difference between 20w-40 and 20w-50?

[imadoofus]

as of now, I have mixed 20w-50 with the earlier existing engine oil. The recommended one is 20w-40.
The bike seems exceptionally hot nowadays even after a small spin.. with the downpipes being very hot and all.. I know they get hot, but now I think its getting hotter than usual.

Anything else that controls the engine temeprature other than the presence of engine oil?
And I havent fiddled with the air/fuel mix yet, so i doubt that its running leaner.

[Kickstart]

Hi

Doubt it would have much effect on the engine temperature. 20W50 is more viscous than 20W40 when hot.

Which bike is it?

All the best

Keith
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[imadoofus]

82 yam 650.

will the throttle speed adjustment affect anything? I havent fooled around with anything else..
and the oil filter hasnt been changed in ages also
and currently the oils have been mixed

[Kickstart]

Hi

Idle speed will not make much difference. It will heat up more quickly when idling (same amount of cooling air, but more heat generated).

Personally I would change the filter with the oil.

Adjusting the carb idle air screws would make quite a bit of difference and could well make the exhausts hotter if you leaned the mixture off.

All the best

Keith
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[imadoofus]

[ZRX61]

The only thing the idle screw does is move the butterflies or raise the carb slides.... (depending on CV or DC carbs)

[Kickstart]

Hi

As above.

Presume to do this you have taken the tank off. Double check that you have connected up the vacuum line to the fuel tap, and you have not disturbed any of the caps for the other vacuum line take offs.

With age the rubber pieces that connect the carbs to the engine can crack. this will allow extra air in and cause a lean mixture.

All the best

Keith
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[imadoofus]

[Kickstart]

Hi

Running on prime all the time means that should the needle valves stick then most of the contents of the petrol tank will dump themselves into the engine while you are parked.

If the vacuum line is perished then it will allow extra air in after the carbs and cause a lean mixture (and this make the engine run hot). It might not be the actual line, as it could also be the actual fuel tap. Basically in the tap you will find a rubber diaphragm attached to a piston. The vacuum of the intake is used by the tap to suck the piston across and thus open a passage to allow fuel to pass.

If the vacuum pipe or the diaphragm is partially holed then the vacuum is not as strong and the piston might not be pulled across properly.

Note that the air leak would only affect one cylinder. However a lack of fuel from the fuel tap not opening fully would affect all cylinders.

The fuel tap rebuild kits are not expensive. We replaced one recently in Charlottes GPZ500 and it was quite cheap (cannot remember how much, but under £10 I think).

All the best

Keith
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[imadoofus]

I didnt know the fiel taps were as critical. Thanks.
The petcock leaks slightly in the ON position, so i guess I would have to replace it to correct this proble and it might not really be the vacuum hose
thanks

[Kickstart]

Hi

Sounds like it is the diaphragm. There is probably also a rubber O ring in there. One side of the diaphragm is subject to a vacuum while the other side has a vent to fresh air on it.

Suspect if both were gone you might have problems with it running very rich on one cylinder.

Think the best thing to do is to take the fuel tap off and strip it down and check the bits. They normally come apart fairly easily.

All the best

Keith
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[imadoofus]

[Kickstart]

Hi

Mmmm, maybe a new diaphragm is not available from Yamaha. If you look at the back of the fuel tap I would suspect you will find 3~4 bolts. Undo these and the back of the fuel tap will come off to reveal the diaphragm (do this with the tank empty as otherwise fuel will pee out all over the place).

All the best

Keith
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