OSSA MAR oil leak

[ScottyA]

Hi everyone ,

I’m hoping to get a bit more advice regarding my MAR. Over lockdown I’ve rebuilt the bike which I inherited in bits, I had never seen one in the flesh so was a bit lost initially  but got some great advice here. 

The bike is pretty much done now, I didn’t attempt an totally accurate restoration just wanted a presentable bike I could actually use. And after some debate I decided to get the engine professionally rebuilt . Riding it round the garden it seems to run well but I have an oil leak(s) 

From reading other threads it seems that one of the leaks is common with other MARs in that there’s a small weep from the right side of the gear selector shaft. Don’t think it adds up to much and I’m not too worried. 

I initially thought the other leak was from the sump plug as that’s where the drips formed but having changed the washer and re tightening the plug I now think it’s weeping from inbetween the crank cases adjacent to the plug. I could be wrong, the oil is clean and its a slow drip so it’s hard to track. Volume wise it’s literally just a drop or two over a 24 period while the bike is parked up.
 

However, this increases if the engine is running. Its hard to measure accurately while using the bike but if I run the bike for 10 mins, shut it off and put a tray underneath I will have a patch of oil about the size of my hand by the end of the day . This continues for a day or so then reduces back to the odd drop 

After all my rambling here’s the question. Is what I’m describing normal? If this is what I should expect from an old Spanish trials bike then fine, I won’t lose sleep over it. But if not I’m going back to the guy that rebuilt it . Just trying to set my expectations really!

I will try to include a pic of what I collected in a Chinese container over about 6 hours post the engine running. As I said if it hasn’t been running for a day or two the leakage is fairly insignificant . 

Thanks in advance! Scott 
 

[djr]

Hello, I have an Ossa MAR and it has always leaked a little from the gear lever shaft - probably because it doesn't have a proper oil seal - I think it has something like a felt washer on the inside and an O ring on the shaft

I have renewed these and it still drips now and then

There should not be a leak between crankcase halves as this has a gasket , and if your engine has recently been rebuilt with a fresh gasket then it should be oil tight - you also don't want this gasket to leak gearbox oil internally into the crankcase area, or air to leak from the crankcase area - probably the most important gasket on the engine & the hardest to change

The only other place I have had a leak is from the gearbox sprocket oil seal { a new seal fixed this }- this could possibly run down underneath the engine

If the leak really is between the crankcase halves , and you have paid to have the engine rebuilt - then I think you should have a chat with whoever did it , to confirm what work was done 

[ScottyA]

Thanks Djr

You’ve confirmed what I suspected, I just didn’t want to go kicking up a fuss if it was a well known fault that they all came out of the factory with. I think I’m going to clean it off and start the process again to see if I can be confident of the source

Leaks aside Im really fond of the MAR, they are lovely little bikes 

Thanks again 

[trialman]

Hi scotty, really it should not leak if its done properly?? I would say lean it right down onto its side and you should see green? gasket between the cases, if you can't I would say return to builder.. I used to work for the local ossa agent in the 70's and used a 310 model, I also had outings on the works cantilever model that also had a reed valve manifold fitted, which really gives the motor some grunt. my 310 had extra flywheel weight fitted to improve grip, but the 250 is a gasper in std trim. youv'e made a good job of restoration and hope you get some good outings on it. See if the vmcc have any events in you're area, as they are great fun and cater for early twinshocks. see attachment below.. all the best.

 

[ScottyA]

Thanks Trialman, 

No sign of gasket poking through only what I assume is a white assembly/gasket paste or something. I’ve attached a picture. I tied this string over where I suspected the leak is to stop the flow continuing downwards. it’s at a slightly higher level than the drain plug and as you can see in the pictures it’s wet with oil. So pretty confident it’s not the plug and no sign of it flowing from another source higher up .

Thanks for the info, I’m going to give the builder a ring 

Scott 

[woody]

They shouldn't leak. I've found using talc helps pinpoint where it first comes from, dry it all off, shower it in talc and then you can see where the wet patch first appears

What can happen with the MAR is that the bashplate gets bent upwards in the middle from repeated contact with the scenery and this can expose the sump plug. If the plug then starts taking hits it can crack the casing around the plug but yours looks fine. It could possibly cause distortion which stops the cases mating fully, not sure

Some of the gaskets these days are horribly thin and if there is any imperfection in the mating surfaces oil finds a way past and drips

Yours has grey sealer as well as a gasket., possibly 3 bond as that is grey but that would usually fill any imperfection in the mating surface I'd have thought as it's good stuff

The gear shaft has an O ring either end but from the ignition side it can't be replaced without splitting the engine as the shaft can't be removed without splitting. It might be possible with the end of the gear shaft cut off flush with the casing to expose the O ring if the shaft is pushed fully inwards with the clutch cover off

I've found with these older engines that it's best to put a little oil in before fitting back into the bike and leaving for a day or two to see if there are any leaks.

A short term fix is dry it all off once you've pinpointed the leak and apply some plastic padding leak fix along the gasket which should hold it. The only correct fix is a strip and inspection of the mating surfaces which might need facing off or to see if there is a hairline crack anywhere

First though, see if you can tighten the crankcase screws any further - you never know...

 

 

[larry s. k.]

Hi Scotty   , most  engine builders welcome , please come back , upon a problem , , you cannot see where oil leak , they might have  a black light , engine die additive ,  to find leak ,  or other abilities , , it happens on new rebuilds , loos shafts  older worn bushings ,  cheapie seals ,, bashed under carriage ,,  it’s a vintage classic ,  CHEERS