036 carb/ intake boot air leak

[idiotwithasaw]

Pressure test in which way, through the fuel inlet, or by blocking off the venturi and testing it that way some how? I've heard of ppl doing this but don't understand how it would work because of the choke and throttle.

This saw starts good and revs out good, good throttle response, but I haven't cut any wood with it so I don't know if it runs erratic.

 

[idiotwithasaw]

Though honestly I haven't cut with most of my saws, CAD is BAD and time is short in supply lol.

 

[stihltech]

Look up how to do a vacuum and pressure test on a chainsaw. Many places on the Internet. Just guessing will get you a new piston and cylinder. Maybe even a crank and bearings.
Your call.

 

[irhunter]

Pressure test in which way, through the fuel inlet, or by blocking off the venturi and testing it that way some how? I've heard of ppl doing this but don't understand how it would work because of the choke and throttle.

This saw starts good and revs out good, good throttle response, but I haven't cut any wood with it so I don't know if it runs erratic.

Here is my favorite carb video. In it, Smart and Smarter talk about pressure testing carbs.



As far as, maybe, having a saw or two too many. Join the club.

But, you might find you really like the 036 once it is running correctly.

Roy

 

[pioneerguy600]

The first boot in the post is the original

The second one thats in the saw was the oem used one I found, it's a little smaller than the original.

If you look at the back of the carb where it mates with the boot it's rough from factory, I don't know if this is causing any problems

That carb would seal against rubber , I fail from looking from here while it will not seal. For chasing issues like air leaks the pressure test is invaluable.

 

[SteveSr]

I'm also starting to wonder if my leak isn't the throttle rod being wore and letting air around it. I found a used carb in my pile and swapped it out just to see, surprisingly it fired right up but it is still showing the same symptoms.

This is being done INCORRECTLY! Carb shaft is a definite leak! Block-off goes in place of or BEHIND the carburetor.

Remove the paper carb gasket. It is NOT required. The boot should sit proud of the metal circular washer that goes around the carb studs. If it doesn't replace the boot with new OEM.

 

[muddy42]

In my experience the way to definitely find pressure leaks is to put a saw is underwater. Strip it down, seal the muffler and behind the carb, attach testing gear to the impulse or spark plug and dunk in a big basin of water. Bubbles indicate where the leak is, no guessing required.

 

[idiotwithasaw]

Ok I think some ppl are getting confused here, as far as me vac testing the saw it was done by sealing off with rubber behind the muffler AND carb. This is how I found the flywheel side seal needing replaced. The issue I am having is since replacing the seal, and not related to it is, the saw stumbles and dies when hit with brake clean at the point where the carb and boot meet.

And I agree it should seal without the gasket. I installed a brand new carb and it still died so at this point I'm waiting for a new boot.

 

[idiotwithasaw]

Could over tightening the studs cause a leak?
And thank you for posting the video I hope it helps many ppl in the future.

 

[idiotwithasaw]

In my experience the way to definitely find pressure leaks is to put a saw is underwater. Strip it down, seal the muffler and behind the carb, attach testing gear to the impulse or spark plug and dunk in a big basin of water. Bubbles indicate where the leak is, no guessing required.

I have done this in the past and works really well if you have a big enough container. Only bad thing with doing this is if you have a saw that holds pressure but fails vaccum this method isnt advisable.

 

[muddy42]

I have done this in the past and works really well if you have a big enough container. Only bad thing with doing this is if you have a saw that holds pressure but fails vaccum this method isnt advisable.

Yes agreed

Ok I think some ppl are getting confused here, as far as me vac testing the saw it was done by sealing off with rubber behind the muffler AND carb. This is how I found the flywheel side seal needing replaced. The issue I am having is since replacing the seal, and not related to it is, the saw stumbles and dies when hit with brake clean at the point where the carb and boot meet.

