vwitte

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Does anyone know,
if I removed the rear baffle from a K&B .65 muffler would give me more RPM or Power?

carlgrover

When that engine first came out, RC Report magazine did a review on it. One funny thing they found was that if you added a length of silicone tubing to the end of the muffler (I forget how long but I think it was 12") there would be quite a power increase. Aerotrend used to sell the tubing. I don't know what would happen if you pulled the rear baffle out. I think I've only had one of those apart and there are several pieces to it. It might not even be possible without gutting the rest of it. Darn effective muffler and feather light too. Be careful of the nut at the front holding it all together. It's pretty easy to break the piece of all thread when trying to unscrew that nut.

carl

vwitte

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Yes I got the rear baffle out. It does appear quite restrictive. But, the K&B may need the restriction to run properly. I don’t know?
I can’t get the front baffle out. I may leave it in for a little pressure.
if I do decide to put the rear baffle back in should I line up the holes or perforations the best I can with each other. ?
I’ll run soon

vwitte

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Another question. I have about 3 Thunder Tiger .40 pro engines and about 3 Thunder Tiger .46 pro engines. Is it true the PRO engines with the straight needle valve are older and have true ABC liners ?
and the angled PRO needle valves have ABN liners??
thank you. Happy Holidays.

GREG DOE

The straight needle carbs are the earlier version. All of the Thunder Tiger 40/46's (straight needle, and angled needle) are true ABC. From your first post on muffler baffles, the TT's will benefit slightly from removing their baffles, but it's hardly worth it, unless you are racing, or are in need of every last RPM. They also have the same problem as the K&B's muffler bolts breaking, which were often replaced on the TT's with 4/40 all thread, even sometimes before they broke, as a precautionary measure.

vwitte

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I’m sure the engine tunes differently once the baffle is taken out.
But, if I’m careful and successfully remove the baffle would it hurt anything to run without the baffle?
If I’m not racing and just flying for fun any little boost would help, correct?
Also noise is not a factor where I fly.
thank you again.

1QwkSport2.5r

Y’all are not quite correct. The K&B Sportster .65 muffler has a single baffle tube that runs the length of the muffler. It’s the only baffle inside a Sportster muffler.

ALL Thunder Tiger PRO engines are ABN. The GP series are ABN too. Virtually no difference between the blue box engines with straight needle valves (I have one; the box was marked ABC, but it’s not ABC.) and the red boxed engines with angled needle valves. The carb is the only difference.

vwitte

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Ok thanks. There’s a lot of confusion/theories on the ABC/ABN controversy. I hear if you look at the bottom of the cylinder liner after removing the back cover the true ABC sleeve will actually show a little bit of brass on the bottom. This supposedly is due to the fact the Chrome plating is more resilient than Nickel and doesn’t need to cover the entire cylinder liner completely to avoid peeling.

I read only straight needle valve TT engines will have the true ABC. I just wanted some clarification prior to taking off the back plate.

I just thought I’d ask.
ok…. The K&B .61 baffle is one piece. The K&B .45 baffle appears to be two pieces that slide into each other. I have both and took off the .45 first. And the .65 second.

1QwkSport2.5r

No confusion other than if you believe what the label on the box says. Chrome is rarely plated inside and out - some are. I have an ST S25 that’s chromed inside and out. However the vast majority of true ABC only has chrome in the bore. Nickel needs to be plated inside and out to properly adhere. The Sportster engines come with a 5-piece exhaust. They’re all alike amongst the 4 displacements other than the size of the muffler. Two end caps, the single tubular baffle, the flange that fits inside the muffler that the exhaust extension attaches to, and the extension itself. There is only one baffle in a Sportster muffler. I have (3) .65s, (2) .45s, (2) .20s, and (3) .28s. If you have an actual Sportster muffler with two baffles, I’d like to see a photo. They never came like that from the factory.

vwitte

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Ok here’s a photo. Maybe the piece broke off and it’s not a two piece. . . . How would this affect the running now that the other piece is gone. ? Maybe the exhaust will escape better??

vwitte

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What’s the best way to keep this little screw and nut safe from stripping out on this muffler. ??

GREG DOE

Vwitte, Well that's what forums are all about? Different opinions. I don't want to get in an argument with QwkSport so 'l differ to him that TT cylinders are nickel plated, and not chrome. If you are just going to sport fly your TT, I wouldn't recommend removing the baffle. By the way there were two different baffles. One that was a "waffle" style, and one that was a "turbo" style. It's not of any value to explain the differences, and I wouldn't go to the trouble of dissembling mufflers for the purposes of photographing them. As far as the "tuning" changing with or without the baffle, it would be of LESS effect then changes in temperature or humidity. I have 8 or 10 of the TT Pro .40's that I race, and I consider it an amazing engine that is a power house, yet very docile. It's was not designed to be a racing engine, yet it performs as well or better then a lot of more expensive engines. It is common knowledge that the Pro engines were designed by an OS engineer who retired to Taiwan, so they have a good heritage.

vwitte

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Thanks. I attempted to disassemble the muffler to see how it would run without the baffle. Apparently the baffle broke.
I feel it’s a little small to be a 1/4 wave pipe, but we’ll see how it works w/out the baffle.

I was told baffles are added to increase pressure for the tank pressure as well as quiet the engine as opposed to the much older flow through mufflers. Which I hear the flow-through mufflers dont do much of anything, let me know if you think is different. ?

