How to clean the fuel pump?

[Luca]

Hello everyone
I'm about to clean the fuel system. The fuel tank, carbs, fuel lines and the pump.
I was wondering what's the best way to clean the fuel pump?
Is there any guide to open the pump to clean it?

 

[MaxMidnight]

I have to ask, why do you think it needs cleaning?
IMO provided that the fuel filter has been changed as recommended and you aren't aware of any 'bad' fuel there wouldn't be any benefit...unless you have nothing better to do?

However if the urge is too great then put some fuel system cleaner through and let the chemicals do the hard work.

 

[Luca]

I have to ask, why do you think it needs cleaning?
IMO provided that the fuel filter has been changed as recommended and you aren't aware of any 'bad' fuel there wouldn't be any benefit...unless you have nothing better to do?

However if the urge is too great then put some fuel system cleaner through and let the chemicals do the hard work.

I'm having trouble to run the engine.
Normally it was running on 2 cylinders (#2 and #4)
I've never cleaned the tank to be honest and the bike hasn't been running for almost 10 years.
Yesterday after finishing all the gasoline in the tank it started to run only on one cylinder (#2)
I'm assuming that some dirt clogged the carbs.

 

[lizzywhite45]

I think if it's running fine then don't need to clean it, but if you seriously want to do it then use any fuel system cleaner to clean the carbs.

 

[MaxMidnight]

Can we assume that you have fresh fuel in the tank?
Is the running problem with the choke on or off?
Can it be coaxed into running by giving some throttle?
After trying to start have you pulled the plugs to see if they are wet or dry?
If not already done I'd also replace the spark plugs and check that there is a spark at each plug.

If the fuel pumps cause problems it is usually because they are unable to deliver sufficient fuel rather than being dirty. You can check that the pump is delivering fuel.
Have you looked inside the tank to see if there is any flaking corrosion? If so then that will need to be addressed.
My next step would be to drain the float bowls into a container to see what comes out.

If you are satisfied it is a fuel issue within the carbs then trying the Shotgun may help but failing that I'd be inclined to take them off so that you can thoroughly inspect them.

 

[Fire-medic]

I'm having trouble to run the engine.
Normally it was running on 2 cylinders (#2 and #4)
I've never cleaned the tank to be honest and the bike hasn't been running for almost 10 years.
Yesterday after finishing all the gasoline in the tank it started to run only on one cylinder (#2)
I'm assuming that some dirt clogged the carbs.

Your bike needs carburetors disassembled and cleaned. An ultrasonic bath works best in my experience. The pilot jets are probably all-plugged with hardened deposits. A small stiff wire will allow you to make short work of the cleaning of the pilot jets. Be careful you do not scratch/gouge the brass!

In cases like this, you may need to do this more-than once if you aren't thorough-enough the first time. I'm speaking of the ultrasonic bath and then poking through all the jets, off the carburetors, and also getting confirmation of cleared passages in the carb bodies. There ar probably hundreds of threads on here dealing with dirty carburetors. You will see some things repeated over and over. Use the search function, and do lots of reading on what replacement parts other than stock Yamaha will work, one name you will see is K & L. You will also see how the carbs are disassembled, cleaned and re-assembled.

This is a guide for your efforts. Print out a copy and put it into a 3 ring binder for easy reference. Save this file on your computer. Read it ffrom beginning to end. The first ~64 pages are annual service updates. After that begin the chapters by what area of the bike: engine, suspension, electrical, brakes, etc. The Appendix has lists you will refer to many times. One is nut/bolt sizes, torque values, and where they are on the bike. Another is cable and hose routing. If you do not become familiar with the service manual, your efforts will probably be unable to fix your bike. Between the service manual, and the search function here, you can fix your bike.

This is going to be repeated: Take lots of pictures as you begin disassembly of anything.

https://dn790009.ca.archive.org/0/i...ice-manual/yamahavmaxvmx12-service-manual.pdf
Do not buy the ebay all four carburetors replacement parts in one kit! These often don't have the correct parts. You will be doing your carburetors more harm than good trying to make these work!.

Take lots of pictures as you begin disassembly, you cannot have too-many pictures. This will help in re-assembly.

After your carburetors are properly re-assembled and thoroughly cleaned, you have to synchronize the carburetors. If you do not do this, your bike will not run properly. It has to be done.

 

[Luca]

Can we assume that you have fresh fuel in the tank?
Is the running problem with the choke on or off?
Can it be coaxed into running by giving some throttle?
After trying to start have you pulled the plugs to see if they are wet or dry?
If not already done I'd also replace the spark plugs and check that there is a spark at each plug.

