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My TR2 daily driver has a high port head and 1 3/4" SUs. I'm not sure when I fitted the new carbies but I'm guessing they have done 50-60,000 miles/80-100,000km.

It has been running too rich.  Getting the mixture right at idle requires the adjusting nut to be screwed all the way up.

To give some adjustment I have lowered the needle a mm or so allowing me to screw the nut down a turn. I don't think this is satisfactory long term.

The float height is right and the carbies nicely balanced.

I'm thinking the needles need replacing. Any advice welcome, on my thinking and on the best needles to use (currently SM).

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Hi John, interesting this one, I look forward to hearing some answers as I am currently trying to get my carbs set up and had the same problem of rich running.

In your case if the carbs have just gradually got richer it probably is wear in the needle/jet assembly.

I bought new jets thinking that must be the problem, the needles were already new, but it has made no difference. I have checked the float heights several times and fitted new Grose valves thinking the float chambers were flooding. My current thinking is that it is somehow drawing fuel up from around the outside of the main jet as well as through it even though the carbs were re built with all new washers and seals. I suspect the  washer at the top of the jet bush has not seated properly and am going to check these next.

Ralph

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Hi John, I had this for years without being able to solve it. I think based on your discription the jet is probably going to be worn. You might actually be able to see it if it bad. The hole will look oval rather than round. If that's happened then the needle will be worn as well. As Ralph has said the level in the float chamber can make a big difference and so you need to check that the valve shuts at the right height. 

On rebuilding the carbs this time I didn't really find anything massive (lots of small things and one that I think solved it). But on putting it all back together it ended up in a similar position, everything screwed up to as weak as possible. 

The main thing I found was one of the floats had a small amount of liquid inside, so this will mean the shut off is late on this carb and push more fuel through. But initially this didn't seem to make the improvement I wanted. In the end I looked at the timining and after resetting this I managed to get it under control. I think I'm down about 1 1/2 turns on the adjustment nuts now. Not far but at least I'm in control now. 

I'd also check the throttle spindles for wear and play. Not sure this would make rich however. Its possible to put the spindle springs on in such a way that the butterfly is pulled hard against the side of the chamber which leads to wear on butterfly and more importantly the chamber meaning you get more flow at idle than wanted. But thats just a heads up on another problem rather than directly related to running rich I think. 

I went down the lowering the SU needles myself as a last resort when previously trying to solve. 

Neil

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Throttle spindle wear would not make it richer, more the opposite. worn jets are a possibility, needles should be SM.

Do the pistons rise & fall cleanly, if the don't rise as they should that would richen the mixture (but not at tickover)

Are the correct piston springs fitted. Float height is not critical as long as fuel is not flooding into the carbs (check by taking top off carbs, remove piston, & while priming the fuel pump look at the top of the jet, fuel should be just below the top.

Bob

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15 hours ago, Lebro said:

Throttle spindle wear would not make it richer, more the opposite. worn jets are a possibility, needles should be SM.

Do the pistons rise & fall cleanly, if the don't rise as they should that would richen the mixture (but not at tickover)

Are the correct piston springs fitted. Float height is not critical as long as fuel is not flooding into the carbs (check by taking top off carbs, remove piston, & while priming the fuel pump look at the top of the jet, fuel should be just below the top.

Bob

Thanks Bob. The springs came with the carbies and are the same height but what grade they are I don't know. I would have thought they are more likely to affect acceleration and pick up rather than idle mixture.

The pistons drop nicely with a clunk at the bottom. The fuel is visible in the jet when the engine is cranked over. The jets are round not oval. I can't see any scoring on the needles and they look normal.

I've given the carbies a clean with brake cleaner and will see how it goes in the next few weeks. I have a run next week that I can drive at high speed for 10kms and then pull over and check a couple of plugs to see what the mixture is like at cruise revs.

 

 

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... and if the SM needles are worn then replace the jet body as well, it will probably have worn oval if the needle has been rubbing it.  PS.. I use two Colour Tunes, in #1 and #4 - it does make setting the jets easier and you can see if the richness is constant or an over reaction on revs increase. Just a thought.

Mike

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On 10/3/2020 at 8:45 AM, John McCormack said:

My TR2 daily driver has a high port head and 1 3/4" SUs. I'm not sure when I fitted the new carbies but I'm guessing they have done 50-60,000 miles/80-100,000km.

It has been running too rich.  Getting the mixture right at idle requires the adjusting nut to be screwed all the way up.

To give some adjustment I have lowered the needle a mm or so allowing me to screw the nut down a turn. I don't think this is satisfactory long term.

The float height is right and the carbies nicely balanced.

I'm thinking the needles need replacing. Any advice welcome, on my thinking and on the best needles to use (currently SM).

Which 1 3/4" SU carbs?

H6 (TR3-4) or HS6 (TR4A) or HD6 or even HIF

If HS6 from TR4A consider changing the needles to TW spec (orig TR4A)

Peter W

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John, 

          I wasn't clear on my reply, I think when I had this issue it was solved by changing a float what had liquid in it. I then had further issues because clever me took out the distributer whilst refurbing the carbs and hadn't realise the timing was out when trying to set up the carbs. 

