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SU Rebuilding

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Voda2000 Avatar
Voda2000 Andrew McMillan
Winnipeg, MB, Canada   CAN
When I rebuilt my 78 Spitfire 15 years ago the one thing that was never really touched was the engine internals and it has been a great car the whole time. So the plan now it to rebuild the motor over the next year but haven’t decided if I’ll wait until the fall so that I can still enjoy the summer driving. I’ll be posting the details of my rebuild plan once I finish my research.

One decision was to replace the single ZS with duel HS4s. I’ve always wanted them since I bought the car in 2001. Last night I finally got a set complete with all linkages, manifold, heat shield and new air filter. I have a few questions.

There are no tags on the carbs but they appear to be FZX1258. I’ve rebuilt carbs before but these are my first SUs. They seem faily straight forward but is there any pitfalls I should watch for?

What’s the best way to clean the carb bodies?

The previous owner soldered the valve in the butterflies shut. I’d like to replace them with solid disks. Are all the solid disks the same for all hs4?

The idle screws seem to turned in along way which indicates to me they had trouble with it idling. I suspect there is a leak around the throttle shafts. I’m going to pull them and see what the wear is like. I’m hoping it might just be ware in the shaft and not the bushing but if it is, is it best to ream out the bushing and then install an over sized shaft or just I still new bushings and standard shafts? Also, is there any shop in the Winnipeg area that has done this for someone?

These carbs have waxstats in them. I have no idea of the condition of the jets. Is there a way to test them? Is it best just to to replace them like for like? Replace them with non waxstats and change the choke linkage?

Last, I have a local Moss dealer that I’ve worked with forever. Is Moss a reasonable place to get rebuild kits?

Sorry about the long post.

Andrew



1978 Triumph Spitfire

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clshore Carter Shore
Beverly Hills, FL, USA   USA
NEVER mix up the parts between the pair.
NEVER drop the suction chamber.
NEVER drop the piston.

Other than that, they are very simple and easy to work on.
Take pictures as you disassemble, and keep the parts in baggies with labels inside.

There are some parts that have Left/Right versions

Use regular cleaning supplies, and rubber/plastic bits will get eaten by aggressive solvents, just like any other carb.
An old toothbrush works well for cleaning nooks and crannies.

It's possible to ream the shaft holes yourself, but some precision is needed to avoid misalignment,
else the throttle disks will never again seal properly.
So most folks have it done, Joe Curto is the go-to guy in the US.

Burlen is the current manufacturer and parts supplier, their site is a very handy reference.

DerbyRam54 Neville Wardle
Branford, CT, USA   USA
Pinesol works quite well as a cleaner and doesn't, as far as I can see, attack rubber or plastic. I've cleaned up quite a lot of parts by simply leaving them in a Pinesol bath for a day or two and then as Carter suggests giving them a scrub with an old toothbrush. You could of course use a new toothbrush instead.

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roncohudd Avatar
roncohudd Gold Member Ronald Huddleston
Muenster, TX, USA   USA
1967 Triumph Spitfire "Lucy"
1969 Triumph Spitfire MkII "Lucifer"
1997 Ford Ranger "Little Red"
2001 Yamaha MC XV1600A "NOT THE HONDA"    & more
Did mine with the help of my wife and B.V. Not so complicated.


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Tonyfixit Avatar
Tonyfixit Tony M
Duncan, BC, Canada   CAN
I have always used Solder Seal Gunk Carburetor cleaner, soak the parts overnight clean with a toothbrush and rinse in water. Work on one carb at a time.
I buy parts direct from Burlen (who are SU) they might better understand that your rebuild kit is 'custom' if you change the butterfly discs to plain ones or convert away from Waxstat jets.

As Carter says, you can ream for new shafts, Joe Curto has a video on doing this. You might best judge if you think you are up to it.

I have a collection of SU spares, needles etc. PM me if you get stuck or wish to borrow/try a different needle.



Edited 1 time(s). Last edit at 2018-02-02 10:55 AM by Tonyfixit.

DerbyRam54 Neville Wardle
Branford, CT, USA   USA
Besides being an excellent source of parts and so on, Burlen also publishes a very useful shop manual for SUs which you might find helpful if this is a new venture. As I recall it's not very expensive. Their reference catalogue is also invaluable and can be had for the cost of shipping.

No connection with Burlen other than satisfied customer.

Tonyfixit Avatar
Tonyfixit Tony M
Duncan, BC, Canada   CAN



Many years ago I wrote (snail mail) to Burlen asking a bunch of dumb questions about rebuilding SU's

I recived back a had written letter from Don Siddle explaining (and often rambling ) about their carbs. Don has retired now, but I still have his letters, they are quite lovely. I also bought their manual and parts catalogue.

Latter on I got to contact Joe Curto.
Funny thing, two guys, both near the top of my list of the nicest people I have had to deal with, and BOTH SU guys!

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DerbyRam54 Neville Wardle
Branford, CT, USA   USA
The other thing that Burlen has done a very nice job with is a history of the S.U. company and the family. It is a very well-produced book and must have cost quite a lot to have printed. It's rather heavy and I had to pay extra shipping, but well worth it.

Joe Curto is one of the good guys in the hobby, he's coming to CT to do a tech session next month. He's also being inducted into the British Sports Car Hall of Fame in June.



