Running Rough NT 650

[Jasma50]

Hi Everyone
I’m an old guy who hasn’t ridden a bike for twenty years. I’ve bought a 2002 NT 650 specifically because they are a reliable, tamed and safe. This bikes been in storage for 12 years and looks absolutely mint, it’s done less than 4000 miles from new. Its had an oil and filter change and all the other levels are clean and good.
it starts first time and runs smooth on choke, but pops and bangs on no choke.
It only occasionally hits full power on both cylinders when on test.
I've had the tank off and cleaned it out, and changed the fuel.
The air filters clean, but you can see residue from the backfiring on one cylinder.
The needle floats were very dry and sticking, I lubed em and they are as smooth as silk now.
I test ran it and it’s just the same.
I’m going to fit two new plugs. But, can anyone who’s had a similar problem please point me in the right direction, I can’t wait to get touring, I love the bike.
Jim.

 

[seagrass]

This is probably the wrong forum as the NT650 was never sold in the US.

The most likely problem is that the carburettors are all gummed up and will need a complete tear down and thorough cleaning of all the jets and emulsifier tubes etc. These internal parts typically get calcified which prevents the fuel from flowing at the correct rate and vaporising correctly.

If you need more help you could try the UK Deauville site at the following link as they should be able to help you,

Deauville Owners UK • Index page

Seagrass

 

[DirtFlier]

If it runs OK on choke but misbehaves off choke, it usually means a blockage of fuel flow from the low speed circuit. My guess is that the slow jets are partially or fully plugged.

At least on all US-models, the idle mixture screw had an anti-tamper cap but if that could be removed, and the screw removed, you can squirt carb cleaner directly into that hole and that will help some but taking the carbs off and apart is the best solution. By the way, don't try and pry that cap off because the mixture needle has a necked-down section designed to break if you use pliers on the cap!

ps. Using a carb cleaning solution, such as SeaFoam, poured into the tank sometimes works but it takes forever.

 

[mikesim]

Yup! The carbs get my vote as the culprits as well.

Mike

 

[Brillot2000]

Yup, another vote on the carburetors. They need to be removed and clear out all the passage ways of all obstructions.

 

[Jasma50]

This is probably the wrong forum as the NT650 was never sold in the US.

The most likely problem is that the carburettors are all gummed up and will need a complete tear down and thorough cleaning of all the jets and emulsifier tubes etc. These internal parts typically get calcified which prevents the fuel from flowing at the correct rate and vaporising correctly.

If you need more help you could try the UK Deauville site at the following link as they should be able to help you,

Deauville Owners UK • Index page

Seagrass

Thanks for the help Mate.

 

[Jasma50]

If it runs OK on choke but misbehaves off choke, it usually means a blockage of fuel flow from the low speed circuit. My guess is that the slow jets are partially or fully plugged.

At least on all US-models, the idle mixture screw had an anti-tamper cap but if that could be removed, and the screw removed, you can squirt carb cleaner directly into that hole and that will help some but taking the carbs off and apart is the best solution. By the way, don't try and pry that cap off because the mixture needle has a necked-down section designed to break if you use pliers on the cap!

ps. Using a carb cleaning solution, such as SeaFoam, poured into the tank sometimes works but it takes forever.

Thanks for the advice Mate.

 

[Jasma50]

Yup, another vote on the carburetors. They need to be removed and clear out all the passage ways of all obstructions.

Thanks Mate I appreciate the help.

 

[Jasma50]

Yup, another vote on the carburetors. They need to be removed and clear out all the passage ways of all obstructions.

Thanks Mate.

 

[Brillot2000]

Thanks Mate.

No problem. Carburetors are a primitive device that mixes fuel with air. All passageways must be clear in order for the carburetor to do its job. A complete tear down is required. I would also recommend that you replace any gaskets such as the carburetor bowl. Please buy yourself a kit. You will need to physically remove all jets from the housings. Use a carburetor cleaner spray solvent. Then use compressed air to blow out all the passage ways. You might also need a set of fine wire gauges to pass through any stubborn jets or passageways to clear them out.

You will also need these, Welder Tip Cleaner Set.

 

[Hondafan]

I agree with Brillot on the carb kits. Them may seem expensive for what you get, but the old bowl gaskets have probably shrunk and got hard.....and will probably leak. You get a new tiny O-ring for the mixture screw, and a new metal washer/seal for the float needle seat. There is a small nylon filter that snaps onto the float needle seat. You should make sure those are clean. I would change the fuel filter as a precaution and check the fuel tank for rust, including the top. You will need a small mirror for that. Before you remove the mixture screws, screw them in until they lightly seat and record the number of turns. do the reverse when you re-install them.
I have ridden the NT 650 and really liked it. Well balanced with a very smooth motor. Well worth investing some time and money

 

[Jasma50]

No problem. Carburetors are a primitive device that mixes fuel with air. All passageways must be clear in order for the carburetor to do its job. A complete tear down is required. I would also recommend that you replace any gaskets such as the carburetor bowl. Please buy yourself a kit. You will need to physically remove all jets from the housings. Use a carburetor cleaner spray solvent. Then use compressed air to blow out all the passage ways. You might also need a set of fine wire gauges to pass through any stubborn jets or passageways to clear them out.

You will also need these, Welder Tip Cleaner Set.

Thanks again.

 

[Jasma50]

Yup, another vote on the carburetors. They need to be removed and clear out all the passage ways of all obstructions.

Cheers.

 

[Jasma50]

I agree with Brillot on the carb kits. Them may seem expensive for what you get, but the old bowl gaskets have probably shrunk and got hard.....and will probably leak. You get a new tiny O-ring for the mixture screw, and a new metal washer/seal for the float needle seat. There is a small nylon filter that snaps onto the float needle seat. You should make sure those are clean. I would change the fuel filter as a precaution and check the fuel tank for rust, including the top. You will need a small mirror for that. Before you remove the mixture screws, screw them in until they lightly seat and record the number of turns. do the reverse when you re-install them.
I have ridden the NT 650 and really liked it. Well balanced with a very smooth motor. Well worth investing some time and money

Thanks for that, I like it too.

 

[DirtFlier]

My memory about Honda carbs is semi-foggy at this point but I believe they are fitted with a large diaphragm on top to lift the slide so be sure and check those for any holes that could prevent the slide being lifted. One lifting all the way and the other only partially can cause some weird running symptoms.

 

[Jasma50]

My memory about Honda carbs is semi-foggy at this point but I believe they are fitted with a large diaphragm on top to lift the slide so be sure and check those for any holes that could prevent the slide being lifted. One lifting all the way and the other only partially can cause some weird running symptoms.

Thanks, I’ll have a look, they easy to get off.

 

[Jasma50]

I agree with Brillot on the carb kits. Them may seem expensive for what you get, but the old bowl gaskets have probably shrunk and got hard.....and will probably leak. You get a new tiny O-ring for the mixture screw, and a new metal washer/seal for the float needle seat. There is a small nylon filter that snaps onto the float needle seat. You should make sure those are clean. I would change the fuel filter as a precaution and check the fuel tank for rust, including the top. You will need a small mirror for that. Before you remove the mixture screws, screw them in until they lightly seat and record the number of turns. do the reverse when you re-install them.
I have ridden the NT 650 and really liked it. Well balanced with a very smooth motor. Well worth investing some time and money

Thanks for that.