         I've attached a copy of the info for setting up the fuel level. The view is it can lead to flooding and I think this is what was happening, particularly at tick over where you mostly spend you efforts trying to get the fueling right. When I reved the car the colour tune was always OK but it was rich at tick over and I could never find the issue. I following this discription but it didn't solve it. I only found the liquid in the float when I was rebuilding the carbs, so I cannot be certain. 

         One other thing but I think you would know this. Have you checked the needles return fully up when the choke goes back in. Sometimes you get one that will stick slightly down but I would think you would pick this up when you come to tune them. 

    It's worth a check. Especially if you have done everything else more obvious. 

Neil

16018479498548889638794565378273.jpg

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16 hours ago, BlueTR3A-5EKT said:

Which 1 3/4" SU carbs?

H6 (TR3-4) or HS6 (TR4A) or HD6 or even HIF

If HS6 from TR4A consider changing the needles to TW spec (orig TR4A)

Peter W

They are H6s. SM needles.

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8 hours ago, Drewmotty said:

Are the needles mounted correctly in the slide with the bottom of the mounting spigot flush with the bottom of the slide and the jets properly centred?

 

I did have the needles about 0.5-1.0mm protruding below the flush position to try and weaken the mixture a bit.

I have just adjusted the rear carbie back to almost flush, maybe 0.5mm protruding.

I've adjusted the timing and nipped up the jet securing nut about 1/8th of turn.

It seems to idle Ok now but I will need to check it at cruising revs.

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9 hours ago, NCS_TR3A said:

John, 

          I wasn't clear on my reply, I think when I had this issue it was solved by changing a float what had liquid in it. I then had further issues because clever me took out the distributer whilst refurbing the carbs and hadn't realise the timing was out when trying to set up the carbs. 

         I've attached a copy of the info for setting up the fuel level. The view is it can lead to flooding and I think this is what was happening, particularly at tick over where you mostly spend you efforts trying to get the fueling right. When I reved the car the colour tune was always OK but it was rich at tick over and I could never find the issue. I following this discription but it didn't solve it. I only found the liquid in the float when I was rebuilding the carbs, so I cannot be certain. 

         One other thing but I think you would know this. Have you checked the needles return fully up when the choke goes back in. Sometimes you get one that will stick slightly down but I would think you would pick this up when you come to tune them. 

    It's worth a check. Especially if you have done everything else more obvious. 

Neil

16018479498548889638794565378273.jpg

The floats are good. The fuel level is about 3/16" below the lip on the front carbie and maybe 1/4" on the rear. The SU book says anywhere in this range is OK, the only real issue is if it overflows and floods which it isn't doing.

This is a work in progress.

Colourtune would help but at $80 each it is expensive and I've been able to sort it without in the past.

Damn, just went for a drive and it just won't idle smoothly when it is hot. I have had to richen the mixtures slightly and it now idles between 8-900 occasionally dropping to 6-700 then recovering. The revs go up slightly when I lift the pistons a 1/32", then drop if I lift them further.

It is a 31-33 degC day here, maybe I'm expecting too much. 

Edited by John McCormack
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I had a similar issue some years ago, carbs were all rebuilt with new jets, re-bushed etc. Is the choke mechanism sticking ? A thorough clean,  lube with some high temp grease resolved mine.

Iain

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4 hours ago, NCS_TR3A said:

John, we're I have written needles resenting after taking the choke off, I meant jets resetting (going all the way back up). I guess the same as Iain is suggesting.

Neil

Thanks Neil, Yep, the jets are returning all the way back. I am pretty sure it is the needles and jets or the pistons causing the problem but the car is back together now and running OK.

It is a lot cooler here today and will be tomorrow for a longer run for coffee with TR mates. I'll pull over on the freeway after a few minutes at speed and check the plugs to see what the mixture is like at cruise speed.

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Checked the plugs this morning after a high speed drive and they were white, running too lean.

When I got home I pulled the top off the carbies and cranked the engine.

The rear carbie looked to be flooding through the jet. I installed new needles and seats in the bowls and set the float level to the book at 7/16".

I also reset the needles so the shoulder is flush with the piston. I had dropped them about 1/32" to try to lean it out but that is probably the reason it was running to lean at speed. If I leave it too lesn I could end up burning a valve or damaging a piston.

Crank the engine and all seemed ok, fuel level just below the top of the jet and no fuel pumping through when cranking.

However the issue remains. The rear carbie still has the jet all the way up and is still running rich at that setting. 

I have a spare set of rebuilt carbies so may try the pistons and needles from them and then swap the carbies if that doesn't work.

Edited by John McCormack
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I had a similar problem years ago, everything was set up as per the book and it was still flooding, I progressively lowered the float level until it stopped flooding, this works fine and has no effect on the running of the vehicle, I can floor the accelerator in third gear and keep it there whilst going up a long steep hill with no sign of fuel starvation. hope this helps, Cheers, Bill.

