How to Tune SU Carburettors

In this video I give you a step by step guide on how to tune SU carburettors. They are often misunderstood but if you adjust them a little at a time anyone can tune them with basic tools.

Other Video you may like:

Affiliated links:

#su #carb #carburetor

[frankpowell]

Hi Adam, your video is the first to pop up on my search for SU carb adjustment!

[lee]

You so much for posting this!! Unbelievable, because I've never seen this until yesterday. I was 17 yo and I was there! That is a 17 yo me standing near James Browns' getaway limo out in front of the auditoriym after the ceremony!! An unbelievable day!!

[junglejoose]

These videos are completely enlightening and motivating. Going to refurb some roundtops now to replace the flat tops in my 510. Thanks!

[guyledouche]

Thanks for the video. It has been a great reference for me to keep my customers 240z running as it should. Hadn't touched a set of su's since the 80's, now in the past 3 years I've had 2 customers show up with 71 240z's both with carb issues that the local z specialist would not touch. Thanks to your video I can tune them peffectly.

[boatman]

Great video on the basics of working on SU Carbs. I worked as an MG, Austin Healey mechanic in the 1960s and early 70s and although the SU Carbs used in them are similar to the ones on this Jag there are some slight differences in design. To adjust the jets for rich/lean mixture on MGs you use a wrench to move the jet up or down by changing the height of the seat. They used to sell a special tool for this but I always just cut most of the handle off a suitably sized open end wrench which gives you a stubby sized wrench which is much easier to use underneath the carbs. For synchronizing the carbs I just removed the air filters and held the end of a small rubber hose on the edge of the carb throat and placed the other end in my ear. The sound of different air velocities is quite distinctive and with a little care very precise adjustments can me made with this method. One point not made in this video is that it is absolutely key to do a thorough job of cleaning the inside of the dashpots as well as the skirt of the piston that runs up and down inside it. Many times varnish that collects on these surfaces can cause the piston to hang up, or lag behind in responding to throttle changes. As mentioned in this video these pistons and dashpots are a matched set. The reason for this is that fairly tight tolerances are required for them to work properly. Unfortunately this eventually became a problem with MGs (at least in Calif) as EPA requirements forced MG to tighten up these already tight clearances. I owned a small sports car repair shop in Calif in the early 70s and MGs sold in Calif at that time were very difficult to set idle speed on as the dashpot pistons were constantly hanging up. It would have been illegal to hone out the dashpot chambers a tiny bit but doing so may well have solved this problem.

[EcBuddy]

Getting my hands on a 71 xj6 this Friday so this is going to be helpful, as most of your other videos! I'm extremely excited!

[andrewfreeborn]

Really useful video! Thank you Adam. I've got a 1976 Mini GTS, which is a South African model that came with twin SUs.

[FabienProxTrm]

Restoring my 240z and I have 2 SU carbs!! Your videos will help a lot! Cheers man and happy new year :)

[dornosaur]

Thanks mate! I have a datsun 240z. I found out my su carb was completely unresponsive to the mixture screw. I took it to a professional tuning shop and the took the bell housing off and unstuck something. I wish I had asked them exactly what they did, but if you find the min and max of the mixture adjustment makes no difference, that could be your problem too. The weather in Seattle is starting to get a bit colder so I'm expecting to try again in the next few weeks. Thanks for your video, I think it's a great summary and plan to follow it next time.

[tonycollingridge]

Hi Adam, another great video. Thank you. There are so many different schools of thought on tuning SUs and I definitely think it is an art rather than a science! Everything you did on the XJ mirrors what I do on my Mark 2 except that I think you suggested that you should undo the throttle linkage before tuning and tune the two carbs completely separately before re-connecting the linkage. My manual (Jaguar and several others including Haynes) is/are clear that the linkage should be loosened at the beginning to ensure that the butterflies can be and are both completely closed and then re-tighten before going on with the rest of the tune up. I've always followed that practice and it works well for me. Interested to hear your thoughts on

[michaelbahe]

It is great to see how the Unisyn actually works. My car is a Jaguar E-Type V-12 (73) - so it's 2 sides to tune (4 SU's) which is (I think) balance each side and then balance the 2 sides.
Thanks again!

[relmdrifter]

Thanks for the video. Tuned a set by ear. Buying a tool for air flow to fine tune them. Also learned how to properly use the dashpot lifter, thanks again.

[theoriginaljc-j]

Very impressive and clear instructions. I am now looking forward to getting stuck into tuning up my carbs - 👍

[DuskersHusky]

thanks for your video, i have been having a nightmare with my dolomite, im going to give this a try tomorrow cheers!

[qazandrew]

Thank you for a truly excellent video! HUGE help for my twin SU carb mini!

[AthelstanEngland]

Thanks very useful recap. The graphs made it easier to remember too.

[chrisscott]

I'm glad I found this. I'm installing the engine in my '66 Austin Healey Sprite.

[rhyshanrahan]

Hey mate I have a 1974 triumph 2500tc manual really needed this video thank you

[phabel]

Really helpful, off to reset my 61 mark 2 Jaguar 3.4. Thanks

[zenoclarke]

Thank you for sharing and nice work. I'm attempting a series 1, e type, 4.2 tomorrow. Thank you 👌👍