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Discussion Starter · #41 ·
What would the cork paper or rubber gasket equivalent be in this case? The green stuff on the outside of the seal? I thought I was doing metal to metal. So you think the wetness is coming from the outside of the seal and not the inner rubber part? I just figured it was moving around so much because of a sloppy crank bearing that it was still allowing air in/oil and gas out.

Oh and yes I know they were talking about thread locker but as I was about to install it and looked around for some, I saw that anaerobic sealant on the pegboard from when I rebuilt the manual trans in my rusted out crapbox and thought it would be perfect for this. Live and learn I suppose.

Honestly as I was sitting there messing with it it seemed like it was running better but then just running out of fuel. But as soon as I tipped it up to see if the crank was dry and saw that it wasn't I just went right back to that being the issue and dismissed fueling as the problem. I need a break from this lol. Maybe sleep on it.
 

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If you order from Toro, which I do through my dealer, the 611396 is the rubber coated seal. Looks like you got the metal cased seal with the boretite coating. That coating is designed to react with the friction of the seal install to bond it into the recess. I would guess any sealant on that style would defeat the purpose of the coating. If you read the excerpt about the anaerobic sealant it says that used in that manor in can degrade rubber. I don't know. Just what I read. Bill
 
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Discussion Starter · #43 ·
Ah so the green coating is what it will react with so to speak. I'm not even sure how much of it even remained, it seemed like it all just scraped off when it was driven in.

I'm thinking I'll wait until I can rig up a magnetic base/dial indicator to see exactly how much slop there is in the crank and maybe try the 611396 seal next time if the slop is deemed acceptable. And if it's still running the same, concentrate on fuelling again. Do you still think I need to look into this primer not sealing?
 

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Here is a link to your wear limits. I think it’s a .0065 crank run out limit. I’m with Bill. I don’t think your main issue here is a sealing problem. Your runout seems pretty typical for a 50 year old machine. I believe your problem is a fuel issue. The carb is not the original for you 68, who knows what has been swapped out. I wish I were closer I’d just loan you a known good carb to temp install just for troubleshooting purposes. It does seem like it’s too lean, fuel starvation issue. I would get rid of the aftermarket fuel filter that you installed to. It already has a screen at the tank valve and at the nozzle, no need to increase restrictions in a gravity feed system.
 

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Discussion Starter · #45 ·
So I shouldn't be too concerned that it was still leaking out of the seal? Not to mention it seems like there's a lot of fuel if it's collecting down there and leaking out when it's supposed to be flowing through that area and into the cylinder, but again I still don't fully comprehend how a 2 stroke engine even works if I'm being honest. And I am. I guess since that's the lowest point it's inevitable that it will collect and leak down to there.

Well more things to try at least. Thanks all
 

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So I shouldn't be too concerned that it was still leaking out of the seal? Not to mention it seems like there's a lot of fuel if it's collecting down there and leaking out when it's supposed to be flowing through that area and into the cylinder, but again I still don't fully comprehend how a 2 stroke engine even works if I'm being honest. And I am. I guess since that's the lowest point it's inevitable that it will collect and leak down to there.

Well more things to try at least. Thanks all
You are correct it should be dry around the crank, but I've seen D-400s leak much worse than that and still run great. My little 5024 D-400 is kind of a late a 60's commercial clone. I upgraded it with an NOS C-19 shortblock (Extended snout crankcase), did a crank swap using an NOS crank as well, a C series crank won't work in a D series anyway. Long story short, I didn't put a new oil seal in the lower end, it looked good so I went with it. Well, I got it all together for it's initial cranking, it cranked right up and ran great, and it should of, it was just about all NOS, carb included. The only problem was the lower seal being about 50 years old just disintegrated from old age and oil was slung out all over the place under the deck, and would drip and pool under the mower rather quickly after shutdown. Now I realize that was with zero wear parts, but still, if it ran that good with massive amounts of oil running out then I would think that your wet area on the crank would be no big deal in regards to engine performance. I've had my 7260B leak about the same as yours due to a slightly pitted crank sealing surface, it ran fine and had about the same wear your's has. My conclusion is that the extended snout crankcases are pretty forgiving when it comes to a leaky lower seal, probably due to the large dual plain bearings and the fact oil pools down there and still makes a good enough seal for both the vacuum and pressure. I doubt that rollers like the F series have would work too well without a seal down there though, but the D-400 will for sure run just fine. I accidentally proved it. Yeah stay away from 50 year old oil seals. The good thing about the extended snouts though is that they are super easy and quick to change a seal. If you have the correct tools it's basically a 5 minute job. Now having said all this, I would still get a good seal down there, and if the runout is not too bad you should be able to do it, it just requires a polished crank sealing surface. I did notice that the end of your extended snout has been dinged up a bit, and I hope that it hasn't distorted the end enough to prevent a good seal.
 

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Do you actually have fuel pooling on the floor? From my experience the leaky substance coming out of the lower seals is just very clean oil. I think at that point in the crankcase the fuel in the mix vaporizes just about all the fuel is drawn into the cylinder, what's left on the inside surfaces is just super clean oil, almost like sewing machine oil, and it runs down and pools in the bottom. It's amazing to me at how clean the oil in these old 2 strokes are. You can take some of these apart after 50 years and judging from the outside think that it's going to be real bad, but it's just the opposite, if it's been ran on a good mix it can be very clean, almost like new in there, other than a few places like the wrist pin area that is obviously subjected to much more heat.
 

