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Oil tank leaking thru cap

olvinut13

Website User
Non-VOC Member
My rapide throws oil out thru the tank cap,at speed.Is a deflector the answere or is there a better solution.
 

Albervin

Well Known and Active Website User
VOC Member
My rapide throws oil out thru the tank cap,at speed.Is a deflector the answere or is there a better solution.
Don't fill the tank. Remember there is always some oil in the sump & pipes (unless you have drained the whole system) so when putting oil in the tank you need to allow for the extra volume PLUS the expansion when the oil heats up. It is a mistake that even experienced hands occasionally make & a little (hot) oil goes a long way! You will (eventually) learn to only fill to within a couple of inches from the top.;)
 

olvinut13

Website User
Non-VOC Member
Don't fill the tank. Remember there is always some oil in the sump & pipes (unless you have drained the whole system) so when putting oil in the tank you need to allow for the extra volume PLUS the expansion when the oil heats up. It is a mistake that even experienced hands occasionally make & a little (hot) oil goes a long way! You will (eventually) learn to only fill to within a couple of inches from the top.;)
Thanks for that. I never fill to anywhere near the top,only to the bar inside the tank.Also have a Conways non return valve to prevent sumping.
 

Tnecniv Edipar

Well Known and Active Website User
Non-VOC Member
Hi I made a new cap seal but the oil even comes out thru the cap breather hole. Makes a mess all over the engine after a long run

Sounds like pressure build up , which is strange as the engine doesn't breathe into the oil tank. I take it there isn't excessive venting from the breather ?
 

olvinut13

Website User
Non-VOC Member
Hi Engine breathing seems as adequate as other Vins Ive had. I believe there was a Minivin deflector mentioned in a past MPH,so I guess others have had this problem.?
 

Len Matthews

Well Known and Active Website User
VOC Member
Oil Tank Cap

Another thought; has the chain oiler at the rear of the UFM been blanked off? That also acts as the Oil Tank breather.
 

tonythecat

Well Known and Active Website User
Non-VOC Member
Hi Engine breathing seems as adequate as other Vins Ive had. I believe there was a Minivin deflector mentioned in a past MPH,so I guess others have had this problem.?

Minivin has them for sale in the Classified section of this site;

Look for Minivin Oiltank Deflectors.
Tony
 

greg brillus

Well Known and Active Website User
VOC Member
Greg Brillus

Hi there, I've seen this on a couple of our section members bikes, including my own Rapide. What i put it down to is, firstly check and see if your tank vent ie: chain oiler pipe has been blanked off. Or on a "C" tank, that the adjusable chain oiler screw inside the mouth of the tank hasn't been screwed right in, blocking the oiler all together. From what i can work out, this set up is fine at around town speeds, but at speeds of 75 to 80 mph and above at a constant you will find that the oil tank is only able to vent through the tiny hole in the cap. When you understand that the return volume of oil and air back to the tank is far greater than the oil being used from the tank, its easy to see how all this extra volume of oil, mist, and air must escape somewhere. I can only conclude that you must either vent the tank via its original chain oiler (breather) pipe, maybe redirected more toward the rear of the machine (away from the tire at least!). Or slightly open up the tiny hole in the cap to say 2mm.Try that... cheers.. Greg.
 

Howard

Well Known and Active Website User
VOC Member
Funny this, my Ugli used to do the same thing (with a 2 start pump). It was more of a mist through the vent than a leak, but a little leak can cause a lot of oily surfaces.

I cured mine by dropping a smaller bore tube (about 25 mm from memory)with a flange on top into the neck of the oil tank. The flange sat on top of the neck, held in place by the filler cap. The bottom end of the tube was below normal oil level. There was a small vent hole in the tube on the opposite side to the oil return pipe.

I think it was due to hot oil returning too close to the filler cap vent, probably splashing on the opposite side of the oil tank neck forming a mist close to the vent. The vent is there to let air out (as I understand it) so naturally the air came out oily.

I expect to do this on a bitsa, but not on a real Vin. It's a long time since I had a real Vin UFM, but I don't think you could mod it in this way, I think there are "things" in the way.
 

nkt267

Well Known and Active Website User
VOC Member
My rapide throws oil out thru the tank cap,at speed.Is a deflector the answer or is there a better solution.
Is this a new problem or has it always done this..John
 

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