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| Engines Discuss engines |
Topic Review (Newest First)
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| 01-28-2024 06:36 AM | ||
| Cougar429 |
Re: How to Change your Bearings Yser, you are not limited to the same manufacturer. Except for your comment on Pac Rim copies, ( I fully reinforce that and have repeatedly made the same warnings in the past) there are several quality bearing lines out there. One other problem is our eastern friends are quite good at counterfeit so I can only state order from a reliable source that has their reputation on the line. Boca is one, the other my local bearing house, (in this case Canadian Bearings). Even with good quality there are other factors to consider. You generally want a bearing with a C3 rating as it will not only have good dimensional qualities, but hold them through the expected temp range. This is why I generally ask right off for bearings rated for at least 18K. That tells my bearing house supplier what I need. I have to add one more point: A bearing is only as good as the installation and environment it rides in. First requires the area be clean and free of damage. Burnt lube and other residue must be cleaned from especially the rear face as the bearing must be fully seated and straight. I have seen countless signs this is not the case, one prime example the crank pin rubbing the rear cover. A lot argue this is due to the use of electric starters and reply that should not be true, (a politically correct way to put it) as no intact and quality bearing installed properly should allow for any crank to shift that much. As Len states you must always push against the part of the bearing that is in direct contact with the fixed surface, ie. the engine case. Any force applied that has it travel through the bearing elements can cause damage to the rollers, balls or races. I had an extreme example of that when trying to field service our hand grinders, (basically an air driven dremel) used to dress out our aerospace parts before distribution. These were relatively small, (which increases the price) and ceramic, (even more costly). Found even the very slight loading our fingers imparted when sliding the bearing onto the central shaft at room temp ensured their rather rapid destruction, usually within minutes. 100K tolerates no mistakes at all! To this day can only make assumptions on how this is accomplished during manufacture. Even after cleaning i sometimes preheat the case to ease installation. One trick I have used is to slide the bearing onto the crank, drop them loosely into the case and using an oven or welders mitt, hold the crank nose up while heating the case with a heat gun, (NEVER use any open flame!!!). This way allows me to also rotate the case to point the heat where needed. Gravity often will do the rest, but you must allow time to adequately preheat. If this does not allow for full seating I can then turn the case over and drop the crank nose down over a vice open enough for clearance. This allows me to use a steady and smooth pressure with a long rod or punch in the crank center to gently push the crank and bearing fully into place. The important factor is to ensure the crank remain straight and I sometimes partially reinstall the original front bearing to help that along. I remove the heat and allow the assembly to cool before removing the crank, then the old front bearing again. I really should make a video of this next time to ensure all that makes sense. Now onto the final point. That front bearing almost always contains some form of seal or shield to keep the bearing clean. From past experience shields are usually used in more temperature and mechanically stable environments where the protected bearing does not "Breathe". They are also best when lube is actively replenished. What that means is with the fact that regardless of 2 or 4-stroke, our engines change interior volume: what causes the "Breathing" I stated earlier. That tries to force an exchange of inside and outside air, and all the bad with the latter. This also happens as the engines and environments change temperature, so at the end of every flight, session and season the engine can be trading air from inside to outside. A shielded bearing, (with a -ZZ designation) simply will not hold back that exchange. So I try to never use them if favor of sealed and recommend the same to others. The can come double sealed, (-2RS designation) which is good as it keeps any manufacturer added lube clean till installation. I carefully remove the inner seal and leave the lube alone. This ensures good lube for startup and allows engine oil access to it for the rest of its life. The front bearings are usually not that difficult to install, just be sure the case is clean like recommended before. I often use the old bearing seated outside the new as a way to push the new into the case as it can place the force on the outer race. And to top it all off, everything just mentioned can be upset right from the start. The first few seconds of running can have more of an effect on how long they live than later treatment. You need to not only follow the rules already written, but proper prelube ensures no heavy metal-metal contact till the fuel borne lube makes it to the internals. I personally have been using a 50/50 mix of air tool oil and ATF, but really either alone should suffice. Don't be stingy, these are really not that expensive when compared to the