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Near fatal encounter with a new Premier Amal 928

craig

Well Known and Active Forum Website User
VOC Member
I was having problems with my 3 year old Amal 928 on my Comet. I had recently run some contaminated gasoline thru it and clogged up the low speed portion.
This Amal had performed well with the following settings for years running my local 10% ethanol -
Amal 928 with fixed low speed jet
Slide marked 3½
needle marked two grooves
Main jet 250
106 needle jet
standard, uncut spray tube
Extended screw for low speed
Extended screw for idle slide set
So I had a new Amal 928 Premier sitting for install on a Rapide, but it was going to be a while, and I thought “why not install this new Premier 928 on the Comet?” This new Premier had been purchased with a new hard anodized slide 3½, RJ17 low speed jet and two groove needle. So I fitted this new Premier with a 250 main, 106 needle jet and the extended screws.
All this time on the Comet, I guess for the last 2 years, I have been running a TTO temp readout, about $40 off Ebay. This readout installs under the spark plug, pretty easy. So I have a general feel for what the temperature at the spark plug gasket would read in normal Comet service. The reason initially for the temp readout was my local rides included some long steep inclined hills, nice paved roads, but steep for couple miles. These readings are in degrees F.
So my riding style on a normal day temp of 70 deg F running on flat and rolling roads the TTO reads between 260 and 310, depending on speed, load, etc……..whenever I start a long hill climb the temp rises quickly to 320 and on up to 350-370 by the end of climb. I remember doing a very long climb and reaching 390. This temp is at the sparkplug gasket!
So I installed the new Premier Amal 928 and fired the Comet up. Temp in shop and outside was 50 degF. I had trouble trying to set low speed, seems nothing would smooth this out, probably 10 minutes of run while strapped to the lift table with fan running maybe less. I finally looked at the TTO and it was reading 330degF, I looked at the pipe which was beautiful chrome (2 years) and it was starting to blue! So shut off and figured low speed jet was too small, had an new RJ19 lo speed, so switched out. No discernible change at all. So I thought I wil take this out for a short ride maybe that is the issue, 50deg. As I was riding about , at nite, I had to tape a led flashlight to my helmet, but the TTO reading were ranging 350-370, just putting around! Insane!
So my fix was to go back to the original clogged 928 and clean it and install. Which I did, but because the new Premier slide and needle looked so good , I left them installed and put these into the standard, now clean 928. Fired up the Comet and found the idle more adjustable…………….but the temp problem was only moderately reduced to what I experienced in the recent past at 50deg. I put a few miles on this setup, but I knew I was faced with a 120 mile run with a steep hill, so I was still nervous.
So I changed the slide out for the original chrome plated and the needle two groove and YIPPEE, everything was resolved. Idle easy to tune and set, temperatures radically lowered to original temperature ranges. I am not sure what was learned from this but sumpthin aint right!
Cheers
Craig
 
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vibrac

Well Known and Active Forum Website User
VOC Member
Ah !(a bit of google required) now I understand a "premier" is a revamped MK1 concentric what is it they say?.... you cant make a silk purse out of a sows ear?
 

usefulidiot

Well Known and Active Forum Website User
Non-VOC Member
sounds to me like an air leak with that combination. I had an amal premier on my Norton Atlas that exhibited similar symptoms that ended up being a warped mounting flange causing an air leak. Almost sounds like your problem is the fit of the slide to the carb body.
 

ClassicBiker

Well Known and Active Forum Website User
VOC Member
sounds to me like an air leak with that combination. I had an amal premier on my Norton Atlas that exhibited similar symptoms that ended up being a warped mounting flange causing an air leak. Almost sounds like your problem is the fit of the slide to the carb body.

I think you're on the right track there Useful. Measure both bores and slides and determine all the possible radial clearances as Craig said he put the new slide and needle in the old 928. Myself I would also compare the needles and other components.
Let us know what you find out Craig.
Steven
 
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