Goodbye Wassell carburetors , Hello Amals

Status
Not open for further replies.
Joined
Oct 1, 2018
Messages
63
Country flag
Hi All,
When I first got my MKIII it needed carburetors. I bought the Wassell EVO carbs and began installing them. Right off the bat , one of the removable pilot jets was supplied with metal swarf in the orifice-- that could not be dislodged. The seller kindly sent me a new jet. One of the throttle springs had flakes of plating stuck all over it --similar to a flocked Christmas tree--and I chose not to use it and used one of the old springs instead. This is sloppy QC, but I figured that they would probably work. But over the long haul, at idle , I could never get the right side to feel as solid as the left when putting my hand behind the exhaust, no matter how I adjusted cables or screws. Then the left carb tickler kept sticking. I finally took it apart and Wassell uses a steel washer at the base of the split pin that forms the plunger to depress the float. The taper on the flared end of this split pin was just right to wedge into the washer and jam solid with engine vibration. To top it off, the ends of the split pins are so sharp they have started to dig holes in the floats.
To sum it up--I am a novice at tuning and I started to feel that I did not need the fundamental quality of the carburetor being a question mark--and I feel that I could never trust that I was getting the best out of my bike with these carbs, even if I fixed all the overt defects.
I just got the Amal Premieres lashed up on the bike this evening and right off the bat I got a stronger left side idle than the right and the transition from idle to driving in first gear is much more solid and predictable. I have much more to learn regarding optimizing these new carbs but the omens are promising.
Very Sincerely,
Kara
 
Hi All,
When I first got my MKIII it needed carburetors. I bought the Wassell EVO carbs and began installing them. Right off the bat , one of the removable pilot jets was supplied with metal swarf in the orifice-- that could not be dislodged. The seller kindly sent me a new jet. One of the throttle springs had flakes of plating stuck all over it --similar to a flocked Christmas tree--and I chose not to use it and used one of the old springs instead. This is sloppy QC, but I figured that they would probably work. But over the long haul, at idle , I could never get the right side to feel as solid as the left when putting my hand behind the exhaust, no matter how I adjusted cables or screws. Then the left carb tickler kept sticking. I finally took it apart and Wassell uses a steel washer at the base of the split pin that forms the plunger to depress the float. The taper on the flared end of this split pin was just right to wedge into the washer and jam solid with engine vibration. To top it off, the ends of the split pins are so sharp they have started to dig holes in the floats.
To sum it up--I am a novice at tuning and I started to feel that I did not need the fundamental quality of the carburetor being a question mark--and I feel that I could never trust that I was getting the best out of my bike with these carbs, even if I fixed all the overt defects.
I just got the Amal Premieres lashed up on the bike this evening and right off the bat I got a stronger left side idle than the right and the transition from idle to driving in first gear is much more solid and predictable. I have much more to learn regarding optimizing these new carbs but the omens are promising.
Very Sincerely,
Kara

There are ample reports of Premiers having issues too, especially swarf. But it sounds like you got some good ones. Glad they are working!
 
I am dealing with a new set of Premier carbs, the pilot jets supplied were 17 and thanks to the guys here I changed them to 19 the bike is running ok and now needs a little more adjustment. But in general they seem well made.
 
850 premier carbs have been supplied with the 19 pilots for some while now as standard. The days of swarf in them should be over, we pestered them hard enough.
Nearly all the setting up can be done with carbs on the bench. Just need to do the final check when the engine is at working temperature.
They also meter well, the fuel trace from the dyno of mine is on their website, overlaid on a stock 750 Commando trace, both using Premiers. The fuelling response through the gears was also very good when the bike was being warmed up.
 
850 premier carbs have been supplied with the 19 pilots for some while now as standard. The days of swarf in them should be over, we pestered them hard enough.
Nearly all the setting up can be done with carbs on the bench. Just need to do the final check when the engine is at working temperature.
They also meter well, the fuel trace from the dyno of mine is on their website, overlaid on a stock 750 Commando trace, both using Premiers. The fuelling response through the gears was also very good when the bike was being warmed up.

Wasn't the major change to the pilot jet? What else was changed with them that would improve their performance?
 
Slides not wearing out like the original Amals did ???

That was due to moving to the anodize slides and I assume different body material. But that wouldn't explain any changes to the performance from new.
 
