Sitting bike with fuel that is nearly varnish: help!

[jimster]

Hi all,

My diversion 900 project has been sitting for ages (nearly 2 years now) and is rough running due (partly) to I suspect very old fuel. It might sit for another few months before I get it back on the road. This is a noob question I know but what's the best way to handle this so the fuel doesn't completely turn to varnish and wreck the inside bits of the engine and/or rust the fuel tank from the inside? Shall I flush the old fuel out and replace it with a small amount of new fuel (or a full tank)? If yes, can I just siphon the tank with a plastic tube (carefully...) and then just run it for a bit on the new fuel? I realise the carbs probably need cleaning and plan to do this when I get a chance.

Thanks!!
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Current: Yamaha Diversion XJ900
Previous: Yamaha Diversion 600cc, Piaggio Zip 50cc, Honda CG125-W, Siamoto Caddy 50cc moped

[stinkwheel]

I just did similar with a bike that had at least 11 year old fuel in. it was stinking stuff and I suspect wouldn't burn even if you tried to light it with a match I emptied out as much as I could, then added a small amount of fresh fuel, drained that out then repeated until the stuff coming out was clean and didn't smell stale. I drained it through the tap as I was confident it didn't have any solids in it that would block the filter screen (had a good look with a torch first).

I would then totally drain and store it somewhere dry it if it was going to sit for longer.

Repeated flushing with a small amount of fresh fuel is better than a big flush with a lot.

I've just used the stuff I flushed out to wash/de-grease parts.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[MCN]

Fuel is the remnants of primitive prehistoric lifeforms. Like all life forms they die and decompose.
We remove the decomposition products and use to fire motorbikes along our highways, byways and people's private fields (when BFC BBQs were 'a thing').
There are other lifeforms that can digest those remnants and make a living from doing so.
Certain Bacteria are one form.

Such bacteria live in water and digest those petrochemical products.

They die and add to the sludge of their brothers and sisters. A Gloopy sludge that can be sooked into mechanical systems and do no good when they get there.

Solution:
Short term. Drain and flush the system (if a flush is even possible).

Fill the system with fresh fuel.

Long term:

Only buy clean fresh fuel (even though it's already 300 million years old before you buy it.)
If storing the machine then consider adding a fuel stabiliser which can help reduce bacterial growth.
There are specific bacteriacidal chemical compounds designed for that problem.

Although, storing fuel can have other problems of the fuel oxidizing, absorbing moisture and reduction of additive efficacy.
So draining and refilling with fresh before use after storage is recommended.

Also, keep the fuel tank brimmed.

Airborne moisture can condense on cool surfaces. The more cool surface presented means more condensation is produced.
The air can re-absorb the condensate but what normally happens is the condensate rcollects into beads which then run down below the fuel level where they cannot be re-absorbed by atmospheric air.
Thats when the shite starts.
The water dissolves into the fuel, collects bacteria (maybe airborne) and also can encourage corrosion.
Funnily enough, where the bacteria live can become rust-free. I dont know why that is. Possibly they absorb any free oxygen so limit oxygen related corrosion.
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

[stinkwheel]

With the higher ethanol content fuels these days, it can split if left sitting and leave a layer of water at the bottom of the tank.

If a bike's standing for a prolonged period, it's probably better to run the carbs dry then drain the tank and take steps to prevent condensation rather than brimming it like you used to. That could be storing it somewhere warm and dry. I'd even consider bunging a big silica sachet in the drained tank.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[MCN]

[grr666]

The petrol in my bike was 3 years old, filled up with super unleaded just before going into storage. Found the receipt
in my coat pocket yesterday, 19/08/19 - £12.40 for a full tank.

When I got her running again, she started on the second press of the starter button after simply fitting a new
battery. The bike rode and ran just fine yesterday, never skipped a beat. It was more of a shakedown rather than a pleasure
ride, wanted to clean up the brake discs and make sure all was well. I just stayed local and did a few laps of Bristol so I
wasn't too far from home if I had an issue with the bike given how long it's been laid up. She's not quite as backfirey as
usual so I guess it's lost some octane but otherwise I can't really tell the difference. Had the oil and filter changed while it
was in for MOT. Yesterday I found the reason why it was a bit wooly feeling when I took it from storage to MOT after
I checked my tyre pressures before going out. It had 20 odd PSI front and rear and should be 42R and 36F. Felt like a
different bike after a few minutes on the compressor from my car to top them up, it felt like my bike again. Cleaned
it up a bit too before going out, it was a quiet grimy after a ride in the wet to MOT and 3 years of storage dust. Used a
whole pack of baby wipes to de scuzz it a bit but it looks much better now.
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Currently enjoying products from Ford, Mazda and Yamaha
Ste wrote: Avatars are fine, it's signatures that need turning off.

[doggone]