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Amal Carbs #783781 09/08/19 4:22 pm
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SJS Offline OP
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Hi there. The benefit of superior minds appreciated !
Scenario - T160 - Brand new AMAL Carbs fitted, factory set needle positions and jets. The Factory Workshop manual says you should set tick over with throttle fully shut and adjust air screws on carbs from an initial 2 turns out from fully screwed in. I've done this by increments of half turns in and out from this setting even so far as 3 turns out but seems to have no real effect on tick over control. The only adjustment I can use to get a good static ticker ( engine warm ) is by the gantry adjuster screw. I assume standard tick over to be 1000 rpm.
Questions:
1. Should it be possible to adjust tick over purely by adjustment of the air screws with a closed throttle and if so how far out would you expect to screw them to be achieving this on average.
2. Would you expect to fine tune tick over adjustment by screwing in the gantry adjuster screw in conjunction with the air screws and if so at what adjustment of the air screws would you set them ( turns out from fully in ) if they alone cannot set the tick over.

Many thanks
Steve

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Re: Amal Carbs [Re: SJS] #783784 09/08/19 4:34 pm
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The pilot air screws are for adjusting the idle mixture, not for setting RPM.

Last edited by L.A.B.; 09/08/19 5:37 pm.
Re: Amal Carbs [Re: L.A.B.] #783793 09/08/19 6:57 pm
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SJS Offline OP
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Yeh but the ability to idle the engine, transposes to an rpm suitable for tick over which is around 750 - 1000 rpm.
But thats not my point. My point is, the book says you can idle the engine speed off the throttle, namely fully shut position, to tick over purely by adjusting the air screw settings, the start point of which is 2 turns out from fully in.

Re: Amal Carbs [Re: SJS] #783795 09/08/19 7:24 pm
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Originally Posted by SJS
My point is, the book says you can idle the engine speed off the throttle, namely fully shut position, to tick over purely by adjusting the air screw settings, the start point of which is 2 turns out from fully in.


Which section of the factory manual?
http://www.classicbike.biz/Triumph/Repair/Trident/1975Triumph-T160.pdf

Re: Amal Carbs [Re: SJS] #783804 09/08/19 10:30 pm
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L.A.B is correct! The throttle stop is located on the gantry figure B10 page B14 illustrated as "H". As L.A.B. said, the pilot air screw adjustment sets the idle fuel mixture. You turn it in and out looking for the highest idle (and best throttle response from idle). You then set the final isle with the throttle sop screw on the gantry. Read page B16 "SLOW RUNNING"


Re: Amal Carbs [Re: SJS] #783851 09/09/19 3:38 pm
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Its worth noting that you need to balance the carbs, the manual for the Rocket 3 suggests usings 3 rods to do this with, moving the gantry will indicate if one slide is higher than the other... Unlike with none gantry carbs, you don't adjust the/a throttle stop screw (if there is one on the 627). Vacuum gauges will be better for this if you can accomodate them. a colour tune will give you the best method of checking your idle mixture, when the idle mixture is correct the engine will run at its fastest..... This doesn't mean you slow it down again by enrichening or weakening the mixture... the position of the slide denotes this and if the slides are balanced then you slow the whole lot down on the gantry as John and L.A.B mentions above.


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Re: Amal Carbs [Re: SJS] #783862 09/09/19 6:13 pm
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There should be no throttle-stop screw on carbs for triples, the throttle stop on the gantry sets idle speed. I have read that worn bushings on the gantry can adversely affect idle and synchronization.
About the best most of us can do to synchronize is to inspect the slide heights from the engine side with the complete assembly on the bench. Using vacuum gauges requires installing small tubes in the bottom of the manifold. Though I have been able to check with a Unisyn if I can manage to keep the bike running without the airbox on.
Setting idle mixture on triples is a bit fiddly. Set to lowest steady idle, then turn each screw the same way by the same amount to see what happens. A Color Tune might be nice, but swapping it around between cylinders is still a bother.
BTW: The engine must be fully warm with chokes fully off to make this adjustment. It would be wise to ensure that all three choke slides are fully retracted with the lever engaged.


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Re: Amal Carbs [Re: DavidP] #783869 09/09/19 7:39 pm
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Hi, thanks for replies. The crux of my point regarding the pilot screw settings is that they have an influence on the idle speed ( RPM ), its states that in the Factory Workshop manual that I have and I quote: " Pilot Mixture - It may be necessary to make small adjustments to the pilot mixture to suit different climatic conditions and give good idling ".
I know and fully understand that the gantry screw can and is used to also fine adjust the idling speed but after the optimum pilot screw setting has been achieved.
Again, my point was how do you know what setting for the pilot screws in isolation, is correct from the base adjustment of 2 turns out from fully in. I was assuming that their adjustment would materialise in a higher or lower idle speed ( RPM ). My experience of any adjustment to them doesn't materialise in any noticeable effect on idling speed to the extent that with a fully closed throttle, I cannot get the engine to idle on their setting alone. I'll pursue some of the advice given here and see how it goes. Thanks for replies and advice.

