The Triumph Dolomite Club - Discussion Forum

The Number One Club for owners of Triumph's range of small saloons from the 1960s and 1970s.
It is currently Thu Mar 28, 2024 12:43 pm

All times are UTC




Post new topic  Reply to topic  [ 21 posts ]  Go to page 1 2 Next
Author Message
PostPosted: Tue May 08, 2018 3:28 pm 
Offline
TDC Member
User avatar

Joined: Fri Apr 15, 2016 11:08 am
Posts: 691
Location: Ayrshire, Scotland
My 1850HL has the twin SU HS4 carbs. I am not unfamiliar with SU carbs having owned several MGs. I have had the carbs to pieces, cleaned them, fitted solid butterfly discs, and put two one penny coins in place of the waxstats. The pistons both move freely and I have fitted new ABK needles. The linkages are all working properly and the jets are not being held in the lowered position.

BUT the engine is incredibly rich. Even with the jets wound right up to the highest position, so they are actually sticking out slightly above the bridge, the mixture is much too rich. Pressing up the lifting pin a tiny amount just increases the revs, and my Gunsons gastester shows a CO level of over 6%. It will never pass an MOT.

I'm baffled. Any suggestions?

_________________
Mike
(1969 MGB GTV8, 1977 Dolomite 1850HL, 1971 MGB roadster now all three on the road)


Top
   
PostPosted: Tue May 08, 2018 4:11 pm 
Offline
TDC Member
User avatar

Joined: Wed Nov 15, 2017 3:35 pm
Posts: 956
Location: Filey, North Yorkshire
Is the level in the float chambers about right? It's not over-filling and peeing fuel out of the jets?

_________________
Image


Top
   
PostPosted: Tue May 08, 2018 4:40 pm 
You need to find out which carb is running rich, a Colortune would do it.

I had something similar which was a duff jet.


Top
   
PostPosted: Tue May 08, 2018 4:50 pm 
Offline
TDC Member
User avatar

Joined: Fri Apr 15, 2016 11:08 am
Posts: 691
Location: Ayrshire, Scotland
Quote:
Is the level in the float chambers about right? It's not over-filling and peeing fuel out of the jets?
Well I'm not sure what the right level is, but the plastic floats aren't adjustable anyway, or are they? In the SU instructions which I have it says that "The fuel level is not critical and need not be treated with meticulous accuracy - the normal level is 3/8 inch under the rectangular inner facing known as the jet bridge, but this is rather difficult to observe even with the suction chamber and piston removed and the jet fully dropped."

It then goes on to say how to use a 5/16 inch rod to check the float position when the needle valve is shut off and to bend the metal support if it needs correcting, but you can't do that with plastic floats.

_________________
Mike
(1969 MGB GTV8, 1977 Dolomite 1850HL, 1971 MGB roadster now all three on the road)


Top
   
PostPosted: Tue May 08, 2018 4:51 pm 
Offline
TDC Member
User avatar

Joined: Fri Apr 15, 2016 11:08 am
Posts: 691
Location: Ayrshire, Scotland
Quote:
You need to find out which carb is running rich, a Colortune would do it.

I had something similar which was a duff jet.
It is both carbs. That's what's so strange. All plugs are sooty black even with the jets on both carbs turned right up as high as they go.

_________________
Mike
(1969 MGB GTV8, 1977 Dolomite 1850HL, 1971 MGB roadster now all three on the road)


Top
   
PostPosted: Tue May 08, 2018 6:21 pm 
Offline
Future Club member hopefully!
Future Club member hopefully!
User avatar

Joined: Tue Aug 18, 2009 6:28 am
Posts: 167
Location: Nanaimo Vancouver Island BC Canada
The float level can be adjusted by placing shim washers under the
needle and seat valve housing.

_________________
DOUG
1980 Dolomite Sprint lhd


Top
   
PostPosted: Wed May 09, 2018 8:30 am 
Offline
Future Club member hopefully!
Future Club member hopefully!

Joined: Wed Oct 04, 2006 7:58 pm
Posts: 55
Location: South West London
You’ve changed the needles, are you sure the shoulder of the needle is flush with the piston? If they’re set high in the piston it’ll be the effect as having the choke pulled out.

Worth double checking.


Top
   
PostPosted: Wed May 09, 2018 11:31 am 
Offline
TDC Member
User avatar

Joined: Fri Apr 15, 2016 11:08 am
Posts: 691
Location: Ayrshire, Scotland
Quote:
You’ve changed the needles, are you sure the shoulder of the needle is flush with the piston? If they’re set high in the piston it’ll be the effect as having the choke pulled out.

Worth double checking.
All good thoughts, but the needles are mounted exactly where they should be. I don't know quite what to do. Should I splash out on new jets and/or float valves, or am I throwing money away? The jets aren't exactly cheap at around £80 the pair.

_________________
Mike
(1969 MGB GTV8, 1977 Dolomite 1850HL, 1971 MGB roadster now all three on the road)


Top
   
PostPosted: Wed May 09, 2018 3:17 pm 
Offline
TDC Member
User avatar

Joined: Sun Oct 22, 2006 10:31 am
Posts: 121
The jets aren't exactly cheap at around £80 the pair.

That is a bit rich for jets (pun intended), http://sucarb.co.uk/abk-090in-jet-needle-spring.html .