If the fuel pumps cause problems it is usually because they are unable to deliver sufficient fuel rather than being dirty. You can check that the pump is delivering fuel.
Have you looked inside the tank to see if there is any flaking corrosion? If so then that will need to be addressed.
My next step would be to drain the float bowls into a container to see what comes out.

If you are satisfied it is a fuel issue within the carbs then trying the Shotgun may help but failing that I'd be inclined to take them off so that you can thoroughly inspect them.

Hi max, gasoline is fresh because I started to restore the bike last year and I've ridden it sometimes.
During this year the bike has ran more or less "good" for about 1 week
I've rebuilt the carbs and cleaned them when I started the restoration on April 2022.
Right now the problem is occuring on choke ok and choke off.
Revving it sometimes solve the problem on 1 cylinder.
I've tried spraying some gasoline when the engine running with the air filter off, and it seems to increase the rpm in the instant I spray.
I checked if there is spark on each cylinder and that seems to not be the problem.
I tested the resistance of the 4 ignition coils and the pickup coil and they're all in spec.
Anyway I ordered this coil tester just to be sure.

I've drained many times the carbs to read the wet level and sometimes I found some black little particles in the gas.
So I started to think that the problem is the carbs are clogged again.

Your bike needs carburetors disassembled and cleaned. An ultrasonic bath works best in my experience. The pilot jets are probably all-plugged with hardened deposits. A small stiff wire will allow you to make short work of the cleaning of the pilot jets. Be careful you do not scratch/gouge the brass!

In cases like this, you may need to do this more-than once if you aren't thorough-enough the first time. I'm speaking of the ultrasonic bath and then poking through all the jets, off the carburetors, and also getting confirmation of cleared passages in the carb bodies. There ar probably hundreds of threads on here dealing with dirty carburetors. You will see some things repeated over and over. Use the search function, and do lots of reading on what replacement parts other than stock Yamaha will work, one name you will see is K & L. You will also see how the carbs are disassembled, cleaned and re-assembled.

This is a guide for your efforts. Print out a copy and put it into a 3 ring binder for easy reference. Save this file on your computer. Read it ffrom beginning to end. The first ~64 pages are annual service updates. After that begin the chapters by what area of the bike: engine, suspension, electrical, brakes, etc. The Appendix has lists you will refer to many times. One is nut/bolt sizes, torque values, and where they are on the bike. Another is cable and hose routing. If you do not become familiar with the service manual, your efforts will probably be unable to fix your bike. Between the service manual, and the search function here, you can fix your bike.

This is going to be repeated: Take lots of pictures as you begin disassembly of anything.

https://dn790009.ca.archive.org/0/i...ice-manual/yamahavmaxvmx12-service-manual.pdf
Do not buy the ebay all four carburetors replacement parts in one kit! These often don't have the correct parts. You will be doing your carburetors more harm than good trying to make these work!.

Take lots of pictures as you begin disassembly, you cannot have too-many pictures. This will help in re-assembly.

After your carburetors are properly re-assembled and thoroughly cleaned, you have to synchronize the carburetors. If you do not do this, your bike will not run properly. It has to be done.

Hi, fire-medic
I rebuilt the carbs on April 2022, maybe I didn't clean them too well, because since then I've never had the engine running 100% ok, but way better than today.
To be honest I rebuilt the carbs with the AliExpress kit but I only replaced the bowls gaskets and the membranes.
I've ordered the ultrasonic cleaner I wish I'll solve the carbs problems with that.
I'm sorry for my English but it's not my mother tongue.
Thank you guys for the replies by the way.

 

[Fire-medic]

Thank-you for the feedback. Sounds like you are on the right path.

 

[marsmax85]

If you rebuilt your carbs they need to be sync again if no one mentioned it ..as for the fuel pump take it out and the inlet side 3 or 4 screws pop that off and clean away . I had white crap build up in a few bikes I had ... either way it's nice to know it's clean

 

[Luca]

If you rebuilt your carbs they need to be sync again if no one mentioned it ..as for the fuel pump take it out and the inlet side 3 or 4 screws pop that off and clean away . I had white crap build up in a few bikes I had ... either way it's nice to know it's clean

Hi mars, I didn't mention but the carbs have been synchronized many times.
You mean these screws?

 

[marsmax85]

Hi mars, I didn't mention but the carbs have been synchronized many times.
You mean these screws?
View attachment 91257

yes