amals

Err apologies for the late reply , and thanks for the responses.
They are 32`s not 34`s my mistake.
Ive measured the gaps between the slide body and slide with feeler gauges and it varies from 0.3mm to 0.5mm. the slides are 34.80mm to 34.88mm diameter.
Greased the slides and restarted, no difference noticed.
I guess I`ll have to spend some cash and go for the premiers.

blacklav said:

Err apologies for the late reply , and thanks for the responses.
They are 32`s not 34`s my mistake.
Ive measured the gaps between the slide body and slide with feeler gauges and it varies from 0.3mm to 0.5mm. the slides are 34.80mm to 34.88mm diameter.
Greased the slides and restarted, no difference noticed.
I guess I`ll have to spend some cash and go for the premiers.

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Hi blacklav
Thanks for the update/correction. The knicker twisters can stand-down now.
The slides are in the range of the half dozen I just measured.
Before you spend big money, make sure the pilot jet bush is not blocked and the two pin holes either side of the slide skirt are clear on both carbys.
If you do proceed with the purchase of premiers, how much do you want for the ones you currently have? PM me a price.
Ta.
PS: A while ago, I found a throttle twist that fouled the housing and would not allow slides to fully seat. Found this by allowing slides to seat without cables attached and the bike ran better.

needing said:

Thanks for the update/correction. The knicker twisters can stand-down now.

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Or maybe thats the proofreaders here have proved their worth,
and demonstrated once again they they (alone ?) are on the ball. :mrgreen:

Its possible to buy new slides, and apparently anodised slides even.
Could be worth a try, if new carbs aren't entirely necessary yet.
Carbs can be resleeved also, and this makes them as good as new again.
The comparative cost against new carbs is a consideration though.
hth.

Grease on slides can tell ya how much that area temporary fix improves things to predict benefit of new slides but if grease really made a difference, especially on nice fast idle down stabiltiy then likely are bores worn too so can order anodized with one less cut out number which can then be finer tuned with a file but might like the crisper low end response to leave em be like me. I was surprised plain ole red axle grease lasted a couple roadster tanks before not idle down and boggy annoying again. If anything the grease made easier throttle return no restrictive risk at all. Do note carb bores can get oval shaped as well as fluted.

Hi Guys. When I renewed all the jets and needles I blew out all holes with high pressure air hose and replaced the fuel filters.
It still would not tick over reliably under 1200rpm. Ive rechecked the ignition timing - which is boyer - and the spark plugs are of the correct colour at all ranges, except tick over when they have to be rich.
I`ll get the new carbs soon and NEEDLES I`ll pm you if I decide to sell them.
thanks
chris r

I suspect you are correct that they are 32, not 34. But I feel compelled to point out that you can fit two of the 1000 series to a Commando. It takes special manifolds and rubber connectors, and you certainly can't fit an air box. I tried a pair of 36 mm 1000 carbs on my PR way back in the day. They came off a Norton flat track bike I bought, and actually worked pretty well. Also had to use different throttle setup to get enough travel. I later switched to a pair of 34 mm MK2 Amals bored out to 36mm. Fit great, and worked well with 920 engine.

Maybe a picky point, but I'm sitting here at the rally in the middle of a thunderstorm, with nothing else to do but nitpick.

Ken

Oops! Missed reading a couple posts before I replied. Sorry about that.

Ken

If you've already replaced all the innards that wear out, it would be more cost effective now to just have the slides sleeved and the bores trued at Lund's or similar. If you were going from scratch, Premiers would be cheaper. At least that's what I figured out. I thought I could get by with just the anodized slides, but no, so I sold them for half price barely used. I had already replaced the floats, jets and needles in hopes of making it work on the cheap.

blacklav said:

Ever since I bought my 1974 mk 11a 850 it has had a mind of its own when at idle. Sometimes its ok , then when you want it to idle,say at lights, it stalls. Also if you give the throttle a quick blip, it will splutter. Its ok if you rev it gradually, just not too fast.
I`m assuming the carb slides are worn out, as when I fit them there is a good 0.5 to 1mm side to side movement in the throttle body. Is this normal?
The motor has had new valves ,guides and springs plus a pw3 cam. This made no difference to the idle which will not go below 1100rpm.
The carbs are amal 34mm and have only done 9000 miles. I have replaced all jets and needles.
Any ideas,
thanks

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TRY THIS:

Start the bike, dial the idle stop screws up to the lowest rpm that will maintain the engine running.
dial one of the idle air screws inward until the engine begins to stumble.
Slowly twist the throttle so it only moves up to 1/4 throttle and then lower it back
Turn the idle screw out 1/8th of a turn and lift the throttle up to 1/4 throttle again and lower it.... did it feel smoother?
Again turn the idle air screw out another 1/8th of a turn and again lift the throttle to 1/4 throttle....
Continue doing that until the engine begins to run roughly and you know you've passed the best placement for that Idle air screw
Work backward to find the spot where the screw position was that made the tickover transition the smoothest to 1/4 throttle.
NOW do the same procedure to the other carb, exactly the same way.

See if you can now back the idle stop screw down to lower the idle and get a more stable lower idle...

Also,...... The reason I say to do it this way is that at a dead idle, the idle screw has usually about 3/4 of a turn where it seems like it's ok, but seems like it's not changing anything. What is different across this 3/4 of a turn range, is how smoothly the engine accellerates from idle to 1/4 throttle, so you have to keep lifting the throttle to dial in the idle screw position.

Float needle seat height also effects idle. You should use the site's search engine to look it up and read about it

the only other thing I would suggest is retard the ignition timing a few degrees and see if that helps your idle.

HTH...