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Disston DO 100

mrvalleyboy64

Registered
Old mercs.com? What the hell is brian's problem! I gave him $75 for a remaned carb 6 weeks ago. Now I can't get ahold of him. He doesn't answer the phone. Anyone know why??? This is kind of ridiculous. It doesn't take this long to mail something from colorado to Washington:rant::bonk::wave: Have a good one Derek:confused:
 

bigGURN

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Last Subscription Date
04/01/2012
I am confused old mercs.com is based in PA, if you are referring to Brian at APSE outside of Denver, he has been out of the office this week. I needed to get ahold of him and he was gone. He has always been very good about getting things out, but sometimes with as much as he has and a one man show, it gets backed up. Shoot him an email or just keep trying the phone. Its frustrating but unfortunately sometimes life gets ahead of us.
 

APSE

Registered
Well Derek...

As Ryan pointed out I am a one man show, internet, phones, ebay, parts orders, mechanic, on the road for purchases of saws/parts, janitor, etc. I am aware after talking to your wife? that the first one shipped out seems to be missing through the virtues of the USPS. However, I have not had any messages or phone calls that I have not returned, and of course cell phones as we all know are perfect. The second fuel meter had to be rebuilt by me personally, as it wasn't available at the second window at the McDonalds drive thru. It is on the way to you as we speak.
Perhaps a phone number correction might help, 720-260-0157, my email is apse-llc@live.com. I hope that the fuel meter is the only problem with the failure riddled fuel system on the DO series of chainsaws from Mercury Disston.

Geez, I dunno, maybe the call was missed due to the blizzard we had last week?!?

BTW...Thank You, Big Gurn!

Brian
 

mrvalleyboy64

Registered
sorry about that. My wife said she called twice with no answer. I just wanted to know what's going on. I know it's hard to get parts and I don't trust the internet much. But without the internet that old disston my dad gave me years ago would still be sitting under the bench doing nothing. I hope to see a package soon. Thanks Derek.
 

K-Tron

Registered
Ive bought about $500 of parts from Brian, anything from one of a kind NOS Disston gasket kits to chain link repair kits. He's a man of his word. Its the mail system which is questionable. For example I live on Beech Place, there are 9 different Beech Place's in zipcode 11743, all spelled slightly different "Beach" "Beache", etc etc. When buying something I always give out the second 4 digit zipcode extension. It usually solves all of the USPS miss-delivery problems! Maybe that's the same issue you are having. Anyhow, I hope the issue gets resolved quickly!

Chris
 

bigGURN

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Last Subscription Date
04/01/2012
I hope that the fuel meter is the only problem with the failure riddled fuel system on the DO series of chainsaws from Mercury Disston.
You mean my DO-101 isn't the top tier saw of all time? Besides the fact that the Stromberg-Bendix Mechanical Fuel Injection is complicated, prone to flooding the engine (easily avoided so long as you never try and start the saw), and hard to fine tune, not to mention makes what could have been a great engine way overly complicated, I thought it was a miracle system. I mean atleast ir runs right.:bonk: (thanks for the parts for the fuel meter!) Oh and I nearly forgot, how about that scratcher chain (and that quality straddle chain to boot), talk about a great cutting set up! Then don't even get me started on the internal mechanical clutch and the slip friction spur drive on the chain! Yep, she's a real peach to operate! Enjoy:


Oh, I nearly forgot, make sure to check all the lines for the pressurized bar and chain lube system, small cracks in the lines or plugs and fittings that are loose or not sealed tend to cause issues with this other wise near perfect saw. Oh did I mention the saw floods easily? (I really do like mine, it's must a little complicated for the average Joe). Enjoy yours and remember to wear hearing protection! The oversized muffler seems to make a great amplifier.
 
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mrvalleyboy64

Registered
I would be happy with that. That saw sounds great!!! Mine will run but it shoots fuel from the exaust. It runs better on a home made gravity feed drip but only till you pull the throttle then it floods and dies. I do think those saws are over engineered but if they run that's great. nice job! Derek Klein
 

bigGURN

Registered
Last Subscription Date
04/01/2012
Mine will run but it shoots fuel from the exaust. It runs better on a home made gravity feed drip but only till you pull the throttle then it floods and dies.
Yep, sounds like a Disston DO saw! Told you not to start it! Once the fuel meter is rebuilt it gets better... still if it doesn't start on the first or second pull, it's flooded, so pull the plug. If I was going to spend any time running mine, I'd place a fuel shut off valve between the fuel pump and the strainer so that I could turn off the fuel while I started the saw. If I get ambitious I may do that just so I can start it when the wife comes up with honey do's...."what's that sorry, can't here you and it's going to be atleast 15 more minutes before I cut through this log":crazy:
 

