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Hi all, having trouble with a suspected air leak on a rubber mounted PWK 28mm on a Casa 186 kit that’s been bored out to 200cc. I have the correct grooved inlet manifold and a matching ridged inlet rubber. My problem is that every ‘Jubilee’ type clip I use is distorted where the screw is i.e. the bit the screw mounts on is thicker and thus grips the hose in a distorted non round manner. This means that the rubber is gripped and tightened in an uneven way and I suspect is causing an air leak. Are there any specialist clips out there that grip evenly as they’re tightened? I wonder if the twin wire loop style might be better as they’d grip the rubber either side of the ridge and groove inside?

What about trying the spring clips that are used on modern coolant hoses on cars the ones with the ears that u use pliers on sorry don’t know what there proper name is

Yep, know the type you mean. Don’t think they’d be any good as you can’t adjust them- the tightness is fixed.

Those clips are spring loaded and are self tightening. Access to use the pliers may be an issue and it means carrying an extra tool. You need to get some of the narrower jubilee clips, they fit better than the wide ones.

I use these off E Bay Thinner type

https://www.ebay.co.uk/itm/PRIMA-jubile ... 2749.l2649

Ok, I don’t think they’re ideal though as they don’t tighten up up in a uniform way due to the extra metal under the screw. This then leads to the potential air leaks. I like these better, but I cant find any that are narrow enough for the rubber. https://m.ebay.co.uk/itm/ASH-Hose-Clamps-Heavy-Duty-Exhaust-Hex-Screw-New-T-Bolt-Stainless-Steel-Clips-W4/222607620197?_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D1%26asc%3D20180213162448%26meid%3D79331caa45a2423fbe089debafdcc9ea%26pid%3D100930%26rk%3D3%26rkt%3D8%26mehot%3Dpp%26sd%3D121179363544%26itm%3D222607620197&_trksid=p2056116.c100930.m5375

Pompeydave wrote:Ok, I don’t think they’re ideal though as they don’t tighten up up in a uniform way due to the extra metal under the screw. This then leads to the potential air leaks. I like these better, but I cant find any that are narrow enough for the rubber. https://m.ebay.co.uk/itm/ASH-Hose-Clamps-Heavy-Duty-Exhaust-Hex-Screw-New-T-Bolt-Stainless-Steel-Clips-W4/222607620197?_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D1%26asc%3D20180213162448%26meid%3D79331caa45a2423fbe089debafdcc9ea%26pid%3D100930%26rk%3D3%26rkt%3D8%26mehot%3Dpp%26sd%3D121179363544%26itm%3D222607620197&_trksid=p2056116.c100930.m5375

Will they fit ?

Whist offering an option used these for a while and done a few miles with no carb issues ( famous
Last words )

MB do some good ones, with a slightly rolled lip to avoid them cutting into the rubber.

However, the BIGGEST issue with carb / rubber / manifold issues is the match of rubber and locating rib on carb stub and manifold. When you get the right match you'll have a job even pulling the rubber back off without a clip fitted! So many times the diameter is slightly wrong and/or the rib (or ribs) are in the wrong position. If the rib is even slightly off from where it should be then you'll find that the carb wants to pop off easily, with tightening the clip just making it worse; forcing it off or causing it to split.

Get the rib position right and you'll never suffer this again. Don't take the word of anyone supplying you with a rubber, look at it and compare the rib position. Frustratingly, there are many different carbs, manifolds, diameters and rib positions and you must get the right combination. Many dealers will sell you a rubber of the correct diameter BUT with the rib in completely the wrong position. Even the same manufacturer may cause you issue, e.g. PHBH and VHSA carbs are very similar diameters but the rib location is at a VERY DIFFERENT position and yet many dealers supply the same rubber for both. PM me your email address and I'll send you a photo that I posted on a similar thread a number of years ago.

The other way to address this issue is to rework your carb stub and/or manifold so that the rib position is correct.... but try to find the right rubber before going down this route.

Good luck.

Adam

Wise words Adam.

I did an Oily Rag on this subject many years ago, and it explained how I had to modify the carb stub to get the groove in correct place.

What a faff, but no more clip issues.

I have also switched to using flange rubbers, as these need only one clip. It might need modification of the manifold if it is not already suitable for a flange rubber, but it is worth it.

Flange rubbers are available from Allen's Performance.

It would be nice to have a thread or section with the all the historical oily rag articles...

Just saying... Again

Knowledge wrote:Flange rubbers are available from Allen's Performance.

Oooh... what a great tip/link... I've recently fitted a LTH manifold and the flange rubber that came with it doesn't look up to much. I've been looking at the MB one but the Allens site looks really useful! Ta...

Feersum Injun wrote:

Knowledge wrote:Flange rubbers are available from Allen's Performance.

Oooh... what a great tip/link... I've recently fitted a LTH manifold and the flange rubber that came with it doesn't look up to much. I've been looking at the MB one but the Allens site looks really useful! Ta...

Please let me know if you do get 1 from Allen’s and how you get on. I also have bought an LTH for my muggi project.

Shane