TR2/3/3A SU H6 Mixture Adjustment Nut

[BillyB62]

All,

My TR3 is running super rich and I've been reading the recommendations and procedures to lean it out. I have black sooty smoke when I start the car and I'm told whenever I shift. Last night, I tried to adjust the mixture adjustment nut all the way lean (up) and was going to then turn it back 12 flats (2 full turns) as recommended in several spots. The problem I had was I could turn the nut (as shown in the picture below....I hope) and it just spins and spins - never reaching the top and stopping. I had the carbs rebuilt last year at a reputable local carb shop last year using the Moss rebuild kit.

Am I doing something wrong?

 

[NutmegCT]

Bill - do you have the same "loose and spinning nut" problem on both carbs?

Tom

 

[BillyB62]

I do.

 

[NutmegCT]

Just a guess, but I wonder if the nuts were never ever adjusted after the carb rebuild? Maybe screwing them upwards with some force will get the threads to mesh. Remember you're screwing them clockwise as seen from below.

Did the black smoke, etc. just start recently? or has it existed ever since the carb rebuild?

 

[BillyB62]

It has always run rich since the I started messing with it. I took the carbs off to paint the exhaust manifold and decided it was as good of time to do so as any.....I don't remember why, but I assume there was something going on with it because I usually don't change things just to change them. The car runs good (really good) sometimes and flutters (not sputters) at other times - but always runs rich. My plugs usually have deposits on them and are wet when I pull them. I do remember I tried NGK plugs before the carb rebuild and went back to Champion because they had deposit issues...so something was happening before I chose the rebuild.

I'm hoping to have it sorted out for the Quabbin trip a week from Saturday that NET is hosting. I took it to the Newport show (actually Portsmouth) this Sunday, which is about an hour away. It drove ok....but just ok. Not sure I'd feel good about doing the Quabbin trip (66 miles and probably as much to get there from my house) in its current condition.

Thanks to all for any help/suggestions you can give me,

 

[BillyB62]

Thanks Tom, I'll try to push up on them when I attempt tonight. I'm pretty sure I'm screwing them "in" the right way. Looking at my pic, the wrench goes from left to right.

 

[titanic]

Bill-You are turning the nut in the proper direction. Sound like the lower jet bearing turning. It should be "clamped" by the jet lock nut. Check the diagram of the jet assembly and note the location of the thin washers on the upper&lower jet bearings, unlikely, but they could be missing. Another culprit can be the cork seal just above the jet locking nut. If it isn't completely compressed (just a thin line visible)the jet locking nut may not exert enough pressure on the jet bearing to keep it from turning. Also, incomplete compression of the cork seal will prevent the jet from being raised high.
When the adj. nut is fully up, the jet should be about level with the top of the bridge (carb body). The recommendeds starting point of 2 turns down will be about .060" and my final adjustment was about .050". Checking the jet heigth with dial calipers is the best method.
Having said all of the above gibberish, returning the carbs or car to the shop who rebuilt them would be my first choice of action.
Berry-I am the guy that sold you a float chamber cover.

 

[BillyB62]

Thanks Berry, it seems you may have saved me for a second time. I pulled the rear carb off tonight and went piece by piece to make sure it was assembled correctly. It appears I am missing the copper washer on the top bearing. I'm not fully sure whether it would cause my problem in this thread, but it might explain why my dashpots empty quickly. I've ordered replacement washers from Moss and I'm having them overnighted - expecting to have them Friday so I can work on the car this w/e. The owner of the carb shop is a good friend of mine so although I'll mention it to him, that'll be the end of it. Had he not been down on his luck and needed the money, I would've done this all by myself anyway.....this is why I struggle to farm out any work on my car.

I'll update my post this weekend after I've completed the repairs. Thanks again to all....

 

[tr3aproj]

Might want to check your float level at the same time.
Robert

 

[titanic]

Bill-You might consider Joe Curto for your carb parts, he is the recognized SU guru, is located in NY, and charges reasonable shipping.
https://joecurto.com/
Berry

 

[CJD]

So...

I just rebuilt my carbs last week. I noticed that once the mixture nut bottoms all the way closed, and you still try to turn it, the jet bearing will rotate. That's the same issue you are having, Bill. But I am certain that my copper washers are correct and in place. Is the solution to that just tightening the large locking nut down tighter?

 

[poolboy]

Is this something that you've seen ?
https://www.teglerizer.com/sucarbs/techtip6.htm

 

[BillyB62]

It is exactly what I'm experiencing John.

I ordered all new washers and had them overnighted on Wednesday night prior to reading Berry's post above so I will get my order today from Moss. If push comes to shove and I can't figure out what I'm doing wrong, I'll give Joe a call.

Otherwise, this looks like great reading poolboy. I might have come across it before, but I lost all my browser's internet bookmarks during a computer crash. I've printed it out and will read with a fine tooth comb tonight before engaging in my re-rebuild.

My wife is really excited/pushing me to have Lucy finished so we can attend NET's Quabbin rally next weekend. I might just have to be sick a day or two :-D

 

[CJD]

I finally got your link to work, Poolboy. I can't wait to read through it tonight...

 

[CJD]

I read thru the nozzle part. It appears that cranking on the large locknut is the solution to the loose nozzle. They call it the "nozzle set screw". The carb configuration in the article is different from our SU's. For one thing, we have two packing washers with cups. This posed a problem for me...

The instructions say to remove the jet when centering the nozzle. I tried that, but the packing washers would not allow me to re-insert the jet. The little packing washers expand and block the hole. I had to leave the jet in place while setting the nozzle position. I am sure there is a trick...but I don't know what it is. It just took me a dozen or so tries to get it all centered.

 

[poolboy]

Maybe this has something:
https://sucarb.co.uk/technical

 

[titanic]

The "Terlerizer" article pertains to Hitachi carbs, which may operate on the same principle as the SU,but shares few if any parts. Kind of like using an SU manual to overhaul a ZS carb.
I have always used a very simple process to center the jets on SUs:.
Remove air cleaners (not absolutely necessary, but helpful) and dampers.
Run just adj. nut all the up-make sure jet contacts the nut.
Loosen jet locking nut.
Constantly raise&lower piston while tightening nut. If needle sticks in jet, lightly push jet in different directions while tightening nut. When correct, the piston will produce a nice audible click when dropped and strikes the bridge of the carb. Variations of this technique are found in most manuals and John Twist (MG guru) has a u tube.
Berry