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So you think you know all about overhauling carbies eh !!

PostPosted: Sat Jul 30, 2011 4:33 am
by Stuart SS
Well I thought I was reasonably savvy on overhauling carbs ! That was until I got this email from one of our Guru Triple mates, that has just overhauled my #1 set of 626 Trident carbs and gantry !


I’ve finished the T150 complete carb set.

Some points I wish to explain.

The manifold plate the carbs bolt onto was bent by .100” and had to be straightened. I guess this was caused by bolting the manifold using the 2 centre bolts to the air filter plate too tightly by someone?

When you fit them don’t do the bolts up too tight please as it will bend again.

If bent again the carb bodies will distort also.

There should be lock nuts to secure the 2 x 5/16” bolts in place at filter plate.

# 3 float bowl needle seat was lose plus the gasket surface was badly pitted and would have only sucked air and not fuel for the idle circuit so I replaced it with a new bowl and needle seat.

All 3 slides were # 3 cutaway and not 3 ½ cutaway so I have fitted Amal’s new Hard Anodized 3 ½ slides. These will never wear out, trust me, they are brilliant.

# 1 carb had a T160, 5 groove identification needle on the middle clip while # 2 & 3 had worn T150 needles but on the top clip position, and # 2 slide was .080” higher up at rest than the others, not good.

All of the 3 piano wires were bent beyond; well I don’t now what.

All of the float levels were set at 3/16” down way too low plus someone has heated and bent the plastic float needle tangs to try and obtain a correct float level. This should never be done.

I have replaced all 3 floats & float pins with new and re-set the floats to the correct level and fitted Viton Alloy float needles.

All of your main jets flowed much higher than they should have and were closer to 160 mains not 150 mains, so I fitted 3 x new flowed mains and 3 x 106 new needle jets including 3 x T150 new 2 groove identification needles. (T150)

All 3 carby top plates were bent so I straightened those and resurfaced them. All 3 x carby body gasket faces were re-surfaced including the float bowl gasket surfaces including the new one as they stupidly come not flat also.

It is very important the carbs can’t suck air here at the gasket face or else it won’t draw fuel from the bowl feed hole for the idle circuit.

All 3 welch plugs were removed and the mixing chamber under was bead blasted and cleaned; they were chockers with crap. Every carb and associated parts were also bead blasted and cleaned.

# 2 carb had an incorrect short Air Mixture Adjusting screw which would not have worked at all to adjust idle mixture and the others were badly pitted and rusty so I replaced all 3 screws with new O rings.

Your carbs were mounted with 1 3/8” factory O rings to the manifold plate but I’ve since learned the O ring receiver groove in the carby body is never deep enough and causes the carby flange to bow, so I have fitted gaskets to the carbs and not O rings, should seal better and not warp the flanges.

Your carby slide springs; well; while they were the correct light type of spring for a Triple they all varied in length greatly which meant one springs was not anywhere near long enough to be effective so I re-set these to 3 1/2 “ the correct free length.

I replaced your stainless steel spring washers on the 10-32 socket head screws with the correct steel type and removed your stainless 5/16” spring washers on the carby mounting bolts with flat AN washers and fitted 5/16” unf AN self locking nuts. Your 5/16” washers need too much pressure to work correctly plus they will bruise and scuff the bolt face plus the carbs should be fitted with self locking nuts not plain nuts and spring washers.

Remember the carbs are not Alloy but merely Pot Metal or almost Zinc in construction and need to be handled carefully or else they buckle.

All 3 slides are now set equal to each other and shouldn’t need further adjustment; the air screws are set at 1 ¼ turns out each so the only adjustment by you when hot is the final air screw adjustment and idle speed, but, I would try it at 1 ¼ turns out first and only adjust the idle speed screw.

However, if when you first start the bike from dead cold and it spits in the carbs if you have adjusted the air screws out to say 1 ½ to 1 ¾ turns out this means they should be screwed back in to richen the idle, that’s why I have them at 1 ¼ turns out.

If spitting occurs at idle it is Only the air adjuster screws need adjusting in and nothing else.