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  • 4 weeks later...
On 10/3/2020 at 9:05 AM, Ralph Whitaker said:

Hi John, interesting this one, I look forward to hearing some answers as I am currently trying to get my carbs set up and had the same problem of rich running.

In your case if the carbs have just gradually got richer it probably is wear in the needle/jet assembly.

I bought new jets thinking that must be the problem, the needles were already new, but it has made no difference. I have checked the float heights several times and fitted new Grose valves thinking the float chambers were flooding. My current thinking is that it is somehow drawing fuel up from around the outside of the main jet as well as through it even though the carbs were re built with all new washers and seals. I suspect the  washer at the top of the jet bush has not seated properly and am going to check these next.

Ralph

Sorry to refresh this old post, but today I finally got round to looking at my carbs and trying to sort out the problem listed above. It was the copper washers at the top of the jet bush that were not sealing as I had suspected. I replaced them with fibre washers and there was an instant improvement. It needed the choke to start (first time I have had to use it because of the flooding), and with the jets set 1.1/2 turns down I was able to get it ticking over like a sowing machine. Next is to put the colortune plugs in and do the final tuning of the mixture.

Happy days, Ralph.

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I have been working through this issue on both my TR2s.

With the daily driver, the subject of the post, I am pretty confident the needles are worn. The jet isn't oval and the piston drops with a nice little thud at the bottom but looking at the needle with an amplifying glass they appear to be worn at the top. I'll replace them next week.

Now to my other TR2. It has a stock low port head, 1 1/2" carbs with FV (normal) needles, 87mm liners and a half race cam, exactly which profile I don't know.

It performs very well indeed but on this tank I got only 17mpg. There were some tuning issues and the vacuum advance wasn't properly connected for much of the tank. 

What impact would the engine mods, especially the cam, have on economy? Would the engine mods require a change from the recommended needles and which way, lean or rich? 

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On 11/1/2020 at 2:14 PM, Ralph Whitaker said:

Sorry to refresh this old post, but today I finally got round to looking at my carbs and trying to sort out the problem listed above. It was the copper washers at the top of the jet bush that were not sealing as I had suspected. I replaced them with fibre washers and there was an instant improvement. It needed the choke to start (first time I have had to use it because of the flooding), and with the jets set 1.1/2 turns down I was able to get it ticking over like a sowing machine. Next is to put the colortune plugs in and do the final tuning of the mixture.

Happy days, Ralph.

Right, following on from previous report above. Yesterday after having the engine running and fully warmed up, idling beautifully, exhaust clean with no smoke, I decided all was good and re-fitted the air filters, which are classic gold TR4 oval paper type. Instant return to flooding and black smoke from exhaust.

I gave up in frustration and came out of the garage. This morning I am going out to remove the air filters and see if normality has returned, If so I will be taking a close look at the new filters.

Ralph.

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1 minute ago, Richardtr3a said:

Hi Ralph, 

Where did you buy your fibre washers. I would like to try this myself.

Thanks Richard & B

I was given a load ages ago which were just the right size. PM me your address and I will send you half a dozen, though after yesterdays debacle I am less sure that this was the cause of the flooding. As far as the copper washers go I think they are too hard and probably need annealing before fitting to soften them and give them a chance of sealing.

Ralph

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  • 2 weeks later...
On 11/8/2020 at 9:25 AM, Ralph Whitaker said:

Right, following on from previous report above. Yesterday after having the engine running and fully warmed up, idling beautifully, exhaust clean with no smoke, I decided all was good and re-fitted the air filters, which are classic gold TR4 oval paper type. Instant return to flooding and black smoke from exhaust.

I gave up in frustration and came out of the garage. This morning I am going out to remove the air filters and see if normality has returned, If so I will be taking a close look at the new filters.

Ralph.

OK, latest instalment, it seems that the carb wasn`t flooding, it was leaking out of the cork washer on the main jet holder but I couldn`t see it because the filters were in the way. Strange it had not done that the day before though. Also I was not happy with the way the pistons were falling as every time I went to tighten the main jet it jammed just before reaching the bottom, but managed to resolve that by keeping the piston pressed down hard when centering the jet.

Fitting the colortunes I tried to get the mixture right, but if I get the colour right at tickover it is too weak at higher revs, so I have had to settle for a rich mixture on tickover, however on opening the throttle quickly it pops and farts which would indicate too lean. It could be that the pistons are moving up too quickly as I have filled the dampers with auto trans fluid (said Everyman oil in Mr Haynes manual for TR4 and 4a, which is very thin), but lists GTX for the TR2/3/3a. I have a 4 engine so went with the thinner oil, but  will try changing it for GTX. Also the springs are the originals so I have ordered a new pair of those. Hoping a combination of new springs and thicker oil will stop the piston lifting too quickly and allow the engine to rev cleanly.

Wouldn`t life be boring if we did not have all these problems to keep us occupied.

Ralph

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