petrol in oil

22-08-2008, 08:46 PM

hi to you all
i bought a 1997 600 monster last year, it had been stood up for a number of years. i change the belts,oil and filters & plugs,i cleaned the carbs and put new petrol in it. i took it for mot today and when i got back i notice the oil level had gone up,i drained about half a litre out to get to were it was before. i only went about four miles to the mot statio ,it must be petrol getting in the oil any ideas how many thanks

22-08-2008, 09:25 PM

The only way this could happen is if your carb float needles are sticking / worn / incorrctly fitted or adjusted. fuel could flow from the carbs through the inlet valves & into the cylinder where it could bypass the piston rings & flow into the sump contaminating the oil.
I am supprised you havn't noticed fuel leaking out of the carb float bowl overflow?

It needs sorting as the excess fuel could wash all the oil from the cyl bores & cause premature bore wear.

Strip the carbs again, check the condition / sealing of the needle valve above the float & them set the floats to the correct height, also make sure the overflows form the float bowls are not bunged up.

22-08-2008, 09:54 PM

cheers desmo
i put new float valves in and cleaned overflow out.the overflow pipes are damp but it looks oily .it only went up when the engine was running would that be right,what is the correct way to put the floats valves in and how do you set the floats many thanks

23-08-2008, 02:24 PM

Quote:

Originally Posted by catman

cheers desmo
i put new float valves in and cleaned overflow out.the overflow pipes are damp but it looks oily .it only went up when the engine was running would that be right,what is the correct way to put the floats valves in and how do you set the floats many thanks

Your bike may have a vacuum operated fuel tap, which would explain why the fuel only leaks into the oil then the engine is running.

Not sure of exact float setting measurement on your bike, but as a general rule of thumb, the correct way to adjust them is to remove the carb & float bowl, turn the carb upside down, look at the float, they usually have a raised ring on them about two thirds of the way up, this ring is usually horizontal with the top section of the carb when set correctly (carb held upside down)

That said, most vehicle manufacturers do have a set measurement for the float height.

03-09-2008, 09:03 PM

i've took the carbs off and put on bench at the same angle as in bike and filled the carbs up with petrol no leaks. took float bowls off every thing look ok, it mite seem sily but its the first multi cylinder bike if it was only firering on one would that be the case if so what is the easiest way to check

slob · 03-09-2008, 09:11 PM

Does the bike have a carb heater circuit on the oil system?

03-09-2008, 09:20 PM

i think so, oil pipes go in the float bowls

slob · 03-09-2008, 10:06 PM

Some sort of leak within the carbs allowing fuel into the oil possibly?
I believe there should be a tap that allows you to turn off the carb heater,
that might allow you to see if stopping the oil flow thtough the carbs solves the problem. You probably don't really need the carb heaters at this time of year anyway.

04-09-2008, 08:08 PM

oh well, just a thought, sorry I can't be more help.

05-02-2010, 08:53 PM

an old thread, so its probly sorted. But i had a similar thing with dads aprillia 500 scooter.The problem was it running way too rich - caused by automatic choke staying on due to temp sensor not set up for cold places.Taping up the oil rad was a temp fix, but replacement of the sensor was the permanent fix.
With that in mind, and your misfire, did you check the choke mechanism?

22-08-2008, 08:46 PM	#1
catman Guest Posts: n/a	petrol in oil hi to you all i bought a 1997 600 monster last year, it had been stood up for a number of years. i change the belts,oil and filters & plugs,i cleaned the carbs and put new petrol in it. i took it for mot today and when i got back i notice the oil level had gone up,i drained about half a litre out to get to were it was before. i only went about four miles to the mot statio ,it must be petrol getting in the oil any ideas how many thanks

22-08-2008, 09:54 PM	#3
catman Guest Posts: n/a	petrol in oil cheers desmo i put new float valves in and cleaned overflow out.the overflow pipes are damp but it looks oily .it only went up when the engine was running would that be right,what is the correct way to put the floats valves in and how do you set the floats many thanks

03-09-2008, 09:03 PM	#5
catman Guest Posts: n/a	fuel in oil i've took the carbs off and put on bench at the same angle as in bike and filled the carbs up with petrol no leaks. took float bowls off every thing look ok, it mite seem sily but its the first multi cylinder bike if it was only firering on one would that be the case if so what is the easiest way to check

03-09-2008, 09:20 PM	#7
catman Guest Posts: n/a	fuel in oil i think so, oil pipes go in the float bowls

22-08-2008, 09:25 PM	#2
desmo Guest Posts: n/a	The only way this could happen is if your carb float needles are sticking / worn / incorrctly fitted or adjusted. fuel could flow from the carbs through the inlet valves & into the cylinder where it could bypass the piston rings & flow into the sump contaminating the oil. I am supprised you havn't noticed fuel leaking out of the carb float bowl overflow? It needs sorting as the excess fuel could wash all the oil from the cyl bores & cause premature bore wear. Strip the carbs again, check the condition / sealing of the needle valve above the float & them set the floats to the correct height, also make sure the overflows form the float bowls are not bunged up.

03-09-2008, 09:11 PM	#6
slob . Join Date: Jul 2003 Location: East London Bike: Multiple Monsters Posts: 9,713	Does the bike have a carb heater circuit on the oil system?

03-09-2008, 10:06 PM	#8
slob . Join Date: Jul 2003 Location: East London Bike: Multiple Monsters Posts: 9,713	Some sort of leak within the carbs allowing fuel into the oil possibly? I believe there should be a tap that allows you to turn off the carb heater, that might allow you to see if stopping the oil flow thtough the carbs solves the problem. You probably don't really need the carb heaters at this time of year anyway.

04-09-2008, 08:08 PM	#9
catman Guest Posts: n/a	oh well, just a thought, sorry I can't be more help.

05-02-2010, 08:53 PM	#10
Bigxr Guest Posts: n/a	an old thread, so its probly sorted. But i had a similar thing with dads aprillia 500 scooter.The problem was it running way too rich - caused by automatic choke staying on due to temp sensor not set up for cold places.Taping up the oil rad was a temp fix, but replacement of the sensor was the permanent fix. With that in mind, and your misfire, did you check the choke mechanism?