Inlet rubber manifolds

Maestro, SEI-V
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bigred
Posts: 64
Joined: 05 Dec 2022 19:19
Location: swindon england

Inlet rubber manifolds

Post by bigred »

Hi I recently recommissioned my 1981 500 sport. After a few runs one of the rubber inlet manifolds split so I bought some new ones from medinaitalia. I am having big issues with air leakage at the head end of the rubber manifolds. Both appear to be leaking air and if I spray some quickstart at the head ends both cause the revs to drop and engine to cut out. Its worse on the rear cylinder for some reason. The new ones are not identical to the old ones in dimensions being a few mm bigger in length and the depth of the head end seating area seems a mm shorter depth. Theres also a bigger external flange.
Has anyone had this issue and come up with a fix?
Can I buy rubber manifolds else where that are better?
Have I got the right screw in manifolds?
morini_tom
Posts: 920
Joined: 05 May 2006 13:47
Location: Northampton

Re: Inlet rubber manifolds

Post by morini_tom »

Are you using the plastic collars which go around the rubber manifold at the head end, underneath the jubilee clip? Not using them is a good way to accelerate the splitting of the manifolds.

Are the metal stub tubes in the head tight? They can loosen, again introducing air leaks.

The part numbers for 501 (30.01.88) and 500 (30.01.54) are different for the rubber manifold. Are you definitely using the correct one. I couldn’t be sure without comparing side by side but the 501 has bigger carbs and valves etc so I expect it’s probably a larger diameter manifold too.
norbert
Posts: 750
Joined: 15 May 2007 15:15
Location: Lübeck/Germany

Re: Inlet rubber manifolds

Post by norbert »

Yes the 500 an 501 manifolds are a bit diferent. On the carb side they should be the same. Or that´s what I guess, being the 26 and 28 PHBH. At least the diamenter of theses carbs to the filter is the same.
But the studs in the heads where the manifold is mounted has a bigger diameter in the 501 than 500 (don´t know exactly the mm)

I remember a time when there seemed to be only 501 manifolds on the market, don´t know how the situation it is actually.
bigred
Posts: 64
Joined: 05 Dec 2022 19:19
Location: swindon england

Re: Inlet rubber manifolds

Post by bigred »

Hi thanks for the replies. No I dont have any plastic collars under the jubilee clips. There wern't any when I got the bike so I did not know they were required. Do you have a part number?
I have the 500 part from Medina and not the 501.
bigred
Posts: 64
Joined: 05 Dec 2022 19:19
Location: swindon england

Re: Inlet rubber manifolds

Post by bigred »

Hi I have found the part number for the plastic collars and ordered from medina. Has anyone got a picture of how they go on. There seems to be a flange on one side.
Many thanks. Hope this solves the issue
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