barn find T350 carb leak

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jabcb
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Suzuki 2-Strokes: 69 T350 thru 75 GT750
Location: southwestern Pennsylvania

barn find T350 carb leak

Post by jabcb »

Now that the GT250 cafe project is just about done, I’m working on a 72 T350 project.
It was last inspected in 1977 and has Inoue tires.
Throttle cable had a few broken strands, which may be the reason it was put away so many years ago.

Am trying to keep it original as possible.
Replaced the throttle cable & rear brake cable.
Using a different petcock but may switch back to the original if the rebuild works out.

Carbs were cleaned & have new Mikuni pilot+main jets & needle valves.
Used fuel level to set the floats — fuel level is below the gasket when the carbs are level. Also below the gasket when installed & the bike is on the center stand.

But when on the sidestand the carbs slowly leak from the gasket on the air cleaner side.
Have run out of ideas. Have tried NOS & some different aftermarket gaskets, including rubber.
Used sandpaper on a flat surface to make the float bowl surface flat again.

Have run out of ideas short of sending the carbs out to a shop.
Any suggestions?
BAS (Bike Acquisition Syndrome) - too many bikes but have room for more

Suzuki:
GT750 2x75
GT550 72 & 75
GT380 72
T500 69 project & 73 project
T350 69 & 71
Honda 85 CB650SC & 86 CB700SC
09 Triumph Bonneville SE
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jabcb
Moto GP
Posts: 4240
Joined: Mon Dec 13, 2010 4:32 pm
Country: USA
Suzuki 2-Strokes: 69 T350 thru 75 GT750
Location: southwestern Pennsylvania

Re: barn find T350 carb leak

Post by jabcb »

Happen to find an interesting observation for post-1972 Suzuki Mikuni carbs.
Seems that they recognized the structural limitation of the carb design. This pic is for a GT380 float bowl that uses the same gasket as the T350 carbs. They added two stiffeners on the intake side of the float bowl where I’m having problems. (Might have also improved the carb body as well.)
Image
BAS (Bike Acquisition Syndrome) - too many bikes but have room for more

Suzuki:
GT750 2x75
GT550 72 & 75
GT380 72
T500 69 project & 73 project
T350 69 & 71
Honda 85 CB650SC & 86 CB700SC
09 Triumph Bonneville SE
sportston
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Suzuki 2-Strokes: FZ50, GP100, RG125 Gamma, GT380, Bandit 1200S

Re: barn find T350 carb leak

Post by sportston »

You probably have a warped surface still. They sometimes go like that with age. You either get new float bowls or get your float bowl and reprofile it by rubbing it in a figure 8 in a flat surface with some sand paper on it. But I see you have already tried that. I actually use a diamond sharpening stone instead of a flat surface with sandpaper. It takes off the high spots and allows the gaskets to seal. It is a bodge, but it usually works. Also have you definitely cleaned off all old gasket from carb body?
However....
Where did you get the measurement for checking the fuel level? Is it accurate?
Some of the guys on here might shoot me down for saying it, but I usually prefer to set the float level using a steel rule according to the level specified in the manual. After that you can double check the fuel level with the bowls fitted just to make sure that both sides are the same and that your float valve is sealing properly, if you want.
The wrong float level, even buy as little as a millimeter, can mess up your carburation, giving you running problems and making it difficult to tune accurately.
Last edited by sportston on Mon Aug 28, 2017 11:18 am, edited 1 time in total.
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jabcb
Moto GP
Posts: 4240
Joined: Mon Dec 13, 2010 4:32 pm
Country: USA
Suzuki 2-Strokes: 69 T350 thru 75 GT750
Location: southwestern Pennsylvania

Re: barn find T350 carb leak

Post by jabcb »

Already tried making the surface flat with sandpaper. But I’m an amateur home mechanic & maybe I’m missing something.
BAS (Bike Acquisition Syndrome) - too many bikes but have room for more

Suzuki:
GT750 2x75
GT550 72 & 75
GT380 72
T500 69 project & 73 project
T350 69 & 71
Honda 85 CB650SC & 86 CB700SC
09 Triumph Bonneville SE
sportston
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Posts: 1119
Joined: Wed Jul 10, 2013 12:04 pm
Country: England, UK
Suzuki 2-Strokes: FZ50, GP100, RG125 Gamma, GT380, Bandit 1200S

Re: barn find T350 carb leak

Post by sportston »

jabcb wrote:Already tried making the surface flat with sandpaper. But I’m an amateur home mechanic & maybe I’m missing something.
Have just edited my previous reply
sportston
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Re: barn find T350 carb leak

Post by sportston »

