In a foul mood....

[Motu]

Its seriously rich at idle / off idle - say 2,000 rpm in 4th (pootling speed)

What cutaway do you have? Normally Triumphs do well with a richer cutaway,like a 3 instead of 3.5.It's easy to richen them,just file a bit off the bottom....to lean you have to file the cutaway.But rich at those speeds is a bit odd.

Do you have the late model primary case with the cover you remove to do strobe timing? I'd run it up at those revs and see what the timing is doing....it could be advancing up too early,or late....or fluctuating.Just because you set it at idle or max advance doesn't mean it's doing it right at 2,000rpm.I chased this exact problem for years on the XS1 - I was sure it was carbs and went to Mikuni's,then Blue Magnums,then a good set of original carbs.After a couple of years of major mucking around I found it was retarded just off idle.But this gave an apparent lean condition...rich is a different matter.And it was points with mech advance.

I did have a concentric that ran rich at idle - strange,it was good as a single carb,but was way off when run as one of twin carbs.If it was a Mikuni you could change the primary jet......so how can you do that on an Amal...?...?

[koba]

Actually - thats not daft - I'll check the breather tonight. Thanks

I remember some of the old buggers around here getting very tecnical about breathing on old triumph twins, somthing about a more restictive US market system that made 'em run shit for the sake of emmisions control....

Not really adding anything here, just rambling!

[FROSTY:Me]

How long between rides is it?Is it possible that the fuel is sitting in your tank too long and going off?
If what the poster above suggests doesn't work try buying 20l of avgas and running the bike on that.If it settles down then you've found your problem.

wot he said

[Paul in NZ]

Pretty sure the gas is OK (well its not OK but its as good as it gets here)

Soo... I got mr magnifying glass out.... The float needle (fuel cut off) was 'scuffed' on the rubber tip so i replaced it with a used spare in better condition (old coots never throw anything out).

I dropped the float level slightly (much debate in some circles where it should be and its a pia to measure / change), set the valve clearances back to where they should be (opened em up in case one was not sealing) and fitted new plugs - Instantly 75% better pootling ability even without twiddling......

Still a bit sooty on the new plugs so I re advanced the ign to try and keep a bit more heat in there to get the plugs to self clean. Little inprovements but not so foul tonight by a long way!

Next I will order a new needle and needle valve (prob $30 or so) and continue to tinker...

[Paul in NZ]

wot he said

Good to see ya back Tony? I thought you were off some place?

[FROSTY:Me]

welcolm to the hotel kiwibiker. You can check out any time you like.--but you can never leave.
HOTEL KIWIBIKER UNDER NEW MANAGEMENT-- nuff said?

[pete376403]

AMAL? AKA the metered leak? Stick a Mikuni on it.
I had a (very) high compression single that originally came with a Del'Orto. Useless thing was replaced with an Amal mk II which was equally useless. That in turn replaced with a 40mm Mikuni. Not only did it make more power than ever, it would even idle at about 1500 and could be started by flicking the back wheel while on the pit stand.

(was a Jawa 4V speedway bike, about 14.5:1 compression and running methanol)

[Motu]

Ha! Wouldn't you know it....I'm chasing the very same thing with my latest acquisition,a 1977 TL125.I cleaned the carb last week,and the filter disintegrated.So last night I made a new element,oiled and fitted it tonight.I have a really bad stalling flatspot off idle,not good on a trials bike - and I can't get a steady consistent idle....keeps changing.Someone has made a really nice billet manifold spacer,but that will feed heat into the carb.....is that going to be good or bad I wonder?

Right,off to the TL125 forums to see how they cure flatspots - I know they have them,because my much more refined TLR200 is prone to the problem too.

[stanko]

Have you tried putting the old carbs back on?

[Paul in NZ]

Have you tried putting the old carbs back on?

Carbs? Whats this carbs thing - a gentleman only needs one...

Besides - after the wed night ride - down the drive and it idled like a good un.. sweet....

[F5 Dave]

Motu
I've made to odd filter but never had much joy & found a new or 2nd hand one worked properly, even when using unipro filter foam. Sometimes the internal drillings can be a sod to clean out (perhaps bits of old filter?)

I would imagine the billet manifold would be a nice source of vibration to froth the fuel. Mind you I can't imagine the original Honda resin thingy was much betterer.

Old bike, check the emulsion tube for wear.

[Motu]

Yes,I've used Uni foam - I have other foam,but it goes out of shape with oil.I use this dry for precleaners.Something inbetween is needed.

After setting the float level last night and double checking my rechecks,I used the old standby - turning off the gas.As it runs out of fuel the motor revs up and runs sweet.A sure sign of richness - I was sure it was lean.They say an XR100 carb sorts these TL125's out,same with the TLR too.Another weekend in the shed....but it's so damn hot in there!

So that's another trick to try Paul - turn the gas off at the trouble spot and see if it runs better or just dies.Tickle to richen.....I how I miss the tickler.....

[Paul in NZ]

I should post a link to the most amazing amal tuning guide ever - astonishing info - but I can't find it - just as well I have a paper copy...

Had a long chat with a hexpert in these matters (a man who not only runs classics to die for but whos everyday mech transport is a preunit 650 with sidecar)... He assures me I'm an idiot.. (adds to his credentials) as he has told me previously to run hotter plugs as the unleaded gas runs 400F cooler (than I cannot believe) and impairs the self cleaning ability of the plugs.. Whats more - when the unleaded 1st came out NGK advised the trade they would need to go 1 grade hotter to avoid low speed fouling.

he runs 2 grades hotter no prob in the outfit so I'm very safe going 1 ...

Interesting though!

[riffer]

So I was bloody right!!

Hah!

It is the bloody unleaded fuel at fault.

And you thought i was taking the piss.

[Motu]

So how come the pre ignition with unleaded? You'd think running cooler there would be no problems.None of my old cars (Falcons,Escorts,BMC's etc) would run on unleaded without octane boosters....or retarded timing.The plugs look like they are running cooler,being black and all that....but I dunno if I'd take the risk.But I run the Lada 5 degrees advanced and use a plug that spans 2 heat ranges,standard and one up....and it's factory lean.

Try some race or aviation fuel,if that fixes it then you can stand with the fuddy duddies moaning about unleaded ruining their bikes.