luftewaffe

I just installed an Evolution 26 GT on a Goldberg Pitts 12 and am having difficulty starting it. It doesn't want to prime. The ignition is working fine and sending spark to the plug, but I can't seem to get gas to the cylinder. So far I have been hand flipping it with the choke closed like the manual says. I tried my starter for my .40-.60 sized planes but it doesn't have enough torque to turn over the Evo. Has anyone else run into this problem, and if so how did you get around it?

Brian

BankYank

My Feedback: (63)

That little hole you see in the choke butterfly,,,,,Plug it.
Pat

luftewaffe

I tried that - covered it with a piece of tape - still wouldn't prime.

ramduster

My Feedback: (2)

If you can squirt some gas in the carb and get the pump wet with gas it will work a lot better and once you do that it will get better over time believe me I feel your pain

luftewaffe

Thanks ramduster - I squirted some gas into the carb and it started right up. It idles ok, but when I try to give it any throttle it quits around 30% power. This is my first gas engine. It may be fuel tank placement issues. The fuel tank is slightly above the carb (inverted mount). There are some guys at my club that fly gas, we can probably work it out. Thanks again

RevGQ

This is the best advice I have come across...


In general, engine manufacturers set their engines to run when they leave the factory. This does not mean, they are set at best needle settings, it just means, that the needles are adjusted in a way that the engine will start and run. Obviously, some needle tweeking is required if you want the engine to show what it is capable of.
Walbro carbs, as well as other carbs without floats, normally have two needles to set. The high speed needle labeled "H", and the low speed needle labeled "L". See the Walbro manuals http://mvvs.nl/manuals/wbmanual1.pdf and http://mvvs.nl/manuals/wbmanual2.pdf . It is important to remember that the low needle is always active, and that the high needle is only active avove 1/4 throttle, when there is sufficient low pressure in the venturi.
Here is the drill to start from scratch:
idle mixture
Open both needles two turns. This will ensure a rich setting.
Start the engine at slightly high idle rpm, and let the engine warm up a bit.
Adjust the idle needle (closest to the engine, and marked "L") for best rpm, and then open it 1/4 to 1/2 turn. This will be the setting to start tuning, and from here, the high needle can be set.
High speed mixture:
With the idle needle set about right, slowly apply full throttle. If the engine stays too rich, close the high needle a bit so the rich condition is cured, but no more than that.
This is the basic high speed needle setting, at which the engine will run without damage due to lean mixtures.
Keep this setting while running in the engine.
If the engine has run about five minutes, the plug can be checked. It should have a desert sand tan, or slightly darker. Not black, because that is an indication of an overly rich mixture, nor pale-white, because then the engine is too lean. This causes damage!
to be continued.
_________________
Pe Reivers model engines
Dealer for MVVS and 3W engines, Mejzlik, MTW
www.mvvs.nl
www.prme.nl
www.mvvs-nl.com

Tennwalker41-delete

My Feedback: (15)

Luft i can help u with that .. I have a 26gt on my giant ucando. U will love this engine. WHen a gas engine is new the diaphragm in the carb that actually pumps gas to the carb is dry. It needs to b wet.Thats y it starts when u shoot gas into the carb. This is the case with all gas engines. U can either take the screw off the top of the carb facing u and wet it down with gas or either put ur finger on the choke butterfly itself blockin the hole in the butterfly with ur finger and push it closed with the ignition OFFFFFF~~~. Turn the prop about 10 times with the throttle about half open till u feel gas come up on ur finger. HOld the choke shut for about a minute and let the gas flow into the diaphragm to soak it. It will start on the first flip. It will get better everytime u fly it. Mine was the same way as well as all my gas engines. Or if u want to get it done now just take that screw off and pour some gas on it and let it soak in. This is a great engine and produces a ton of power. Mine will turn an APC 18x6w at over 8600 static runnin rich with a stock inverted pitts muffler from Evolution. THe first thing u will find is it sips gas. I have a 24 oz tank and i can fly 40 minutes and have half a tank left. Thats economy. As far as it cuttin out open both needles 2 turns out like someone suggested earlier. After some runtime u an lean out the low end till it starts to speed up slightly and then back offf just a bit. The high end is done just like any other 2 stroke. Hope this helps.

