C1 750 Fuel/ oil mix from air filter housing

[71 V12]

First start up after winter layup of 750 C1. A bit hesitant to start but got going. Suddenly I notice fluid under the engine amassing at a rapid rate. Switched off and i could see fuel/ oil mix gushing out of the air filter housing.

I am guessing I have carb float valves stuck open, but how how is fuel mixing with oil and finding its way to air filter? Is it something to do with engine breathing?

Appreciate any feedback.

Kevin

[Freddy]

What's the oil level look like in the sight glass?

[71 V12]

Hi Freddy,
Completely full!

[Freddy]

Well there's your likely explanation.

The crankcase is full of oil/fuel mix from the flooding carbies. Because its full its being pumped up into the airbox by the rotating motor through the short breather hose that runs between the bottom of the air box, and a round plate directly below it (on the top of the crankcase, just behind the cam chain tensioner).

[Shedman]

You will need to drain your oil and change your filter after you sort out the flooding problem, fuel in your oil is not good for your engine.

[71 V12]

Thanks for the feedback, very grateful for your help. With luck an oil/ filter change and carb fix resolves the issue.

I must have left the fuel tap on after last use. Most disconcerting to see liquid gushing out of your engine! Need to use the bike more as well.

Thanks again guys,

Kevin

[Shedman]

Hi Kev, has your bike had a replacement fuel tap? as you shouldn't be able to leave it "ON", if it is the original tap you can't actually switch it "OFF". It should be a vacuum controlled tap with "ON", "Reserve" and "Prime" do you perhaps mean you left it on "Prime" as that would explain the fuel flooding? Just trying to be clear what the problem is.

[Freddy]

If I lived somewhere were the seasons dictated I could only use the bike some months of the year, or I rode it infrequent ...... I'd actually replace the vacuum tap with a simple ON/OFF/RESERVE. Why? Because before every time I put the bike away I'd turn the tap to OFF and then let it run till the engine cuts out from lack of fuel. In effect draining the carbies.

If you always drain the carbies before putting an infrequently used petrol engine away there is WAY less carburetor maintenance. Float valves don't get stuck shut, jets don't block up from fuel constantly evaporating out of the bowls.

This is exactly what I do with my XT250. Was used everyday as a commuter when I was working. Never a single carby problem. Then when I stopped working it only got used occasionally. Pretty soon carby problems, even thought I always (well 99.9% with the occasional forget to turn the fuel tap off). Since reverting to always running the bike to drain the carby I've had zero problems.

I know exactly the distance to turn the tap to the OFF position when approaching home, so that by the time I've pulled up and have taken my helmet and jacket off (with the bike in idling in neutral) it cuts out. Just remember to turn off the ignition before putting it away.

[71 V12]

Hi Freddy and Sherman,

I replaced the original tap 4-5 years ago with the genuine Kawasaki tap from Cradley Kawasaki. The tap was on prime!

Drained oil and replaced filter with 10/40 Halfords semi synthetic and all seems well. I will get out on it when stops fing raining.

Out of interest is there an traditional off/ on/ reserve tap out there that is direct replacement?

Brilliant help, thanks for all your comments and valuable experience.

Kevin

[Shedman]

Hi Kev, three things lead me to believe that you are in the UK from your last post, Cradley Kawasaki, Halfrauds and this effin rain that just won't sod off! Am I right? I had a simple on/off/reserve tap on my bike when I bought it but the lever part was missing and had been replaced with a bit of crappy tin. I don't know what make it is or what bike it was originally from but If I still have it in the shed then you are welcome to it.