850 premier carbs have been supplied with the 19 pilots for some while now as standard. The days of swarf in them should be over, we pestered them hard enough.
Nearly all the setting up can be done with carbs on the bench. Just need to do the final check when the engine is at working temperature.
They also meter well, the fuel trace from the dyno of mine is on their website, overlaid on a stock 750 Commando trace, both using Premiers. The fuelling response through the gears was also very good when the bike was being warmed up.

Amal Dyno Results

Goodbye Wassell carburetors , Hello Amals


Am I reading it correctly? The 850 had the Premiers and the 750 did not? Why does the A/F ratio get all silly at 6K+? I would have expected the Full Auto head to preform a little better, especially with the Premiers. Was this beaten around the bush in another thread?
 
850 premier carbs have been supplied with the 19 pilots for some while now as standard. The days of swarf in them should be over, we pestered them hard enough.

Well now, I just recently bought a new Premier directly from Amal. It came with a chuck of swarf inside the mixing chamber. Took a combination
of a fine wire and compressed air to get it out. While not for a Commando, it came configured correctly as per the specification and had
the 17 Pilot in it. It was VERY difficult to start but ran ok when it did start. The air screw had to be only 1/2 turn out to get it to start. I bought a
19 Pilot and installed it. It started 1st kick and idled just fine with air screw out 1 1/2 turns. Response is perfect throughout the throttle.

This all was after trying to save money when I bought a new non pre-premier that was a nightmare to get started. I sold it for a big loss.
 
Swoosh, no you’re not reading correctly, BOTH the 850 and 750 had Premier carbs.

I‘m with you on the performance aspect though, I also see no reason why a Premier should give better performance than an equally ‘as new‘ standard concentric. To my mind all of the mods are about longer life and easier maintenance. Perhaps with the exception of the changed pilot jet? I don’t know if that functions any better than the old one? Even if it does though, I can’t see how that would show itself on the dyno. They’re all good mods though IMHO and I think the Premier is a great carb, in fact I don’t know why anyone would buy a new standard concentric anymore.

The graphs shown are really interesting. @ Madnorton, is the 750 Combat or ‘normal’?

I’m also with you re the FA head Swoosh, I’d have expected the FA 850 to look better, but, of course, we don’t have the ‘pre FA’ graph for the 850 to compare it against unfortunately.

Shame the torque curve is missing, I’d expect to see a noticeable difference in the 850s favour there.
 
Last edited:
The original carbs were poorly machined, and I suspect many were not even close to tolerance before they even saw a drop of fuel.

The 750 is not a combat, original and the owner had not even swapped out the cam. It is running lean though as can be seen from the trace, my 850 was running rich, needles now lowered one slot. The head is FA on the 850, but the valves are standard. I did speak to Steve Maney and he said that the 850 will roll off sooner with standard valves their size is not ideal for the 850 to allow it to breath correctly, but just about right for the 750. The 850 is stiffled by its own design.

I have the torque curve for the 850, and yes it is impressive.
 
The 17 Premier pilot is 17 thou diameter which converts exactly to the old 25 pilot bush which was std for all 4 strokes since the Concentric was introduced, that suggests the Premier changes to the pilot chamber and the route both the air and fuel take has made a subtle but noticeable difference and the 17/25 pilot is now weak at least in the 850. Amal have changed this for the 850, but I have seen the same issue reported on other engines when fitted with premiers so maybe they should all be altered to 19 pilots (which I assume is the old 30 pilot bush).

I converted an old unworn Concentric to the Premier spec and that also was weak on the pilot, so based on a dubious sample of 1 the change is not in the body but the change from a pilot bush to a screw in pilot jet. The path is more restrictive as you have gone from the full fuel gallery feeding the bush to 4 holes at 90 degrees.
 
Yes Kommando, I had to swap out #17 pilots for #19s in my 650 Bonnie‘s 30mm Premiers too.

Given the size info you stated, and the fact that Amal agree with you in their cross reference chart, I’d say you are correct, it is evidence that they are working differently to old Concentrics with regards to the pilot metering.

I also think Madnortons point about better machining and tolerances could have merit, although I’ve no evidence.
 
I have 17 pilot jets in My Premiers on the 750 ... id be interested to know how the 19's perform??
 
Status
Not open for further replies.
Back
Top