bowl when the float valve  has full closed.
The easiest way to do that is with the float bowl secured in a vice/jig etc and a remote fuel supply.

[V500]

Back to basics- did the bike run before you fitted the new carb?

[Allan G]

spitting on kicking over so i referred to this - taken from vintagebike mag article - MY COMMENTS IN CAPS & IN BRACKETS
1- There is a new anodized aluminum slide. The cutaways match the earlier pot metal
slide. - (MY 928 HAS THE NUMBERS 0603? IS THIS A 3 1/2 LIKE IT SHOULD BE FOR A SINGLE CARB HEAD?)
2 - The pressed in pilot jet is replaced with a new screw in jet. This jet allows easy changing, or cleaning. (JUST BLAST IT WITH CARB CLEANER?)
3- Because of some dimensional changes from the original white plastic float they should be used with an aluminum float needle. (MINE IS OK)
4- Also these dimension changes require the top of the float be aligned with the top edge of the bowl. (PREVIOUS LEVEL WAS 2mm BELOW??)

I've been a small time Amal dealer for the best part of 15 years or more.

1- 0603 will be a #3 slide. You want a 06035 for a 3.5 slide.

2- the screw in pilot jet does replace the bush. However the welch plug (the area where the metered fuel is mixed with air is prone to blocking and furring up. Though this is less of an issue in my experience since the screw in pilot jet. Ideally when you have the idle circuit tuned in on the mixture. You should be between 1 to 2 full turns out. A change in jet size is roughly equal to 1/2 a turn on the pilot air screw.

3- not sure what you mean by "mine is ok" id appreciate if you could elaborate. However if using the black stayup float, it should ONLY be used with the aluminium needle. This is because the stayup float is more likely to bob with a brass needle and potentially close early under its own weight.

4- different things will affect the float height. But density changes in fuel will have the biggest effect. This affects how deep within the fuel the float sits. The black float will sit higher in the fuel than the plastic float so yes the float height has changed. The fuel level if using that method is still the same. It is however much easier to set by the float height. Like you mentioned I too set my float height by the top of the float in line with top edge of the bowl. It's easiest to turn the bowl upside down and allow the weight of the bowl to close the needle valve. Instead of pressing against the needle.


But this isn't all. If your having starting or running problems in general, check that float bowl top is LEVEL. Place it on a sheet of glass and see if it rocks. If it has an air leak it can affect the seal around the pilot fuel transfer circuit. It's also a potential leak point.

If it is deformed, DONT sand it flat, you'll only weaken the bowl and it'll fail again sooner. You can use a press (or even a press drill at a push) place a 10 thou feeler gauge under one side. We do this as the aluminium or Mazak (depending how old the carb is) has a memory and you need to over flex the bowl to get the top edge flat again. 

[nablats]

 V500 - When bought, The bike ran but badly, The engine has now been rebuilt (I wanted the sludge trap end float etc checked) by my engineer buddy, and the old carb - smk or summat, replaced. I had the head done by a specialist, and rewired it with a new boyer ignition and power box. The stator and rotor are new and there is a good spark, timing set statically with the flywheel locked. The bike fired up last week after a dozen or so kicks, warmed up thoroughly, and it did restart, but only after more tickling, which I thought odd.

[nablats]

cdsdorset - I will try that, I suppose the ends of the float pivot will need to be held/taped down while the bowl fills?

[nablats]

Allan G - thanks -
1- sounds like I was supplied the wrong slide for a single carb head thunderbolt
2- the welch plug is new to me - will find that and clear it (couldnt see it on the Amal diagram)
3 -my float needle is alumin, so I have the right one (just as well as its brand new!)
4 - I will re-check this on my carb
I would not be surprised if there is a serious blockage, with all the alumin. swarf that had not been cleaned out of this new carb at the factory

[Allan G]

Allan G - thanks -
1- sounds like I was supplied the wrong slide for a single carb head thunderbolt
2- the welch plug is new to me - will find that and clear it (couldnt see it on the Amal diagram)
3 -my float needle is alumin, so I have the right one (just as well as its brand new!)
4 - I will re-check this on my carb
I would not be surprised if there is a serious blockage, with all the alumin. swarf that had not been cleaned out of this new carb at the factory

Did you buy the carb direct from Burlen or another re-seller? I buy all mine as I go, so I don't keep any on the shelf. I do however check each one on receipt. The only time I have ever found swarf was from when the new premiers first came out about 12 years ago. I have been lucky ever since. But I don't just check swarf, I also check needle jet sizing (this is the only jet with a physical measurement instead of flow rate), all jetting as per requirements (bike model) and overall QC. (It's not that I don't trust Burlen, I just beleive that I become responsible for sale and like to reduce possible isssues down the line)

My guess is you have been supplied with a generic model carb. So would be 928/1 on the side by the tickler or something like that. You also want to be sure the idle mixture screw is the same side as the throttle slide height screw, and the brass jet is on the opposite side (they can interchange - but won't work if they do).

If you screw the idle mixture screw in all the way, remove the pilot jet and spray some carb cleaner down the hole where the pilot jet resides. You should see 2 good streams of carb cleaner come up under where the slide sits.
To do this you really need the carb off the bike and the carb top with slide removed.

One of the little holes is between the engine and the carb slide. This is the tick over jet. The one under the slide is for increased fuel/air mixture as your taking the bike off throttle. It aids good transfer between the idle part of the carburettor and the main part of the carburettor. You essentially have two carbs in one. If one of these is blocked then you will find that the bike will either A, not idle or B, stall when opening the throttle.

The welch plug itself is the little silver plated plug which sits under those holes (or better said, jets as they are of a specific size).

The lower number slide will richen the mixture between throttle off idle position and 1/4 throttle. A 1/2 size won't have much ill effect but it will make the engine slower to pick up when the throttle is opened and worsen MPG as most of our riding is done within that throttle range.

Hope this helps.

[nablats]

That helps a lot, thanks for your efforts