Sticky Carb Slide - Odd Residue

[Magista]

Good Morning (at least in the US),

My A7 has been hanging up on decel/idle and it's been driving me nuts. I've pulled the carb slide and found sticky residue on it as you can see. Prior to my ownership, it had be been sitting for a long time.

My theory is it's old fuel varnish in the intake manifold and when the bike gets hot it melts, gooping up the slide causing it to stick and hang.

My initial solution would be to use solvent and a brass brush to remove as much as the varnish as possible inside the manifold.

Has anyone experienced this? Am I on the right track?

Thank you!

[muskrat]

G'day Magista.
Is that a PWK carb? Is it flange mount or spigot? Does it only happen when hot? Has this only just started or since you got the bike?
Your thinking could be right. Most motors give a bit of blow back when running especially when running a 357 cam.
Try putting a bit of Injector cleaner in your fuel. Not only cleans the carb but also the inlet tract.
Cheers

[chaterlea25]

Hi Magista,
Has the fuel tank been lined ?
The similarcsymptoms I have come across  were due to tank liner breaking down

John

[Magista]

G'day Magista.
Is that a PWK carb? Is it flange mount or spigot? Does it only happen when hot? Has this only just started or since you got the bike?
Your thinking could be right. Most motors give a bit of blow back when running especially when running a 357 cam.
Try putting a bit of Injector cleaner in your fuel. Not only cleans the carb but also the inlet tract.
Cheers

Yes, it's been a niggling issue since I've had it. The PWK is a JRC so it has the flange. There are no air leaks. Only appears to happen when hot.

I pulled the carb and blasted the intake manifold with carb cleaner then used a brass brush to clean it all out. We shall see.

Thank you.

[Magista]

Hi Magista,
Has the fuel tank been lined ?
The similarcsymptoms I have come across  were due to tank liner breaking down

John

Yes, it was lined at some point. It's a pink-ish colored liner.

Hmmm...if that's the case, what is the best way to remove old liner? I can also just Google it.

Thank you.

[muskrat]

G'day again Magista.
Good job John is on the ball, I missed that point.
Many years ago I use Kreem to line a tank. After time it had a pinkish hew. It doesn't like alcohol so E fuel will eat it.
Removing any liner is a very messy job and can take weeks. The last one I did I used a mix of paint stripper and acetone.
Cheers

[Sav]

I had the sticky carb slide and petseal in the tank.

https://villiersservices.co.uk/product-category/oils-paint-consumables/gasket-sealer-tank-sealer/

Used sealeater/fertan/tapox - bag of old nuts and bolts rattled around to loosen the petseal.

Did the job very well but you must have a means of ventilating the tank as the new sealer dries, to prevent runs.

[Magista]

G'day again Magista.
Good job John is on the ball, I missed that point.
Many years ago I use Kreem to line a tank. After time it had a pinkish hew. It doesn't like alcohol so E fuel will eat it.
Removing any liner is a very messy job and can take weeks. The last one I did I used a mix of paint stripper and acetone.
Cheers

Great, thanks for that. Looks like I have a nice upcoming winter project.

The liner is orange, not pink (as I get older my short term memory is worse). You can see where some has come off. It appears to be a fairly thin coating.

[muskrat]

There's your problem Full carb strip & clean would be in order as well.
I the mean time strip out what you can with metho/acetone and nuts & bolts. Filter on the tank side of the tap and another in the line.
At least then you can run her.
Cheers
ps: I forgot to mention. There are some very small passages in and under the jet block and the funny shaped O ring is a PITA to get back in.

[Magista]

There's your problem Full carb strip & clean would be in order as well.
I the mean time strip out what you can with metho/acetone and nuts & bolts. Filter on the tank side of the tap and another in the line.
At least then you can run her.
Cheers
ps: I forgot to mention. There are some very small passages in and under the jet block and the funny shaped O ring is a PITA to get back in.

I've run a filter on the fuel line since I installed the new carb, but did pull the carb yesterday and give it a good cleaning to make sure.

As a rule I run only ethanol free gas in the bike (we have a place nearby)...however, last month (totally forgot about this) I rode to a neighboring town about 40 miles away. On the way back I ran out of petrol on the highway (yes, I know silly). Called my friend I was visiting who brought me a couple gallons. He did say it was a bit old and had been sitting for a while. That might help explain the goo and bad performance lately.

Today I will drain the bad gas and refill with ethanol free. At some point I will work on removing the old liner.

On another note, I ordered a stiffer spring for the PWK from Japan, the original one felt way too soft. Installed it yesterday and it feels much, much better.

[chaterlea25]

Hi Magista and All
A further Warning  The residue from the tank sealer can cause the inlet valves to stick with nasty consequences
One of my friends had this happen on a newly rebuilt BSA Gold Star, It bent the valve damaged the seat and also damaged the piston

  to be the bearer of more bad news
John

[Magista]

Hi Magista and All
A further Warning  The residue from the tank sealer can cause the inlet valves to stick with nasty consequences
One of my friends had this happen on a newly rebuilt BSA Gold Star, It bent the valve damaged the seat and also damaged the piston

  to be the bearer of more bad news
John

Thank you for the heads up. Just means the tank will be cleaned sooner than later.