OK...firstly I tend to fly heli's so this article is mostly about heli engines but can be applied to plane engines of course. This is also to introduce my bearing tool to make these bearing changes easier.

Maintaining your engine is important for a powerful and reliable powerplant that is unlikely to fail if it is getting the correct mixture. Even a dodgey glowplug doesn't normally stop an engine and won't necessarily show up until the next start.

So how do we do this and what is the most common problems?

1. Fuel delivery and mixture.

2. Glow plugs

3. For heli's bearings appear to be the most common problem. More so on 50's rather than the 90's but the bigger engines still require them once or twice a year.

4. compression due to ring

Lets deal with the easiest one. Buy decent glowplugs. for heli's I like enya 3's and OS 8's. The enya 3's appear to last a bit longer due to a better filament and I find a slightly better idle. Of course they tend to be a little more expensive. When you engine dies after start or when you take the glow driver off suspect the plug first. The plug shouldn't have a black (rich) look to it on the filament nor a crazed silver appearance indicating lean-ness and in the worst case will be blown out completely. (this will stop your engine mid flight!)

Now mixture. I am not going into the fine points of tuning as this is a whole subject in itself. If you have a temp reader then aim for 100 degrees celcius from the air immediately below the outlet of the head IMMEDIATELY after landing from a high temperature manouevre like tic tocs. Other wise 8 to 10 secs of your finger on the backplate before you would like to take it off!!. Replace your plumbing regularly. Most failures I have had and seen relate to broken or blocked fuel lines.

The ring piston and liner should be in good condition for maximum power. The liners are very hard and often last the life of the engine. The pistons are light but if well tuned last a long time as well. too lean and you will pop a hole in one as soon as look at it. (ask me how I know!) The ring should be inspected and as long as the tension still exists it will most likely be fine and can be reinstalled. They are a relatively cheap replacement however. Bear in mind if you replace this you will need to do a minor run in again to seat the ring or localised heating in areas of the ring may affect it. We want a nice seal all around.

Bearings cause a lot of problems. These range from...loss of power, making metal particles head through your engine (yeah...far from good!), vibration and a rattling sound.

I suggest replacement after an extended period without use or when power is down. Also a rattle or unexplained vibes as well. Even after running for a while the bearings get a bit of play. too much and the crankpin rubs on the backplate and the worst is the radial play. My OS 91 HZ has not done a lot of running...perhaps 60 or 70 flights and I notice the radial play in the bearing after detecting a vibe and noise.

DO NOT run your engine with a suspect bearing. Mostly it is the rear bearing but you need to be aware that a front bearing needs to be in good condition as well. The crank has a gas seal around the front of it with a minimum clearance to the crankcase.....too much movement here and the gas seal is affected allowing crankcase pressure to bleed out the front bearing causing a loss of power.

I usually replace my bearings twice a year. More running does not mean they wear out faster necessarily! Lack of use is just as bad. They often rust due to the residual nasties created by the fuel we use.

You can use ceramic bearings but be careful here. They last well until they too fail with catastrophic results normally resulting in the disintegration of your motor. I won't use them.

I also don't bother going to SKF, NTN or genuine OS bearings. I buy cheap bearings. I get the same running time from them given the above considerations. Replace regularly.

Introduce my bearing tool.

Designed to make this job fun rather than a chore. A no guess, no damage approach.

Can you do this job without the tool......absolutely! But it is a PITA!

I have seen guys using everything from pin punches to sockets to tap the rear and front bearings in. I see them pulling them in with the crankshaft and heating the engine way beyond what it attains in normal service so the bearings just drop in. You cannot install a bearing by pulling it in using the crank!! That simply loads up the balls and in fact the races are quite soft. not designed to be used to pull the bearing in. I have seen and even done it myself where the bearings go in a bit wonky...the case cools a bit and grabs the bearing and now you have to reheat it and try to get it in straight.

My tool elminates the need for excess heat to install new bearings. It eliminates the guesswork and any possible damage to the bearings. It pushes on the correct part of the bearings to install.....the outside cage. It self aligns. It allows you to install without having to wear a big mitt due to the case being 200 degrees c!

When installing I only heat the case to 100 degrees c. Normal operating temperature. When removing I heat to 160 degrees c but I am working on a removal tool to reduce this to 100 c.

Heres the installation action.

Step 1. place the tool in the vice (not required)

Step 2. Place the correct bearing press onto the tool (50 or 90)

Step 3. Place the rear bearing onto the tool with the retaining ring facing up

Step 4. Heat the case to 100 degrees c. (paint stripper, pot of boiling water, oven) If using water it will dry quickly

Step 5. Place the case over the tool and pop the front bearing onto the tools stem

Step 6. Place the front press over the bearing and install bolt bring the press down till the bolt tightens

step 7. Crack bolt off half a turn and rotate crankcase 180 degrees. tighten again just to ensure bearings are seated fully.

Step 8. remove bolt and remove tool. Note. If the back press sticks in the bearing due to a minor expansion from heat DO NOT HIT IT OUT!. You will risk unseating the bearing. If you leave until cool it will just fall out. Personally I leave the tool inserted until cool.

This makes the job easy, no fuss and quite fun.

PM me if you would like to get your hands on one.

cheers

Glenn