mrvalleyboy64

Registered
Ok got my new fuel meter on. The saw flooded after running for about 5 seconds. I was wondering about the fuel lines one goes to the fuel pump, the other goes to the fuel meter. I'm not sure what fell apart in the fuel tank. It was part of the line that goes to the fuel meter. something sticking in the tank like a one way valve or a filter??? I was wondering if anyone knows what that thing is or what it does. Thanks Derek:crazy:
 

coyote62ny

Registered
what about a bad fuel pump.i have never worked on a do-100 but if the fuel pump is leaking could gas be going directly into the crank case. i have had that happen with mikuni fuel pumps on the older polaris snowmobiles. the diaphram gets holes in it and crankcase vacume sucks fuel into the crankcase bypassing the carbs instantly flooded engine. just a thought. i can see one of these saws will never end up in my collection. these saws sound like the old remington bantem they were another saw that had fuel system problems but you could take off the old carb that was the problem and replace it with a tillotson hl carb then they ran .
 

bigGURN

Registered
Last Subscription Date
04/01/2012
Ok got my new fuel meter on. The saw flooded after running for about 5 seconds. I was wondering about the fuel lines one goes to the fuel pump, the other goes to the fuel meter. I'm not sure what fell apart in the fuel tank. It was part of the line that goes to the fuel meter. something sticking in the tank like a one way valve or a filter??? I was wondering if anyone knows what that thing is or what it does. Thanks Derek:crazy:
That tube in the fuel tank is the fuel pick-up, it draws fuel from the lower or bottom portion of the tank, it is the same parts used on the two man saws as an oil pickup. It has no screen or filter as that is inline before the fuel pump, however it does have a spring inside to keep it from pinching and occluding fuel flow. There is no check valve as it makes a long arc in the tank and works like a siphon. Brian did have them in stock recently. You should have a line from the middle of the tank to the fuel pump. Then from the pump to a valve that is the "choke" from there the fuel line should enter the bottom of the fuel meter. There should also be a line from the top of the meter to the bottom of the fuel tank, this is the over flow line or return line, make sure the line nor the screen in the tank are plugged or all extra fuel goes right in the engine. While running be sure the choke valve is closed, or it will flood really bad.

---------- Post added at 11:47 PM ---------- Previous post was at 11:43 PM ----------

what about a bad fuel pump.i have never worked on a do-100 but if the fuel pump is leaking could gas be going directly into the crank case. i have had that happen with mikuni fuel pumps on the older polaris snowmobiles. the diaphram gets holes in it and crankcase vacume sucks fuel into the crankcase bypassing the carbs instantly flooded engine. just a thought.
The fuel pump is actually mechanically driven off of the transmission, the only was gas could possibly get from the fuel pump to the crankcase would mean a bad seal between the crank and transmission, which would mean no compression and therefore the saw would not run. As I mentioned above, these saws are extremely touchy...did I mention they like to flood easily?
 
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bigGURN

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Last Subscription Date
04/01/2012
Here are pictures of the entire fuel system.

First up the semi-high pressure (for the late 40's) fuel pump (in the lower right corner), driven off the transmission in the front center is the choke valve, really not needed as in case i have forgot to mention, they flood easily. In the background bottom center is the fuel strainer / filter on the inlet side of the pump


Next up the fuel meter as seen with the intake removed, as you can see there are a number of large fuel lines running all over the place! The lower hose is the inlet line that would be attached to the "y" valve (the choke) supplying fuel from the fuel pump to the fuel meter. The upper line is the fuel over flow / return line that allows the excess fuel from the fuel meter to flow back to the lower portion of the tank, check this line for occlusion


On the upper body you will notice that this was built as a Stromberg-Bendix cooperative, Stromberg on the body. The inlet needle is located in the lower half of the fuel meter body (where the big brass plug can be seen at the bottom) from this angle the fuel line on the left is the return on the right the supply.


And Bendix Aviation on the top cover
 
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bigGURN

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Last Subscription Date
04/01/2012
The four new diaphragms:


This picture shows the cam in the center (bright shinny part) the inlet needle of the fuel meter is actuated off of this cam instead of vacuum like in a conventional carburetor.


This last picture is the top side of the fuel meter, on the top there are two diaphragms that help meter and pump the fuel on the side is the impeller to atomize the fuel as there really is not small ports to accomplish this task.