Re: Amal Carbs [Re: SJS] #783871 09/09/19 7:58 pm
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"My experience of any adjustment to them doesn't materialise in any noticeable effect on idling speed to the extent that with a fully closed throttle"

Nor should you!!!!!!!!!!!!!!!!!!!!!! They are not related in a discussion about setting idle speed. Only the throttle stop can set the idle speed.

The pilot air screw adjusts the idle air/fuel mixture. The typical pilot air screw will end up around 1 1/2 turns out from fully seated. If you screw it in or out from that point the engine should start to stumble. You are looking for smooth running and the ability to take throttle without stumbling (too rich - screw in too far) or stalling (too lean - screw out to far). You are not looking at the idle speed. When you get the pilot air screws adjusted then you adjust the idle speed using the throttle stop screw on the gantry.

Time for control-alt-delete with that factory manual.


Re: Amal Carbs [Re: SJS] #783872 09/09/19 8:36 pm
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Originally Posted by SJS
The crux of my point regarding the pilot screw settings is that they have an influence on the idle speed ( RPM ), its states that in the Factory Workshop Manual that I have and I quote: " Pilot Mixture - It may be necessary to make small adjustments to the pilot mixture to suit different climatic conditions and give good idling ".


Yes, to give a good steady idle.

Originally Posted by SJS
I know and fully understand that the gantry screw can and is used to also fine adjust the idling speed but after the optimum pilot screw setting has been achieved.


Not quite. It states in the manual under slow running: "Following adjustments to the pilot mixture, the engine idling speed may require re-adjustment." note it says RE-adjustment so the adjuster (H) is used to set idle speed both before and after pilot air screw adjustment.

It appears you are under the impression the idle speed can be set only by the pilot air screws (with the adjuster H backed off) which is not correct.


Originally Posted by SJS
Again, my point was how do you know what setting for the pilot screws in isolation, is correct from the base adjustment of 2 turns out from fully in.


Set the pilot air screws to give the smoothest running once the engine has been fully warmed up and also check there is no hesitation or stumbling as the slides begin to lift.
If you cannot detect any noticeable change in the quality of the idle then just leave them 2 turns out.

Originally Posted by SJS
I was assuming that their adjustment would materialise in a higher or lower idle speed ( RPM ).


There may be some slight change in RPM during pilot adjustment but not as much as you seem to think.

Originally Posted by SJS
My experience of any adjustment to them doesn't materialise in any noticeable effect on idling speed


Exactly. Turning the pilot air screws within their normal range of adjustment probably won't have all that much noticeable effect on RPM.

Originally Posted by SJS
to the extent that with a fully closed throttle, I cannot get the engine to idle on their setting alone.


....Which is what we've been saying as it isn't what the pilot screws are for.

Last edited by L.A.B.; 09/09/19 9:51 pm.
Re: Amal Carbs [Re: L.A.B.] #783921 09/10/19 5:20 pm
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Thanks for that. I knew that I'd read something somewhere which lead me to my initial conclusions on the pilot screw adjustment and this was on the AMAL Carb Literature that comes with the new carbs. In it there is a section on Parts to Tune Up - Throttle Adjusting screw ( 26 on their diagram ) Set this screw to hold the throttle open sufficiently to keep the engine running when the twist grip is off. An O ring is fitted to the screw to hold this adjustment.
I've only got the one screw adjuster on each carb which corresponds to their exploded diagram layout as 26 which they describe as Throttle Adjusting Screw so I'm maybe mixing up terminology with Pilot Screw as seems to be referred to in the Triumph blurb as the same thing ??
Either way, it doesn't respond in the manner AMAL say it should above.

Re: Amal Carbs [Re: SJS] #783923 09/10/19 5:35 pm
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Originally Posted by SJS
I knew that I'd read something somewhere which lead me to my initial conclusions on the pilot screw adjustment and this was on the AMAL Carb Literature that comes with the new carbs. In it there is a section on Parts to Tune Up - Throttle Adjusting screw ( 26 on their diagram ) Set this screw to hold the throttle open sufficiently to keep the engine running when the twist grip is off.


That explains it.
Individual Concentric carbs normally have a throttle stop screw (angled).......

