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Giant Scale Engine Tip — How To Rebuild a Walbro Carburetor

One of a good facilities that make hulk scale RC airplanes so popular, is a bulletproof user-friendly estuary of a Walbro carburetors used with many of a gas engines powering them. Once a gas engine is scrupulously adjusted, a carburetor customarily won’t need to be tweaked again for most, if not a whole drifting season. As an example, my Hangar 9 quarter-scale Piper J-3 Cub PNP is powered by a Zenoah G-20 gas engine, and in a 4 years of operation, we have never indispensable to adjust a  high- or low-end needle-valves. But, to say best engine operation, we should do some simple engine upkeep and cleaning.

There are a few things that can impact a opening of your Walbro carburetor and these include, unwashed un-filtered fuel, waste ingested during a drifting field, and presumably H2O that can means middle corrosion. No matter what a cause, whenever we notice apparent sand or sand in your carburetor or if we notice a graphic decrease in your engine’s performance, a initial thing we should do is open adult a carburetor and take a demeanour inside.  This takes a smallest of collection and time and this essay shows how we keep my Zenoah engine and Walbro carburetor happy. You can make any RC aeroplane some-more arguable by gripping a Walbro carburetor clean.

What we need

 To get inside a Walbro carburetor a compulsory collection are a common conduct and Phillips conduct screwdrivers, Allen wrench or conjuration driver, a amiable mist well-off like WD-40, some bamboo BBQ skewers and Q-tips. Don’t use a high vigour atmosphere gun to purify a carburetor as this can expostulate sand deeper into a fuel passages not to discuss pinch a garland of a smaller reconstruct collection and pieces.  A soothing string broom or towel to cover your work aspect is a good thought too.


Start by dismissal a fuel from your indication afterwards mislay a engine cover so we can undo a stifle linkage and fuel line. You can do this pursuit with a engine trustworthy to a indication or we can mislay a engine and work on it that way. It’s adult to you. If we mislay a engine, you’ll have to undo a hint retard lead, a ignition timing sensor lead and a engine connection bolts. You competence as good mislay a scarf also so we can give a whole engine a good cleaning before reinstalling it on your model.


Here’s a engine private from a Piper Cub. we cite to do this pursuit detached from a indication to give me copiousness of space to work in. With a really unwashed engine, place it on tip of a paper image or a disposable foil tray so we can keep your work are as purify as possible.


Remove a carburetor from a engine. Simply mislay a dual connection bolts and a spacers from presumably side of a intake. Be clever not to repairs a gasket. Unless your carburetor has suffered a major, murky belligerent strike or it has suffered a serious fuel blockage, all you’ll need to is give a carburetor a good cleaning and presumably rinsing out a categorical filter screen.


On a estuary side of a carburetor body, a dismissal of a singular core screw gives we entrance to a fuel siphon diaphragm, gasket and a unit’s fuel filter screen. Remove a screw and side cover afterwards check a skinny diaphragm and a flapper tabs to make certain there is no deterioration. Clean out any apparent waste regulating a BBQ skewer. Don’t use a pointy apparatus or a hobby blade as these can repairs a aspect of a passages.


Should we find that a filter shade is blocked with gunk or has trapped some dirt, purify it out with a discerning mist of WD-40. If that doesn’t do a trick, a deputy shade is enclosed in many Walbro reconstruct kits. These kits are accessible from gas engine manufacturers as good as during internal tiny engine shops. This one is from Enforcer during Warehouse Hobbies. Some prohibited shot pilots have suggested we can drop a filter shade all together afterwards use purify filtered fuel. we don’t suggest this as a boost in fuel upsurge is minimal.



In many cases, a good cleaning of a estuary side and presumably a deputy of a gaskets is all that’s compulsory to revive correct engine operation. If however that does not help, we can check a fuel metering territory by stealing a other side cover that’s hold in place by 4 dilemma screws. Again, check for any apparent waste and give a light mist of WD-40.



Held in place with a tiny screw, a middle metering needle, open and push arm can wear over an extended period. These collection automatically adjust a fuel upsurge to say correct fuel upsurge relations to outward windy pressure. If these collection uncover wear, delicately reinstate them with a reconstruct pack parts. Use caring and don’t force anything in place.


Again, it critical to extent your cleaning usually to soothing non-metal collection to equivocate repairs to a carburetor components. Gasket scrapers, razor blades and any other pointy mechanism can severely mistreat a relatively-soft aluminum a carburetor physique and cover plates are done of. Using them can lead to atmosphere leaks that are not a good thing!


The final collection to purify are a high- and low-end needle-valves. Give them a good outmost cleaning before stealing them from a threaded reduction ports. Before stealing them completely, kindly screw them in (clockwise) and count a series of turns it takes before they bottom out. When replacing them, a high-end needle should be screwed in totally afterwards practiced out 1 ½ turns out. The low finish needle should be tighten to 1 1/8 turns out. Make certain a needles and threads are clean, give them a light shot of WD-40 and reinstall.


With your carburetor scrupulously spotless and burning of any debris, reinstall a components regulating presumably a unimpaired strange parts, or a indispensable deputy collection from your reconstruct kit. When we reattach a carburetor to a engine, reinstate a intake gasket between a carburetor and a engine. It a gasket leaks atmosphere it will means a engine to run lean. Check a fixing of a carburetor’s vigour holes and make certain they line adult scrupulously with a holes in a connection block. They concede crankcase vigour into a carburetor to activate a fuel pumping diaphragms. If they do not line up, a engine won’t start.


Being means to remove, inspect, purify and reconstruct your Walbro carburetor will safeguard a well-spoken using engine and will save we a few bucks from not carrying to send your engine in for service. Glitches with Walbro carburetors are distant and few in between, though should something come adult you’re now prepared to repair it yourself. Happy flying!

Quick Field Tips

  • Always filter your gasoline. Use a filter in your fuel siphon plumbing and check your fuel enclosure to make certain zero gets in a fuel.
  • Add a fuel filter to a fuel estuary line for your model.
  • Snug down a carburetor cover screws snuggly though do not use thread locker. This can repairs a aluminum threads in a carb body.
  • If we are going to store your indication divided for an extended duration of time, empty a fuel tank and afterwards run a engine to bake adult a fuel left in a fuel lines and inside a carburetor. Use a spritz of WD-40 into a atmosphere estuary and flip a column over a several times to cloak and strengthen a middle fuel passages.

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