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ET: Engine (Twin) Persistent oil leak

Gerry Clarke

Active Website User
VOC Member
When we started nobody in my circle knew what a torque wrench was and even if we did, nobody could have afforded one! Consequently I have never used one but never had a leak. Best to work with short spanners and check over time on the road. The motors seem to tell you when they're right.

Gerry
 

Vinthou

Website User
VOC Member
I had a similar leak on my Shadow - oil would show up on the front exhaust rose, and on both the inside and outside of the mag cowl, and then, of course streaked along the cases. I changed all the seals on the oil lines and the mag gasket to no avail. Then I read somewhere that due to the air currents around the engine, oil can flow forward. It turned out that there was a leak at the junction of the rocker feed pipe and the banjo for the front cylinder inlet valve.
 

SteveW

Active Website User
VOC Member
Look at the forward cylinder's intake valve oil line fitting (234) If this is leaking it will run down then forward along the fins then drop down onto and into your mag. very inconveniently. Also, I traced this by using terry cloth strips to see where the oil is coming from. Good Luck.
 

Chris Launders

Well Known and Active Website User
VOC Member
Having finished the current job on my twin and it being sat in exactly the same position for two months I decided to tackle finding possible leaks, starting at the top.
After removing the tank the first I found was a drop of oil hanging off the tank return banjo (bearing in mind I haven't run it since November) so whipped that off and fitted two new Dowry seals, then cleaned as much old oil/muck off the engine as possible (4 cans of clutch/brake cleaner).
Removed all the rocker feeds and found the rear exhaust and front inlet fibre washers had collapsed, replaced all four with strange size Dowty seals I had that were exactly the right size. next was off with the two accessible valve caps and the rocker caps, these looked to be sealing well (put a bit more tension on the two under the UFM) then found the timed breather banjo loose, feed and return banjo's were also not tight enough.

Next day there was oil under the bike in two places, one was coming from the crankcase joint which when I checked the nuts holding the front stand plates on these weren't properly tight.
The other was below the bend in the feed pipe, now this one was really sneaky, it was coming out at the back of the rubber hose where it is on the the steel pipe by the top of the timing cover and running down the back of the pipe, the ferule wasn't a crimped one so wasn't sealing. rather than rip the whole thing, off as temporary measure I fitted a thin Jubilee type clip behind the ferule.

A week later and there is no sign of any leakage, of course I haven't run it yet but that is at least four leaks fixed
three of which leaked even without it being run.
 

998cc

Website User
VOC Member
Look at the forward cylinder's intake valve oil line fitting (234) If this is leaking it will run down then forward along the fins then drop down onto and into your mag. very inconveniently. Also, I traced this by using terry cloth strips to see where the oil is coming from. Good Luck.
My leak was at the hose ferrule that slides over the 234 fitting--same result. Crimping the ferrules might fix it; however, crimped ferrules are ugly. While my order from the spares company is in transit, I am removing that entire line from the engine to the oil tank return. To prevent leaks at the ferrules, I am soldering a small ring made from copper wire around the tubing. Pushing the ferrule over the rubber tube with the ring in place takes a bit of silicone grease and considerable effort to fit it all together, but it makes a good and tight connection. Will post some photos if anyone is interested...

Best regards,
Russ
 

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