K&B 48

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K&B 48

Postby fastpace » Sat Jun 02, 2012 2:33 pm

I have a K&B 48 and I want to know if it is worn out. I have an 11/7 zinger prop and the best it does is 10,000 it is not running lean but still gets real hot. it has compression cold and hot. It starts easy and idels good but it strugels to get off the ground. If it does need a new PC can I trade in a NIB Gold head 61 in exchange. I had sent in a 6550 for a repair and the guy says for a little more you can get the new one. So it cost me $130.00 for the new one and he wanted $100.00 to repair my old one so I took the deal of course after that you dropped the price. I hope you can give me some help. I ran the engine today and when rich it smokes a lot but will not clean out. Fuel is powermaster 15% with castor added. When it was new it was a great engine,I have not used it in a long time and now I got trouble. Thanks for any help....[/b]
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Postby chiefss » Sat Jun 02, 2012 9:44 pm

An 11x7 is a 60 size prop. Try a 10x6, 10x7 or and 11x6.
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Postby fastpace » Mon Jun 04, 2012 8:00 am

I was just going by the owners manuel which says to run an 11x7 prop on the engine, I got this engine a long time back and it ran well with recomended prop and did not over heat. I thought it might be time to ask some questions and see if I have an engine issue. thanks for the help.[/b]
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Postby SteveM » Mon Jun 04, 2012 10:44 am

The manual does mention the use of an 11x7 prop so that sounds fine. How much use has your motor has seen and have you recently switched airframes? Do you fly in dusty areas that might require ai air filter? What fuel type and oil content are you using?

BREAK-IN FORMULA: 20% Degummed castor oil, 5 to 10% nitro-methane, and the balance methanol.

AFTER BREAK-IN: The nitro-methane percentage may be increased to 15% if desired. LOW QUALITY FUELS CAN RUIN THE ENGINE IN A SHORT PERIOD OF TIME. Never use fuel with less than 18% oil content by volume.

Check the bearings to be sure thay are still smooth. Look at the sides of the piston and check for scoring or nicks. Does the cylinder bore still have the chrome plating intact or has that been eroded?

Some times poor running can be attributed to dirt or other debris in the carb. Look in the spray bar or the mixture disc for anything odd. Make sure you are using muffler pressure as well.
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Postby chiefss » Mon Jun 04, 2012 5:37 pm

oops, I thought it said 40.
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Postby MECOA » Sat Jun 16, 2012 9:33 am

What exhaust sustem?

If it is the original muffler, check the baffle. Sometimes it can collapse and cause excessive back pressure. This would cause your problem.

Sorry for the late reply. We are trying to get ready to move our facility.
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K&B 48

Postby fastpace » Wed Jun 20, 2012 8:51 am

You hit the nail close, the person I loaned it to had put a rolled up screene in the muffler and when I took it a part I found this, the baffle was gone and this engine was bought when tower carried the K&B line. I test ran the engine and it was turning 11,000 on the ground rich and did not over heat. How would I determine if I should replace the PC? Thanks so much for the reply...Don
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Postby MECOA » Sat Jun 30, 2012 7:29 am

You can run it without anything inside. They actually run better with the baffle removed.
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Screamin' 48 idles but dies

Postby kbfan » Fri Sep 14, 2012 7:49 pm

I have a .48 that has previously run well. Broke it in per the manual, ran well, crashed plane, broke off carb, installed new carb, ran well again, crashed again - no engine damage (even closed throttle prior to impact, so no dirt inside, either). Cleaned the dirt out of the carb, took carb apart to make sure it was clean through and through. Now it starts immediately, idles well, but dies between 1/2 and 3/4 throttle. No lean out, doesn't sound too rich, just runs well, then dies - even if I gradually increase throttle, when it gets to about 3/4, it just suddenly dies. No bubbles in fuel line, either. Tank in proper position, clunks OK (brand new fuel system and plane), needle valve clear, less than 4" line from tank to carb. Have noticed a blackish oil leaking at muffler screw. Discharge from muffler looks normal. I'm really getting frustrated and hate to give up on an engine that I really like! Any suggestions?
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Postby MECOA » Sat Sep 22, 2012 2:52 pm

Is this the carb that went through the second crash? If it is a K&B carb then you probably broke off the inner part of the spray bar that is part of the mixture disk.

Check out these pics to see what I am referring to.

http://www.mecoa.com/faq/carb/mixdisk/mixdisk.htm

http://www.mecoa.com/kb/carbs/carbsptstr.pdf
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Screamin' 48 idles but dies

Postby kbfan » Sun Sep 23, 2012 6:13 am

No, nothing broke. I've had the carb completely disassembled and cleaned it, though I am going to take it apart again and make sure that all of the ports are completely clear and clean.

Idle seems to be good, but acts starved when throttle is slowly opened to between 1/2 and 3/4 - just stops like it ran out of fuel (no surge or lugging either).
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Re: Screamin' 48 idles but dies

Postby fastpace » Mon Oct 08, 2012 11:23 am

kbfan wrote:No, nothing broke. I've had the carb completely disassembled and cleaned it, though I am going to take it apart again and make sure that all of the ports are completely clear and clean.

Idle seems to be good, but acts starved when throttle is slowly opened to between 1/2 and 3/4 - just stops like it ran out of fuel (no surge or lugging either).

I will wait for that answer because mine does the same thing, I have to run a 10/6 prop to get any rpm, flying a tower 40 size trainer and the engine takes for ever to lift off, just does not have the power I expected form a 48. Accleration seems very slowThe engine has good compression and idels well, have tacked it at over 12,000 but still does not do well in the air until the tank gets low on fuel. I do have a fuel filter in the line and a carb filter on the engine because we have a dusty field.
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Postby MECOA » Sat Oct 13, 2012 1:13 am

As for the the engine running better when the tank is low, it is because the engine is leaning out. Try running it withour the air filter and see if the problem still exists.

As for the engine acting starved at mid range. Check and see if the inner spray bar has the slotted hole and an additional small 1/32 hole next to it.
The additional hole was added for the .48 and larger engines. So at full throttle you should see 2 holes in the spray bar.
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