TR4/4A New TR4 tuning

[Chasman3]

I finished jet assembly on the SU’s. Before I started, I pulled the plugs. They were NGK and all were black. Car was running ok.i thought carbureration. Plus the jets were weepy. I synched and engine revs great. I replaced wires, cap, rotor plugs (Champion) and then rechecked synch. Runs strong and smooth. But all plugs are black. Gap is .025. I read that with electronic i may open it? I was wondering about lean needles? Or hotter plug?

Thanks

Charlie

 

[mctriumph]

Weepy????The float levels are too high.
MD

 

[Chasman3]

Weepy????The float levels are too high.
MD

I don’t think so. Per p135 in the Complete Official Truumph…base of the jet probably that 3 cork gland washers….

But all plugs including new ones are black. And this morning after starting with choke I fouled one. It ran smooth yesterday after tuning but still black.

No smoke. Engine sounds healthy. My next job was check valves but think I should try lean needles.

Interestingly in this repair manual under maintenance history, previous owner wrote engine rebuild at 24187 miles. It shows 34,320 now. That was 1990. He says; bore .020, pistons, rings valves ground head surfaced at 27389 a year later timing chain and cam sprockets and some 3000 miles later. Not sure why that was done at intervals or with such low mileage. The car definitely it low mileage as evidence by the underside. Any help appreciated.

 

[sp53]

If the front carb is carboning up first the choke is probably not returning to the base of the carburetor body. The choke return on these cars is critical to stop carbon build up because the choke works by enriching the mixture of fuel not shutting off the air to the engine to choke it.

Once the choke is working correct you can move on to other carbon build up problems. Turn the mixture nuts up one or one and half flats at a time and then drive the car around the block with clean plugs to get some air in the engine. Do not idle the car too much because this causes carbon build up in an un-tuned engine. After each drive check the plugs again and repeat until you can visually see the carbon build up lessoning.

steve

 

[Chasman3]

If the front carb is carboning up first the choke is probably not returning to the base of the carburetor body. The choke return on these cars is critical to stop carbon build up because the choke works by enriching the mixture of fuel not shutting off the air to the engine to choke it.

Once the choke is working correct you can move on to other carbon build up problems. Turn the mixture nuts up one or one and half flats at a time and then drive the car around the block with clean plugs to get some air in the engine. Do not idle the car too much because this causes carbon build up in an un-tuned engine. After each drive check the plugs again and repeat until you can visually see the carbon build up lessoning.

steve

Hi Steve. Thank you. All 4 new plugs were black as coal. The choke seems to be repositioning but the pull seems off. I need instruction on proper cable adjust.

Before I took off the carbs, I checked the plugs. NGK BP6Hs. They were all black.

Yesterday after tuning and a terrific ride I checked the plugs. Black. This morning on cold start with the choke I fouled a plug. I tried cleaning it and widened gap to .030 but no good

The jet adjusting nuts were both 2.5 turns from top when I refitted. I don’t know how far I leaned them till no noticeable increase in rpm. I purchased two new brass jet arms since the front one was bent.

I just now checked again feel slippery moist at bottom of jets. I don’t have a jet centering tool and I’m certain the gland nut needs to be tighter. I have one on order and it looks like carbs are coming off again.

Thoughts on the lean needle? It’s going to be blistering hot coming toward weeks end. Choke can be disengaged for plug evaluation providing carb jets are properly centered.

Thanks

Charlie

 

[Chasman3]

One last comment. I removed both pistons and both jets are nearly to the top, front slightly higher than the back. Soaking the pistons needle now. But that doesn’t look like a good job removing needles. I’m baffled why it’s so rich to foul the plugs. I did not replace jet head or bearings. I wonder if new jet heads are indicated over needles?

 

[sp53]

I would not put the lean needles in yet.

Are the jet and the needles new ?

I have never had good luck with a centering tool, they are too ideal for floating fits. I center them by putting an old needle in the piston then hold the piston down a little on the jet and tighten the glad nut slow and steady. I always end up having to fiddle with the gland nut some afterwards.

It sounds like your carb linkage and choke linkage need work. Is the jet back up against the mixing the nut when the choke is pushed in? it has to be back up tight. can you push the jet up any by hand after the choke is pushed in?

I ground and cut down an old cheap sheet metal wrench to fit the glad nut nice, so I could get a nice grip.

How far down are the jets in the case? The jets end up being about 1/8 or so from the top.

Once the carb bodies are mounted, I usually fix the carbs parts mounted to the car.

Steve

 

[Chasman3]

I took off the chambers and the jets were nearly all the way in. My deduction is the jet heads are worn? The choke was not hooked up correctly when I got the car. I’ve only had it since May 30th. The jet link was bent. I replaced both of them. But yesterday I had it working. I know it needs more adjustment but both jet levers are firmly down.. Also yes I understand about the needles. I carefully removed the needle locking screws and soaked but they are firm. Very reluctant. Really didn’t want to damage. So will pause on replacing for now. I haven’t check float levels but eyeballing the forks, they are close 7/16”. Didn’t replace needle or seat.