Antique

My Feedback: (4)

The pump diaphragm works only with the engine running, it has no function when you're choking the engine....
With the venturi completley closed off the suction from the piston pulls fuel into the engine through the inlet needle...If you can't get fuel when choking the inlet needle must be stuck shut...If you doubt this, take the diaphragm under the cast cover out of the carb, put the cover and gasket back on and choke it, you will get fuel if the needle is not stuck...

luftewaffe

Thanks everyone for the suggestions. I did get it started by putting some gas into the carb to wet the diaphragm. It started up on the first flip. I haven't had a chance to tune the engine yet, but hopefully this weekend. I really appreciate this forum and all the helpful people who contribute!!

jrtaub

I am also new to gas and have the EVO26 engine. My problem is the fuel line routing. I have a bison pitts style muffler and the fuel line is very confined between the muffler and engine. After a few runs which total ~ 30 minutes the fuel line has a burnt area where it was touching the engine. I was using Aerotrend gas and diesel fuel tubing 1/8" od. I have tried the 3/16" tubing, but it is very difficult to install. I was told to use neopreme tubing. Will there be problems with vapor lock because of the heat?

I also had problems starting this engine and needed to prime it.

I will be putting this engine in a Pacific Laser 200.

Joel

RevGQ

Burnt my fuel line with first run also. Thank goodness there are zip-ties, which I used to hold fuel and vent lines away from muffler. I also use a plastic bottle to catch fuel from vent line when filling tank. This bottle has a nipple on the cap to which I attached some tygon tubing that has a small diameter plastic tube at its end. I insert the the small plastic tube end into the fully opened carb and squirt a liberal amount of gas into the carb and close the throttle after doing so.

jrtaub

Could you elaborate more on how you did this, there is not much space between the muffler and engine? Also did you use the neopreme fuel line?

Joel

NM2K

My Feedback: (14)

Let's use some logic here.

It costs money to drill a hole. It takes time to drill a hole. We all know that time is money. Why would Walbro put the hole in the choke plate if the engine ran better with the hole plugged? This makes no sense at all.

If all is well with the engine's set up, the hole does not need to be plugged to draw fuel. I would find out what is wrong with the engine set up and then fix it. Not Rube Goldberg it by plugging a hole that the manufacturer of the carb feels is necessary, in spite of the cost of making the hole.

No offense intended to the preceding poster, or anyone else.


Ed Cregger

RevGQ

Not quite sure of the explanation you're looking for, but in my P40, the fuel and vent lines originate some 4-5" behind the wrap-around exhaust and the plug wire is routed back toward the firewall. Using a piece of dowel secured in the engine compartment I secure fuel line, vent line and plug wire to the dowel using zip ties.

As far as the primer bottle is concerned, it is simply a plastic bottle with a hole in the cap with fuel line attached. After filling tank and catching the overflow in bottle, I secure the top and use bottle to squeeze gas into the carb.

jrtaub

I guess I was vague in my question. My problem is at the Carberator. The fuel fitting on the carb makes a 90 deg bend and is pointed toward the rear of the engine. About 1.5 inches after the carb fitting the fuel line is getting overheated and gets burned, right between the engine block and the muffler. I am using a beam mount, maybe that makes a difference??

Joel

RevGQ

We may be using different mufflers. I am using the Evo wrap-around. You might consider drilling out a piece of dowel to accommodate your fuel line as the wood should protect line from heat.

Panzlflyer

My Feedback: (15)

Because Walbro never designed a carb for an RC model!!!
Whatever it takes do it.
Or did you never hear of the pressure problem on the diaphragm...they drilled a hole in that as well

jrtaub

Well I think the problem with the burnt fuel line is solved. I have been using a hanger 9 beam engine mount on the evo 26 and a bisson pitts style muffler. With the muffler attached to the engine the side of the muffler is resting on the side of the engine mount and not letting the muffler sit square on the engine, thus letting gases out right over the fuel line. I think the combination of the hot muffler and the exhaust leak may have caused the problem with the fuel line burning through. I will be using neoprene and a radial mount on the plane now that I know the muffler doesn't work with the beam mount.

