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200T carburetor accel pump block off.

ptjeep

ptjeep

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In the last couple of years i've gained a bunch of knowledge from this forum that has allowed me to fix a bunch of saws. I always wanted to give back to the forum but never had the knowledge to give. I've got a couple of 200T's on the bench right now that have accel pumps causing the typical carb issues that so many of the saws have. I figured since i was fixing these carbs that i might do a step by step thread with pics for the people who share my frustration with the carbs. I got the knowledge to fix my first 200T carb a year or so ago from this thread http://www.arboristsite.com/chainsaw/145024.htm, but figured a couple of pics wouldn't hurt any.

Zama carb that i've got

Brass plug that has to come out to remove the accel pump piston

Butterfly shaft has to come out so pop off this spring and E-clip
 
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ptjeep

ptjeep

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Remove the screw and pull the butterfly or whatever its call off, its a snug fit so it may take some finesse.

Now the shaft is ready to slide out

This slot is what pushes the pump when throttle is applied.

It may not be visible but when the shaft is slid out the piston which is spring loaded will slide up into view and you will be able to see the o-ring that leaks causing part of the problem.
 
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ptjeep

ptjeep

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Since the piston is spring loaded, i had to push the pick through from the back side to hold it down so that i could use this curved pick to pry against the carb body to force out the brass plug.

Plug popped out with little effort.

The piston and spring will fall out once the carb is turned over, this is what has been removed so far.

Applying a little JB weld to seal off the hole that the piston rides in so that it no longer functions. The spring and o-ring are discarded.
 
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ptjeep

ptjeep

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I dabbed a little JB on the piston just to help seal the port off.

Apparently i applied to much JB and the piston wont push down any further.

A little dremel work and its all better. Lesson learned.

Since i'm doing two of these right now, i decided to grind a little off the next piston so that there would be no clearance issues on the next one.
 
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ptjeep

ptjeep

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I let the JB weld set up over night, reassembled the carb to day and installed it. Saw ran like a new one with great throttle response and acceleration. Saved myself $100 by performing this easy fix.

Heres a pic of what happens to the piston. After repeated throttle blips, the piston o-ring wears which allows the piston to make contact with the carb body and basically starts to score similar to a burnt piston just not as hot. Atleast thats what it looks like to me. Hope this helps.
 
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ptjeep

ptjeep

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Thanks guys, hopefully it will help somebody out in the future. If i left something out, or wasnt clear, just ask. I'll do my best to make something up.
 
Thommo

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Thanks for posting that bit of information. I have been having trouble trying to get another o ring for the accelerator pump in a C1s Zama carby on an Echo 300 EVL. Our local Echo dealer said he had never heard of an accelerator pump on a chainsaw carby. I took the o ring off the piston and tried using high temp silicon to fix the problem but it didnt last long. I had thought about tapping a thread in the hole and screwing in a grub screw, but the JB weld looks easier.
 
ptjeep

ptjeep

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Thanks for posting that bit of information. I have been having trouble trying to get another o ring for the accelerator pump in a C1s Zama carby on an Echo 300 EVL. Our local Echo dealer said he had never heard of an accelerator pump on a chainsaw carby. I took the o ring off the piston and tried using high temp silicon to fix the problem but it didnt last long. I had thought about tapping a thread in the hole and screwing in a grub screw, but the JB weld looks easier.
I would think the jb weld would be easier and quicker also, and if it doesn't work, you can still drill it out and tap it. I'm curious to see if jb weld works for you also so keep us posted of the outcome.
 
showrguy

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very well done..
i was gonna send my bad carb to someone else to "fix"......... now i thinks me can do it myself..
thanks pt..
 
LowVolt

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My personal 200T would not run right this year. The problem I am having is the saw will fire on full choke as normal, on half choke it will rev up as normal but as soon as you hit the trigger to put it in the run/idle position, it will not idle. I have read the previous thread a few times and I am still unclear if this is the fix for my saw. I don't know what carb I got, I need to look.

Heck of a write up I might add.

:cheers:
 
StrataTree

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Tried to take mine to one of two local dealers...said I should mess with it myself, he wouldn't even take it in to his shop.

I think he was scared....
 
Saw Dr.

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I'm not trying to rain on anyone's parade here, but isn't this mod effectively just removing the accel pump? That is fine, but the pump is put there for a reason. One of the great things about the 200 is the instant throttle response. Just wondering how it performs without that extra shot of fuel? I am particularly fond of the pumps in circumstances where the saw has started to cool off (after lunch) and a couple of squeezes of the trigger makes the start go alot easier.

BTW, $140 for a 200t carb is highway robbery. We retail them for $96. They are usually special order, but I am thinking on keeping one in stock as they have been requested plenty lately.
 
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