SU Carbs - Bush replacement Tool

[richardACS]

Presently rebuilding a set of H4 carbs, endeavouring to find the 3/8 to 5/16 long pilot reaming tool for taking out the old bushes - can't find one anywhere - any ideas please?

You would think this could be a good tool for Burlens to sell

[Peter Laidler]

Taking OUT the old bushes...... Done loads of 'em Rich. I use a thread cutting tap to grip the bush and gently pull it out. Or am I missing something?

[m1cH1]

Peter, I wouldn´t try this method on H4s!

At least not, if they still have their original bushings, as they were cast in. If you would try to pull them out, you would crack the carb bodys!
I´ve recently bored out the original bushings oh H4s (on a faceplate, on the lathe) and they were kind of knurled on the outside to have a better connection when cast in. I did not dare to remove the remains of this knurling fully, as the remaining wall thickness would have probably been not sufficient to rebush.

Cheers, Mike

[Peter Laidler]

Got that Mike. My explanation got lost in not reading Rich's thread properly. But yes, simple on a lathe faceplate or set up on a pillar drill

Apologies for the H2 and 4 confusion Rich and thanks Mike.

[1071bob]

Done mine on a pillar drill. Made some tooling to fit tight in the bed which was bolted from underneath. Then drilled and tapped the top to take the 5/16" pilot shaft, this was set to a length and acted as a travel stop for the 9.5mm drill. When you drill the old bush out you'll find the last part of the bush will come loose as the drill tip hits the pilot shaft. You have to have the carb body bolted down tight as the drill 'grabs' on the brass bush.
Turn carb body over to do the other side.

[timmy201]

I believe Joe Curto sells the type of reamer that they use to rebush H4 carbs

https://www.britishsuperior.com/

A video of the process
https://youtu.be/Yeu-t9ojtBc

[richardACS]

I believe Joe Curto sells the type of reamer that they use to rebush H4 carbs

https://www.britishsuperior.com/

A video of the process
https://youtu.be/Yeu-t9ojtBc

Thanks Timmy - I did find this a while back and enjoyed JC's style and ease of working. I can only assume that the video was a while back and JC is no longer operating. I did search everywhere to see if one could purchase his reamer but to no avail. (Unless I wasn't opening the web page in the right way) I couldn't find his tool. (please no smirks)...

There was also a thread on a stateside MG forum who mentioned a reamer available from ENCO, but I believe the company is no longer in existence...

[richardACS]

Done mine on a pillar drill. Made some tooling to fit tight in the bed which was bolted from underneath. Then drilled and tapped the top to take the 5/16" pilot shaft, this was set to a length and acted as a travel stop for the 9.5mm drill. When you drill the old bush out you'll find the last part of the bush will come loose as the drill tip hits the pilot shaft. You have to have the carb body bolted down tight as the drill 'grabs' on the brass bush.
Turn carb body over to do the other side.

Lovely work there Bob. I may eventually have to go down this route but instinctively "Turn carb body over to do the other side" provides a possibility of error - should we call it 'the line boring' method would remove any possibility of getting things wrong.

I did call Burlens and ask why they don't sell a removal tool (they sell the punch for tapping in the new one). They do have special tools however for their rebuild service!

They recommend setting the body up in the lathe (as Mike from germany has done) and removing the old bush with an 8mm drill - they say anything left in the shaft should be left before tapping in the new bush with the punch (which is no longer a brass one). This method would enable an accurate depth for drilling with the drill stock. Thanks to my dear old step dad I have inherited his small lathe and could use this procedure.

If I had a couple of spare bodies I could feel confident to do a trial but the need to set up the body twice is unnerving or maybe I'm just over thinking the whole thing!

I'm not in a deperate hurry to do this so not rushing to get it done - but JC's reamer/long pilot is a no brainer - with one caveat - I think JC used his own bushes so his reamer would have been sized to suit....

A crazy notion - how could one get a reamer made? how difficult would it be to turn down one end of a long 8mm reamer - I'm guessing the hardened steel would not allow such a procedure?

