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Maintenance Sup - In the future just invest in a can of Red Kote from your local O'Reillys, one $40 can will do 15 or 20 fuel tanks. I make a rig to turn the tank slowly in my lathe with the tank 1/2 full or so of BB's. Half and hour to one hour in each direction and the tanks come out spotless inside. I quick rinse with acetone and then the Red Kote treatment.

DSC07111.JPG

Mark
 
No. Just experimenting for entertainment. If they work, then I will put them to work and share the recipe.

In the meantime, I would encourage folks not to scrap their 82 cc cylinders of any vintage. Nor scrap 8200 cranks with rods.
Ron
 
can someone inform if the air filter in a pro mac 850 should run dry or wet, or in other words if the air filter need to be dry or have a coat of proper air filter oil??
and please advise on how to proper clean it.
thanks to all
 
RolandM said:
Thanks from here too.. I have an SDC 44 on a ProMac 555 which has developed a big flat spot off idle, and I am assuming nozzle check valve. Job to do sometime, robbed a carb from a parts saw which runs OK for now. I like this 555 for quartering up unsplitable chunks, fitted with with just a 13" bar and .325 chain. Its had some work to do, just had a 5L can of fuel through it over last few weekends, I suppose you work out which tool is best for a particular job, and this tweaked 555 is great.
A carb made in ~1977, probably never opened before, its time for a good service!

Roland.
Click to expand...

Right, finally got this stripped down. Been right up to my neck in it with work, firewood and family along with chairing a sports club in this covid 19 mess.
So to recap - mcculloch promac 555 with big flat spot. Carb is a sdc 44a and this has a check valve under the hi speed nozzle which acts as a one way valve and stops air bleeding back in to the idle circuit, when saw is at idle.IMG_0705[1].JPG
Under the core plug there is a circlip and stainless screen, then under that brass housing is a rubber disc, or remains of it!
IMG_0704[1].JPG

The kit I have ordered has everything right down to the circlip and screen. but no check valve. How useful is that?? I think the check valve is made of similar stuff to the diaphram, so it may be a careful cutting job.

Any thoughts on check valve material? they dont seen to be easily available.

Roland.
 
RolandM said:
Right, finally got this stripped down. Been right up to my neck in it with work, firewood and family along with chairing a sports club in this covid 19 mess.
So to recap - mcculloch promac 555 with big flat spot. Carb is a sdc 44a and this has a check valve under the hi speed nozzle which acts as a one way valve and stops air bleeding back in to the idle circuit, when saw is at idle.View attachment 828421
Under the core plug there is a circlip and stainless screen, then under that brass housing is a rubber disc, or remains of it!
View attachment 828422

The kit I have ordered has everything right down to the circlip and screen. but no check valve. How useful is that?? I think the check valve is made of similar stuff to the diaphram, so it may be a careful cutting job.

Any thoughts on check valve material? they dont seen to be easily available.

Roland.
Click to expand...
What kit or part number did you order ? I've ordered like 8 of them and the always have the diaphragm?
 
RolandM said:
Right, finally got this stripped down. Been right up to my neck in it with work, firewood and family along with chairing a sports club in this covid 19 mess.
So to recap - mcculloch promac 555 with big flat spot. Carb is a sdc 44a and this has a check valve under the hi speed nozzle which acts as a one way valve and stops air bleeding back in to the idle circuit, when saw is at idle.View attachment 828421
Under the core plug there is a circlip and stainless screen, then under that brass housing is a rubber disc, or remains of it!
View attachment 828422

The kit I have ordered has everything right down to the circlip and screen. but no check valve. How useful is that?? I think the check valve is made of similar stuff to the diaphram, so it may be a careful cutting job.

Any thoughts on check valve material? they dont seen to be easily available.

Roland.
Click to expand...

Roland,

@Hoggwood came up with a way to make the check valves. I checked some spare pump diaphragms from an HS or an SDC and came up with around .008 - .009"for gauge. I used a leather punch to get the diameter Cory got in his write up below. Use diaphragm material.

Pretty slick idea. Your SDC 44 takes the same Walbro PN 86-523 check valve that's used in the HDC he tested it on.

That said, there are lots of check valve kits out there. I think I saw one for around $4

His his write up.

Making an HDC check valve diaphragm (from Cory, Hoggwood)

Hi Folks,

Long time Terry Industries Homelite nut. I don't post as often as I would like, but I thought I would share. If this is not in the ideal place, perhaps it can be moved accordingly.

