How to prime a Tilly HL to ease initial start up

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promac850

formerly promac610
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Due to a request by another member here, I spent a few minutes out in the barn tonight to show folks how to prep their Tilly for their saw. Priming it before you even pull on the cord makes a huge difference.

Even while priming the saw with fuel down the throat of the carb, it just wouldn't draw fuel. The fuel pump flaps in the carb worked properly and are flexible like they should be, but with nothing to help them seal or anything to draw on in the beginning, which meant the saw just wouldn't run off of anything except the little bit squirted down the carb throat.

So here's what I did.

First, the Tilly needs to be off of the saw (this is my spare carb that will be going onto a Mac at some point; this trick probably would work with other similar functioning carbs as well, feel free to try it and report back)

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Then you need to lightly clamp it in the bench vise. It is easier to put mix into it when you don't have to hold the carb. We all have the shaky hands problem every now and then. (including not that old me)

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Next, take the carb apart... pay attention to how it comes apart. The first thing on top is that fuel pump flap diaphragm thingy. The gasket that goes with that is right under the diaphragm.

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Now you check the lever and make sure it's set right, and then when you're satisfied with it, fill the while thing up with fuel.

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more in the next post... and the post after that.
 
Then you slap the big diaphragm on... and the metal piece on top of that. Press down firmly to ensure the fuel stays put.

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... put some mix in the passages on this layer...

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Then put the fuel pump diaphragm gasket in, then the diaphragm itself... note in the second picture that the tabs are off of the layer underneath... this is critical. Eccentric specifically stated, with a stern point, that the carb will not pump fuel for #### if you get the gasket and diaphragm backwards.

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Now the last piece goes on...

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Still more yet...
 
Start the screws, then press down on the cover and ensure everything is lined up right. Once you're sure it's properly put together (somewhat hard to screw up, since there are neat little locating tabs and whatnot) then tighten the screws lightly in a star pattern, then snug them down a little more.

No farmer's tight here... just snug them down.

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Now you need to reposition the carb in the vise. Clamp it down lightly with the fuel inlet nipple facing up. Take off the carb adapter as this will be in the way of your medicine syringe that will be used to work the impulse to get the fuel into the carb.

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Next is adding fuel into the inlet. Fill it up.

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Then put the syringe over the impulse hole... press firmly to ensure a decent seal. Draw the plunger back to suck fuel into the carb body. Repeat a few times to get some more fuel into the passages and other areas inside the carb body. You will see the fuel level in the inlet nipple go down when you draw the syringe back. If it doesn't go down, then you either mixed up the fuel pump gasket/diaphragm or need a carb kit to replace worn out parts.

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Here is the adorable little oil can that I use for squirting mix down the throat of carbs, and inside the carb body itself. Works real nice for either purpose.

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Hope this helps folks get their saws up and running in the easier way. I pulled and pulled that starter cord and it would not draw fuel in the 250. Once there was fuel inside the carb, problem was solved. It needed something in there for it to work with... the carb was completely dry from sitting, and no varnish was present in the carb.
 
Interesting. I believe most of the benefit you saw came from the diaphragms being wet with fuel. Tillotson recomends soaking the diaphragms/gaskets in fuel before assembly (in one of their instructional vids on line). This promotes good pump valve flap sealing, makes the diaphragms more 'supple', and lessens the 'set' that the gaskets/diaphragms take after assembly (lessening the need for retorque). On the last HL I rebuilt (an HL19E to swap into RandyMac's McCulloch 790), I soaked the diaphragms/gaskets briefly beforehand. Seemed to help.

I only had to prime down the throat once upon first startup. It lit off after a few pulls and started pumping right away. This was with dry/empty fuel lines on both sides of the tank bulkhead fitting. I used a fuel cap with a good 'duckbill' check valve, and that helped the tank pressurize (from the fuel sloshing that happens when you start a large Mac without a comp release) as well. As I've seen with freshly rebuilt HL's before, the carb seemed to take a minute or so of running to 'break in' the pump diaphragm and tune right. I think those big diaphragms stretch and loosen up a tad during that first minute...
 