That is a quick tutorial, if you have any other issues let me know. If you do not already have digital copies of the owners manual and IPL they are available here http://chainsawcollectors.se/phpbb3/viewtopic.php?f=140&t=8822 see the 4th post down from the top, click on the links and they will download.
 
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mrvalleyboy64

Registered
Looks like I have it all hooked up right. Thanks for the pics. I was wondering if that was a return line. The fitting that threads into the tank had something on it. I'm not sure what it is. It might not be anything important. I know it needs a fuel pump diaphram because it leaks. I might try the idea of putting a shut off between the fuel strainer and the fuel pump that sounds like it will work. Thanks guys! Derek Love the Idaho plate!
 

bigGURN

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Last Subscription Date
04/01/2012
Looks like I have it all hooked up right. Thanks for the pics. I was wondering if that was a return line. The fitting that threads into the tank had something on it. I'm not sure what it is. It might not be anything important. I know it needs a fuel pump diaphram because it leaks. I might try the idea of putting a shut off between the fuel strainer and the fuel pump that sounds like it will work. Thanks guys! Derek Love the Idaho plate!
On the return line, the fitting has a screen that is attached that prohibits the return from becoming blocked by any garbage that might be free floating in the tank. Pull your pump and make sure it is clean, then you can put a light layer of fuel resistant sealant around the edges of the diaphragm when you reassemble and it should seal (so long as there are no crackes in the diaphragm its self). Good luck and above all have fun!
 

K-Tron

Registered
WOW! That fuel system is complex. Ive never seen anything like that before on a chainsaw. I wonder if the factory put one of those orange tags on the saw which said "CAUTION PATIENCE REQUIRED" :p

Chris
 

bigGURN

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Last Subscription Date
04/01/2012
WOW! That fuel system is complex. Ive never seen anything like that before on a chainsaw. I wonder if the factory put one of those orange tags on the saw which said "CAUTION PATIENCE REQUIRED" :p

Chris
They should have! It was billed as the future! The system was a derivative from the system used on the WW2 fighter aircraft also developed by Bendix (which worked extremely well). It truly works well so long as you a) never need to adjust it or b) you never need to start it!:shrug:
 

mrvalleyboy64

Registered
We have improvement!!! It started after I drained the fuel from the tank. It ran really good till it leaned out then I quickly dumped some fuel in the tank then it flooded and died. I played with the needle setting and got it to run. now it will not idle, it's either all or nothing. I think it's because the fuel pump is shot. It did have good throttle response. I think a new diaphram for the fuel pump will help.:D:O
 

equad99

Registered
this is an interesting thread..brian has been known to pass large projects to me as he generally doesnt have time to do them,,,(he works like very few ive ever seen).one of the projects is a do 101 made from nos parts.we found after several days of digging through parts,(thousands of parts!!!) there wasnt enough to get it done.i do have in my garage though,a complete nos powerhead for a do 101,and we were discussing what to do with it.we came to the conclusion that it will be turned into one that actually runs and cuts well.the stock fuel system will go away,amongst other changes.the kiekhaefer corporation made military drone engines during ww-2,and the fuel system is most likely surplus from the drone engine production.the reason i say most likely is i wasnt there (the outboards had surplus parts on them into the late fifties at least) but bear in mind that a drone engine only has to run for an hour or so at most before it is blown to smithereens.they dont have to idle either,as they are started and maybe tuned a little and released.putting a system designed for drone use wasnt a good idea.these saws came about to compete with the mcculloch 3-25 saw,but carl kiekhaefer was an almost diabolical over engineer,and ultimately the do saws put the kiekhaefer corporation out of the saw business.with the other projects going,the do saw will probably be ready for baraboo in 2014.im now working on a kb-7 saw that i wont say a lot about it except ive got about 120 hours of time in it so far,brian says it looks awesome,and it will be about 15-20 pounds lighter,and will look and perform unlike any other kb7 you have ever seen...we will have it at baraboo this summer...art b
 

bigGURN

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Last Subscription Date
04/01/2012
I've looked into the drones and they all ran two cylinder engines and from what i read they used a regular carb. This system was developed based on the system used on the fighter planes, they used either a two or four venturi system. Disston looked at this and as you said saw a means to make a better saw that would be the technology of tomorrow. Unfortunately he was also trying to under mine Mercury by bringing on old Mercury employees tobbuild engines of his own. He wad sued by Mercury and given the failure of the DO saw and the court cost they left saw production. Later Mercury would bring back the DA saw but out was outdated by that time. Really too bad, rumor is Disston and Mercury had a new one man saw in the works that would have been light like the McCulloch but with the Disston refinement.
 
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