I now have a K&B 65 sportster that is having a problem... I understand that they were not built to be long lasting but to be strong... Mine seems to be running with an air leak but I can not determine... Air pressure into the carb inlet produces liquid bubbles at the front of the bushing..It requires a rich mixture and does not come down from full throttle well at first... Surges coming down after take off...It idles good ... Appears to only have only the main needle for the adjustment.. Any suggestions or history on the use of this engine...Do they still make this engine? Thanks

What fuel are you running? Prop size?? Glow plug???

These engines do not like all synthetic fuels, they like castor oil. I am running a 12X6, 13X5,6, 14X4,5, on this engine. There should be a brass disc on the left hand side of the carb with a "-" and a "+" sign. You turn the disc to change the mid and low end.

I have run many gallons of fuel through mine and it is still running well so I am not sure about They are not ment to last a long time. Treat this engine like a 4 stroke and you will be happy.

Dru.

Richard:

The K&B Sportster 65 was made in an early version with the crankshaft running directly in the aluminum case. Pull the prop drive washer off and look at the front where the crank comes out. If you can not see a brass ring around the shaft you have the early version - go on line to MCoA and order the late style case with the bronze shaft bushing. The last one I bought was about $22, so it's not an expensive upgrade.

But some leakage around the shaft is necessary, that's how the oil gets up front to lubricate the shaft.

And as Dru said, running synthetic oil in a plain bearing engine is a fast way to destroy one. ALWAYS use a fuel with a good amount of castor oil.

And again echoing Dru, prop it up. Don't try for high rpm, again, that will shorten its life. Keep the rpm down by using a larger prop than you think it should have, try not to go too much over 10K rpm, let the torque pull your plane, not sheer horsepower.

Bill.

Thanks to both replies... I will look into your suggestions... I am running a 12X6 with a Syn/Castor oil and I added 5 oz castor to the gal of fuel...Plug is idle bar and not sure of make... Again, thanks.. It would not hurt for me to put a new plug in and try to see if that stops the surges at the high end... Understand the 10,000 rpm... will go with bigger prop also.... Richard

As for the plugs. I forgot to mention mine like the Fox Miricle plug.

Air leaks are common on the needle valve side of the carb. Pull it apart and see if the "O"-ring(s) are any good. They will split and let air trhough.

Dru.

Thanks Dru...will do on the o-ring... Would an o-ring cause high end surges? I am having no trouble with the idle and the motor does not quit in flight if set to run rich... Richard

Mine have always had a rich mid range. They will idle for days and have good top end but going from idle to the top this will spit, cough, gag and then pick up and run. The split o-ring may cause a surge as it will let the vacum from the carb to pull air past and not do it at idle becasue of less vacum.

Dru

I have a K&B .61 that I was having similar problems with. It has the black Perry carb with the brass wheel on the high speed side. I broke the carb down and found a very small piece of trash in the spray bar of the mid/low adjustment. I searched high and low to find out how to adjust the Perry carb. I finally found some forum postings like this and it shared that you will get an enormous change with very little adjustment 1/32 of an inch. After looking at how this carb works, I understand it better.

The spray bar has a VERY fine slit with a small hole at one end. By adjusting the wheel you align this with the barrel. A very slight change in the wheel and it doesn't line up. The forum said that the wheel adjustment is up to 1/8" either side of the whitness mark @ 90 degrees.

Once cleaned and properly adusted, mine starts and runs great.

Hope this helps someone.

The Perry carb and the K&B "Ribbed" carb are the same in metering concept, but different in executiion.

The Perry has the metering slit next to the fuel inlet nipple, where the least bit of trash can clog or restrict the flow immediately.

The K&B version runs the fuel through a similar inlet chamber, but the fuel goes past the main needle before reaching the metering slit, which is moved inside the spraybar in the venturi. This isolates it a little better from trash in the fuel.

With either carb DO NOT use anything hard to clean the slit, enlarge it and you've ruined the carb until you get a replacement part. Use a piece of paper or card stock to wipe it out and be sure it's clear, nothing else.

Pictures are first, the Perry metering disc. The slit goes to either side of the hole visible in the relief between the o-rings. Second is the K&B version, the slit can be seen near the end of the tubular extension.

Bill.