Well thought-out and nicely arranged photographically. A good idea when installing a new kit or when simply cleaning one up. Pumps of all kinds have needed priming in order to work and that's all your carb is basically. Many thanks for arranging this tutorial, it will provide help to many users of this site, not just newbies! For some reason the powers that be won't allow me to rep 'ya right now.
Igpoe:cheers:
 
Of the hundreds of Tilly HL`s that I have rebuilt, for all makes of saws, using OEM Tilly rebuild kits the Pioneer 600 series saws have been the most difficult to get primed. They have that big glass fuel bowl inline that needs to be filled and 1/4" lines in the tank and between the bowl to the carb. If all the lines are fitting tightly so that there are no air leaks they will prime within 5-7 pulls with the carb rebuilt dry. I have not ever had to fill the carb with fuel beforehand but maybe in the future I will try this as it certainly would make starting the saw much easier.
 
pioneerguy600 said:
Of the hundreds of Tilly HL`s that I have rebuilt, for all makes of saws, using OEM Tilly rebuild kits the Pioneer 600 series saws have been the most difficult to get primed. They have that big glass fuel bowl inline that needs to be filled and 1/4" lines in the tank and between the bowl to the carb. If all the lines are fitting tightly so that there are no air leaks they will prime within 5-7 pulls with the carb rebuilt dry. I have not ever had to fill the carb with fuel beforehand but maybe in the future I will try this as it certainly would make starting the saw much easier.
Click to expand...

I think a lot has to do with how the fuel line is run on the saw... seems like top tank saws aren't much of a problem since the fuel lines are fairly short and right at the same level or near the same level as the carb inlet.

But the tank being in the front on the Mac 250 seems to make for a longer fuel line and a near vertical run, which takes more effort to get fuel into the carb. I tried getting it to go with the carb dry, but the fuel got to the inlet and the carb just couldn't draw it any further.

It may also have had something to do with the fuel cap not having a duck bill valve... it's long gone. Going to pick up one of those little Homelite replacements like I read about here.
 
On all my dry start up saws i just add fuel
down the throat. After a couple pulls when the saw
starts i take a piece of card board like whats on the
back of a note pad and cover the throat. This chokes
the saw completely and pulls fuel into the carb
instantly. Another couple pulls with wide open throttle
the saw is alive.

Nice job Kyle but to me it seems like
alot of work to get a saw started.



Lee
 
Lee, I will have to try that next time. I do know that my trick could be a lot of work on certain saws. I find pulling the carb is easy on the Macs that I have. I'm sure there are a few saws out there that are a PITA when it comes to pulling the carb.

Stiff Member... changed my user title to Head Waiter. Thanks for the promotion! :D
 
thomas1 said:
Nice pics and write up. :msp_thumbsup:

But, if you need to pull the carb off the saw to prime it I think you may have other issues.
Click to expand...

I honesty don't think it has a problem with the carb... it probably had a kit put in a few years ago. If you watch the vids in the Mac thread, it runs well. Cold, it starts up first or second pull, every time. (knock on wood, this is the only useable saw that I have at this moment... the 610 is giving me running fits and leaks bar oil everywhere, the 850 still needs an auto oiler and/or I need to figure out how to fix the one that I pulled out of it, and the 790 is not done yet)
 
promac610 said:
I think a lot has to do with how the fuel line is run on the saw... seems like top tank saws aren't much of a problem since the fuel lines are fairly short and right at the same level or near the same level as the carb inlet.

But the tank being in the front on the Mac 250 seems to make for a longer fuel line and a near vertical run, which takes more effort to get fuel into the carb. I tried getting it to go with the carb dry, but the fuel got to the inlet and the carb just couldn't draw it any further.

