bleeding oil

[martync]

I put too much oil into the engine as i couldn't see the level and guessed it was low when it wasn't.

I ran the bike all last week and now there are small areas where oil has leaked from the rocker cover gasket and where the barrel joins the engine, there not bad but now ive lowered the oil level is it nessasary to replace these gaskets as the bottom one is a real pain.

I'm hoping the reduced oil pressure should now be OK and they won't leak again or is it the case, once leaked now they will always leak?

[ekaphoto]

Once a leak always a leak. If its not leaking bad just keep an eye on the oil level. It may only leak a small amount so you will have to top it off every 500 mi or so. Eventually you will have to repair it. Dont try to overfill it to compansate for the leak and get a few extra miles out of it. All you will do is make the leak worse and may spring a few more.

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John

[ekaphoto]

I forgot. I would replace the ones that are easy fixes if possable. Again money, time, mechanical ability and riding conditions all are factors. If you are going around the world, fix all the leaks asap imho.

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John

[martync]

thanks for the replies, i took of the oil cap when it was running and a hell of a pressure coming from there so I guess something caused the leaks. The most obvious is the piston rings so a costly job on the way but anyone know of any other obvious things to look for such as blocked oil breethers? I'm not familiar with XT's and there problems.

[Steve Pickford]

Martyn,

You should not remove the oil filler cap when the engine is running. The "pressure" you mentioned is perfectly normal and is caused by the downwards stroke of the piston pressurising the crankcase - the breathers are there to act as a "bleed" for this pressure. When the piston rises in the cylinder, air is sucked in to the engine cases as a partial vacuum starts to form. There is no need to touch your piston rings. The reverse happens on the downwards stroke, you may have noticed that the pressure came out of the filler cap in a series of pulses in tune with the engine revs.

If you fitted a larger piston, you would have increased pressure in the cases. This is why big bore street/drag bikes have additional breathers fitted. The pressure is increased to the extent that without the additional, breathers, engine oil would also be blown out via the breathers - not a good thing.

If you overfill an engine, the volume of air moved by the downwards stroke of the piston is compressed in to a smaller space, hence an increase in pressure. If the breathers are not sufficient, oil can be forced out through any weak points i.e breathers or weak gasket joints. I'm not familiar with XT's but would not be surprised if the main breather vented in to the airbox. If so, you may well find an oil residue in the airbox also.

If the oil leak at the base gasket is such that it needs to be replaced, then this would be an ideal opportunity to check the overall condition of the top end i.e. rings. ring gaps, cylinder bore, de-coke the cylinder head & maybe lap the valves in. Sounds complicated but a single cylinder four stroke is an ideal engine to learn the basic principles of how afour stroke operates.. Another option is buy a knackered CG125 engine or similar from a breakers & take it apart. Aside from a few design differences, the basics are identical, only on a larger scale. Multi-cylinder bikes are basically more of the same with another cam & water cooling.

I learnt on my DR600 & now do all of my own work on my GSX-R, R80GS & K100.

Steve

[martync]

Steve

Thanks for that reply, I did think for a moment that was supposed to happen, I had recently overfilled it too which probably blew the gaskets. The pulses were in time to the piston as you say but there was quite a pressure there, eg could feel it like an exhaust pulse from seat height.

at present this is my only transport due to my main bike being stolen a few weeks back so I need it up and running as son as poss thus trying a 4 stroke rebuild may be a bit time consuming!.

when the weather gets a bit better I'll be after a GS and the XT will out of there and replaced with a stroker (CR) or simular.

This and an RD350 years ago has given me the final straw and I'll not buy another yamaha again, just something about them, me and bad luck.