Dynamark 12Hp, 39" deck riding mower belt replacement

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  #1  
Old 08-25-13, 10:28 AM
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Dynamark 12Hp, 39" deck riding mower belt replacement

So, about a year ago my wife and I bought a riding mower used off of a neighbour. I'm not 100% regretting that decision, yet. Woman gave us the original manuals for the mower and the B&S 12HP engine. The stupid mower manual doesn't mention the model # for this thing. It's basically a manual for a "12HP riding mower with 39" deck".

Today, get on the thing and start mowing. All of a sudden the blades stop. I look back and there's the belt lying in the grass.

My question is how do I tell exactly which replacement belt to get for this thing? The manual does a great job of explaining how, but not with what.

I laid it out flat and it measures 5/8" X 76" (roughly). But it looks ancient. Not sure if it could have stretched.

I took the belt out to the local guy who repairs these things, who's also completely insane and often heavily intoxicated. He says he needs the model # for the mower. I can't find it anywhere on the thing and I checked under the seat and the engine compartment.

Any ideas?
 
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  #2  
Old 08-25-13, 11:39 AM
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It's 5/8" X 77 1/2" #30068. A 78" belt would probably work fine.
 
  #3  
Old 08-25-13, 11:52 AM
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You're awesome Cheese! Thanks.

Now I just have to find a dealer around these parts that sells them!
 
  #4  
Old 08-25-13, 03:04 PM
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While we're on the subject of this mower Cheese...

What length blades would you recommend for this mower, and can I just look for any mower blade or are they different because it's a riding mower with twin blades?

As well, I've just built a new shed to house this thing and the floor of the shed is 16" off the ground. What rise/run do I need the ramp to be so that the deck of the mower doesn't bottom out when I get to the top of the ramp? That's the final carpentry type thing I have to do to make this shed complete and I'd love to call that part finished. Running 100' of extension cord out there every time I have to work on it is getting annoying.

Thanks again!
 
  #5  
Old 08-25-13, 08:14 PM
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It takes blades specifically for that mower. They aren't very common, as this is a pretty old mower and the company has been out of business for a long time. Your local small engine shop can get them for you or they can be bought on ebay and other online retailers.

As far as the run of the ramp, that requirement isn't the same for all riding mowers. I imagine a 5 or 6 foot ramp should do it.
 
  #6  
Old 08-26-13, 10:05 AM
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Thanks Cheese. Looked all over town today and couldn't find a 77.5" belt. Went one small town over and found a 78" at a farm supply store. They said they've never heard of 1/2" increment belts? Either way, it was cheaper than any price I saw online by a long way and the one I got is kevlar!

Looked for blades there for this thing. Not sure I'm going to find ones for a 39" deck. Found them for 38, 40 and 42". Would it be a real problem if I went with the blades for a 38"? Obviously can't go larger.
 
  #7  
Old 08-26-13, 11:42 PM
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Shorter blades won't meet in the middle, so you'll leave a strip of uncut grass making you mow every spot twice. The hole in the blade is important too. You can't just get a set of blades for any mower and stick em on any mower, even if they are the same size. Like I mentioned, they are specific to that make and model mower.
 
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Old 08-27-13, 04:03 AM
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I know they have to mount correctly but could a 40" blade be cut down to 39" I know it's not quite that simple as you need to keep the blade balanced but might that be an option?


I took the belt out to the local guy who repairs these things, who's also completely insane and often heavily intoxicated.
I've been looking for an excuse to comment on that statement - did the guy used to be a painter
 
  #9  
Old 08-27-13, 04:37 AM
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Hmm, well I guess I'm stuck continuing my search for the blades. I've found them online, but it just seems silly to have to order lawnmower blades from Oregon and have them delivered to Canada. I'm sure once they hit the border I'll get hit with some weird charge as well.

Not gonna try cutting them Mark. Last year I tried sharpening my own blades with my angle grinder. Honed them to a razor edge. Put them back on. Thought I'd done a good balanced job. They wobbled to the point I wanted to run in fear for my life.

.....and yes, he did tell me that he'd done some painting at one point! Ha!
 
  #10  
Old 05-16-14, 07:05 AM
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Well, here I am back again with this mower. Grass has finally started to green up and grow now that the snow is finally gone.

