mac pro 10-10 auto gas in exhaust

[giver]

You could try the old lever, but it sounds like a compression test is next on the list.

 

[poppiecarver15]

i can try to do a compression test ,but it did run before the carb.rebuild,but sometimes at WOT it got doggy and rough so i thought i would do a good cleaning and carb. rebuild. the rebuild kit is not an OEM but after market. what should the compression be for this saw?? thanks

 

[fossil]

Minimum compression is 100 psi.

In good condition I would guess 130 - 150 psi.

Have you tried a new spark plug?

 

[poppiecarver15]

i have a new spark plug i am using,Tim question do you know the thread size for this saw going to buy a compression gage just want to make sure it has the right adapter for it. old plug was a champion DJ8J parts store crossed it to a NGK6720 BM6F. i think gap shoulds be .025 correct. thanks Jim

 

[Chevboy0167]

A small engine, short hose gauge with low pressure valve cores is the most accurate. Worth the price if you do a lot of small engine work. If not, you may wanna swing by a small engine shop that has one to get a test done.


https://www.ebay.com/itm/224135684974

 

[Chevboy0167]

14mm thread...

 

[poppiecarver15]

thanks for the info. going to see if i can get the local Stihl dealer to do a test for me .thanks again will let you know what i find out.

 

[Maintenance supervisor]

High speed check valve? Did you replace it?

 

[fossil]

thanks for the info. going to see if i can get the local Stihl dealer to do a test for me .thanks again will let you know what i find out.

I don't have a large amount of MAC 10 series but I've had three with bad spark plug wires. Symptoms were from a miss at full throttle to the saw going dead on acceleration.

 

[poppiecarver15]

do you mean replace the high speed adjusting screw .?? i did not replace any screws just the gaskets and metering level and the pin under it.thanks Jim

 

[Maintenance supervisor]

do you mean replace the high speed adjusting screw .?? i did not replace any screws just the gaskets and metering level and the pin under it.thanks Jim

No the high speed check valve is under the smaller welch plug. Its a vacuum operated disk that shuts off fuel flow at lower rpms and brings it on higher.

 

[poppiecarver15]

i did remove the plugs and cleaned the screens but did replace any pins .did not have any in the rebuild kit that i found put in new plugs under the small i plug i did remove the clip and clean the screen , i will also check my plug wire. thanks for the help Jim

 

[Maintenance supervisor]

i did remove the plugs and cleaned the screens but did replace any pins .did not have any in the rebuild kit that i found put in new plugs under the small i plug i did remove the clip and clean the screen , i will also check my plug wire. thanks for the help Jim

Under the screen should have been a small disk either black or tan in the sdc walbro carburetor.

 

[poppiecarver15]

i will check and see if i missed that in my rebuild kit,but do not think i did,i did not remove it just cleaned the screen. if i remove the plug i will probably ruin it so will need to get another kit unless i can get it out without ruining it. will check and see going to try again tomorrow to get running suppose to be warmer,going to put old plug back in also it looks good and is clean.thanks Jim

 

[Maintenance supervisor]

Jim the check valve is a separate kit it comes with a new screen ,diaphragm, and brass insert.

 

[fossil]

Here's a good video for replacing the check valve. The carb in the video is a Walbro HDC carb so there is no welch plug to remove but the procedure is the same once you have removed the small welch plug on your SDC.

He has good tips for kitting a carb as well.

The Walbro PN for the kit is 86-532

 

[poppiecarver15]

ok thanks guys for the info. Tim thanks for the video a big help ,i will get a kit ordered today,thank you both again. Jim

 

[vizette]

Here's a good video for replacing the check valve. The carb in the video is a Walbro HDC carb so there is no welch plug to remove but the procedure is the same once you have removed the small welch plug on your SDC.

He has good tips for kitting a carb as well.

The Walbro PN for the kit is 86-532

I like Leon, he's got some good videos and seems like a good guy. Occasionally find some hard to find Mac stuff on his site, but he's definitely a Homelite guy.

Unrelated: I sent him an old Prestolite coil off an SXL that stopped working. Theory is that you can heat them up in the oven and they start working again. For how long? Who knows. I was going to toss it, but he experiments with this, so hopefully it helps "the cause".

 

[fossil]

I guess I should have mentioned that you can easily test the check valve.

Check out Leon's video on that. Start looking at 6 minutes to view the easy test.

 

[Maintenance supervisor]

ok thanks guys for the info. Tim thanks for the video a big help ,i will get a kit ordered today,thank you both again. Jim

No problem, I struggled with my first check valve fails , until some knowledgeable people informed me about them.
Once the welch plugs are removed you can hold a flashlight on the orifice and look down the throttle bore ,most of the time you'll see light from the CV port, that means its disintegrated but they also deform and scruch up over time (also non functional) .
There's special pullers to remove the brass insert but i have had good luck heating the carb in an oven at 200° for a half hour then use a blunted wood screw to extract it, careful not to damage the aluminum body below it.