The throttle gantry bushes were ok so I left them alone to save you some money and only cleaned and re-greased them and fitted new circlips and washers including the correct gantry return spring retaining end washer with the correct item.

The carbies on the complete set are a mixture and are L15, 1969 Trident, R68, 1973-74 Trident and R66, 1973-74 Trident but that doesn’t matter as they were all 27mm bore carbs except someone had fitted rain hat ticklers to the L15 carb.

I haven’t done anything with the 3 lose carbs, do you want me to repair them?

I can supply 3 x re-sleeved Teflon coated 3 ½ slides for this set but it would have to be done first.

Fit new Rain Hat Ticklers.

Re-surface the carby bowl gasket face and manifold faces.

Bead blast all and remove and fit 3 x new 11/32” welch plugs to the mixing chamber.

Chase all threads and true up carby bodies.

Could be another $200.00 + or so, as I don’t have a firm price on the Teflon Coating, as I’ve only played with this surface treatment and wasn’t charged back then.

Let me know please.

Re: So you think you know all about overhauling carbies eh !!

PostPosted: Fri Aug 12, 2011 9:13 am
by Stuart SS
The Super carbs arrived this week ~

Bloody superb finish and quality ~ So glad I decided go with a second set ~


Re: So you think you know all about overhauling carbies eh !!

PostPosted: Sun Aug 21, 2011 3:13 pm
by scubabiker
thats insane, my carb standards go like this, open carb, look in flota bowl, pull out the gunk, shout at the other dirt, put float back on, run new fuel through with drain screw undone. start bike, repeat above every two weeks!
guess i should get my tank de rusted and put a filter in the fuel line.....

Re: So you think you know all about overhauling carbies eh !!

PostPosted: Sun Aug 21, 2011 9:34 pm
by Stuart SS

I agree to a point but when some one can return a fuel consumption on a British 60-70s triple from <35 mpg> to 48 MPG ! ~ I am interested ~

Bob emailed me last night `

Hey Stuart,

Just got home from the Aussie Triples Rally in Ballina. Left Thursday morning and got home Sunday 12.30pm.

Terrific weekend lots of rides and lots of rain, bugger it.

Just did my mileage and fuel check; best highway was 57mpg and best on winding mountain back roads up and down the gearbox was 48.8mpg.

Needles to say I’m pretty happy with that.

Filled up in Ballina rode home and I still have more than half a tank left after 218k’s.

Glad to hear the bike is running fine.

Re: So you think you know all about overhauling carbies eh !!

PostPosted: Sat Aug 27, 2011 10:12 am
by Graham B
"shout at the other dirt" lol that tickled me worm

Stuart - are you using the five scribed ring needles in your Trident? They were a later needle to give better economy and have a longer taper.

Re: So you think you know all about overhauling carbies eh !!

PostPosted: Sat Aug 27, 2011 10:26 am
by Stuart SS
"shout at the other dirt" lol that tickled me

Almost as classic at "Talk to the Hand!"

Ironically when I fitted the Super carbs there was an issue and so I refitted my own rebuild set and they work just fine .. and furthermore mine were based as the template for the Super carbs! (That is the needles, main jets and slides are all stock !

But in both sets the needles are stock three notch T150/ A75 !

As far as my knowledge base goes, Graham , the alternative needles were fitted to T160's so as to allow fine tweaking of the #4 slides which were fitted to the T160 ~ And the 3 1/2 slides as fitted to the T150/ A75's were a more flexible and tolerant original fixture ~

I noted this afternoon as I checked over the bike for a short club outing tomorrow morning that fuel levels were in fact excellent ~

Bob; who built the Super carbs did a number of precision tests on his own triple Amals and returned 48.8 mpg! And if anyone has any knowledge of triples the best stock fuel return is about .. on a good day <35 mpg> !

Re: So you think you know all about overhauling carbies eh !!

PostPosted: Wed Dec 26, 2012 1:26 pm
by Alext900
almost impossible for so much to be owed to so few people who really know Carbs!

Re: So you think you know all about overhauling carbies eh !!

PostPosted: Thu Dec 27, 2012 3:49 am
by Stuart SS
almost impossible for so much to be owed to so few people who really know Carbs!

WHaarrrttt the ????????????