It may also have had something to do with the fuel cap not having a duck bill valve... it's long gone. Going to pick up one of those little Homelite replacements like I read about here.
Click to expand...

The Mac 250 has a sintered bronze insert that fits into the fuel cap and it acts as the vent on these saws. The Pioneer 600 series saws has to draw its fuel almost straight up from its bottom mounted tank, always found them to be difficult if the lines don`t fit tightly on the fittings. If everything is tight then they pull fuel up with 5-7 pulls. Like Lee stated a couple squirts of fuel into the carb throat will get most of them going enough to pull fuel up from the tank. For its first start up after a rebuild it would not be any problem to start them if the carb is primed as you have done but a lot of work to do this each time it would need to be restarted. Good tutorial on a HL rebuild by the way.
 
I actually just went through this problem on a Poulan 43, I knew everything was right but it just would not pick up fuel. I ended up using a squirt bottle and forced fuel through the fuel line while slowly pulling the saw over, picked up fuel and away it went. Problem was it would have been nice to have had 3-5 hands to squeeze the bottle, hold the saw down and pull it over all at the same time............

These Poulans are one of those PITA saws you mentioned. Not to mention the carb is mounted upside down to typical, meaning the fuel inlet faces up, and the fuel tank is below the carb.
 
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gmax said:
Nice pics, but I'll continue to prime with a syringe down the carb throat or in the plug hole, it's easier
Click to expand...

I did this. A lot, down the carb throat with the little oil can. It barked on every prime, but just could not pull that fuel into the carb.

It was just too dry inside the carb for the fuel pump tabs to seal and draw fuel. Once they were wet, she barked right to life. I don't suspect I will ever need to do this again to this saw, since it fires right up on the first or second pull now. No prime needed. Don't even need the choke either.
 
Roanoker494 said:
I actually just went through this problem on a Poulan 43, I knew everything was right but it just would not pick up fuel. I ended up using a squirt bottle and forced fuel through the fuel line while slowly pulling the saw over, picked up fuel and away it went. Problem was it would have been nice to have had 3-5 hands to squeeze the bottle, hold the saw down and pull it over all at the same time............

These Poulans are one of those PITA saws you mentioned. Not to mention the carb is mounted upside down to typical, meaning the fuel inlet faces up, and the fuel tank is below the carb.
Click to expand...

That would work on some saws.

I thought of another reason why the 250 may have had a little trouble pulling fuel... I remember someone saying these Macs with the carb adapters have to be lined up fairly well or the impulse holes in the adapter plate don't line up with the one in the intake. Partially blocked impulse lines or holes can be a problem.
 
promac610 said:
Lee, I will have to try that next time. I do know that my trick could be a lot of work on certain saws. I find pulling the carb is easy on the Macs that I have. I'm sure there are a few saws out there that are a PITA when it comes to pulling the carb.

Stiff Member... changed my user title to Head Waiter. Thanks for the promotion! :D
Click to expand...

The top tank Macs (like a 790) are more of a PITA to R&R the carbs on than the front tank Macs. Not much clearance for the 7/16" wrenches to swing because of the air filter flange. Thin ignition wrenches help, especially if they've had cleanrance notches ground in the right spots. Be sure you tighten them evenly..............and don't overtighten. My 790 came to me with a broken carb flange on the lower tank half. You also need to make sure the carb (and adaptor/spacer if it's a front tank saw.....neither are used on top tank Macs) is pushed all the way down with the bolts seated in their notches. As you mentioned, the impulse passages have to be lined up right. Congrats on the promotion.............but don't let it go to your head. It's still easy to get demoted to Shop Monkey......:D

pioneerguy600 said:
The Mac 250 has a sintered bronze insert that fits into the fuel cap and it acts as the vent on these saws. The Pioneer 600 series saws has to draw its fuel almost straight up from its bottom mounted tank, always found them to be difficult if the lines don`t fit tightly on the fittings. If everything is tight then they pull fuel up with 5-7 pulls. Like Lee stated a couple squirts of fuel into the carb throat will get most of them going enough to pull fuel up from the tank. For its first start up after a rebuild it would not be any problem to start them if the carb is primed as you have done but a lot of work to do this each time it would need to be restarted. Good tutorial on a HL rebuild by the way.
Click to expand...