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Discussion Starter · #48 ·
I think I saw a drop come out when I tipped it back this morning. Also I removed the fuel line off the carb and opened the valve and it seemed to come out at what seemed to me would be a much faster rate than what can go through the needle and seat. As for the needle and seat, I usually just try to blow through the fuel inlet and lift up on the float to see how effectively it cuts off flow. Again it seemed to function the way it should so idk why it would be experiencing starvation. Unless it's flooding. But I was able to kind of keep it running by pushing on the primer just before it was about to die so what, the bowl has adequate level but it's having trouble getting it to the venturi?
 

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It sounds like you cleaned the crankshaft and installed the seal properly From the video, that is way too much crank play. Seals have a range of off center they can tolerate and still seal. You are probably exceeding it. The crankshaft and bronze busing are both worn. Usually on high hour D's the bronze bushing wears to one side and also puts deep grooves in the crankshaft. I would tear the engine down .
 

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Discussion Starter · #50 ·
Alright, I opened up the carb again, being careful to hold the carb upright so I could observe the fuel level in the bowl. Oddly, gas began to run out as soon as I loosened the L shaped bolts. Well that's unexpected, that suggests to me that the fuel level is too high.

There was also a bunch of crap in the bowl again. I began to suspect that there was some stuff stuck to the inside edge of the gasket from before or something, which might have gotten caught in the needle and seat and held it open? Seemed clean, where on earth could this be coming from?

Well, I continued to disassemble it and double check the float level setting. Then I started seeing these little dark particles all over the blue towel I had laid out. It's the coating of the float. Apparently when the coating breaks down the fuel can soak into the float? Now why priming it while running helped to keep it going is beyond me but regardless this is an obvious problem that needs addressed. I'm hoping there's some kind of upgrade float available, I'll have to do some searching. I'm sure this isn't the first time this has come up.
 

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Discussion Starter · #51 ·
It sounds like you cleaned the crankshaft and installed the seal properly From the video, that is way too much crank play. Seals have a range of off center they can tolerate and still seal. You are probably exceeding it. The crankshaft and bronze busing are both worn. Usually on high hour D's the bronze bushing wears to one side and also puts deep grooves in the crankshaft. I would tear the engine down .
That's something I didn't want to hear but the design of this seams really simple. From what I read there's no replaceable bearing in the bottom of the d400, but you can have it machined out for the later needle bearings?
 

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That's something I didn't want to hear but the design of this seams really simple. From what I read there's no replaceable bearing in the bottom of the d400, but you can have it machined out for the later needle bearings?
The problem with installing a needle bearing in a worn D engine is the grooving wear on the crankshaft. A Needle bearing need a smooth surface to bear against otherwise you're defeating the purpose.
 

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It would be interesting to see exactly what the crank runout is with a dial indicator. It’s hard to tell from the video. It looked like to me when the OP was moving the lower end of the crank back and forth it was moving the entire SB, which seemed to make it look much worse than what it actually is.

FWIW I still think the poor engine performance is carb related.
 

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Discussion Starter · #56 ·
I keep running across plastic floats that say they work for the same application as the old cork ones. Is this worthwhile or should I just get a tried and true cork one that will last another 50 years?
 

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I like the cork floats. You never have to worry about whether they get a pin hole leak and fill up with fuel. Just don't clean them with carb cleaner. Bill
 

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Discussion Starter · #58 ·
So being only .0035" out of spec, do you guys still think the runout thing is no big deal? If not I'll keep focusing on this carb.

I found some floats but what about a carb kit? The kits I've found sure look like the gaskets are the right shape and they have the right jet and needle/seat, but the engines they say they work for don't include the d406. Or do I just need to piece meal a kit together?
 

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I don’t think it’s a big deal. I guarantee there are plenty of these old Lawnboys out there that have more than .0065 runout at the crank and are still daily runners. I’ll bet my 7260B is one of them. It has an extended snout crankcase from a 1969 Model 7259, and it is right there with yours in regards to wear. All my other D-400s have NOS short blocks so they should be below that .0065 mark. I’ll measure mine when I get a chance…just curious about what the difference will be between an NOS and a high-timer like my 7260B.

The carb on yours is not off of a D-406, it's more like a D-433 from 1973 or so. The fuel inlet connection on yours is integrated into the carb body, on a 1968 model the inlet is a brass barb style inlet that is held in place with a brass nut. The 1968 carb will also have two thumbwheels for adjustment, one low speed and one for high speed. Your carb has only one adjustment thumbwheel and it is for a fixed speed 3200 rpm engine. While you're into the carb again check for wear at the throttle shaft and hole at the body, there is no published wear limits for that, at least not that I know of, so just use good judgement, air leaks there may warrant a new shaft and carb body. It looks like you definitely need a new cork float, maybe a new needle and seat and a new primer kit. If you can find the correct NOS carb that would be great, but maybe more than what you want to spend since carbs are crazy expensive these days. One other thing to watch out for in that carb is the main nozzle, there are different versions of that and they are not interchangeable between carbs. They run like crap when you have the wrong nozzle installed. I think the main differences are the amount of holes and location.
 

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So being only .0035" out of spec, do you guys still think the runout thing is no big deal? If not I'll keep focusing on this carb.

I found some floats but what about a carb kit? The kits I've found sure look like the gaskets are the right shape and they have the right jet and needle/seat, but the engines they say they work for don't include the d406. Or do I just need to piece meal a kit together?
Is the seal still leaking?
 
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