Choke?

[Menno van Rij]

Last Saturday, I took the TR out for a spin. I pulled the choke knob completely and the car started effordlessly. But after a few sec. the engine started running erratically, lumpy. A blip on the throttle didn't help much: it appeared as if the car wasn't running on all cylinders. When I took off, things improved for a few hundred yards. When I shifted down, the car allmost stalled and putting my foot on the throttle woke up the whole neighbourhood: it backfired.

 

I tried to keep the car going, which wasn't easy but I succeeded. When the engine warmed up, the car began to run more and more effordlessly. Somehow, I suspect one of the carbs. On Sunday, I asked one of my kids to pull the choke knob fully, me watching what would happen under the carbs. Both levers pulled the spring etc. down. I noticed some leakage, not really bad, just a little wet. Petrol. I pulled the plugs from cylinder 2 and 3 that Sunday, after Saturday's run (50 kms) and both were black. Not coffee brown or wet, just black with soot on them. imho, that's a sign of running too rich.

 

Apart from the choke problem, I also suspect that some washers (new!) have perished. But before I start pulling the carbs apart, I really would like to know your opinion / experience on this!

 

Menno

 

I added a pic of the carbs. Perhaps you can point me into the right direction after seeing the carbs.

 

[stuart]

Menno the usual problem with the H6s is the cork seals in the jet housing underneath the carb. I have had similar problems before with these and you not only get a slight weep of fuel but also the jets dont return properly thus causing a rich mixture. It does seem as if the cork available these days isnt the same as original quality as the same goes for the corks sold to refurb the original fuel taps. I have sort of cured it on some by new washers and careful polishing of the jets although Im sure I have seen somewhere a rubber seal alternative but cant recall where. Check also that your choke cable outer isnt being pinched too much in the clamp under the front carb as this can sometimes contribute to the chokes not coming off entirely.I know some people have made up a ferrule to fit over the end of the outer cable to prevent this happening.

Stuart

[Don Elliott]

All the conditions you describe make me think that you may have accumulated sediment in the fuel line from the tank to the fuel pump. My 1958 TR3A was like that and it took me about 7 to 10 days from April 1st to the 8th or 10th - of trying everything. I had drained the fuel tank dry of 10 liters of fuel left there over the winter from last year and then I added 7 liters of new fresh fuel. I swopped hi-tension cables and the distributor cap. Then I swopped the coil. Then I changed the condenser. All the plugs were sooty and black. Then I cleaned and re-gapped the plugs and points again Nothing I did made a difference. It would start and idle but when I drove about a kilometer accelerating up to speed, it would suddenly backfire, chug, miss, etc. and it felt like I was running on three cylinders. Or maybe like I was out of fuel. I took off the tops of the flat bowls and they were empty. I poured fuel into the bowls from a small bottle of spare fuel and it would run again. I checked the fuel pump and it was splashing fuel all over. Then I opened the fill cap for the fuel tank and took the air gun from my air compressor and blew backwards in the fuel line and I could hear the bubbling and splashing in the fuel tank.

 

It ran fine after that and in the past five days, I've had had no issues at all. It is running sweet and I've driven 150 miles during those 5 days. I'm convinced that 20 years of sediment since I had my original tank "slushed" with an epoxy type of coating on the inside must have been blocking the fuel line until I blew it back into the tank.

[sidescreen]

Menno you have PM.

 

Regards,

[Menno van Rij]

I called the BCCP, a Dutch carb. restorer and long time SU 'enthousiast'. A lady on the phone asked me if the symptoms appeared after taking the car out of the winter hibernation. And yes, that's what happened. She told me that the cork seals are broken... Her advise: replace the seals, but she also had an advise for next year! A day before you're taking your car for the first spin of the year, take off the air cleaners, lift the piston inside the carbs. and insert a drop of oil into the small hole where the needle goes in. And leave it for 24 hrs! According to her advise, the oil will soak the cork seals, and thus preventing them to tear when you start using the car.

 

I orded new seals for my carbs: two large and two small ones. She also insisted that I soak the new seals for 24 hrs. before I install them!

 

Just something I would like to share!

 

Menno

[Don Elliott]

Menno - I can't see how the bottom cork seals about 20mm diameter will ever get oil down there. I agree that the upper smaller cork seals will get some oil. But just this spring, I rebuilt mine because the seals were leaking last summer. But mine had been in my SU carbs for 20 years. And I never added oil to lubricate them. And for the first 19 years (after storage every winter for about 5 months), I never added oil as your expert suggested.