I managed to find the parts manual for this thing. The model number for the mower is a Noma b3912.

I've been finding blades online that say they replace the specific part number (306 932) for this mower. The manual says they are 19.69" HI lift blades. The various ones I'm finding online appear to vary slightly in length. Not much, but I know Cheese said you have to get the exact one or you're going to have problems.

Anyone know what my play is here? Or know of a reputable online dealer of these items? I don't do a lot of buying online.
 
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Old 05-16-14, 09:51 AM
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If you can find one with the correct size mounting hole or pattern, then you can use one the same length or slightly shorter. You might be able to use one 1/8" longer and get away with it, maybe.
 
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Old 05-16-14, 11:34 AM
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So, found one on Amazon.ca that says it's a replacement for the noma 306 932 and gives the dimensions. It says it's 61cm long.

As I mentioned above, the manual for my mower says the blade is 19.69 (not sure why they used decimals for that since every other replacement part mentioned is in fractions.) or 50.01cm.

That means the one on amazon is 11cm too long? Kind of regretting buying this mower at this point, but it seemed like a good deal at the time.
 
  #13  
Old 05-16-14, 01:30 PM
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I can empathize with you a bit . . . . I'm the proud owner of a couple of these mowers: a 36" and a 38". I've had them a long time and replaced and rebuilt many parts.

In my case, when I go to get replacement parts, I seek out parts for AMF, NOMA, Dynamark, Murray, and Montgomery Ward (and maybe one more that I can't think of at the moment); just like MTD, they were produced under many different names.

I've had the best luck getting parts through Tulsa Equipment Warehouse:

[URL=http://www.tewarehouse.com[/URL] (you may have to copy and paste this URL into your browser).

With them, I try to make my orders as big as possible by saving up my miscellaneous needs to take advantage of their fixed shipping price of $8.95 regardless of order size (I don't know how they handle Canadian orders).

Introducing a set of new blades used to be a chore. The AMF blades are typically 2" wide, with only a 3/8" center hole. I know I have to change blades when we start creating "mohawks" of uncut grass that are left behind in-between the two blades . . . . one of the reasons you want to get the blades long enough to delay the appearance of the "mohawks" as the blades wear.

I often take old worn blades from my 38" deck and grind a bit of stock off their ends to make them fit the 36" deck. It doesn't take much!

I always mount new blades (or freshly ground down blades) the 1st time while the deck is off the chassis and upside-down. That way, I can inspect how closely they rotate relative to one-another. I want them to start out as close as possible; but without touching; then I balance them. With the deck off, and blades removed, this is a good time for me to slosh some old drain oil on the underside of the deck to retard rust.

The quill assemblies (spindles) for the AMF units provide a "cradle" that supports the 2" blade and sometimes that cradle gets bent. Also, the bearings inside the spindle sometimes wear and require replacement to make the blades spin smoothly.

I have recently taken to using Oregon's Gator Blades on my AMF/NOMA/Dynamark mowers . . . . they're really heavy duty mulchers and about 3/16" thick; but they're 2.25" wide, so I now grind notches into them at the appropriate points where the cradle will be allowed to get a grip on them at 2" when they are mounted.

I'm not recommending this approach for everyone; but it's what has worked for me, and one of these mowers (my 1973 36") just turned 41, and runs like new, and I still value its "floating deck" highly.
 
  #14  
Old 05-16-14, 06:24 PM
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Using 42" blades would probably require quite a bit of grinding to make them fit. Using 38" blades might leave an uncut strip in the middle. I see lots of 39" dynamark blades on Ebay.
 
  #15  
Old 05-17-14, 07:31 AM
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Your blades are available from after market:
Oregon
96-005 low lift same as 309069 or 57299 or 76860
96-120 high lift same as 306932 or 58190

Stens
305-599 low lift
305-631 high lift
 
  #16  
Old 05-17-14, 07:44 AM
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Thanks AJ. I'm gonna give the drunken maniac small engine repair guy one more try now that I've found the parts manual and have dimensions. Hopefully he'll have them lying around and won't freak out on me for asking him for something.

The shipping costs from the US to Canada are pretty steep so I'd like to try and avoid that. Basically it comes down to 1/2 the price of the blades just to get them to the local post office.
 
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