Joel

Jaime_Arenas

My Feedback: (4)

I seem to have a related, but slightly different issue. I have my Evolution 26GT installed in a Seagull Yak55; it's been in that airframe for about 6 years now. A few weeks ago when the weather finally got better I serviced the fuel tank (new lines and filter) and took this plane out for it's first flight of the season. Right off the bat it took a bit longer to prime the engine than I remembered, but I finally got it primed. I fired it up and it ran for about 30 seconds and died. I tried restarting, but It would not even pop. I primed again and starter the engine up and again it ran for about 30 seconds and stopped. At this point I pulled the cowling off to see if I could determine what was going on. First thing I noticed was that the fuel line leading to the carb was completely dry. I primed the engine again, the fuel line was filled with fuel too, started the engine and again it ran for a very short time and died. Again the fuel line leading to the carb was empty. I thought there may be an issue with the fuel line so I disconnected it from the carb, leaned the plane forward (to make the clunk higher than the fuel outlet) and fuel began to flow at a pretty good rate. I believe this means that the fuel is not significantly obstructed. After years of service I thought maybe it was time to replace the pump diaphragm and the other membrane on the other side of the carb. I took the carb apart, cleaned it with carb cleaner, removed a fair amount of debris from the screen, put in new diaphragm, membrane and gaskets, put the whole thing back together. Same behavior: pain to prime and will only run for about 30 seconds.

in summary:

• Needles are set where the manual asks them to be set
• new plug
• Freshly charged ignition battery
• Good spark from the ignition system
• Fuel is fresh and mixed in with the proper amount of oil
• New gaskets, diaphragm and membrane
• Filter screen inside the carb is clean
• No blockage of fuel flow

• Engine is difficult to prime (I plug the little hole in the butterfly with my finger and I lift the plane's tail to ensure the tank fuel level is higher than the engine's fuel inlet
• Engine runs for about 30 seconds and stops

Any ideas on what else I should look for is greatly appreciated.

Thanks,
Jaime

ahicks

My Feedback: (2)

2 thoughts.
1st, it's really easy to get the gaskets and diaphragms reversed/assembled out of order when reassembling these carbs. When that happens (either side), the fuel pump won't pump fuel. Refer to diagrams for both sides, as they are different!

2nd, many (most!) carb gaskets have a hole in them to allow crankcase pulses to pass to the carb. If the gasket is reassembled in a manner where that passage is blocked, same result. The fuel pump will not pump fuel.

Jaime_Arenas

My Feedback: (4)

well... I'm a dummy. After going back and checking membrane orientation, membrane / gasket sequence and making new carb gaskets (one was looking a bit ragged and I thought it may be leaking a bit) same deal; won't prime without lifting the plane's tail and then it only runs for a few moments. I pulled the carb off the engine and applied a bit of vacuum directly to the carb with a syringe and nothing happened. I opened the carb again and made sure the passages were all clear and still nothing. I pulled the tank out of the fuselage and right away I spotted the problem... the feed line inside the tank was off the nipple in the cap. Looks like I simply inspected the tank earlier (I wrote it down as "serviced with lines replaced" in my little log book) and din't notice that the feed line was almost completely dissolved. The vibration of the engine must have completely knocked it off. The fuel line was literally turned into jelly at the joint with the cap's nipple. I replaced the feed and the fill lines inside the tank assembled everything. closed the choke, flipped the engine about 12 times and I started to feel the fuel on my thumb. Now she's priming like its suppose to. Oh well, live an learn. I must have simply inspected the tank without taking it apart (it's one of those clear tanks where you can easily see all the guts) and simply changed the lives outside the tank. On the bright side, I think I can take that carb apart and put it back together with my eyes closed.

-Jaime