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Jan 22, 2018, 04:32 PM
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Wanted

OS 61 SF Muffler - #744B


Hello all,

I'm looking for an OS Muffler #744B (for an OS 61 SF), preferable new or in good and clean condition. Delivery must be done to 33195-5649, Miami, FL. Paypal payment.

Regards,

Omar
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Jan 22, 2018, 05:13 PM
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kablake's Avatar
Let me look, I know I have a 744 but not sure which one. I had 2 of them in the past and they both said 744 but were different. Neither had a B on it. The one you want is for the 61 SF, correct. I also have other mufflers that will fit the 61 SF if you are willing to use not that exact muffler..

I am off to look and see what I have and will let you know in a bit..
Jan 22, 2018, 05:21 PM
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I have it. It does not have "B" on it, just 744, but it has 42mm between mounting bolt hole centers. I have a 61 SF and it fits.

$15 if that is OK, I would get $10 for it and pay $5 to ship it..

If you want photos let me know...
Last edited by kablake; Jan 22, 2018 at 06:16 PM.
Jan 22, 2018, 05:25 PM
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Photos of the muffler...

The first photo is the measurement of the mounting holes. The NON 744 is a muffler that will fit the 61 SF that I took photos with the 744 if you wanted something else, so just ignore it. The 744 is clean and looks almost new as you can see... I will even throw in a gasket..
Jan 23, 2018, 09:06 AM
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Dear Kablake,

Thanks a lot for your message and offering your muffler. I found a new #788B muffler on ebay last night. Please see attached photographs.

The #788 muffler is for the OS .61 FSR engine. The difference is that in the #788 the engine crankcase is threaded and the bolts go from the exhaust flange to the crankcase, whereas in the #788B the bolts go through the crankcase and bolted in the muffler - i.e. the muffler is threaded. I think the #788 muffler can be installed on the SF using nuts on the exhaust flange. I haven't checked the dimensions but I think they are the same.

I will contact you in the future if I need this muffler,I have plans to buy an OS .61 FSR.

Regards,

Omar
Jan 23, 2018, 11:38 AM
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Just to clarify the difference between the two 744 mufflers. One on left is the 61 fsr and one on right is 61 sf. The muffler offered earlier is correct for the 61 sf. The mufflers are not interchangeable from fsr to sf engines due to the flange size even though the casting number is the same.
Jan 23, 2018, 05:59 PM
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Quote:
Originally Posted by tiporare
Just to clarify the difference between the two 744 mufflers. One on left is the 61 fsr and one on right is 61 sf. The muffler offered earlier is correct for the 61 sf. The mufflers are not interchangeable from fsr to sf engines due to the flange size even though the casting number is the same.
Yep, I have both types of these engines and as I said earlier, the 744B I have ONLY HAS 744 on the muffler. If you look at the photo of the muffler It is correct..
Jan 23, 2018, 06:10 PM
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Quote:
Originally Posted by omarhazbon
Dear Kablake,

Thanks a lot for your message and offering your muffler. I found a new #788B muffler on ebay last night. Please see attached photographs.

The #788 muffler is for the OS .61 FSR engine. The difference is that in the #788 the engine crankcase is threaded and the bolts go from the exhaust flange to the crankcase, whereas in the #788B the bolts go through the crankcase and bolted in the muffler - i.e. the muffler is threaded. I think the #788 muffler can be installed on the SF using nuts on the exhaust flange. I haven't checked the dimensions but I think they are the same.

I will contact you in the future if I need this muffler,I have plans to buy an OS .61 FSR.

Regards,

Omar
I have BOTH the 61 FSR and the 61 SR so I know the difference...

The 744 I showed you was for a OS 61 SF. As me and others have said, OS produced the 744B for the 61 SF but only labeled it as a 744. Others were labeled 744B. Maybe they though it wouldn't matter and people got confused so they added the B. But if you look at the photos I displayed, especially the first one, you can see threads in the holes. Therefore it is a 744B...

I see your 744B is not labeled a 744B either...
Jan 26, 2018, 12:14 AM
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does anyone have a macs tuned pipe 2850 for sale, it's for my os max 61fsr motor. looking for a tuned pipe also for the same motor.
Jan 26, 2018, 08:13 AM
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Thread OP
Quote:
Originally Posted by tiporare
Just to clarify the difference between the two 744 mufflers. One on left is the 61 fsr and one on right is 61 sf. The muffler offered earlier is correct for the 61 sf. The mufflers are not interchangeable from fsr to sf engines due to the flange size even though the casting number is the same.
Thanks a lot for the tip on the muffler size!

Omar
Jan 26, 2018, 08:42 AM
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Thread OP
Quote:
Originally Posted by kablake
I have BOTH the 61 FSR and the 61 SR so I know the difference...

The 744 I showed you was for a OS 61 SF. As me and others have said, OS produced the 744B for the 61 SF but only labeled it as a 744. Others were labeled 744B. Maybe they though it wouldn't matter and people got confused so they added the B. But if you look at the photos I displayed, especially the first one, you can see threads in the holes. Therefore it is a 744B...

I see your 744B is not labeled a 744B either...
Hello Kablake,

Sorry I didn't understand your message. I don't have the engine in my hands yet, but it will arrive soon. I bought a new OS SF .61 but ringed for only 100 USD at ebay. I also bought the new muffler, but I'm interested in your #744B to have a spare one. I will send you a private message.

Thanks a lot,

Omar
Jan 26, 2018, 02:24 PM
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Mufflers that fit the OS 61 SF


Hi Omar,

These are all the mufflers that I HAVE that will fit the SF 61. As I mentioned OS pretty much standardized the 61 size exhaust mount with the 61 SF. They all have a 42mm bolt to bolt center. At least the ones I own, there may be some OS 60 size engines that differ. I also have a few NON-OS made mufflers that are made to the same size as the OS brand.. And there are many more than the ones I own. The photos have a description of the muffler. I looked all over my shop and I no longer have a totally stock OS 61 744B muffler. I never intended to use them anyway and I just sold the totally stock one as I said in the PM. The small version of the E-4010 I received with one of the SF 61s I purchased a while ago.

The Just Engines link..

http://www.justengines.co.uk/acatalog/Silencers.html

Dub Jett link, Dub Jett makes a size that does not require the adapter on the one I have. these are a bit expensive but they perform great!!

http://www.dubjett.com/mufflers2015.html

The one that fits the 61 SF without adapter is the JS-90TT.

So this is what I have. I will sell you the modified 744B or the one from Just Engines. As I no longer have a totally stock 744B.

In addition, and I do not have one of these...

I know the muffler from the OS 65AX will also fit the 61 SF. It is a O.S. Silencer E-4010A 65AX, The link is here..

https://www.towerhobbies.com/cgi-bin...?&I=LXAETL&P=7

So you have many options, if you want a totally stock 744B then I would suggest trying ebay or amazon..
Jan 26, 2018, 02:32 PM
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kablake's Avatar
Quote:
Originally Posted by antech5
does anyone have a macs tuned pipe 2850 for sale, it's for my os max 61fsr motor. looking for a tuned pipe also for the same motor.
Look at my last post. Dub Jett makes nice tuned mufflers... They increase performance. They will require and adapter for the FSR.. And they are a bit pricey, but worth it, at least to me..
Last edited by kablake; Jan 26, 2018 at 02:52 PM.
Jan 26, 2018, 02:50 PM
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Omar,

Here are some photos of the modified input of the 744B I have left...

I know it will mount and works OK so if you want it, it is yours. I will never use it..

Kevin
Jan 26, 2018, 02:52 PM
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Or relook on ebay again, I did a search on it and could not find one...


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