The Triumph Dolomite Club - Discussion Forum

The Number One Club for owners of Triumph's range of small saloons from the 1960s and 1970s.
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 Post subject: SU CARBS
PostPosted: Wed Oct 10, 2018 10:23 am 
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Joined: Tue Jan 18, 2011 11:22 am
Posts: 60
HELP my Dolly SE failed its MoT due to emissions. Having the non adjustable wax stat SUs means there is no easy way to adjust them. Did remove air filters, thinking they could be choking the engine, opened CB points to 15thou. But car now will not rev. No idea what I have done. Also dash pot oil levels keep disappearing.

Anyway, to get car up and running has anybody got a decent pair of SU carbs for the 1500 range with the adjustable jets?

Thanks in advance

Steve - Dolly Mix Editor.....


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 Post subject: Re: SU CARBS
PostPosted: Wed Oct 10, 2018 10:32 am 
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Joined: Wed Nov 15, 2017 3:35 pm
Posts: 315
Location: Halifax, West Yorkshire
I could be wrong, but the waxstat carbs I had on my 1500 Spitfire were certainly adjustable. (Even before I did the penny modification on the jets)

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 Post subject: Re: SU CARBS
PostPosted: Wed Oct 10, 2018 3:26 pm 
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Joined: Sun Oct 26, 2008 7:26 am
Posts: 1921
I have waxstat HS6's on my Toledo. And yes, they are adjustable.
(I know some later strombergs need a special allen key for mixture adjustment, but not SU's)

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Clive Senior
Brighton
Driving Toledo fitted with slant 4, sprint OD box and axle. Needs fettling!


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 Post subject: Re: SU CARBS
PostPosted: Wed Oct 10, 2018 4:45 pm 
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Joined: Thu Sep 28, 2006 9:06 pm
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Location: Bristol
When it is stated that the later jets are not adjustable I believe it is just that there is a plastic cover over the adjusting nut which can be broken off to adjust the jet.


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 Post subject: Re: SU CARBS
PostPosted: Tue Oct 16, 2018 11:05 am 
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Joined: Tue Jan 18, 2011 11:22 am
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After fiddling with timing and removing air filters, slowing tick over right down to almost stalling, it passed an MoT. But I suppose the only way to see if these carbs are adjustable is to get them off and on to the bench? i do remember reading ages ago about getting the wax unit off and sticking a 1p piece in the base of unit.

For now i have speeded up tickover again and will leave the things alone!!!


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 Post subject: Re: SU CARBS
PostPosted: Tue Oct 16, 2018 12:08 pm 
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Location: Bristol
I think if you take the air box off you will be able to see the plastic that needs to be broken off to get at the adjusting nuts. Then it is just a matter of winding it up to reduce to CO emissions.


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 Post subject: Re: SU CARBS
PostPosted: Tue Oct 16, 2018 12:47 pm 
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Posts: 315
Location: Halifax, West Yorkshire
An unmodified waxstat will "self adjust" by a TINY amount depending on temperature. But they aren't very good, so many people "knobble" them to stop them adjusting and then simply adjust the carb for warm running conditions.

Image

The bit marked in red is the mixture adjustment on an HS carb with waxstat jets.

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 Post subject: Re: SU CARBS
PostPosted: Tue Oct 16, 2018 1:17 pm 
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Joined: Thu Sep 28, 2006 9:06 pm
Posts: 787
Location: Bristol
We are assuming that it was the CO emissions on which your failed. One of my 1500hl dolomites passed it MoT yesterday it's CO emissions reading was 3.741 and the hydrocarbons 258. I am always surprised how low the hydrocarbons reads are as my cars do burn some oil. They must just be very good a burning the oil!

What sort of reading do other owners get ?

The car did not require to have a MoT as it is a 1977 car but for insurance purposes I will continue to take my cars in for MoTs. I was glad to see that the DVLA sent me a MoT reminder even though the car did not need one to be driven on the road. For anyone that does not know you have to request to be sent a reminder if you want this service.

I do not have a problem with correct set up waxstat jets.


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 Post subject: Re: SU CARBS
PostPosted: Tue Oct 16, 2018 1:37 pm 
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Joined: Thu Sep 28, 2006 12:13 pm
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Location: Over here...can't you see me?
The tester is allowed to test twin SU set ups at 2000 rpm to alleviate one set of high readings as some carbs cannot be set to run properly at idle and pass the emissions test. As time goes on, fewer testers are aware of this.

Another tester instructed me to remove the air filter from a Sprint before he re-tested the emissions as a slightly damp less than new filter on a car that isn't used much can apparently affect readings; second time it passed with no further adjustments.


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 Post subject: Re: SU CARBS
PostPosted: Thu Oct 18, 2018 3:34 pm 
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Joined: Tue Jan 18, 2011 11:22 am
Posts: 60
Thanks one and all. Car did pass the MoT - removed air filters etc. Will take off air box again - it's a pain especially the bolt at back hidden by servo. Then will remove that plastic tamper cover and weaken mixture a bit more. If nothing else it will improve MPG!


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