Oil smells of fuel

[Steve698 11]

As the title suggests I'm just going about all the usual jobs of oil change, filter change, coolant change, stripping forks for oil change, valve clearances etc first on the  list is draining the oil and as soon as I removed the plug I got a strong smell of fuel. The oil is pretty clean but I don't know when it was last changed so thought for peace of mind I best do it, so what's my new problem ?

[Andy m 23,764]

Classic diagnosis is that something is causing the engine to flood, running rich etc. 

 

What other symptoms do you have? Bogging down at certain RPM? Poor fuel economy? Hard cold starting? Hard hot starting? Sooted plugs? "Performance" air filter or loud exhaust?

 

If you have none of these its just from starting to get the oil hot enough to drain out. Change it and keep an eye out for anything more obvious IMHO. 

 

Andy

Edited December 1, 2020 by Andy m

[Steve698 11]

I don't have any problems, I was totally unaware until I came to do the oil change and the smell of petrol hit me. I've had no starting problems hot or cold the fuel economy last I looked was 68mpg, exhaust is stock and sounds normal, not had the plugs out yet but will do when I do the valve clearances, it's not bogging down anywhere that I've noticed, it has been sitting for a week in the garage without starting could that cause it ?

[Grumpy old man 4,683]

Did you warm the engine before dropping the oil?

[Andy m 23,764]

I think it just either just started on what used to be called a choke and you got a whiff of the excess, or (less likely) the previous owner had something going on that was resolved. 

 

68mpg says there isn't much petrol making its way into the oil. 

 

Andy

[DCTPaul 629]

What bike?

Used to get this on the Suzi Engined, Carbed CCM R30 if you did not turn the taps off.

When on the side stand, the angle would allow for the carb bowls to fill n flow, and the floats would not cut off the valve.

If left could drain the tank in to the sump...

 

If Injection and fuel pump, sounds like a possible perished O ring?

Edited December 1, 2020 by DCTPaul

[Steve698 11]

38 minutes ago, Grumpy old man said:

Did you warm the engine before dropping the oil?

No I have to be honest, I neglected to do that, should I have ? and would that account for the fuel smell ?

[Steve698 11]

8 minutes ago, DCTPaul said:

What bike?

Used to get this on the Suzi Engined, Carbed CCM R30 if you did not turn the taps off.

When on the side stand, the angle would allow for the carb bowls to fill n flow, and the floats would not cut off the valve.

If left could drain the tank in to the sump...

 

If Injection and fuel pump, sounds like a possible perished O ring?

It's an NC750X dct

[Steve698 11]

The oil that came out was clean and not at all watery (still viscous) it was said to be serviced 2k ago but nothing was itemised on the service so I don't know if the oil or filters etc were changed the bikes new to me so for peace of mind I wanted to do all usual's so I know they have been done. 

[Grumpy old man 4,683]

6 minutes ago, Steve698 said:

No I have to be honest, I neglected to do that, should I have ? and would that account for the fuel smell ?

It's normally good form to to get the engine to operating temp so the oil drains fully and quickly.  I was just thinking along the lines that you might have just started to and ran it for a short time to warm it up and that would  have made the engine run rich and could have given that smell. Not sure if draining the oil cold would any effect on the smell. 

[Grumpy old man 4,683]

Just thinking out loud. Do you do lots of short runs. How many miles has the bike done? What was the oil level before draining it was it over full. If it's been running fine then it should be ok but keep an eye on the oil level if petrol is finding it's way to the sump then it would show on the dipstick level.

If you do the valves the engine must be cold, just thought I'd add that.

[Steve698 11]

13 minutes ago, Grumpy old man said:

Just thinking out loud. Do you do lots of short runs. How many miles has the bike done? What was the oil level before draining it was it over full. If it's been running fine then it should be ok but keep an eye on the oil level if petrol is finding it's way to the sump then it would show on the dipstick level.

If you do the valves the engine must be cold, just thought I'd add that.

Well I've only had the bike for a couple of weeks and the weather hasn't been conducive to riding for fun, the few runs I've been on have been about 15/20 miles. Oil level was normal. I will be keeping an eye on it once everything is done but if the weather is 0 degrees I won't be going out for a while. Going to get on with the forks, coolant and valves over the next couple of days but basically working in an open garage freezing my bits off so may take a little longer. Bike has done 22k.

