buzzard bait

I have an HB 15 which I bought mounted in an airplane. They were in someone's attic for several years. The engine is said to be low time, and it does have good compression. The throttle was stuck, so I used some Marvel oil to free it up. When it first started moving the idle disk moved with it, so I lost the setting. Now the throttle moves without moving the idle disk, but it is still rather tight. A micro servo can move it, but it buzzes.

I fueled up the plane with a squeeze bulb, gave the engine a choked flip, and then tried both hand flipping and an electric starter. I could get frequent repeat bursts, but the engine would always die. I tried various needle settings, including almost closed. It would keep re-starting even without further choking or priming. I could see fuel spraying up out of the carb. All this suggested the engine was getting fuel.

I can get fuel back out of the tank easily using suction from the bulb, so I do not believe there is a problem with the pickup inside the tank. I do not see leaking around the ends of the fuel line.

I removed the carb and used the squeeze bulb to force fuel through via the fuel intake. Fuel came out of the carb, but it did take some pressure. I assume there is a fairly small orifice inside and that fuel should not flow completely freely through the carb, correct?

The glow plug glows bright red.

I have run many engines successfully for many years, both glow and diesel, and I have never been stumped like this. I've never had a Perry carb, though. Is there something I need to know about it? Any other ideas?

thanks,
Jim

William Robison

My Feedback: (3)

BuzzardBait:

The Perry carb is different. Pull it off theengine and follow along.

Unscrew the needle completely, and pop off the circlip you see next to the mixture disc.

Next pull the idle stop screw out, and pull the barrel out.

This step can be the hardest: twist the mixture disc, and turn it completely around a time or two. Now, carefully, continue twisting and pull it out of the carb body. You should now have a small pile of patrs similar to photo one. This is, incidentally, the carb from one of my own HB engines.

Now look at photo two - near the inner o-ring you can see a small hole in the smaller diameter section. Looking really closely you can see a slit going off to either side of the hole. If the engine will run at full throttle but will not idle this slit is probably clogged.

Go to next post.

Bill.

William Robison

My Feedback: (3)

-- continued -

The only approved method for cleaning the slit is a piece of thin paper and a solvent. If you enlarge the slit the part is ruined, it wont meter correctly. See picture.

While you are examining the mixture disc, look at the o-rings. If they are damaged the carb wont work.

Also, there is an o-ring inside the needle valve, for an air seal. Check it too.

Go to next post.

Bill.

William Robison

My Feedback: (3)

-- continued, last installment -

The next thing to check is the barrel itself. Scoring on the larger diameter section wont hurt, but do check the fit of the smaller part in the mixture disc. You should feel either no play, or only a small looseness. If it's badly worn there you'll have to get some new parts. Forgot to take a pic of that, but I really don't think you'll need one.

If you find bad o-rings you can try your local auto supply, but I've heard ordinary o-rings don't hold up in these carbswith alcohol fuels, and a proper set isn't that expensive. You can get them from MECoA, or Conley precision.

Initial setting on all Perry carbs is with the mixture disc centered as shown, and the main needle out 3-4 turns.

Put it back together, install it, and have a good running engine.

HTH.

Bill.

buzzard bait

Bill, thanks very much taking the trouble to give such a thorough explanation. Great photos! I will give it a try.

I'm still concerned that something else might be wrong, since I couldn't get the engine to run at full throttle. But the engine was stored a long time, so I'm sure that what you suggest will be a good thing to do. Also, I'm not sure I ever had the needle out as much as 3-4 turns. I'm used to using about 2 - 2 1/2 on my other engines.

Thank you!

Jim

buzzard bait

Hi, I easily followed your fine instructions and cleaned up the carb. It may have been partially clogged--hard to tell, but it's clean now.

The engine ran at full throttle, but only with the needle valve screwed IN to about 3/4 turn! Anything more was too rich. I could see fuel spurting out the carb unless the needle was turned way in. When I throttled down, the engine sounded good at first, then continued to slow and I could see fuel coming out the carb, and the exhaust looked rich. If I tried to throttle back up it would sputter and quit unless I did it after a very short time, and even then it always hesitated.

I decided to turn the low speed disk toward the '-' mark to lean it out. But I had trouble re-starting. I was hand flipping and got frustrated. It seems to start easily by hand when cold, but not hot.

I will try another day if I get a weekend that's not too nasty outdoors.

Thanks for your help. Still hoping for success.

Jim

William Robison

My Feedback: (3)

Buzzard:

What was the height ofthe fuel tank, and were you running muffler pressure, crankcase pressure, or no pressure?

The Perry carb has good fuel draw, so if you are running presure that may be the thing to eliminate, or lower the tank.

If the engine runs at full throttle there's no reason it wont idle, unless it's just worn out.

Bill.

