McCulloch Chain Saws

[Brian Thacker]

Ron, I just got thinking and re-watching the video of the PM800s. If you watch before I start sawing I went over to the truck and readjusted the carb on your saw. If you listen to your saw it was surging at an idle. I bet that the DSP was loose at that point and time and was making your saw loose power. I think we need to fix your saw and try this again and I bet that they will be about equal. I know that DSP had to be loose at that time.

 

[rwoods]

I am sure it loosen up early on, and it may have been loose before we started. I can't remember if I ran it much after I safety wired the muffler and put the saw back together. Ron

 

[rwoods]

I just checked and I have run several tanks through it after I put it back together so more likely than not it was loose. Ron

 

[BigBlue]

Can someone tell me how to clean the gas tank cap's vent on a Pro Mac 10-10S? Just started having issues with it bogging under load and I'm working through troubleshooting it. Replaced fuel line, fuel filter, air filter, fresh gas, and I also want to clean the vent. I can't see a pinhole in the cap though.

Thanks!

 

[heimannm]

You may need to post a photo of the inside of your cap as McCulloch used several different types. The is a small duck bill valve in the cap that is designed to hold pressure (keeps it from leaking while operating) but will prevent a vacuum from being created as the fuel is extracted. The caps with the brass fitting are the easiest to work on, just grab the brass with a pair of pliers and twist it out. There will be a spring, a washer like fitting, and the duckbill valve. The original duckbill is NLA anywhere but you can substitute the small red duckbill valve used for the Homelite oilers, I don't remember the part # off the top of my head. If the spring is missing, I have had success using a few small O-rings stacked up to provide the pressure to seal the duckbill against the fitting. Theoretically the spring will collapse under a certain pressure in the tank and vent so you don't overcome the metering spring in the carburetor and flood it out, I guess I don't work too many saws in the heat to test that.

There are certain other caps with a plastic fitting that will also twist out, you will need to drill the inside to 5/32" diameter by about 1/4" deep to allow the Homelite duckbill valve to fit. I understand there are some green Poulan duckbill valves that work without modification to the cap but I don't have first hand experience with those.















Mark

 

[BroncoRN]

 

[BroncoRN]

Its not running and there is no bar/chain. But I thought it was a cool picture.

 

[heimannm]

You must start them early.



Mark

 

[BigBlue]

Thanks for the info and pics, heimannm. Mine looks like the brass version, I believe. So I went out and pulled the brass piece out of the cap. It has a small spring under it but nothing inside. The brass tube is just empty. Did the duckbill part of mine just disintegrate? I'm pretty sure nobody has ever had the gas cap apart before to lose it. The saw will leak gas if tipped over with a full tank. I assume these things indicate that there is plenty of ventilation and vapor lock was not my problem?

Any idea what the part number is for that duckbill replacement piece?

Thanks!

 

[BigBlue]

Is this the Homelite duckbill valve to use?

https://amzn.com/B001OKFCVC

 

[heimannm]

That is the one, keep shopping as you should be able to get one for $2.00. Try any local shop that has ever worked on an old Homelite, they will likely have a packet of them.

Probe the inside of the brass, I expect you will find some of what's left of the original duckbill valve. I have heard descriptions like "goo", "whale snot", "tar", etc....

Mark

 

[BigBlue]

Thanks for the confirmation on the part. As for the old piece, the brass tube is totally empty. Looks just like looking through a straw. Maybe I somehow blew it out when I tried to clean the vent with an airgun? Can't really see how that would happen, but who knows?

 

[Brian Thacker]

Here is one for 2.93 http://www.jackssmallengines.com/jacks-parts-lookup/part/universal/610345
Here is one for 1.57 http://www.repairpartsmart.com/sten...160248666804&gclid=CKC83oy5xs4CFcsbgQodqr0HUg

Here is one for 1.63 http://maverickmowersupply.com/6103...melite-69451?gclid=CNu9l5O5xs4CFdgcgQod6jQDfQ

 

[fossil]

The Poulan duck bill fits great. No modifications needed in the brass plug ones at least. The Homelite ones are still made as well.

The Poulan one is PN 530026119. It's current product.

 

[BigBlue]

Thanks, Brian. But all those end up way more $$ after you add shipping. The Amazon part I linked to is $5.99 with free 2-day Prime shipping, which is $4-10 less. I'll check locally for a supplier though.

 

[heimannm]

I just ordered 10 pieces of the Poulan duckbill from HyperParts.com, less than $20 including first class postage.

I will report back after they arrive. I am pretty sure my Troy Built strimmers use the same part in their fuel caps and I have had mine for years without any issues.

Mark

 

[rwoods]

Update on keeping an old style muffler attached to a PM 800:

Since proper muffler bolts are NLA, I last used a handle screw for the long muffler screw because the small shoulder fit the hole and the wide head spread the load across the muffler tube. Prior to that I had used a screw and washer resulting in distorting the muffler tube upon tightening. Though safety wired, the handle screw and the short screw would still loosen enough for the muffler to rattle. I tried a new approach last night, I drilled a 3/8" diameter aluminum rod to accept a 10/24 screw through the center. I cut the rod slightly longer than the muffler tube height. This allowed me to put pressure on the muffler flange as designed instead of the muffler tube. At lunch today, I drilled a socket head screw for safety wire and torque everything down. It feels and look pretty good. The aluminum rod seals the hole. See picture. Ignore the shadow that looks like the hole.



As to my homemade bracket attached by the DSP, I found it was broken in two so I use the remnants as a tab to keep the DSP valve tight. Pat on the back for pretty slick thinking. But as usual for me, being in a hurry often results in a misstep which means I have to start over again. In my hurry today, I forgot that there was a reason I made the muffler mount to hold the nuts for the muffler screen and to attach to the cylinder at the DSP - the older saws support the muffler body by screwing the screen screws into two screw bosses on the cylinder. The new big muffler saws lack these bosses. So I now I need to fabricate a new bracket for both these purposes. I think I will try a heavier gauge metal and tap it instead of using nuts. We will see and I will report back.

Ron

 

[Brian Thacker]

Looks good. Now we need to meet down at the wood lot and see A. If it will hold, which it looks like it will and B. compare 800s.

 

[rwoods]

Well, I didn't have the right size piece of scrap - close but not close enough - so I changed game plans. I took from inventory a stock 800 strap and installed it with a hand shortened screw and lock washer into the top of the muffler body. Much easier than it sounds as everything is tight and close. Not even enough room to start a 1/2" screw. I also found that the DSP button was split so I wrapped it with electrical tape which I will likely replace with some shrink fit tubing. End result pictured below. Something tells me that the short screw might not last as long as the electrical tape. Nothing ventured nothing gained. Ron

PS I forgot to mention that I purchased two different style spark arrestor screens with the thought of replacing my home-built grill. Won't work as neither screen is as tall as the muffler body.

Looks good. Now we need to meet down at the wood lot and see A. If it will hold, which it looks like it will and B. compare 800s.

Will do, but I suspicion that MAC might have put more thought in the large muffler than they get credit. Which means other than a little weight savings and have something unique, I have gained little by all my work.

Ron

 

[rwoods]

I'll sleep better tonight. I just remembered that it was a drilled screw that I shortened. Now the weak link will be the threaded thin muffler body. Ron