Edited December 1, 2020 by Steve698

[Bassman 102]

Because your working in the general area it could be the petrol tank overflow pipe you can smell especially if you have fuelled up recently, just a thought, I doubt you have a major problem.

[wjvh 999]

Based on the state of the oil and bike performance it doesn’t sound like

you got anything to worry about. Probably just due to whatever brand of oil was used in the last change. Ride on!

[Grumpy old man 4,683]

33 minutes ago, Steve698 said:

Well I've only had the bike for a couple of weeks and the weather hasn't been conducive to riding for fun, the few runs I've been on have been about 15/20 miles. Oil level was normal. I will be keeping an eye on it once everything is done but if the weather is 0 degrees I won't be going out for a while. Going to get on with the forks, coolant and valves over the next couple of days but basically working in an open garage freezing my bits off so may take a little longer. Bike has done 22k.

What year is the bike and do you have a service history. I'm very much of the opinion,  if it's not broken to fix it . Check the service history and going by what you say one of the best things to do is put a battery maintainer on it. 22k it's not ot run in yet. If you're cold you might make mistakes. Good luck. 

[Steve698 11]

18 minutes ago, Grumpy old man said:

What year is the bike and do you have a service history. I'm very much of the opinion,  if it's not broken to fix it . Check the service history and going by what you say one of the best things to do is put a battery maintainer on it. 22k it's not ot run in yet. If you're cold you might make mistakes. Good luck. 

I'll put my thermals and woolly hat on tomorrow. The bike is 2015 1 owner and I have one gap in the service history but the last service was carried out at 20k it's now 22k but it wasn't itemised so it's belt and braces on my part really. I do have it on an optimizer normally. 

[Steve698 11]

51 minutes ago, Bassman said:

Because your working in the general area it could be the petrol tank overflow pipe you can smell especially if you have fuelled up recently, just a thought, I doubt you have a major problem.

Did think myself it may be coming from elsewhere but there was no smell until I took the drain plug out and I stuck my finger in it and took a close smell and it was definitely from the oil even stuck it under the wife's nose away from the bike and she said petrol.

[Trumpet 216]

Every drop of used oil I've ever removed from engines always has that smell of petrol. You get a constant small blow by on the piston rings of any engine. Apart from shearing, its the main reason to change the oil. On very short journeys it actually starts to dilute the oil as it doesnt get hot enough to boil it off. Hence people recommend an earlier than book recommended oil change if thats all you use the bike for. The crankcase breather used to vent to fresh air, but now all modern engines route it back into the inlet to get burned off by the engine to clen up emissions.

Edited December 8, 2020 by Trumpet

[Steve698 11]

Have been freezing my bits off the last few days but have now taken the front end apart, forks out (bit pitted) rad off (paint peeling off tanks), oil drained. Have got the oil, filter and clutch oil filter all changed and back in, the rad stripped it down and rubbed back then etch primer and satin black, looks good now and back on the bike and topped up. Also done the valve clearances while everything was off, that was my main concern but wasn't that much of a problem to be honest. The forks are next, going to clean them up, new seals and covers, new oil and refit in the next couple of days. Have noticed the inside of the yokes that hold the forks are a bit rusty, any ideas of the best way to clean these up and keep the rust at bay ? Then need to flush the brakes to get new fluid in, change the front pads, do something with the headers as they are covered in surface rust and look orrible. Also need to do something with engine covers as the paint is peeling from them in a couple of places, anyone know of a touch-up colour that matches, it's a dark grey metallic. Grease everything up then wait for some weather improvement to get it out on the road - glad I started, this was only going to be an oil change. Doh.

[Steve698 11]

Not known how to post pics so trying this in the hope it works - this is the engine cover.

https://postimg.cc/K3cL0K02

 

and the rad - 

Edited December 9, 2020 by Steve698

[wjvh 999]

Well done Steve698 ... you’re in deep there. I did a similar set of jobs on my nc700s during the first lockdown, it’s nice when it’s all done. 👍

[MatBin 5,119]

Just check the fork pitting won't be in the area the forks traverse else the new seals will get ruined.

[Steve698 11]

4 hours ago, MatBin said:

Just check the fork pitting won't be in the area the forks traverse else the new seals will get ruined.

Yep have checked and it is higher up the fork than that - thankfully.