I don't often run into problems with the ubiquitous check valve (assembly) used extensively on the HDC, HDB and SDC Walbro carbs. I've perhaps replaced/repaired 2 or so out of the dozens and dozens of carbs I've gone through. But, as parts supplies eventually dwindle for discontinued carbs, I figured I'd pitch my work around. No intent to step around any folks that are selling the OEM kits. Nothing beats OEM in a carb.

The original check valve is made of nitrile (nylon insert) and approx 0.009" thick and approx 0.205" in diameter. I used an old rubber stopper hole punch from work that had an OD of 0.210". I used a round file to taper the ID until I had bore of 0.202". I punched several checks and the results were good. A few had stray nylon threads that needed to be carefully trimmed.

As for the brass seat assembly, I know it is common to just pull them entirely. From experience, I know that in the pocket, there are 4 raised bosses that cradle the check. Above that there is room for the valve to move and check against the rim of the brass assembly. Enough room to get the old check out and a new one in without much difficulty. One can maintain the integrity of the assembly (heck even reuse the circlip and screen) and avoid having to thread and pull the check or use a mini slide hammer.

In all, to remove the clip/screen/check and retrofit/replace screen/clip it takes about 10 min. If your glasses are strong enough and your hands are steady, you can shave a couple min. off.

I used a HDC circa 1973 off of a Terry XL Auto. The original check, which was still supple and functioning well, was removed and replaced with the retrofit. Both OEM and retrofit passed well and checked hard when tested.


1589743224731.png
 
Maintenance supervisor said:
Sorry ,what I mean is if you ordered the correct check valve kit it has the diaphragm in the kit, I was only asking what one he ordered that it didnt.View attachment 828435View attachment 828436
Click to expand...
That is the monkey! The repair kit I have is the full general kit, so I need to find one of the specific 86-523 jobs, seems scarce in the UK- at a glance anyway. I confess to not researching hard for supply of separate and specific kit. I had to order the SDC repair sets from abroad. Would you say the rubber disc is the same stuff as diaphragms?
 
fossil said:
Roland,

@Hoggwood came up with a way to make the check valves. I checked some spare pump diaphragms from an HS or an SDC and came up with around .008 - .009"for gauge. I used a leather punch to get the diameter Cory got in his write up below. Use diaphragm material.

Pretty slick idea. Your SDC 44 takes the same Walbro PN 86-523 check valve that's used in the HDC he tested it on.

That said, there are lots of check valve kits out there. I think I saw one for around $4

His his write up.

Making an HDC check valve diaphragm (from Cory, Hoggwood)

Hi Folks,

Long time Terry Industries Homelite nut. I don't post as often as I would like, but I thought I would share. If this is not in the ideal place, perhaps it can be moved accordingly.

I don't often run into problems with the ubiquitous check valve (assembly) used extensively on the HDC, HDB and SDC Walbro carbs. I've perhaps replaced/repaired 2 or so out of the dozens and dozens of carbs I've gone through. But, as parts supplies eventually dwindle for discontinued carbs, I figured I'd pitch my work around. No intent to step around any folks that are selling the OEM kits. Nothing beats OEM in a carb.

The original check valve is made of nitrile (nylon insert) and approx 0.009" thick and approx 0.205" in diameter. I used an old rubber stopper hole punch from work that had an OD of 0.210". I used a round file to taper the ID until I had bore of 0.202". I punched several checks and the results were good. A few had stray nylon threads that needed to be carefully trimmed.

As for the brass seat assembly, I know it is common to just pull them entirely. From experience, I know that in the pocket, there are 4 raised bosses that cradle the check. Above that there is room for the valve to move and check against the rim of the brass assembly. Enough room to get the old check out and a new one in without much difficulty. One can maintain the integrity of the assembly (heck even reuse the circlip and screen) and avoid having to thread and pull the check or use a mini slide hammer.

In all, to remove the clip/screen/check and retrofit/replace screen/clip it takes about 10 min. If your glasses are strong enough and your hands are steady, you can shave a couple min. off.

I used a HDC circa 1973 off of a Terry XL Auto. The original check, which was still supple and functioning well, was removed and replaced with the retrofit. Both OEM and retrofit passed well and checked hard when tested.


View attachment 828441
Click to expand...
Awesome! beat my ramble a moment ago!

Cheers.

Roland
 
PogoInTheWoods said:
A .22 cartridge casing is mighty close.

View attachment 828457
Click to expand...

If you just pull the bullet and powder the primer will eject the piece when you smack it.

The bookmark feature is at the top of the post just to the left of the post number.

Cory's full post with more pics is on "HOH" in the "HOH" help center.
 

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