Tanaka Carb advice/crossover help needed with a demonic carb!!

[rynosawr]

The saw: Tanaka ecv-5610

The owner: great guy, smart, listens to me advise him on fuel and mix oil, he has bought 3 other saws from me and all are doing excellent except this one

The problem: he bought this saw from me and it ran awesome for three jobs and then it messed up all the sudden and will start and rev up and then die. If the choke is left on about 3/4, it will run and rev without dying, otherwise it will only idle with no choke and stumble and die if the throttle is moved with no choke.

My testing and work thus far:

Vacuum and press test- checked out good, low hour saw
Perfect piston and rings
New fuel line and filter and new intake boot and impulse hose
Very good compression
Very strong spark cold or after running
Doesn't respond much to needle adjustments +/- of carb at the normal baseline of 1L/1H

Carb has been rebuilt/ gone through 4 times and USC'd with welch plug pulled and nothing found in passages

I have not tested pop-off pressure, I plan on that tomorrow.


My potential dilemma:

I believe the carb main fuel discharge brass nozzle to be the problem or a clogged internal passage that I can't fix.

The carb is a WT666a..... Yes, the debil carb. Literally and figuratively.

It is also made of unobtanium as well, as the only one I found new is $300!!!!!

This guy has been super patient with me and I have worked so many hours on this thing that I mess with it on a whim, then set it back up on the shelf while thinking about it and fixing something else. I told him I would get it going again for no charge. It is the right thing to do in my book. I think I have about 45 running saws of all flavors and conditions under my belt and this one is really the only one kicking my butt.



Help!!! Does anyone have any suggestions or ideas on this one for an alternate carb body number that I could swap the shafts out for?

 

[HarleyT]

Take this carb apart, and clean it. Take out the needle/lever/spring, and hold up to a light and look through the passage under the little screen, it is likely partially clogged.

 

[Chris-PA]

Also the main jet check valve could be glued shut (use of an inappropriate fuel container?).

If none of that works, the Tanaka ECV-5610 is a Zenoah/RedMax G5000, and the Chinese make tons of knock-offs of those. Search eBay for "52cc chainsaw carb" and you'll find lots of carbs for under $10, although you'll have to wait for shipping from China on most. Get 2.

 

[Mattyo]

So, plain and simple this is a fuel delivery issue, and likely the carb is clogged somehow. Either ultrasonic it and pray that it unclogs, or you have to find new. I'm with Chris-PA... sounds like an awesome idea if you can find a china carb that'll be a retrofit. Just had this issue on a 200t, swapped w/ another carb, and everything responds perfectly. When those adjustment screws stop doing anything, I've usually found that its time to swap the carb. best of luck

 

[rynosawr]

Thanks all!

I decided to get one of the Chinese carbs. I found a place on eBay that says they have them in California for $15 shipped, so I ordered one this morning. Thanks for the reference to these carbs!

I have already ultrasonic cleaned it twice.... No luck

 

[Mattyo]

I've had some hopeless carbs on 372's.... and the china carbs work brilliantly. keep us posted

 

[rynosawr]

I realize I never updated this one.

Chinese carb came in and worked great!

Only shortcoming was that it doesn't have a lever assembly for a fast idle on the choke/throttle.

It runs and starts great now.

 

[rmh3481]

>>Doesn't respond much to needle adjustments +/- of carb at the normal baseline of 1L/1H<<
Raise the lever.

 

[rd35]

Raise the lever.

Yup, what he said!!! It runs, but starves for fuel and the H needled makes little difference. Likely it is starving for fuel at the metering needle. Raise the lever and pour more fuel to it! Worth a shot and easy to try!

 

[mountainlake]

+2 I had one apart on a Husky 55 maybe 3 times, on the 4th I raised the lever which fixed it. Steve