And I agree it should seal without the gasket. I installed a brand new carb and it still died so at this point I'm waiting for a new boot.

no I understand. You were doing the crankcase test correctly. Its all about testing and eliminating problems one by one. Now focus on the carb. If you still don't know exactly where the leak is exactly, carbs will survive water as well, so you could pressure test the saw underwater with the carb attached.

The bubbles will show exactly which part of the boot is leaking. You could sand this area or apply some liquid gasket or replace the boot.

You mentioned leaking throttle linkages, please note its fine for these to leak a bit. Its not OK for other areas of the carb to leak. You can pressure test a carb in isolation to see if it is working. Don't apply too much air or you can damage it.

 

[pioneerguy600]

Well at this juncture we are not going to be able to fix this problem over the internet, the OP knows where it is leaking from and that it should not leak there if all things are correct, there is a physical reason it is not sealing by the rubber boot . No amount of guessing why it won`t seal from the members will fix this, it is really up to the OP now to change one or more of the parts, be it carb body or the rubber intake boot, those are the two adjoining parts that need to seal to each other and that can only be done hands on. No further pressure tests needed, the area of leakage is known and if all parts are correct for the saw and in good condition they seal without extra gaskets or any type of goop.

 

[idiotwithasaw]

Well at this juncture we are not going to be able to fix this problem over the internet, the OP knows where it is leaking from and that it should not leak there if all things are correct, there is a physical reason it is not sealing by the rubber boot . No amount of guessing why it won`t seal from the members will fix this, it is really up to the OP now to change one or more of the parts, be it carb body or the rubber intake boot, those are the two adjoining parts that need to seal to each other and that can only be done hands on. No further pressure tests needed, the area of leakage is known and if all parts are correct for the saw and in good condition they seal without extra gaskets or any type of goop.

Agreed, and thank everyone for all your input, the next step is replacing the boot.

if that don't fix it the next thing that I'm thinking it could be is that the plastic flange that holds the boot has deformed from over tightening the carb studs. If that's the case then that requires a whole new tank and I'm not sure I want to do that, mainly because I don't want to give up the screw on fuel cap.

 

[pioneerguy600]

It really does come down to swapping parts out or physical alterations at this point, all the guesses and most bases have been posted up already so I really do hope you can solve the issue or issues your saw is presenting, the 036 is a decent saw for its time. I have the 036 Pro, Ms360 and the 362, the 036 is ported and a much stronger cousin compared to the others.

 

[irhunter]

it could be is that the plastic flange that holds the boot has deformed

While waiting for the boot, how about pics of the front and back of that plastic?

Roy

 

[pioneerguy600]

I would like to see this solved, I have read and heard of other 036`s having a similar issue but none of them ever reported back if the issue was found or fixed, would be good to know of a cause, for certain. Warping of the bulkhead is a possibility if the carb holding stud nuts were over torqued pulling the opposing sides up higher than the rest of the supporting area but the larger outer steel backup plate should help mitigate that problem.

 

[pioneerguy600]

+One of the ways I determine tight fits is to coat one surface with a transferable substance like Prussian blue or even thin coat of grease or Vaseline, just a thin coat then push the parts together, withdraw and check the surface for transfer,warpage would be very apparent at least for me.

 

[irhunter]

One could also make a block off plate which replaced the carb. Allowing a pressure check clamp, boot, and bulkhead.

 

[SteveSr]

+One of the ways I determine tight fits is to coat one surface with a transferable substance like Prussian blue or even thin coat of grease or Vaseline, just a thin coat then push the parts together, withdraw and check the surface for transfer,warpage would be very apparent at least for me.

"Paint" the boot interface with black permanent magic marker. Clean the carb face and install it with the proper torque. Leave it sit for a day or so and remove the carb and look for ink transfer.

 

[SteveSr]

Agreed, and thank everyone for all your input, the next step is replacing the boot.

Make sure that you use the Stihl "magic string" method of pulling the boot through the tank housing. If the existing boot wasn't pulled all the way home this might be your issue.