Andy's Model Engine Repair
Your Subtitle text
Andy's Model Engine Repair
Welcome to Andy's Model Engine Repair Website.

Model Airplane Engine Repairs and Reconditioning

I am back in business after about a six-month hiatus due to moving and setting up a new shop. Thank you for your patience.

I will repair or recondition any two or four-stroke model airplane engine, glow or gas, single or multi-cylinder (except radials). Four-stroke engines are my specialty. I can also do machine work and employ various welding methods if necessary for the repair. Such work as the following can be done:

-Restoration of stuck and frozen old engines that are otherwise sound to good running condition (see photos)

-Bearing replacement, two or four stroke.

-New piston rings, including cylinder honing.

-Removal of frozen bolts or screws without damage to the engine.

-Complete engine rebuilding to restore performance.

-Damaged engine repair.

-Straightening of most single-cylinder gas two-stroke crankshafts, and some  others, depending on amount of the bend.

-Glow Plug 1/4"-32 thread restoration (Helicoil) in stripped cylinder heads, two -stroke or four-stroke. These are done on a straight labor-time basis with a $25 minimum, which is generally all it takes.

-I am not currently set up to do broken exhaust port repairs. Clarence Lee still does these using a threaded brass insert. Call him at 818-352-3766. 

Since I have to buy them at retail just like you do, there is no markup for parts and I will use yours if you have them (assuming they are correct). Shipping costs for parts is also a pass-through. Bearings will come from Boca Bearing, other parts will be ordered from the appropriate distributor.


Labor for any skilled service is $25/hr, clean up using an ultrasonic cleaner is billed separately at $10/hr. A typical two-stroke bearing replacement in an otherwise mechanically good engine will take about an hour or less, including light cleaning, plus roughly $15 to $30 for the bearings. The cost of cleaning is impossible to predict but generally runs about  $10.

Four stroke engines, by virtue of their far greater parts count, require more labor for almost any repair. A tear down and analysis of a typical four stroke will require close to an hour's labor depending on the make. Smaller engines (under 1.0 cu. in.) tend to be less cost-effective to recondition if corroded or frozen than larger ones since the labor is the same regardless of size, but the engine's value is much less. Something straightforward  like bearings, piston rings or a connecting rod replacement is pretty much the same regardless of size. Obviously there are more parts to clean in a four-stroke, running around $20 and up.

I will give you a rough estimate after seeing your engine, but I don’t always know what I’ll find until its apart. Often an older engine that has not been used in a while, or has not been properly preserved for storage will be frozen and damaged by corrosion (especially four-strokes and even if you live in a very dry climate, (see photos) to the point that restoration of all the parts will require labor costs in excess of the engine's worth.

If I feel its not
repairable, or the parts or labor cost will be excessive, I will not proceed further without discussion and authorization.                                                        
Often its cheaper to replace than repair. If that is the case, you will only owe me for my time to tear it down, generally less than an hour unless there are broken fasteners, etc. Or I will trade you the cost of assessment for the engine as parts. This avoids the additional cost of shipping and you having a useless engine unless you need it for spare parts. Either way is fine.

After many years of this work I can state that the typical OS single will cost $125 for a full reconditioning. A Saito will run $115 due to the fact that it has two fewer ball bearings. Most twins require much more labor and the OS Gemini for example has five ball bearings so they are around the $300 range. YS engines are pricey to repair as the parts are not cheap and its usually necessary replace all the fuel components. They are more complex and require more time as well. Their cost will vary depending on the model.


PayPal seems to be the easiest way for most people to manage payment.  Personal checks are ok too but slower than PayPal. I will ship your engine asap after PayPal payment.


All work is guaranteed for a period of 90 days from receipt. (No comebacks to date.) I will disregard a winter layover.


Don't overheat or over rev your freshly repaired engine and expect me to fix it for free. I can tell when they've been abused! All ball bearings require a short period of break-in in a somewhat rich condition, about a tank full of fuel. More serious work requires longer break-in.

 E-mail me to discuss your engine problem.

Andy Johnson


Does your engine look like this?

An older Saito120 from Nevada, put away wet with no after-run oil; no compression, lots of corrosion, and from a dry climate, no less. This is a very typical situation with old, and not so old, four-strokes.

And this? Notice the stuck-open valves and far pushrod out of the rocker arm. Not much compression here.

Here's the reconditioned engine. This level of restoration required quite a bit of labor, but even with new bearings, far less than the cost of a new engine, and it ran like new.

To avoid having your four-stroke engine look like this one did, run all the fuel out of while its still good and hot and at a moderate throttle setting, not at idle. Use a good after run oil, or a fuel containing some percentage of castor oil, or both. It is remarkable how much moisture is retained in the crankcase of a four-stroke even after running it dry while hot.

Four stroke engines do not purge the moisture from the crankcase as well as two-strokes, nor do they run as hot in the first place. Its still a good idea to run a two-stroke engine dry at the end of the day.

Here are my recent thoughts on this issue: Using after run oil is fine but the problem of water retained in the engine still exists only now its mixed in with the oil. I recommend first using a water displacement fluid such as WD-40, forced into the engine (I use an old enema bottle as the tip fits the crankcase nipple) through the crankcase vent nipple. Use at least an ounce, roll the airplane around so it goes everywhere in the engine.

Suck out the WD-40 with a different bottle with the nipple at the low point and see if there are any water droplets in the oil. The water will either be in suspension or pooled on the bottom. Dispose of the dirty WD-40 in an environmentally responsible manner. Repeat this until no water is visible in the WD-40, then put in the after run oil.

I use ATF but Rislone, Marvel Mystery Oil, etc. are fine, your choice. Just get something oily on the bearings and steel parts. Yes its a pain but so is paying me good money every few years to recondition your engine.

Gasoline engines, particularly two strokes, run very hot and since gasoline does not have the affinity for water that alcohol does, there is less moisture trapped in the crankcase and it easily vaporizes. I have never seen corrosion in a gas engine that was properly cared for.

A gas engine should be run dry if it is to be stored for more than a month since the fuel will dry out in the carburetor and eventually cause varnish deposits that can plug the very small orifices in the carb.

The carburetor parts in gas engines require replacement every few years due to deterioration, becoming stiff and inflexible. Cleaning of the carb is necessary along with replacement of these parts, but the cost is not great and the engine will run far better. Try to use alcohol-free gas if possible as it will slow this deterioration.
Website Builder