One important note. I replaced plugs and ignition after I tuned. I took it out and it ran amazing. I came back and checked the plugs. Black. I had never used the choke. I rechecked the tune. Minor difference,

I definitely appreciate advice. And at 69, I’m getting plenty of fabulous problem solving!

 

[Sarastro]

You're not sure that the choke cable is right, and your carbs are leaking, but you're talking about the jet head and changing needles. That doesn't make sense. Also, changing the spark plugs or gap will do nothing for a rich mixture.

Start by getting everything in the carbs right. Make sure that the choke is disengaging COMPLETELY when you push it in, and find out where the leak is coming from and fix it. The float valves may not be shutting off the fuel completely. Do you see wet fuel in the bores when you look into them? I didn't understand your response to MD re the fuel level, but it sounds a lot like the float-level adjustment may not be right. Check the floats for pinholes, too.

Once you are SURE that the carbs are right, make sure that the valves are adjusted and the ignition timing is OK, and then do the carb mixture adjustment per the manual. I think you'll find that it falls into place as it should.

These cars run just fine with the stock setup. If one doesn't, there is something broken, and the solution is to fix it, not to start redesigning it.

 

[Chasman3]

You're not sure that the choke cable is right, and your carbs are leaking, but you're talking about the jet head and changing needles. That doesn't make sense. Also, changing the spark plugs or gap will do nothing for a rich mixture.

Start by getting everything in the carbs right. Make sure that the choke is disengaging COMPLETELY when you push it in, and find out where the leak is coming from and fix it. The float valves may not be shutting off the fuel completely. Do you see wet fuel in the bores when you look into them? I didn't understand your response to MD re the fuel level, but it sounds a lot like the float-level adjustment may not be right. Check the floats for pinholes, too.

Once you are SURE that the carbs are right, make sure that the valves are adjusted and the ignition timing is OK, and then do the carb mixture adjustment per the manual. I think you'll find that it falls into place as it should.

These cars run just fine with the stock setup. If one doesn't, there is something broken, and the solution is to fix it, not to start redesigning it

Straight forward advice. I thought I was there. I’m sure choke was my problem this morning. And I discovered the front float chamber attachment bolt was loose. Will check floats and recheck jet. Adjust choke and get a new set of plugs, check timing and valves. But in running sequence. First the carbs. Thanks. Charlie

 

[sp53]

It sounds like you removed the screw, but could not get the needle out (I carefully removed the needle locking screws and soaked but they are firm.) If that is the case, take a pair of side cutters and grab the needle low and lever the needle up with your wrist like pulling a nail. the needles are cheap plus you will probably not damage the old stuck one. I like Steve M advise.

Steve

 

[Chasman3]

It sounds like you removed the screw, but could not get the needle out (I carefully removed the needle locking screws and soaked but they are firm.) If that is the case, take a pair of side cutters and grab the needle low and lever the needle up with your wrist like pulling a nail. the needles are cheap plus you will probably not damage the old stuck one. I like Steve M advise.

Steve

Correct. But have postponed that swap. I reassembled the carbs and believe they are correct. I didn’t use a centering tool. I got the hand how to check and tightened kind of like tuning my Martin! The pistons drop perfectly. I’m still sorting out the choke. I have it adjusted so it pull to a 2nd notch pulling down both jets. They could go farther but I’m inclined to try it where it is. Would like some technical advice there if it’s out there already in video or print.

 

[sp53]

I believe the jet should come down an about ¼ inch on both carbs, and that depends on local climate. These cars are very cold blooded after they have set for few months and a little starter fluid seems to fire them right up. But I hate that and do not like using starter fluid, so I usually do not.

Yesterday I tried starting a different tr3 that has set all winter. I cranked on it with a ¼ plus choke coming down from the jet and nothing not even a cough. I sprayed a very small amount of starter fluid through the air cleaner because the battery and starter were sounding weak and then wooom.

I am not sure what to think about the cold start. Are the bowls set wrong and not enough gas is being pulled into the engine to start it is my latest theory. However, once warm and started from winter the car seems to start fine until the car sits again.

In addition, I belong to an old Ford Truck forum and they use starting fluid and say the gasoline is inferior! I have another tr3 I drive all the time and that car seems start with no starter fluid, but I drive that car more. I will be curious what you find out with the choke. There are a lot of prior threads and pictures about the choke. The choke is critical on these cars

Steve

 

[Chasman3]

I don’t have much success searching. In the forum. It’s probably my inept skill so finding information on choke connection and setting has been limited. And yes about starting fluid. It seems to surface a lot but totally unnecessary if the enrichment is properly set, IMO. I don’t like using it either. The linkage tying the two carbs is a critical adjustment along with the shape of its clevis pins. What I don’t know is how far to go in terms of full choke. One could presumably take the front carb all the way to the jet lever is saddled into the bottom of jet link and cable support. That’s as far down as the jet can travel.