 

An additional point. I also replaced the two small seals (about 8mm diameter) and I bought these from Moss in California. I had the option of cork or Viton (fuel resistant rubber) for these small seals and I bought and put in the rubber ones. They cost a few pennies more than the cork ones. So I will not be dripping oil into the needle hole to lubricate these.

 

BTW, my troubles started this spring after winter storage and it wasn't the seals because they were all new. It was the sediment in my fuel line that caused my burping, missing, backfires etc.

Edited April 14, 2010 by Don Elliott

[stuart]

Menno - I can't see how the bottom cork seals about 20mm diameter will ever get oil down there. I agree that the upper smaller cork seals will get some oil. But just this spring, I rebuilt mine because the seals were leaking last summer. But mine had been in my SU carbs for 20 years. And I never added oil to lubricate them. And for the first 19 years (after storage every winter for about 5 months), I never added oil as your expert suggested.

 

An additional point. I also replaced the two small seals (about 8mm diameter) and I bought these from Moss in California. I had the option of cork or Viton (fuel resistant rubber) for these small seals and I bought and put in the rubber ones. They cost a few pennies more than the cork ones. So I will not be dripping oil into the needle hole to lubricate these.

 

BTW, my troubles started this spring after winter storage and it wasn't the seals because they were all new. It was the sediment in my fuel line that caused my burping, missing, backfires etc.

 

Don thanks for confirming what I thought about availability of Viton replacements. I just couldnt remember where they came from (senior moment) I will have to see if I can get some over here.

Stuart.

[e_ingemann]

Hi Menno,

 

Nice looking engine bay, I recently stumbled on a quite nice page on the internet describing different aspects of the H series SU carbs.

 

Have a look:

 

http://www.jcna.com/library/tech/tech0006.html

 

According to this, the reason for soaking the cork seals is for lubrication and to prevent ruining them on installation.

 

I found it very usefull when I did my rebuild, I haven´t got too much technical experince with cars, but I manage to keep my TR3 running anyway.

 

Cheers,

Esben

[Menno van Rij]

Thanks guys for all the comments.

 

I dismantled the carbs. partly this afternoon. Air cleaners off, dashpots off , carefully lifting the pistons and the needles, putting the away safely.

 

Then I started on the lower end of the carbs. I took off the links to the jets on both carbs. (#60 on the Moss diagram) and that allowed me to undo the complete jet bearing (#93 on the Moss diagram). A lot of small parts and the 4 corks seals were clearly visible. I carefully took them out. The small ones were bone dry, the large one that had been on the rear carb. was soaking with fuel. The large seal from the front carb. looked better.

 

That's my work for this afternoon, I will address this tomorrow or Sunday when I have some spare time on my hands. For now, the new ones are covered with dashpot oil and I'll leave them for 24 hrs. or more. I ordered two extra sets... just in case.

 

In the meanwhile, the viton option got my interest. I'm looking for an address overhere in Holland where they sell viton 'O'rings. Someone pointed me towards a company that restores BMW motorcycles. These guys appear to be on the cutting edge, somehow. They showed met the Beru sparkplugs a few years back. (It's a shame they don't produce these for the TR 4 cylinders).

 

If you have any tips, hints or comments before I reinstall the items, I would really like to hear from you!

 

Menno

Edited April 16, 2010 by Menno van Rij

[stuart]

Thanks guys for all the comments.

 

I dismantled the carbs. partly this afternoon. Air cleaners off, dashpots off , carefully lifting the pistons and the needles, putting the away safely.

 

Then I started on the lower end of the carbs. I took off the links to the jets on both carbs. (#60 on the Moss diagram) and that allowed me to undo the complete jet bearing (#93 on the Moss diagram). A lot of small parts and the 4 corks seals were clearly visible. I carefully took them out. The small ones were bone dry, the large one that had been on the rear carb. was soaking with fuel. The large seal from the front carb. looked better.

 

That's my work for this afternoon, I will address this tomorrow or Sunday when I have some spare time on my hands. For now, the new ones are covered with dashpot oil and I'll leave them for 24 hrs. or more. I ordered two extra sets... just in case.

 

In the meanwhile, the viton option got my interest. I'm looking for an address overhere in Holland where they sell viton 'O'rings. Someone pointed me towards a company that restores BMW motorcycles. These guys appear to be on the cutting edge, somehow. They showed met the Beru sparkplugs a few years back. (It's a shame they don't produce these for the TR 4 cylinders).

 

If you have any tips, hints or comments before I reinstall the items, I would really like to hear from you!

 

Menno

 

Menno I think the Viton option is in the form of a lip seal not an "O" ring, difficult to get good seal otherwise due to the movement of the jet.

Stuart.