SU fiber washers and banjo bolt tightening

So I bought a couple rebuild kits and removed the float bowls to clean and put in new seals.
Still have that annoying leak!
How tight do these banjo bolts have to be to stop the leaks? Or is there some secret ritual to it that I’m unaware of.

Parallelism is important: I’d say, no more than 5-8 ft-lbs of torque.

Stone/chisel off any burrs, “two finger” tight is enough. (Two fingers on the wrench, close up to the end, pull with two fingers until your tendons start to feel discomfort).

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I did the cleanup on the banjo fitting and with it snug more like 8 to 10 ftlbs it leaked fairly bad. Snugging the rear one worked but not the front. I even loosened the float bowl cover to make sure the bolt pulled in even.

After both shoulders being repaired in 2017 tendons feel pain fairly easy.

I guess Sunday I will attack it again and hope for the best.

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It could be you have deteriorated threads inside the alloy float bowl lid

A visual exam under a Jewellers loupe will be indicative

new (or used) lids are quite expensive, but available

if teflon tape stops the leak, that is likely the problem

Thanks for the heads up on the threads. I’ll take a look at them.

you can buy lipped washers
In cross section the lip on the edge is a bit like a Trident [ for those Maserati owners] with 3 seals for 3/8" BSPF. Sold here at places doing high pressure hydraulic lines for earth movers and the like.
The pre war Adderley Park SU foat bowl tops were much better.If the thread deteriorated there was plently of room to run a tap in and extend it and use a longer banjo bolt.
Soaking the fibre washers before use isn’t a bad thing.


I have suffered leaks even though I have tightened up the banjo bolts to within an inch of their life. On an XK150S there are 4 banjos that have magically to all be aligned. Here is my secret ritual …

First, make sure you are using new fibre washers. If not, then reface old ones by rubbing them on fine sandpaper that is laying on a flat surface.

Check that the face of the lids that the banjos bolts screw into are flat and free of nicks, etc. Dress with a wide fine file if needed, or just to be sure. Naturally, use file only once lid is removed, so you can wash away all fillings.

Check that the mating faces of the fuel pipe banjos are also flat - they may be dished because of over tightning, or be nicked. Dress with wide fine file. This filed the nickel plating off my banjos, but it was needed to get them flat.

Check the outer sides of the banjos. I have found old white fibre washers hiding in the recesses, almost invisible, that needed picking out. Check the recesses look to be free of nicks, but not a lot you can do here.

Check fit of new/refinished fibre washers in the recesses. It is possible the outside diameter is too large, in which case sand/file down to fit snugly. Remove washers for now.

Next fit lids, but tighten their bolts so lids can rotate. Grease threads of banjo bolts - this makes fitting so much easier! Trial fit fuel pipe without washers. Screw in banjo bolts barely finger tight. Lids will rotate to optimum position.

Now check that the mating faces between the lids and banjos have no gaps. Gaps happens if relative to each over, faces are not vertically alligned and or spaced correctly. Likelihood is there are gaps and this is cause of leak. The remedy is to bend the fuel pipe untill all surfaces mate perfectly. To bend you have to remove pipe and hold, say, one banjo in vice (with aluminium keepers, of course) allowing you to use hand strenght to make an adjustment.

The key point is that the banjos should accurately line-up without relying on the banjo bolts forcing them into alignment.

On the XK150S, this is a long and tricky process, and takes patience - trial fitting, removing, adjusting, refitting, ad nauseam. Freeing the pipe from the carbs is like untangling those metal puzzles.

When you are satisfied that you have all banjos mating near perfectly with the lids, then you can do the final fitting with the washers. Again, greasing threads makes tightening smoother- and less torque will be needed. Tighten banjo bolts with your Whitworth spanner, but only just nipping them up. Now you can tighten lids up, and then back to the banjo bolts for final tightening.

Follow others guidance for how much to tighten the banjo bolts. Once you run up the pressure with the fuel pump you may have to tighten them a bit more if they weep. If you think you are using too much force, then go back to the trial fitting stage with no washers.

I have also sprung leak in a joint between banjo fitting and the fuel pipe, so look out for that being source of leak. This requires joint to be resoldered, then back to trial fitting stage.

After much patience and divinity, my system is fuel tight, and I didn’t have to apply too much torque, but probably more than others recommend though.

Regards and good luck,


Excellent write up but the problem that I had, from the time I got the 64, was that the fuel rail was “tweaked” and as It appeared that I’d never get it aligned good enough to stop taken a chance of the stripping the caps I dug through my supply of O rings and picked out some that were the proper size to replace the fiber washers and for the past 20+ years just a little more then finger tight does the job. If all else fails or you’re just feeling lazy, consider O rings.

Hi Bob
I thought about orings, but wasn’t sure if they would work. Good to know that they do and last 20 years. So that bag of 100 I have to buy from grainger should last quite awhile. Lol

I’d be reticent about o-rings but interested in what other’s might say. To me, they are intended to seal in a “captive” environment–groove, etc. Otherwise, they are a very weak lock washer, with nothing to keep the fastener from unscrewing. OK with very frequent maintenance but not what I would trust for fuel.

I may be misunderstanding. If there’s a way to squish one in a compartment behind a metal washer that is tight, then that’s different. There are many examples of that in the aftermarket, just didn’t know about one for fuel banjos.

I could never get the fuel rail aligned well enough to prevent leaks without what I felt was over tightening and while not my first choice this ended up being a solution that worked for me. I have no idea of what their original usage was but they were among the huge selection of hydraulic fittings etc that were given to me and others when we shut the mill down for the last time.If I had used what most people think of when they hear O ring I would also be leery of them distorting when tightened but these were fat o rings with quite a bit of "give"and it’s been well over 20 years with no problems with loosening up.

Well today I got the torque wrench out and gave it a little tug it moved fairly easy with the torque wrench. Although I had it set at 18 ft/lbs. it did the trick I’m leak free once again. Yeah!

Thanks for all the ideas.