Replacing carb on GZ125

[Chummers]

Hi,

I’ve bought a little GZ125 as a project bike. There are starting and running issues, which I’ve put down to a hole in the diaghram. Looking online I can get a replacement diaghram for £30 or a replacemant carb for the same money.

I have two questions,

Firstly, does anybody have any experience with these carbs,

Secondly, the carbs look like they don’t have a TPS fitting, does this matter, can I lose the TPS?

Cheers

[Via]

No direct experience with that bike so can't help on specifics.

Is that a 2nd hand carb for same price as diaphragm? If nothing else wrong with carb I'd personally go for diaphragm as you know you're getting a new working piece to replace a failed one, replacing with 2nd hand carb you're risking the same or other issues. Even if sold working and it is fine when you get it could well be a few miles away from a similar failure.

[fastbob]

What's a TPS ?

[Grumpy Old Git]

Why not just fix the hole?

[mikestrivens]

What's a TPS ?

 

Throttle position sensor

Maybe

[Via]

What's a TPS ?

 

Throttle position sensor

Maybe

 

Only thing I can think of but surely you wouldn't have one on a carb as they are for fuel delivery calculations on injection systems

[Grumpy Old Git]

To fix the pinhole / tear in the diaphragm:

use 'Gorilla Glue'

The gorilla glue, being a polyurethane and using the chemicals it does to react with the bonded surfaces, won't let go even when covered with gasoline or carb cleaner. It remains somewhat flexible, but of course is much stiffer than your diaphragm which is just a nitrile rubber coated cloth. You can apply it thinly over tears and cracks and holes and it's not going to let go.

[TimR]

What's a TPS ?

 

Throttle position sensor

Maybe

 

Only thing I can think of but surely you wouldn't have one on a carb as they are for fuel delivery calculations on injection systems

Gz do use a tps ..its not just fi. It controls the ecu timing retard or advance

[TimR]

https://www.themotorbikeforum.co.uk/viewtopic.php?t=62866

May help

[Via]

Gz do use a tps ..its not just fi. It controls the ecu timing retard or advance

 

I stand corrected

[fastbob]

What's a TPS ?

 

Throttle position sensor

Maybe

Thank you If that's what it is then I don't think leaving it off would be a very good idea. It's there for a reason as previously stated .

[fastbob]

Patching up diaphragms with glue ? I mean no disrespect but the idea does not appeal to me . Better just to buy a new diaphragm. Diaphragms operate in a sealed environment where there is nothing to actually put a hole in one . If you do have a hole I would assume that the material has perished and even if you do repair it successfully it's only going to fail again somewhere else. Coating part of a diaphragm with glue is also likely to make it stiff which may well interfere with the smooth operation of the throttle slide . £30 might seem a bit steep for a bit of neoprene but it may well prove to be money well spent in the long run.

[Mississippi Bullfrog]

Back in the day a crisp packet made a pretty good replacement diaphragm.

Can't remember which flavour though.

[Chummers]

To fix the pinhole / tear in the diaphragm:

use 'Gorilla Glue'

The gorilla glue, being a polyurethane and using the chemicals it does to react with the bonded surfaces, won't let go even when covered with gasoline or carb cleaner. It remains somewhat flexible, but of course is much stiffer than your diaphragm which is just a nitrile rubber coated cloth. You can apply it thinly over tears and cracks and holes and it's not going to let go.

[Grumpy Old Git]

Patching up diaphragms with glue ? I mean no disrespect but the idea does not appeal to me . Better just to buy a new diaphragm. Diaphragms operate in a sealed environment where there is nothing to actually put a hole in one . If you do have a hole I would assume that the material has perished and even if you do repair it successfully it's only going to fail again somewhere else. Coating part of a diaphragm with glue is also likely to make it stiff which may well interfere with the smooth operation of the throttle slide . £30 might seem a bit steep for a bit of neoprene but it may well prove to be money well spent in the long run.

 

Sorry Fastbob but that is why I specified 'Gorilla Glue' rather than 'Superglue' - Superglue is too brittle and perishes with humidity (!) whereas Gorilla glue retains some flexibility and does not perish when in contact with fuel. I have used this before and the carb functioned without further failure for over 3 years!

I agree that replacement is 'better' but if the OP wants to save a few pennies - Then this solution works.

[fastbob]

Patching up diaphragms with glue ? I mean no disrespect but the idea does not appeal to me . Better just to buy a new diaphragm. Diaphragms operate in a sealed environment where there is nothing to actually put a hole in one . If you do have a hole I would assume that the material has perished and even if you do repair it successfully it's only going to fail again somewhere else. Coating part of a diaphragm with glue is also likely to make it stiff which may well interfere with the smooth operation of the throttle slide . £30 might seem a bit steep for a bit of neoprene but it may well prove to be money well spent in the long run.

 

Sorry Fastbob but that is why I specified 'Gorilla Glue' rather than 'Superglue' - Superglue is too brittle and perishes with humidity (!) whereas Gorilla glue retains some flexibility and does not perish when in contact with fuel. I have used this before and the carb functioned without further failure for over 3 years!

I agree that replacement is 'better' but if the OP wants to save a few pennies - Then this solution works.

Fair enough, maybe I'll give it a go one day .