What’s your opinion on the TT 42gp ?

thanks for all answers it’s appreciated….

GREG DOE

This is just my opinion, and I only owned two of the GP 42's so take it with that grain of salt! They were set up very tight, and need a lot of break-in running. After that they are a decent non ball bearing engine.

the Wasp

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the thing here is, there are a lot of old rules of thumbs going on here, so this is something you need to test

the old rules of thumbs for 2St mufflers,
1) no baffle less exhaust pressure inside the muffler.
2) less exhaust pressure inside the muffler the more HP/more RPM, more fuel needed..
3) less exhaust pressure inside the muffler less Fuel Tank pressure.
4) more HP/more RPM more Fuel Tank pressure.
5) for the most part #4 cancels out #3.
NOTE) Fuel Tank size comes into paly here. the larger the tank the less the pressure.

I know nothing about the K&B 65 and it's Carb. but for the most part it seams to me that the K&B 65 has a small, restricting muffler, so I would think that removing the baffle would work for you but you would have to re-tune of course.

IF it's true I can understand that adding 10" of tubing to the stinger just may produce some more power at lower RPMs, but I do not see it producing more power at peak RPMs/


I can tell you I have flown my OS 61fx with the baffle removed in the stock muffler and it ran fine. and I have an OS Hyper 50 Heli engine on a P-40 with an over size stock type muffler with no baffle and it runs excellent. NOTE that the Hyper 50 Heli engine has the over sized Heli Carb. it turns peaked at 13,800 and runs extremely well, it will idle as long as you would want it to.

Jim

vwitte

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Thanks for everything… Off the subject.
And I don’t want to start a fireball, but I recently bought two MDS .40 Pro (silver) engines, they start and seem to run well.
Do you feel these engines just got a bad Reputation or are they truly bad engines. ?
TY

the Wasp

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cheaper is cheaper, but for the more part I think the cheaper engines are more finicky. I have seen cheap engine run very well. and I have seen cheaper engines that ran very badly that came to life by simply changing the prop to a longer "longer" prop, because the longer prop produces more "Flywheel Effect". so remember that more Pitch vs Length do not load an engine equally. because more pitch does not make more momentum, more pitch only loads an engine more. so if you have a tuning problem with a given engine, you tune and tune and tune and you can not find the sweet spot please try a longer prop.

Jim

1QwkSport2.5r

This is whet that baffle should look like. Yours is broken or was cut in two.

The Sportsters don’t need and actually run better without muffler pressure (many of mine run faster peak RPM on suction than they do with muffler pressure. The muffler doesn’t rob much power from the Sportster engines because the Sportster is timed so low. This series of engine is often referred to the “Poor Man’s 4-stroke”. But a baseball bat on it and it’ll be happy. Put a toothpick on it and you’ll be sad (and it won’t be happy either). The baffle being removed does improve peak rpm a little bit, but it also gets louder too. It’s a quiet muffler with the baffle in place. The baffle delete is good for maybe 300-400rpm and probably a third more noise. Still not offensive though.

I turn APC 13x6s on my .65s, 12x6 on the .45, and 10x6 on the .20/.28 with glow plugs and 5/22 castor fuel. As diesels, the .45 is happy with a 13x6 and the .20-.28 are happy with an 11x6 as diesels. The .45 will turn a 15x7, but not very fast and only as a diesel.

vwitte

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Thanks once again. I may be purchasing a K&B .61 engine from my neighbor. He’s had it for over 20 years. It’s never been run. I understand they run similar to a high performance .46 engine with just slightly more weight?
again, if I were to drill out this .61 K&B muffler exit hole and place an enlarged chrome insert onto the exhaust port-exit would I gain any performance?? I was hoping to make it similar to a Clarence Lee Custom muffler. I’m sure that must help. Any Advise….


just a question…

vwitte

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Thanks to all of you. HAPPY THANKSGIVING

1QwkSport2.5r

Negligible gain in performance. The Sportster doesn’t need much. The K&B .61 will pick up more than a Sportster, but nothing dramatic. That slight reduction in back pressure/increase of noise is only good for a couple hundred rpm or so. Run the engine open faced and then with the muffler. This will tell you how much power the muffler robs.

vwitte

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Thanks
how about an ‘old school’ flow-through muffler?
for the K&B or other engines.? If I can find a flow-through that bolts up…? I hear the ‘flow-through’ went extinct because they didn’t really cancel the noise, but no restriction….

I bought a MDS .40 pro, the MDS is one loud machine. So far so good with the MDS, i think it’s a winner.
I fly on a private field, noise is no factor unless you’re a tractor… Happy Holidays

1QwkSport2.5r

I wouldn’t use a flow-through muffler unless someone paid me to. I like the Sportster mufflers on the Sportster engines. The only better muffler that’s pleasant sounding and works on multiple engines is the Davis Soundmaster. Very nice muffler. I have two of them and use them as an easy muffler swap on the test stand.

the Wasp

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I see now, I was questioning the muffler. I see on Google Images there are 2 K&B 65 mufflers. I think the smaller one is actually a 61 muffler that came with the first version of the 65. (???)
Jim

https://www.google.com/search?q=k%26...EK&sclient=img

the Wasp

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well here you go, in the first link (version 2) it tells how the peak RPM razed 300 RPM with the 12 extension. that's something new to me. and in the 2nd link, version 1, both use the same muffler.

version 2.
K&B Sportster 65 (2)

version 1,
http://sceptreflight.com/Model%20Eng...ster%2065.html