The Mono saga continues!

[themoudie]

Rather than add to the "Why SRX tanks need to be drained!" thread, I thought this required an additional thread.

100Km short of putting 4,000Km on the Mono after its complete rebuild, today it developed a 'problem'!

We went out for a wee back lane canter to an area we know well for rasps, blackberries and grand views across the Vale of Strathmore into the Angus Glens and Grampian Hills behind the Southern Highland Boundary Fault, from the north side of the Sidlaw Hills. Geography lesson out the way! Having spent ~3 hours picking rasps in 24°C heat with little breeze we felt that we needed to retire for a pie, sweet tasty/ice cream and cool drink in the shade, so made for Newtyle Post Office where the local 'World Champion' Scotch pie maker's wares are available and you can sit outside in the shade. Lovely!

Arrived after a wee 5 mile run and parked up, being careful to avoid the puddle from somebodies leaking power steering (prophetic)!    Bought our lunch, made ourselves comfy in the shade and watched the world go by. 

Time to go and happened to check the rear tyre of the Mono, it was all bright and shiny for the entire circumference on its nearside!    An oil leak from somewhere either behind the bottom of the air box or at the back of the gearbox sprocket, I think! So, nothing for it but to ring the very nice lady at L+V Rescue, who with minimal fuss and interrogation arranged for the collection of the Mono and me from Newtyle for delivery back home, whilst Kat set off on 'The Boy Bros' for home. I was picked up within half an hour, with a Fiesta van and single bike trailer combo and delivered home safe and sound. Then had a mug of tea, with the technician, whilst being regaled about various 'rescue' jobs!   

The technician waxed lyrical about the AJS Regal Raptor DD250E that he picked up for nowt, the previous owner having bought it new, fallen off after 240 miles and never thrown a leg over it again. Scuffed indicator, bar end, mirror and foot peg being the only signs of damage or wear!    The Raptor cruises at 60mph two up, will reach 70mph, but is revving it's "nuts off" and just keeps going with regular oil changes.

So, what will I find after taking the covers off and how much dismantling is involved? If the seal behind the gearbox sprocket has gone, I have a nasty feeling that it is a crankcase splitting exercise!    This is inspite of covering the splines with insulating tape to avoid damaging the seal when rebuilding the engine.

Further reports and maybe some images to follow and hopes that it is all a nasty dream!

[iansoady]

Is that LV= (Britannia) rescue? I have that with my Nationwide Flexplus bank account and have used it twice for bikes - a bit slow on arrival but very efficicient, dedicated bike transport vans, helpful drivers.

[themoudie]

Aye Ian,

Local garages franchised for the job, so they know where to pick you up from and drop you off. 

After the RAC left me to push a Ducati single with nae electrics (there's a surprise!  ) from Victoria Station to Euston Station to get the last train to Hertfordshire in January 1977, I have never used either of the main "recovery" clubs. When I became eligible to use the CSMA service (1981), I did, and have yet to find them wanting when recovering either my vehicles or those of others I have been travelling with and had an unrepairable breakdown.

When L+V bought out the CSMA service, I was wary about the change, but can only be complimentary about their call handlers and the independent garages to whom they award their franchise. Reasonably priced as well. 

My regards, Bill

[iansoady]

My only worry is that LV= has apparently been bought out by one of the big European insurance companies. It's a shame as it was at one time a mutual - ie owned by its members (as indeed was the AA at some far distant time). I hope LV= doesn't suffer from the cost cutting that usually results from these takeovers.

[themoudie]

Aye Ian,

I agree, I believe that it is Allianz, the German insurer.

Good health, Bill

[Ian]

Hope you dont mind my sticking my ten penn`orth in Bill, but is it possible to remove and replace said seal without splitting the cases?
Im sure you have thought of that any way....

Ian twiddles his thumbs......

[Steve Lake]

hi Bill, Ian.... i have #1 (twinshock 600) on the bench .... where it's been for far too long, as you know, 5th gear grenaded a year ago, i've plundered a gear cluster from a 400, all looked good except for excessive end float on main and layshafts, so shims on order.. anyway... whilst split i replaced all the seals, and can confirm that the seal on the final drive shaft and the gear change shaft are changed from the inside
pip pip

[themoudie]

Thank you All for chipping in with your info and experiences.

Having removed the fuel tank, airbox top and air filter to check for blow back into the airbox all was clean as a whistle. Having checked all case joints within the drive sprocket area, all proved dry, checked the gearbox drain plug for weeping, it appeared dry. So out with the 30mm socket and the air impact gun to whip off the nut and "Hey presto!" a puddle of oil sitting in the back of the nut and a weep from the bottom of the sprocket/shaft spline interface. Pulled the sprocket off and in two places the outer lip of the seal was deformed outwards!    Took a 2mm drill and drilled a wee hole into the steel case of the seal. Screwed in a small self tapping screw and then pulled the offending seal out by gripping the screw head with a pair of mole/vice grips. The spring that applies pressure to the seal lips was displaced against the inner race of the bearing; whether that was as a result of my drilling, I don't know? 

The failed seal is a TTO (Made in Taiwan), 25x40x6 mm 2L (twin-lipped) nitrile seal supplied by Yambits as the specific replacement for this application and has covered ~ 4,000Km.

Fowler's web spares list, lists two Yamaha seals for the job. Originally, 93102-25226, 25x40x6 mm L (single lip) nitrile seal that has an indicated anticlockwise rotation. This has been replaced in the list now (July-2019) by 93102-25218, 25x40x5 mm L (single lip), it too is a nitrile seal that has an indicated anticlockwise rotation. From viewing images of these OME seals it appears that the sealing face of the lip has moulded ridges at 45° to the inner lip, so that as the shaft rotates anticlockwise the oil is scraped inwards. No apparent spring to add pressure to the seal lip. So, I have purchased an OEM seal 93102-25218 and will see what arrives! 

I think that with care, insulation tape over the splines and plenty of lubrication, I should be able to tap the seal into the case from the outside, as there are no apparent lips/ridges to prevent this. Care and a length of uPVC white waste pipe should do the trick, making sure that the seal outer face is flush with the outer face of the crankcase.

As for the "Why?" did the seal fail, I am not sure. But suspect that crankcase pressure may rise if overfilled with oil and combined with some long downhill descents on a closed throttle in first gear that I have recently done, would have increased the internal crankcase pressure, sufficient to 'pop' a seal .

I will post some images and see how this goes. I am still tempted to try an alternative machine! 

Bill

[Steve Lake]

cracked it then Bill, well done!. glad it was fixable without a stripdown... rather than insulation tape (which is a bit thick) i use cling film , wound round a couple of times... works well for me
pip pip

[themoudie]

Out for a canter on the Mono today, just to settle the machine in and my nerves after the layshaft oil seal popped behind the sprocket. So far so good.

The replacement Yamaha 25:40:5 S-L seal (93102-25218) 4H7 from a XJ750, is the factory replacement now, as the original 25:40:6 S-L (93102-25226) 4H7 is no longer available. This is a directional seal and will set you back £11-20 plus P&P.

However, as I am a big fearty, I obtained 2 x 25:40:7 S-L oil seals from my local supplier for £6-04, just in case the OEM seal fails!    When I was replacing the blown seal there appears to be plenty of housing depth to accommodate the extra 1mm of depth of the seal and this extra support might help with the longevity of the seal. 

My regards, Bill

[Ian]

 Well done Bill, it's due to your experiences that a lot of people on this site learn a lot.
Thank you for that 😀