Even an amateur home mechanic can fix most problems on carbs with a little dedication and attention to detail.
The key is attention to detail.
Do everything carefully and double check every measurement. It doesn't matter if the outside of your carb looks scruffy, but the inside needs to be very clean and free of debris, dirt and corrosion. Strip carbs completely and clean using carb cleaner and a high-pressure airline. Don't simply clean and blow through each hole once. Do it at least three times, really go to town on it. Blast every hole through from both ends repeatedly and keep applying carb cleaner though each hole each time. This should ensure a clean carb where it counts.
Also you might set the carbs up perfectly during rebuild, but undo your hard work by omitting to fit a fuel filter. If your nice clean carb is then filled with dirty petrol from an over 40 year old tank, that is bound to have a little corrosion in it, then you can get tiny bits of dirt stopping your float valve from sealing well.
sportston
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Re: barn find T350 carb leak

Post by sportston »

and when i say strip completely I mean every jet must be removed and the float valve and seat. Then after cleaning the body, clean each component as you rebuild it. The last thing you do before putting on the float bowl is to check and set the float level. then install the float bowl carefully so as not to bash the float and bend it or knock the setting out again.
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jabcb
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Joined: Mon Dec 13, 2010 4:32 pm
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Suzuki 2-Strokes: 69 T350 thru 75 GT750
Location: southwestern Pennsylvania

Re: barn find T350 carb leak

Post by jabcb »

Came across this interesting product: Permatex Copper Spray-A-Gasket Hi-Temp Sealant
https://www.permatex.com/products/gaske ... p-sealant/
Per Permatex: fills minor surface irregularities. Seals instantly. Fills hot spots and surface imperfections; resists all types of automotive fluids, especially gasoline.
Suggested motorcycle applications: Cylinder head gaskets, carburetor gaskets, exhaust manifold gaskets and
other high temperature applications
BAS (Bike Acquisition Syndrome) - too many bikes but have room for more

Suzuki:
GT750 2x75
GT550 72 & 75
GT380 72
T500 69 project & 73 project
T350 69 & 71
Honda 85 CB650SC & 86 CB700SC
09 Triumph Bonneville SE
sportston
Expert racer
Posts: 1119
Joined: Wed Jul 10, 2013 12:04 pm
Country: England, UK
Suzuki 2-Strokes: FZ50, GP100, RG125 Gamma, GT380, Bandit 1200S

Re: barn find T350 carb leak

Post by sportston »

jabcb wrote:Came across this interesting product: Permatex Copper Spray-A-Gasket Hi-Temp Sealant
https://www.permatex.com/products/gaske ... p-sealant/
If you use it, don't spray it on the carb. It could cause blockages and problems. Make sure you only spray it on the gasket.
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jabcb
Moto GP
Posts: 4240
Joined: Mon Dec 13, 2010 4:32 pm
Country: USA
Suzuki 2-Strokes: 69 T350 thru 75 GT750
Location: southwestern Pennsylvania

Re: barn find T350 carb leak

Post by jabcb »

I didn’t use it. I got it to seal with two Suzuki gaskets.

Wasn’t too hard to get running but it won’t run at low rpm & isn’t very responsive to throttle changes.
The crankcase cover screws are all messed up, so someone was in the motor for some TBD reason.

I drained the gas out of the tank + carbs & put the bike waway.
We’ll work on this motor after we get the GT550 cafe project motor done.
BAS (Bike Acquisition Syndrome) - too many bikes but have room for more

Suzuki:
GT750 2x75
GT550 72 & 75
GT380 72
T500 69 project & 73 project
T350 69 & 71
Honda 85 CB650SC & 86 CB700SC
09 Triumph Bonneville SE
sportston
Expert racer
Posts: 1119
Joined: Wed Jul 10, 2013 12:04 pm
Country: England, UK
Suzuki 2-Strokes: FZ50, GP100, RG125 Gamma, GT380, Bandit 1200S

Re: barn find T350 carb leak

Post by sportston »

check the ignition points are correctly set and also the timing before you check for crankcase leaks.
User avatar
jabcb
Moto GP
Posts: 4240
Joined: Mon Dec 13, 2010 4:32 pm
Country: USA
Suzuki 2-Strokes: 69 T350 thru 75 GT750
Location: southwestern Pennsylvania

Re: barn find T350 carb leak

Post by jabcb »

Have good spark. Have already adjusted the points & used new plugs.
BAS (Bike Acquisition Syndrome) - too many bikes but have room for more

Suzuki:
GT750 2x75
GT550 72 & 75
GT380 72
T500 69 project & 73 project
T350 69 & 71
Honda 85 CB650SC & 86 CB700SC
09 Triumph Bonneville SE
sportston
Expert racer
Posts: 1119
Joined: Wed Jul 10, 2013 12:04 pm
Country: England, UK
Suzuki 2-Strokes: FZ50, GP100, RG125 Gamma, GT380, Bandit 1200S

Re: barn find T350 carb leak

Post by sportston »

and checked timing?
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