Then there is this business about soaking cork seals in the jet with oil for 24 hours before installing. Really? Where in the TR3 or Tr4 shop manual does it say to do that? Mine pulls freely and slides without it.

A simple description on installing and adjusting the choke is all I need and can’t seem to find it anywhere. Not in my “The Complete Official Triumph Tr4 & Tr4a 1961-1968” or “Triumph TR4 Workshop Manual”.

Thanks

Charlie

 

[sp53]

I posted some old stuff about chokes on the forum from the past; you will have to open it. When you say choke travel, do you mean the length the knob pulls out from the dash or perhaps the amount of free cable to get the proper travel to get the jets down?

steve

 

[Chasman3]

Again searching is not working for me. Not sure why.

Travel. The choke knob appears to be notched. Right now it’s set to pull to the 2nd notch. That lowers the both jets but they could go further. At second notch I have it set for faster idle but not first.

Linkage: To get both jets to go down in equal amounts the lever of the rear carb (closest to firewall) has more tension on the return spring than the front. I’d say there is maybe 3/8” thread on both ends of the linkage arm within each clevis. What is the proper adjustment?

Cable attachment: Currently I have 1/2 “ of cable housing protruding from the locking screw & nut affixed to the jet link and cable support.

Thanks

 

[charleyf]

2 peripheral items mentioned here. Soaking the cork parts in oil is not to provide lubrication to smooth movement of the jet. The reason is to get the cork to swell a bit to help sealing.
The second -- needing starter fluid. These carbs do not have any "pump" to spray fuel into the engine when starting. To get that pump effect it comes from either turning the engine over to get the fuel pump to send fuel up the line or if you have a hand primer on the fuel pump and use it with the same result. If the car has been sitting awhile then the fuel level may also be low in the float bowls and need that extra priming.
Charley

 

[Chasman3]

I have a hand primer. And yes no accelerator pump. The former owner used starting fluid. The choke was non functional. It works now. It’s 3 position. The biggest mistake I was making was reaching from the passenger side trying to get the third position or full choke. Sitting in the drivers seat, step on the accelerator pedal and it works perfectly. I set the jet/throttle to 1.5 mm. Works like the manual describes. I’m sure the cork soaking is well known but since it wasn’t described, I didn’t do it. I might try when these jets start weeping the next time. Thanks. On to other items on my check list!

 

[Chasman3]

You're not sure that the choke cable is right, and your carbs are leaking, but you're talking about the jet head and changing needles. That doesn't make sense. Also, changing the spark plugs or gap will do nothing for a rich mixture.

Start by getting everything in the carbs right. Make sure that the choke is disengaging COMPLETELY when you push it in, and find out where the leak is coming from and fix it. The float valves may not be shutting off the fuel completely. Do you see wet fuel in the bores when you look into them? I didn't understand your response to MD re the fuel level, but it sounds a lot like the float-level adjustment may not be right. Check the floats for pinholes, too.

Once you are SURE that the carbs are right, make sure that the valves are adjusted and the ignition timing is OK, and then do the carb mixture adjustment per the manual. I think you'll find that it falls into place as it should.

These cars run just fine with the stock setup. If one doesn't, there is something broken, and the solution is to fix it, not to start redesigning it.

Thanks for the sage wisdom. I was falling into the Moss Motors replacement parts rabbit hole. I removed the carbs and slowly and patiently reassembled the jets, aligning with piston and chamber without a tool. Not a big deal if you carefully tighten gland slowly and checking for click as you go. I checked high middle and low. Perfect. Everything tight. Re installed on the car.

Day 2. Choke searching didn’t help much but I understand how they work. I had 2 notches and was dropping the jets but not enough. I fiddled with that for a while adjusting cable length. Finally I thought to sit in the driver’s seat depress the accelerator pedal and try. Voila 3 positions. Perfect. Push in, both jets firmly placed.

It started on position 1. I had both jets down 2 turns. Synchronized and set the jets. The car runs terrific. Onto next items on the check list. I used the older plugs, cleaned, fired and gapped. Will install new plugs, check valves, timing, recheck carbs. Drive. Pull plugs and assess

I will say, a tutorial on choke assembly and adjustment for the Triumphs using SU H6 would be useful. Nothing in either of my manuals. Viewing older threads is helpful but I like to have a reference. Again, thanks. You firmly grounded my repair. I should have been more patient at 69! Not!

Charlie

 

[sp53]

Charlie did you see the post on this forum--- today called ”Choke operation from the factory” I put it up for you to see from old an old post.

Steve