HELP! Mcculloch 700 & SP81 Carb Base Gasket Leak

[scottspeed95]

Hello again good folks. Had something I'm currently stumped on and needed advice / input on. I feel about as stupid as they come with this one.

Have a SP81 and a pro mac 700 that I just rebuilt the carbs on. Also did new fuel lines & filter too. Anyhow I have never found a SDC carb kit that comes with the carb base gasket (For the life of me I don't know why they don't include one!!!) so many times, I am making one out of carboard or reusing the old one. I had checked the gaskets and they appeared to be good. It may be a given to not reuse the gaskets, but I haven't really had issues before. Of course, if I have the gasket, I will use a new one but out of convenience I have done it a few times. It may be here to bite me in the ass now though..

The 700 part # is 86189 and 84081. I think that one of these is also used on the SP81 as it appeared to be the exact same gasket.

Anyhow is it common to see a leak here even if the gasket looks to be good? I would use motoseal but I didn't want to possibly block the hole for the impulse even though I'm fairly sure I could assemble it without having it slide and block the port.

Here's a short video. I may make another video to show it in action but I think you all get the gist of it all. Basically if you spray carb/brake cleaner anywhere around where the base of the carb is, the saw chuggs to a stall. Albeit the 700 is worse than the SP81. Takes more spray for the 81 to stall out.

Thank you so much everyone!!!!

 

[scottspeed95]

Just to add some final thoughts, it honestly may be a simple case where the gasket "looks" okay but in reality, it's lost its integrity and ability to seal 100%. I have went ahead and ordered gaskets for both as the IPL that have shows the 700 and 81 both share the same gasket number plus the additional one for underneath the 700's spacer block (84081) and I believe this to be the main culprit on the 700 as well.

Still any advice or help would be oh so greatly appreciated!!

Best regards!

 

[heimannm]

Check your inbox.

Mark

 

[Maintenance Chief]

Little info, oem tillotson carb kits come with 2 base gaskets and a needle seat spring. The gaskets can be used on the sdc in the applications that also had tillotson carbs.

 

[Steve]

Little info, oem tillotson carb kits come with 2 base gaskets and a needle seat spring. The gaskets can be used on the sdc in the applications that also had tillotson carbs.

That's exactly what I was going to suggest Ira. Tillotson HS carb base gasket.

 

[Rallyeguy]

Got em if you need em. Fits the 10 series and the SP's carb base

McCulloch 10 series Carb base

McCulloch 10-10, and 10 series carburetor base gasket.

www.oldsawshop.com

Here is 84081 for the insulator base.

https://www.oldsawshop.com/McCullochCarburetor-Insulator-Base-p546266461

 

[scottspeed95]

So I must have the absolute worst luck of anyone but I still cant get it to seal. Even with an OEM gasket or the tillotson gasket. It's like I'm using some special brake cleaner that has the ability to go through gaskets!!! It's just the walmart supertech brand tho..

I stepped away and still have the problem and am now experiencing it on my other saws too. I'm starting to think it's something that literally CANNOT be fixed and i will just have to live with it.

 

[Maintenance Chief]

If you take those carburetors off again check your throttle shaft play. Ive had a few that were worn out to the point of sucking air around then.
Sometimes brake cleaner gets sucked right into the air stream of the carburetor, I 'd pour straight 2 stroke oil into the air box and see if she smokes out . You could use an eye dropper and it would be less messy ( ask the Ms. They usually have one stashed somewhere).Aerosol has too much distribution air born.

 

[scottspeed95]

If you take those carburetors off again check your throttle shaft play. Ive had a few that were worn out to the point of sucking air around then.
Sometimes brake cleaner gets sucked right into the air stream of the carburetor, I 'd pour straight 2 stroke oil into the air box and see if she smokes out . You could use an eye dropper and it would be less messy ( ask the Ms. They usually have one stashed somewhere).Aerosol has too much distribution air born.

Yeah I understand what your saying there but I can spray on the very top of where the two meet (carb and block) and I get a rpm drop or stall.

I also only use a very short pressed button of the spray. Of course if you sprayed enough it would displace the air and get sucked in as normal air would and cause a drop as well. This is why I only spray short intervals and a small amount. I am using the red tube nozzle as well with the tip of the red nozzle placed right between the two surfaces.

I could understand what your saying about the throttle shaft if I was using a wide angle spray and getting it all over the carb. Or even spraying close to the shaft but I am not.

I guess the only thing left for me to try is get a new intake block, gaskets, maybe another carb, and try again. For the 5th time now..

 

[Maintenance Chief]

Yeah I understand what your saying there but I can spray on the very top of where the two meet (carb and block) and I get a rpm drop or stall.

I also only use a very short pressed button of the spray. Of course if you sprayed enough it would displace the air and get sucked in as normal air would and cause a drop as well. This is why I only spray short intervals and a small amount. I am using the red tube nozzle as well with the tip of the red nozzle placed right between the two surfaces.

I could understand what your saying about the throttle shaft if I was using a wide angle spray and getting it all over the carb. Or even spraying close to the shaft but I am not.

I guess the only thing left for me to try is get a new intake block, gaskets, maybe another carb, and try again. For the 5th time now..

Something else to consider, I live in an oven called South Carolina, when i spray anything metal with brake cleaner it immediately sweats!
You could be causing a lean condition due to the extreme temperature drop of the brake cleaner , even icing on the throttle plate? Just a thought, which is why I suggested oil.

 

[Rallyeguy]

Hello again good folks. Had something I'm currently stumped on and needed advice / input on. I feel about as stupid as they come with this one.

Have a SP81 and a pro mac 700 that I just rebuilt the carbs on. Also did new fuel lines & filter too. Anyhow I have never found a SDC carb kit that comes with the carb base gasket (For the life of me I don't know why they don't include one!!!) so many times, I am making one out of carboard or reusing the old one. I had checked the gaskets and they appeared to be good. It may be a given to not reuse the gaskets, but I haven't really had issues before. Of course, if I have the gasket, I will use a new one but out of convenience I have done it a few times. It may be here to bite me in the ass now though..

The 700 part # is 86189 and 84081. I think that one of these is also used on the SP81 as it appeared to be the exact same gasket.

Anyhow is it common to see a leak here even if the gasket looks to be good? I would use motoseal but I didn't want to possibly block the hole for the impulse even though I'm fairly sure I could assemble it without having it slide and block the port.

Here's a short video. I may make another video to show it in action but I think you all get the gist of it all. Basically if you spray carb/brake cleaner anywhere around where the base of the carb is, the saw chuggs to a stall. Albeit the 700 is worse than the SP81. Takes more spray for the 81 to stall out.

Thank you so much everyone!!!!

Not sure if you've fixed the issue or if the base is the problem or not, but I carry these if you need one. I also have the boot gasket for the AV McCullochs like the SP-80/81 in a gasket kit if you think that may be the issue.

SDC Carb Base Gasekt https://www.oldsawshop.com/McCulloch-10-series-Carb-base-p546266460

AV McCulloch Kit with boot gasket included: https://www.oldsawshop.com/McCulloch-Super-Pro-and-CP-7-piece-Gasket-Kit-up-to-80CC-p550796117