Edited 1 time(s). Last edit at 2018-02-02 03:42 PM by DerbyRam54.

Voda2000 Avatar
Voda2000 Andrew McMillan
Winnipeg, MB, Canada   CAN
Thanks for all the help so far. I’m going to try and strip one of the carbs down this weekend and get a better feel for what I’m dealing with. I’ll post some more photos as I get further along.

As for the bushings I’ve got a friend that builds highend pro-touring cars and I might consult with him regarding machining options if necessary.



1978 Triumph Spitfire

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carChips Avatar
carChips Victor Harnish
Kelowna, BC, Canada   CAN
1933 MG Magnette
1973 Triumph Spitfire 1500 "Chip"
1989 GMC Sierra 1500 "Bush Truck"
If the throttle shafts are badly worn, then the bushings are probably fine. If the throttle shafts are loose and hardly any wear then the bushing will need to be replaced.



'S all for now
Vic

Outfect Avatar
Outfect Dave B
La Sal, UT, USA   USA
1940 Ford N Series Tractors "Henry"
1951 Other Not Listed "SnowMan"
1979 Triumph Spitfire 1500 "White October"
1980 Triumph Spitfire 1500 "Tangerine Dream"
Andrew,

I strip carbs with a 50/50 mix of gas and MEK. Then after brushing off as much as possible into the ultrasonic cleaner.
Then blowing out all passages with high pressure air. Polishing depends on how shiny you want them.

Moss sells genuine SU kits made by Burlen LTD. It's about the same price as if you ordered from Burlen and paid
the shipping. One tip, look for any small nuts, bolts or springs you're missing. They are cheap but will cost you $8 to
buy a $1 spring if you're ordering one.



DaveInUtah



Edited 1 time(s). Last edit at 2018-02-03 12:52 PM by Outfect.

Tonyfixit Avatar
Tonyfixit Tony M
Duncan, BC, Canada   CAN
On the subject of bushings, Burlen supply Teflon lined steel bushings whilr Joe Curto seems to prefer Brass.

I have used both, but found that the steel bushings were not as snug on the shaft as I would have liked.

I also had a carb body that had had a very Ham fisted rebushing, where the shaft had been reamed off centre. I assembled the shaft with the butterfly disc, the shaft ends were smeared with Vasoline and set the new busings in the carb body with JB Weld. The disc was held closed while the JB Weld set.
I needed to remove the shaft again and clean up some set JB Weld that had got into the venturi, but it saved the carburetor, that is still performing well now 10 or 12 years later.

Voda2000 Avatar
Voda2000 Andrew McMillan
Winnipeg, MB, Canada   CAN
Still haven't made it out to my shop yet for disably but I watched Joe Curto's video and a few others on the bushing issue and now I see the problem. It's seems the real issue is that the bushings were cast in and not pressed in making accurately removing them a real pain.

I can think of a few ways a jig could be setup to drilled them but if things went wrong it would be extremely hard to fix. Joe's reamer seems to be a fairly simple solution. It also seems that once the originals are removed correctly, future replacement would be fairly straightforward. There doesn't seem to be any prices for the reamers (and it looks like two are needed), any idea on the cost?

I also see there are oversized shafts available but I saw the price of the reamer needed for that from Moss and just about had heart failure.

I would prefer brass over Teflon coasted steel simply because if you have to do a ream for final alignment you would remove the coating.

I did see a note in the Competition Preperation Manual that suggested drilling a hole in the body through to the shaft to allow for oiling. Anyone tried this?



1978 Triumph Spitfire

clshore Carter Shore
Beverly Hills, FL, USA   USA
In reply to # 1511216 by Tonyfixit ...
I also had a carb body that had had a very Ham fisted rebushing, where the shaft had been reamed off centre. I assembled the shaft with the butterfly disc, the shaft ends were smeared with Vasoline and set the new busings in the carb body with JB Weld. The disc was held closed while the JB Weld set.
I needed to remove the shaft again and clean up some set JB Weld that had got into the venturi, but it saved the carburetor, that is still performing well now 10 or 12 years later.

That's a good idea, using the throttle disc to align the bushings, I'll remember that one.

Tonyfixit Avatar
Tonyfixit Tony M
Duncan, BC, Canada   CAN
In reply to # 1511226 by Voda2000 I can think of a few ways a jig could be setup to drilled them but if things went wrong it would be extremely hard to fix. Joe's reamer seems to be a fairly simple solution. It also seems that once the originals are removed correctly, future replacement would be fairly straightforward. There doesn't seem to be any prices for the reamers (and it looks like two are needed), any idea on the cost?

I also see there are oversized shafts available but I saw the price of the reamer needed for that from Moss and just about had heart failure.



Burlen sell a ream and so does Joe (pic) I have no idea of the cost.

My ream is just a modified tapered ream** with a stop. I can move the stop back and ream oversize to allow correction if need be. Bushings are put in with blue loctite. So again the shaft sets the final alignment.
Unlike Joe, I do not stop 1/16" from the bottom, I go all the way. The end of the new bush is first given a slight concave to fit flush with the inside wall of the choke.

By recessing the bushing slightly I can press in a small felt washer at the outer ends. This can hold a little oil, and helps seal a possible air leak down the road.

** The first 3" are cut the the bushing ID and blunt.


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