Motoscrubs.com

Hi folks,
My 250 scrambler engine crankcase breather tube has seriously degraded (full of holes) over approx. 2000 km. I wonder if this might be due to incompatibility with the synthetic lube oil I have been using after the running-in stage?
Has anyone else had a similar problem and found a solution?
I would prefer to continue using synthetic lube oil long-term, it's my belief that it's much better for the engine internals, after running-in on mineral oil.
Cheers,
Al

Hi Al,

Is the tube rubber or plastic? I doubt that it is due to the engine oil, it is more likely due to the heat and the emissions from the engine.



Cheers,

Colin

Hi Colin, thanks for the quick reply.
It's the original-style rubber tube with spiral wire reinforcing, connecting the crankcase breather to the inlet air filter.

To my eyes it looked more like the synthetic oil eating into the rubber - BUT - the engine has been suffering from burning a lot of oil, so I guess it is possible that combustion gases have also been getting into the crankcase.

Maybe my best bet is a like-for-like replacement and keep a close eye on it.

Cheers,
Al

Aye A.I.M,

Here is a link to the clear PVC hose that I use as a breather on the 450 MKIII, whilst using Smith & Allan, 15W-50 Fully Synthetic oil, having previously run the engine in using an old school 20W-50 mineral oil, changed at 20, 250 and a 1,000 miles afore filling up with the 15W-50 Fully Synthetic oil.

Clear-unreinforced-pvc-tubing

I have had no apparent "attack" to the structure of the hose in over 14,000 miles of use, over 4 years. Make sure you warm the PVC hose, with boiling water before sliding it over the male crankcase fitting and securing with a Jubilee clip, or hose clamp of suitable diameter. You'll get a shrink fit!

Good health, Bill

Bill,

Do you use that tube with or without the spiral reinforcement inside? I don’t have the reinforcement so wondering how it performs without.

Regards

Ian

Ian, Same as Bill I have been using pvc breather tubing for years with no spiral reinforcement never any issue's.
Cheers, George

That's good to know, thanks Bill / Ian / George.
For my scrambler I would like to keep the original "cake-tin" air filter, and the tube connects to the back-side of it. The tube has to bend 90° to fit, and it's only about 35 cm long, so I might try to recover the spring from the old tube and install it in a new one to prevent kinking.

All the best,
Al

Aye Al, Ian,

To answer your queries about PVC hose collapse. I have never had problems, with the un-reinforced PVC hose collapsing, providing you keep the radius of the curves greater than 45°. However, the bore required for the MKIII's breather is a "standard" size that I cannot remember off hand, but, moulded straight, "T" pieces, "Y" pieces, 90° elbows and blanking plugs are all available from local DIY suppliers, moulded in nylon that resists most of the chemicals they are likely to encounter in an engine breather.

I found that the nylon mesh reinforced PVC tubing had a thicker wall and with the mesh, made it more difficult to bend to even 65° curves. It also seemed to age harden more quickly than the un-reinforced PVC hose. That was down to the PVC polymer mix used in their manufacture.

I hope this helps.

Good health, Bill

Many thanks Bill.

Ian

A good auto parts store will have a variety of car heater hoses with various formed bends and sizes. Pick one that has the size and bends you need and cut off the rest.
Just a suggestion,,,
Graeme