William Robison

My Feedback: (3)

The kicker is the needle only 3/4 turn open - it's getting the fuel too easily. And when you close the throttle it's going way rich. You had the right idea on turning the disc, but with the main needle just barely open I have doubts you'll be able to lean it enough and still have the high end. Try to get the main needle at least 1 1/2 turns open.

Bill.

PeterC

Something else to check on is the ring, I believe this engine is ringed and after a long storage the ring might be siezed. Gummy residue in and around the ring groove might be a clue. If the ring is stuck it will be difficult to get any performance . Soaking it in Varsol or better yet using an ultrasonic cleaner might help.
I too have a pair of HB 25's in a twin seaplane. It seems that after I don't use the plane for a couple of weeks the idle disk gets loose and it just spins around. I think the O rings shrink between uses. When I go to start it again it takes a lot of time waiting for the rings to swell up again so it will hold a setting. I have looked at the O rings and they seem impossible to remove and replace.
Does anyone out there have any suggestions?
Thanks, Peter

William Robison

My Feedback: (3)

Peter:

The 0.21 ans 0.25 HBs are ringed, but the 0.15 and 0.20 are not. That's why I mentioned worn out.

If you have the right o-rings on the mixture disc it wont come loose between runs - order a new set for yours from MECoA or Conley, they can be replaced.

Bill.

buzzard bait

Thanks for all the replies.

This is a typical upright engine installation that puts the center line of the fuel tank below the carb. A little hard to say just where, but definitely not a high fuel tank.

I am using muffler pressure. Makes good sense to try it without, given how wet the engine seems to be. I think a lot of the starting trouble may come from flooding it, and then the fuel draw is so good that it doesn't clear--every flip draws more in.

The mixture disk stays put just fine and the O rings looked smooth and shiny when I disassembled.

Bill is right--no ring on this engine. Compression is excellent.

I will try again without muffler pressure. First snowfall today, but I hope to give another try on the weekend. I'd love to get this puppy running well.

thank you again,
Jim

buzzard bait

I pulled off the muffler pressure and that improved it enough that I'd be willing to try a flight with it now.

It's still a cranky engine. When I throttle back and then open up the throttle, the engine balks before going full speed. The longer it idles the more it balks when it's opened up. The symptoms sound like it's rich at idle, right? I messed with the idle disk quite a lot and I could make it worse but not better. The idle disk is on the lean side. Either leaning it more or richening it makes it impossible to keep the engine running on anything but high cruise to full speed. Needle valve is open only one turn.

Cold starts are easy by hand but hot re-starts are difficult and I've resorted to an electric starter for those. It's still disappointing, but at least I think I'll be able to do some flying with it now, if the weather improves. Can't help but compare it to my OS .15 FP which sat on a shelf for a couple of years and started on the first flip at a meet. Always starts quickly by hand, hot or cold, and never flames out.

Thanks very much for your help.

Jim

William Robison

My Feedback: (3)

buzzard bait:

If you are willing to go to the trouble, pull the Perry off your HB, and the carb from your OS. Switch them. Try the OS with the Perry, and the HB with the OS's air bleed unit. My Max III 15 RC engines have a smaller spigot than the HB, so I can use the OS carb on the HB but can't use the OS to check the Perry carb. At least this would put a different carb on the HB for testing and comparison.

Or, if you'd like, send me your Perry, I'll stick it on one of my HBs and check it for you.

Bill.

buzzard bait

Bill, thanks very much for your kind offer. I took the carb apart and cleaned it again and reassembled with the idle leaned more by just a hair and I'm now getting a pretty good idle and transition. That low speed adjustment must be incredibly sensitive. The engine still doesn't start easily. I think it starts a little better with muffler pressure--then when it's running I yank it off.

The engine is on a Wicked Wanda someone else built from RCM plans years ago. It's a cute 44 inch low-winger, 2 lbs 6 oz. I took it out to the field today. Wind out of the northeast at, I don't know--the windsock was horizontal. No one else was flying. Kind of ridiculous actually.

Leaned it out, tried the throttle, a friend pointed the nose up and the engine was fine at high and low speed--best it's ever been. Pointed the plane into the wind and let 'er rip. Immediately the plane wanted to leave the ground. I held it down for speed and then let it climb--plenty of power. Trims were a bit off so I throttled back--everything fine. Plane was getting tossed around like a cork in the surf. The wings would suddenly, for no apparent reason, be 90 degrees to the ground. Plane responded fine to corrections--just had to be flown every second in that wind. Not a great day for touch and goes, so I flew it half to full throttle. The tank is only two ounces, so after a little playing around the engine ran out gas and I dead-sticked it in. Engine is powerful, behaving pretty well and now proven in the air, plane still in one piece--I'm happy.

When I sent the post I couldn't even get a high speed run out of it. Thanks again for all the help. Jim

William Robison

My Feedback: (3)

Jim:

Yes, the idle mix adjustment is sensitive. Forgot to mention that, sorry.

Glad it's running well or you now.

Bill.