200t running problem.

[spudulike]

I don't want to be too critical, or damning of others methods, but, in my opinion blanking off the accelerator pump is not so much a 'mod', as a 'bodge'. (I must admit I too have done this bodge in the past)

 

The pump is there for a reason, and that is too overcome the 'flat spot' which occurs in the transition from running on the idle jet, to running on the main jet as the butterfly is opened.

At idle the flow through the carburetor is low. Some of the fuel is evaporated and some remains liquid at the bottom of the intake pipe.

Suddenly opening the throttle will give an immediate air flow increase to the cylinder. The evaporated fuel follows the air flow, but the liquid fuel takes longer to increase its speed. This means that the first second after opening the throttle, the engine will get a lot of air but very little fuel and the response is bad.

This is compensated for by the acceleration pump in the carburettor.

Remove this pump and you need to compensate to some degree by richening up the idle L screw, which sort of works but cannot be done in production because of emission regs.

Why not simply repair the accelerator pump?

 

This is of course correct but it effectively turns the carb back in to one very similar to the 020 carb which didn't have the accelerator pump and many use as a suitable alternative.

 

Barrie is correct in the carb settings that are required and I personally replace the pumps now rather than work around the issue so great minds work alike but if the fix fails to work due to wear on the body of the carb, would still use this work around if the rest of he carb was serviceable.

 

So Barrie - think we agree on this one:thumbup:

[spudulike]

Its a good job we are here to moderate each others advice Steve, but strangely we normally concur.

But never ask me to sing with you again:scared1:

 

Yes, the first one was a bit bad:sneaky2: ......wasn't it the lumberjack song:blushing: Your attire was a bit risqué

[GardenKit]

This is of course correct but it effectively turns the carb back in to one very similar to the 020 carb which didn't have the accelerator pump and many use as a suitable alternative.

 

Barrie is correct in the carb settings that are required and I personally replace the pumps now rather than work around the issue so great minds work alike but if the fix fails to work due to wear on the body of the carb, would still use this work around if the rest of he carb was serviceable.

 

So Barrie - think we agree on this one:thumbup:

We almost agree, except that the old 020t carb had larger jetting as it was built before these new emission regs hit, and did not suffer from the lag. The newer carbs are leaned down so much that accelerator pumps were introduced to overcome the 'flat spot', so remove the pump by all means, but richen the idle up to compensate, and then it's not quite as smooth as the old carb.

Good enough though in practice.

[Gerbutt]

When I've done it on saws before it's not seemed to cause a flat spot, they've gone from running badly, to little beasts again. This saw ran badly before the bodge, and is exactly the same after.

 

The diaphragms did look old so I'll stick a carb kit in and see if that cures it. Have you a link to where I can buy one or should I just ring jones's?

[GardenKit]

When I've done it on saws before it's not seemed to cause a flat spot, they've gone from running badly, to little beasts again. This saw ran badly before the bodge, and is exactly the same after.

 

The diaphragms did look old so I'll stick a carb kit in and see if that cures it. Have you a link to where I can buy one or should I just ring jones's?

Sorry, I should have answered you when you asked earlier. My bad.

 

I have them in stock, not sure of the exact price here at home, but I will pm you in the morning and can post one to you.

That is if I have not offended you too much by inferring you 'bodged' your repair.

I did not mean it like that.

[Gerbutt]

Sorry, I should have answered you when you asked earlier. My bad.

 

I have them in stock, not sure of the exact price here at home, but I will pm you in the morning and can post one to you.

That is if I have not offended you too much by inferring you 'bodged' your repair.

I did not mean it like that.

 

 

That'd be great, thank you very much 👍

[jomoco]

My 020T's carb has been on dang near every 200T I've worn out!

 

My saw today's a veritable Frankentein's monster, but has three adjustment screws!

[htb]

My 020T's carb has been on dang near every 200T I've worn out!

 

My saw today's a veritable Frankentein's monster, but has three adjustment screws!

 

I like your lightweight choice of strop attachment

[peatff]

I like your lightweight choice of strop attachment

 

It's to balance the weld holding the bar together