[richardACS]

Given the new bushes supplied by Burlen - could this 8mm reamer be adapted to suit?

https://www.ebay.co.uk/itm/175342107169 ... 0667.m2042

I've sent them a message to ask for the dia and length of the longer section of the 8mm reamer...

[Peter Laidler]

I have done it Bobs way several times Rich. But very slightly differently........., Same meat, different gravy so to speak. I used the drill bit in the drill head/chuck to align BOTH sides/bushes then clamped the carb body to the drill bed. Then set the drill depth to machine the top bush. Top bush now accurately set

Turn body over and do the same. The end result is a line bored set.

[mk1]

I can re-bush H4's using the correct JC stepped reamers at a cost of £35 per pair. I supply the bushes in on the price.

Contact me if interested.

M

[Spider]

A little agricultural, but my set up does have a pilot to line them up spot on, you can do them with a hand drill with this if you wanted to. It also includes a depth stop.

[timmy201]

Have you done any H4 carbs spider?

[Peter Laidler]

The really good thing about this thread is that it has shown that all those capable of doing this accurate job have done it a slightly different way. And all achieved the same result. Rebushed, line bored air-tight spindles and rebuilt carb bodies.

Good instructive thread.........

[richardACS]

A little agricultural, but my set up does have a pilot to line them up spot on, you can do them with a hand drill with this if you wanted to. It also includes a depth stop.

Agricultural? looks pretty good to me!

[Peter Laidler]

Moving on a step with this thread in mind..... Replacing the butterfly absolutely centrally as possible within the body tube is most important too, for obvious reasons. Always mark the body to match the spindle to match the butterfly. A small scratch mark or felt pen is a good idea.

After rebushing or O ringing, insert the butterfly THE CORRECT WAY ROUND according to the chamfered edges of course while roughly aligning the screw holes in the spindle and butterfly. Insert the screws but leave them loose enough to allow the butterfly to centre itself (or with a bit of help from your dainty fingers). Open and close the spindle and butterfly and it will centre itself within the opening. Nip up the screws and look into the opening from both ends up at a bright light or window. Adjust the butterfly position in the spindle until the best position where there is the least amount of light on show That is the best position for the butterfly. Now it's time to lock down the screws

If you closed the slots just sufficient to remove them, they'll be fine to use again. No need to open them like split pins....

[Spider]

Have you done any H4 carbs spider?

Sorry Tim, I only just saw your post now.

No, I haven't done them. Do the have the same or similar bush arrangement as the HS4 ?

[timmy201]

Have you done any H4 carbs spider?

Sorry Tim, I only just saw your post now.

No, I haven't done them. Do the have the same or similar bush arrangement as the HS4 ?

I haven’t changed both myself so I’m not 100% sure. I bought a rebuild kit for my H4’s but the bushes are “Teflon lined” and are a loose fit on the spindles and seem to have scratched badly from me just test fitting them. They might tighten up during fitting but I don’t see how they can be teamed to size as it’ll remove the soft inner coating

https://sucarb.co.uk/technical-h-type-c ... nd-brushes

[Spider]

,,,,,, but I don’t see how they can be reamed to size as it’ll remove the soft inner coating

Ah, Just to clarify what's going on with the reamer etc, as least on the HS Carbs. Originally, the bodies had no bush, the spindle ran direct in the alloy casting. When that wears, the alloy body is reamed to the OD of the new bush and these are pressed in. They are (or should be) on size when fitted, ready for the new shaft.

The past 5 or 6 years, I have been machining O Ring Grooves in the shaft, such that when the O Ring is fitted, they are flush against the side if the body with only light friction. On assembly, I give the bushes a greasing with some light (instrument) grease. I did this originally to dust proof the carb, but I've found that as a side benefit, the grease remains in place, the shafts and bushings wear so much slower.

[Spider]

The past 5 or 6 years, I have been machining O Ring Grooves in the shaft, such that when the O Ring is fitted, they are flush against the side if the body with only light friction. On assembly, I give the bushes a greasing with some light (instrument) grease. I did this originally to dust proof the carb, but I've found that as a side benefit, the grease remains in place, the shafts and bushings wear so much slower.

I've received some emails and pms on this.

Here's one that I O Ringed, not the best angles I'm sorry;-