What was the original reason for servicing the Carburettors were they running rich before?
If you have changed the needles did you swap the spring that mounts to the top of the needles over from the old ones?


Top
   
PostPosted: Wed May 09, 2018 4:41 pm 
Offline
TDC Member
User avatar

Joined: Fri Apr 15, 2016 11:08 am
Posts: 691
Location: Ayrshire, Scotland
Quote:
The jets aren't exactly cheap at around £80 the pair.

That is a bit rich for jets (pun intended), http://sucarb.co.uk/abk-090in-jet-needle-spring.html .

What was the original reason for servicing the Carburettors were they running rich before?
If you have changed the needles did you swap the spring that mounts to the top of the needles over from the old ones?
I'm not sure what you're getting at with your hyperlink? Your link takes me to the needles, not the jets. The jets from Rimmers are just under £40 each.

Anyway, this car, and it's carbs, have been off the road for 26 years, so I have never heard it running. I have rebuilt the engine, carefully cleaned and reset the carbs and got it running. However, it is fantastically rich. The carb needles didn't look too good, so I bought new ones but they have made no difference. To answer your other question, yes I did transfer over the small springs on top of the needles.

I thought it might be the old fuel in the tank, which must have been 4-star leaded, but having swapped that for some new 97 octane unleaded it is still the same. Thinking about it, it's amazing that it started at all on the 26 year old fuel, but it did, quite easily. They don't make petrol like that any more!

The ignition timing is spot on, as is the camshaft timing. I am going to try new float needle valves as the old ones have a groove round the conical seat.

Thanks for the input. It all helps to organise my thoughts.

_________________
Mike
(1969 MGB GTV8, 1977 Dolomite 1850HL, 1971 MGB roadster now all three on the road)


Top
   
PostPosted: Wed May 09, 2018 5:39 pm 
Offline
TDC Member
User avatar

Joined: Sun Oct 22, 2006 10:31 am
Posts: 121
Sorry for the confusion, this is the link I intended http://sucarb.co.uk/hs-jet-assembly-090in-11927.html, however having double checked I see that the waxstat version is indeed double the price http://sucarb.co.uk/waxstat-jet-assembl ... 12863.html (my car is pre waxstat so I was quite surprised at the price difference)

The wear on the float needle valves could cause an issue, was fuel coming out of the overflow? I think they normally come with the seat as I normally replace both at the same time.

If the car has been standing for 26 years were you running it with the air filters fitted? if they are the originals are they clogged? as this would cause the car to run rich.

Additionally how did you clean the inside of the carbs as they should not be cleaned with anything abrasive as this can put them out of tolerance, further are the piston assemblies free to move fully along their entire travel.

If you are looking to possibly replace the waxstats, and the float needle valves it may be cheaper to buy a service kit:

http://sucarb.co.uk/service-kit-for-hs4 ... 12087.html
http://sucarb.co.uk/service-kit-for-hs4 ... 12086.html


Top
   
PostPosted: Wed May 09, 2018 8:25 pm 
You can get non-waxstat replacements which use the existing waxstat linkages from Burlen
http://sucarb.co.uk/waxstat-jet-conversion.html
http://sucarb.co.uk/waxstat-jet-conversion-10871.html

But whether you need them is open to debate.

You don't say if you have given it a run, perhaps worth trying an Italian tune up (bit of a long shot).


Top
   
PostPosted: Wed May 09, 2018 8:47 pm 
Offline
TDC Member
User avatar

Joined: Mon Aug 10, 2015 8:20 pm
Posts: 1293
Location: Shetland / here & there
A worn jet will look oval, so if the jet is fully wound up, the needle carrier flush with the piston and it still runs rich then maybe you have a float needle valve not seating properly, only thing I can think of that causes really rich running. An argument somewhat ruined by the fact that both of your carbs have the exact same issue.

Is it safe to assume that there is no issue with the cold start mixture enrichment device setting? ;) Seriously though SU Carbs are such a simple device that in reality there is not a lot that can go wrong with them, so it's always component wear when there is a problem.

_________________
Current fleet: '75 Sprint, '73 1850, Daihatsu Fourtrak, Honda CG125, Yamaha Fazer 600, Shetland 570 (yes it's a boat!)

Past fleet: Triumph 2000, Lancia Beta Coupe, BL Mini Clubman, Austin Metro, Vauxhall Cavalier MK1 & MK2, Renault 18 D, Rover 216 GSI, Honda Accord (most expensive car purchase, hated, made out of magnetic metal as only car I've ever been crashed into...4 times), BMW 318, Golf GTi MK3 16v x 3


Top
   
PostPosted: Wed May 09, 2018 9:15 pm 
Offline
TDC Member
User avatar

Joined: Wed Nov 15, 2017 3:35 pm
Posts: 956
Location: Filey, North Yorkshire
It's a billion to 1 shot.... You don't have a fuel pump that's pushing too much psi?

_________________
Image


Top
   
PostPosted: Wed May 09, 2018 9:46 pm 
Quote:
It's a billion to 1 shot.... You don't have a fuel pump that's pushing too much psi?
Or pressure in your tank.


Top
   
Display posts from previous:  Sort by  
Post new topic  Reply to topic  [ 21 posts ]  Go to page 1 2 Next

All times are UTC


Who is online

Users browsing this forum: Bing and 27 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Limited