I need help keeping my engine cool

Post the general engine topics that here.

Moderators: Frank Klenk, SteveM

I need help keeping my engine cool

Postby tewitt1949 » Sat May 31, 2008 7:21 pm

Hi all. I have a old K&B 40 motor that I've had about 22 years. It has always performed great and still does. I haven't changed anything internal infact I've never had it apart. 15% nitro fuel and I've even added extra castor oil which someone suggested.

Anyways, it will run on the ground or in the air for about 1 1/2 minutes 1/2 to full throttle. Then it starts to sag on rpm's. Finally quiting 30 seconds later. At that point, if you wet your finger and touch it, it sizzles. I've always run a 10-6 prop. I tried a 9-6 and same thing. It has great compression and runs like a raped ape at first.

I tryed richening the carb until it starts to blubber from being too rich, but will still heats up. I do have a pressure line to the tank from the muffler.

There is no cowl or any thing around the motor, completly exposed.

Why?? I can't figure it out. Any idea's???? Thanks Terry
tewitt1949
 
Posts: 4
Joined: Sat May 31, 2008 7:18 pm
Location: Ludington Mich

Postby loucrane » Tue Jun 10, 2008 11:55 am

Terry,

Do you still have the instructions? The carb may have drifted off settings, giving you too lean a mixture at some throttle positions. If you have the instructions, you could try going back to square one to set up the carb.

Has it had a crash that could have bent something, or put some foreign matter inside it?

I expect you've run down the usual list: fresh plug, fresh fuel, balanced prop, clean filter(s), no holes in the fuel lines.

It does sound as if some fuel passage is obstructed. Have you chopped throttle as soon as you hear it start to sag? If so, does that help or make it worse.

Twenty-two years old, eh? Sounds like it is somewhere in the 4011 series. Aluminum piston, Dykes ring. Some had the black plastic Perry carbs, many had K&B-made metal carbs. Different set-up process on each.

Carb settings interact. Different carbs have various ways to reach good WOT perfromance, good idle, and good mid-range. If one of those ranges is off, it may affect the others, or the whole engine, as you seem to have run into. Might well be something else, but if it runs too hot, likely it is either too lean or overloaded for some conditions it meets.

Luck!
loucrane
 
Posts: 95
Joined: Mon Jul 26, 2004 2:39 pm
Location: Sierra Vista, AZ, USA

Postby tewitt1949 » Tue Jun 10, 2008 7:44 pm

Hi Loucrane, Yes I've checked all the usual stuff and have tried readjusting the carb to make it richer. No luck. It does have an all netal carb. I've added extra castor also. I'm going to try some 10% nitro fuel. Probably won't help but I'm running out of ideas. I've taken the carb completely apart and blew everything out. It was clean. I'll keep looking for things to try.
tewitt1949
 
Posts: 4
Joined: Sat May 31, 2008 7:18 pm
Location: Ludington Mich

Varnished?

Postby Aaron_Novak » Sat Jun 14, 2008 12:21 pm

could the engine simple be varnished up with years of running? Ive seen often times an engine loose power over time due to excessive varnishing. A good cleaning and soaking in simple green precision parts cleaner floats all the castor varnish off. May take a couple tanks of fuel to build up the "sealing varnish" though.
Just a thought.
-Aaron
Aaron_Novak
 
Posts: 17
Joined: Thu Mar 03, 2005 11:18 pm

Postby Jim Thomerson » Mon Jun 23, 2008 8:32 am

It may be that the ring is stuck, and /or the cylinder varnished. I'd look for shiny spots on the liner and piston which indicates out of round and building up friction with heat. Taking the engine apart and giving a good cleaning couldn't hurt.
Jim Thomerson
 
Posts: 103
Joined: Thu Jan 23, 2003 4:27 pm
Location: Austin TX

Postby tewitt1949 » Mon Jun 23, 2008 9:58 am

Hi All. Thanks for all the hints and suggestions. I've cleaned it very good, in and out but still had the same problem.

What I stumbled on to which seemed to cure the heat problem is I was using 15% nitro and I dropped to 10% nitro. Seems to have just as much power, runs great and doesn't seem to heat up as much as it was. Its still a little hotter than I'd like but it keeps running through till the tank is empty. I don't know if that tell you anything but thats what I found.
tewitt1949
 
Posts: 4
Joined: Sat May 31, 2008 7:18 pm
Location: Ludington Mich


Return to General Engine Tech Talk

Who is online

Users browsing this forum: No registered users and 21 guests