cost of parts and your efforts. In fact. I just last month had to finally replenish my first liter of each that I can remember after 40+ YEARS!!!! For more accurate lubing I use the long nose syringes from Princess Auto. Again, I REALLY need to make a video of all this. visuals would correct for any confusion my sometimes inadequate descriptions convey. So, to conclude good quality bearings are NOT the entire picture. ps. I have used sealed bearings to fix other problems, as well. GMS and their Tower clones were notorious for poor mixture stability, (you could set them gobbing rich on the ground, yet they would inevitably lean out and quit in flight) and the ability to continue to run even with a finger over the carb inlet. I traced the problem to very poor quality control in both manufacture and components, (remember the subject of Pac Rim bearings?). The clearance between the crank and case bore was so bad the engines could literally draw air and fuel through the shielded front bearing and the gap between the two. Closing the throttle could not shut down the engines. Along with the front bearing being narrower than standard, meaning it had less strength to tolerate outside forces on the crank, even if relatively good dimensionally from the start, with the lack of lube reaching it due to air flow and added stress from gyroscopic and flight loads, it most definitely did not hold for long. My fix for this problem was a sealed front bearing. Could not redesign for a more standard width, but the mixture and run-on problems often disappeared immediately. I mention some where this was not the case, but found that was due to them being so new break-in was barely started so they were a bit cranky. |
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| 01-28-2024 01:01 AM | ||
| stegl |
Re: How to Change your Bearings When installing bearings I always press on the outside race ; never in the inside one as you can end up chipping the balls. A drill press and appropriate size socket works well. |
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| 01-27-2024 10:04 PM | ||
| Yser |
Re: How to Change your Bearings I’ve rebuilt many engines and found it’s best to replace with the same brand of bearings of the engine manufacturer. Chinese bearings have metallurgical and quality control issues, poor tolerances. Be careful of Chinese counterfeit bearings too, they are all over especially on eBay. |
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| 11-20-2021 06:54 AM | ||
| Rob_T |
Re: How to Change your Bearings Thank you for posting this. I am getting ready to change the bearings in my thunder tiger .46 and the video is extremely helpful. Cheers Rob |
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| 12-07-2019 12:56 PM | ||
| RevX |
Re: How to Change your Bearings Good information for bearing changes. Seen a few of these videos on youtube worth watching. |
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| 04-29-2018 11:48 AM | ||
| Rod Kelln |
Re: How to Change your Bearings Given the absence of a needle response, the first thing to do is clean the carburetor thoroughly. If you cannot get a rich setting, then there is fuel flow problem. Also, if you are not already using a low nitro content fuel, suggest changing to one. I had a Fox Quickie 500 engine that ran fine on 5% nitro, but at 15% it would overheat and quit running. Since you have overheated it, be sure to tighten the head bolts to an appropriate torque. Also check that the backplate is tight and that there are no issues with the muffler pressure to the tank, etc. |
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| 04-28-2018 10:04 PM | ||
| Digger1 |
Re: How to Change your Bearings Quote:
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| 09-21-2017 09:29 AM | ||
| Kl1952 |
Re: How to Change your Bearings Thanks ! and Thanks ! It is what I am looking source for my Saito FA72 bearings. |
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| 08-05-2017 09:12 AM | ||
| Rod Kelln |
Re: How to Change your Bearings There have been several comments about installing bearings but thought I would add one additional aspect about ensuring smooth running bearings. After installing the front and rear bearings and crankshaft, put on the prop drive washer and install a prop plus spinner nut. Spin the prop and see if it spins freely or if there appears to be any "stiffness" in the new bearings, and there often is, i.e., inherent preload. Regardless, warm the case with your heat gun and then give the spinner nut a hard rap with a block of wood or a mallet, and try spinning the prop again. Repeat as necessary until you have a free spinning prop. Then assemble the rest of the engine. |
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| 08-03-2017 09:17 AM | ||
| Rod Kelln |
Re: How to Change your Bearings Agree totally with Kopter that beating on the crankshaft to remove the prop drive washer from a collet type set up is a bad approach. All my pylon racing engines are collet type and I use a heavy duty battery terminal puller to "pop" off the prop drive washer. Princess Auto has this great tool for $13 CDN. No doubt you will find other uses for it as well. Once you have pulled the drive washer, simply slip off the collet and push out the crankshaft, but if it resists, then can use a block of wood and tap on the end, or, put on a spinner nut (to protect threads) and tap on the end of that directly. |
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