Jerry those caps do/did have a duckbill valve. It's under the sintered bronze insert (and protrudes from the underside of the cap). Most have long ago melted into goo. You pick/pry/push the bronze filter out and the duckbill drops into it's seat. The duckbill has little 'nibs' around the top surface of it. These nibs get pushed against by the bronze filter when it's seated...........keeping downward pressure on the duckbill to keep it firmly in its seat. The McCulloch duckbill is larger than the Homelite part, and MUCH larger than the Poulan part. I have a McCulloch cap that somebody retrofitted with a green Poulan duckbill long ago. Looks like they used a piece of fuel tubing to take up the space between the tiny Poulan part and the hole in the McCap.

The McCulloch duckbills aren't available new (may still be some NOS pieces around.......maybe in Discount Marine's or Bob Johnson's inventory). Randy Duncan sold about 25 or so on feebay a while ago. The Poulan and Homelite duckbills ARE available from the aftermarket, so the 'future' for our McCaps lies with adapting those duckbills for use on the yellow saws. There was also a LARGE McCulloch one way valve that fitted OVER the tube in the underside of some McCaps. Seen those on feebay a few times as well.

Here's Randy Duncan's ended listing for the McCulloch duckbill valves:

http://cgi.ebay.com/ws/eBayISAPI.dl...sspagename=STRK:MEWAX:IT&orig_cvip=true&rt=nc
 
Last edited:
Eccentric said:
The top tank Macs (like a 790) are more of a PITA to R&R the carbs on than the front tank Macs. Not much clearance for the 7/16" wrenches to swing because of the air filter flange. Thin ignition wrenches help, especially if they've had cleanrance notches ground in the right spots. Be sure you tighten them evenly..............and don't overtighten. My 790 came to me with a broken carb flange on the lower tank half. You also need to make sure the carb (and adaptor/spacer if it's a front tank saw.....neither are used on top tank Macs) is pushed all the way down with the bolts seated in their notches. As you mentioned, the impulse passages have to be lined up right. Congrats on the promotion.............but don't let it go to your head. It's still easy to get demoted to Shop Monkey......:D



Jerry those caps do/did have a duckbill valve. It's under the sintered bronze insert (and protrudes from the underside of the cap). Most have long ago melted into goo. You pick/pry/push the bronze filter out and the duckbill drops into it's seat. The duckbill has little 'nibs' around the top surface of it. These nibs get pushed against by the bronze filter when it's seated...........keeping downward pressure on the duckbill to keep it firmly in its seat. The McCulloch duckbill is larger than the Homelite part, and MUCH larger than the Poulan part. I have a McCulloch cap that somebody retrofitted with a green Poulan duckbill long ago. Looks like they used a piece of fuel tubing to take up the space between the tiny Poulan part and the hole in the McCap.

The McCulloch duckbills aren't available new (may still be some NOS pieces around.......maybe in Discount Marine's or Bob Johnson's inventory). Randy Duncan sold about 25 or so on feebay a while ago. The Poulan and Homelite duckbills ARE available from the aftermarket, so the 'future' for our McCaps lies with adapting those duckbills for use on the yellow saws. There was also a LARGE McCulloch one way valve that fitted OVER the tube in the underside of some McCaps. Seen those on feebay a few times as well.

Here's Randy Duncan's ended listing for the McCulloch duckbill valves:

McCulloch MAC # 53766A Carb Carburetor Duck Bill Check Valve NOS | eBay
Click to expand...

That`s cool, I always wondered why my cap on the 250 leaked a bit of fuel out through the sintered bronze disc when turned up on its side. The fuel line in the tank had gone to a blob of goo also, that`s why the saw was given to me.
 

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