[Linked Image from fagengine.com]

and....a pilot air screw
[Linked Image from fagengine.com]

Therefore, your AMAL diagram should show or list both screws?

Specific Triumph triple carbs, however, do not have individual throttle stop screws because all three carb slides are operated by the gantry linkage so the throttle stop for these carbs is the gantry screw 'H'.



Last edited by L.A.B.; 09/10/19 8:18 pm.
Re: Amal Carbs [Re: L.A.B.] #783977 09/11/19 1:33 pm
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Brilliant, thanks for that. I've basically been reading two different sets of info which have confused the issue, certainly for me. My emphasis had been on the AMAL instructions and interpreting their Throttle Screw function to that of a Pilot Screw adjustment. All a bit irrelevant now anyway as went for very short test ride to discover that the gear selection is not working properly ! Was always fine when the bike was last up and running, albeit that was 5 years ago. Will have to assume some sort of lack of use issue or plunger spring issues. Have completely backed off the neutral light switch which I've learned can give similar symptoms but that hasn't improved things. Note that in Neutral position, the lever has quite a bit up and down "play" before it clicks into a gear selection, is that "normal". Annoying but its all part of the game to a certain extent to which we are all afflicted to greater or lesser degrees but it really does test your patience at times. All I want to do now is just ride it, not muck about with it anymore ! I've done 90% of the task but might have to seek more experienced assistance to get that final 10%. Which companies / individuals are generally recognised as T160 gurus here in UK in case I decide to take that option to sort out these last few snagging issues ? Thanks again for previous advice.

Re: Amal Carbs [Re: SJS] #783980 09/11/19 2:06 pm
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Originally Posted by SJS
Brilliant, thanks for that. I've basically been reading two different sets of info which have confused the issue, certainly for me. My emphasis had been on the AMAL instructions and interpreting their Throttle Screw function to that of a Pilot Screw adjustment.


smile


Originally Posted by SJS
Note that in Neutral position, the lever has quite a bit up and down "play" before it clicks into a gear selection, is that "normal".


I wouldn't say it was normal. Possibly something in the cross-shaft mechanism is loose. The cross-shaft quadrant (57-4926) becoming a loose fit on the cross-shaft inside the primary case would be one possibility.


Originally Posted by SJS
Which companies / individuals are generally recognised as T160 gurus here in UK in case I decide to take that option to sort out these last few snagging issues ?


As you're in Northampton then not too far from:

https://www.3dmotorcycles.co.uk/

Re: Amal Carbs [Re: SJS] #784082 09/12/19 7:48 pm
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Thanks again. Certainly look like they know what they're doing ! If I end up with a gearbox in bits and can't put it back together, we're off to Wolverhampton !
With regard to my gear change issue, my plan is to change every spring and plunger involved in system and hope that solves the issue.
There's just one item I can't seem to identify from any manuals. On page A7 of the Triumph manual there is a diagram showing the underside of the engine and gearbox. What is the protruding bolt affair thats immediately adjacent to the drain plug ? It looks suspiciously like some sort of gear change plunger affair in which case I need to give it some attention. Thanks Steve

Re: Amal Carbs [Re: SJS] #784083 09/12/19 8:05 pm
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Originally Posted by SJS
There's just one item I can't seem to identify from any manuals. On page A7 of the Triumph manual there is a diagram showing the underside of the engine and gearbox. What is the protruding bolt affair thats immediately adjacent to the drain plug ? It looks suspiciously like some sort of gear change plunger affair in which case I need to give it some attention.


Yes, camplate plunger housing.
http://www.classicbike.biz/Triumph/Parts/Trident/1975T160PartsManual.pdf
pdf p.32
Fig. 10
Item 32.

Re: Amal Carbs [Re: SJS] #784100 09/13/19 12:52 am
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And re the plunger, there is some discussion on which tip is the best for gear operation. There are wedges, sharpish points, and rounded points...……….sorry I can't remember which one was considered the better option. There are also a couple of versions of camplate. Round and wedge shaped. Somebody else here will chime in.
All I know is I have no issues with mine.

Last edited by tridentt150v; 09/13/19 12:53 am.
Re: Amal Carbs [Re: SJS] #784158 09/13/19 2:46 pm
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Right, more expenditure to LP Williams pension fund, new springs and plungers on the way but Sods Law, the bike seems to be changing gear OK now. Not gone out on road for proper test yet but can get up into 3rd OK down my drive. Will go out early tomorrow morning before the Saturday Nutters are all out in shopping mode and hopefully, game on. Thanks to everyone for your help and advice, if there was a virtual pub here, I'd buy you all a virtual beer !


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