CK1

My Feedback: (60)

I have been finding a lot of front seal (integral to bearing) leaks causing idle and transition issues . I have noticed this enough that the first test on any DLE with performance issues is a pressure test more specifically on the DLE 20 . Have any of you other engine Guru's found a reliable front bearing replacement for the ntn 6000ru bearing ? I have tried many different sealed bearings and only the RU bearings will reliably hold pressure. The NTN 6000ru bearing are scarce and pricey at 16.00 each .
Looking for a better source . Anyone ?
Or am I the only one pressure testing engines ?

Truckracer

My Feedback: (19)

If leaking pressure, I’d be just as worried about the rear bearing as the front. They are both sealed bearings and work together to retain case pressure.

CK1

My Feedback: (60)

While that is true it still remains that RU type bearings , be it the 6000 frt or 6001 rear , are expensive and not easily , affordably or quickly acquired.
I have run RS sealed and also open cage inner bearings with an RU outer bearing and been able to maintain pressure. So I feel the outer needs to be an RU regardless of inner . So far no brand of 6000 rs I have tried has held any pressure at all . Just looking for other tried and true options to the RU type bearing.

Truckracer

My Feedback: (19)

Are you keeping both seals in place? I might need some re-education as I’ve always thought the RS seals were better at holding pressure than the RU ones. I’ve never pressure tested a 20 but I have larger engines. Double seals were always necessary to retain pressure but even then, they won’t hold much pressure like a separate shaft seal would. I have disassembled engines where the front seal in the rear bearing had become dislodged and it was forced into the space between the two bearings. That engine wasn’t holding pressure and it wasn’t a Chinese engine.

CK1

My Feedback: (60)

I always thought the same as you that the rs seals were best but that doesn't seem to be the case any longer. I haven't removed any seals from any of the bearings . I heat the case enough to let the bearing drop in with a few light taps from the driver , so there is no seal contact or damage. I've tried 4 different brands of rs bearings and none have held any pressure at all . So far only ru and 2ru will hold . I guess I'll order up some ZZ bearings and check them out just for ****s and giggles . They just don't make them like they used to do they !

Truckracer

My Feedback: (19)

I wouldn't expect the ZZ bearings to even retain grease, much less pressure. Those are just metal shields and not seals at all. I haven't had any bearing seal problems on any of my Chinese engines, at lease enough that would affect performance, handling or reliability. I have tested DA engines that were having problems and they leaked like a screen door. Those were sent back DA under warranty and came back OK. I have no idea what brand of bearings they are using these days. I know some years back they had their issues also which I believe have long since been resolved.

I asked about retaining the double seals on the RS bearings as those seals will only hold pressure in one direction (if they work) so it takes both in place for a crankshaft bearing. You have me curious now! I have a couple of unemployed DLE engines here and will dig out the pressure tester and see how they hold pressure. Those are all just stock DLE bearings. I always test / inspect crank bearings on used engines but I haven't bought anything used in quite some time. I've never bought a used Chinese engine.

CK1

My Feedback: (60)

Just out of curiosity I looked up the suffix chart for bearings with regard to the seal design and the RS is supposed to have a tighter lip seal on the inner race than the RU style . The RU is supposed to be a non contact seal with regard to the inner race . This confirms what we both assumed should be the better sealed bearing . It doesn't explain why RU bearings seal better than RS . Still mystified !!! I ordered more bearings in the RS and RU types to try. I think some of the bearing mfg's have forgot what QC is all about , if they ever did know. Lol ... I'm locked on like a pitbull now .
I will find a bearing that works if have to wear out a crankcase to do it

Truckracer

My Feedback: (19)

Some years ago Ralph Cunningham use to recommend a certain brand of bearings with a certain colored seal ..... but sadly I no longer remember what that brand was. He always commented they were superior to other brands. He's still around but never comes here any more. You could call him for the info. Some years ago, I had factory installed main bearings fail in Brison, FPE and DA engines but never a problem with the Chinese engines people complain about so much. All were sealed bearings so the problem wasn't the oil being used which was always a popular oil at the time. The FPE and DA were repaired under warranty and I fixed the Brison myself using new old stock SKF 2RS bearings I found on Ebay. They worked perfectly.

CK1

My Feedback: (60)

I looked at all the NTN and other older 2RS bearings I have in stock for several of the older engines. Those older 2RS bearing seals look to fit tighter to the inner race than any of the recent 2RS RS bearings that I have procured lately and that applies to several different brands as well . Curious..

Truckracer

My Feedback: (19)

Spending most of my time at home these days left me looking for a project. I decided to pressure check (3) DLE engines I have that aren't currently in airframes. They include an older 30, a low run time 35 and a 3 season old 20. All of these engines are in good running condition. As is normal, I blocked off the carb and exhaust openings and installed a sparkplug. My pressure tap is in the carb block off plate. I pumped the pressure to 3 - 4 pounds and used gas line leak detector to inspect for leaks by the bubble method. The 30 and 35 were fairly leak free with me finding tiny leaks around the base gasket on the 35 that was easily resolved by tightening the base flange bolts a bit. There was also a tiny leak from behind the prop hub .... but very tiny. These two engine would leak pressure very slowly and then hold about 1 Lb for a longer period. I judged them as quite acceptable as far as leaks go. The 20 showed a bit of a leak from the front bearing area and in at least two places. To see better, I removed the prop hub. There were tiny leaks from between the crank and the inner bearing race, from the seal area and between the case and the outer race. Not big leaks but still they were leaks. There was no trace of oil in any of these areas. The pressure would leak down in a few seconds. Keep in mind, this engine ran just fine. I can't do anything about the seal leak w/o replacing the bearing but a tiny bit of green LocTite on the crank and case quickly resolved the leaks in those areas after it cured for a couple of days. Green works as it wicks into metal to metal joints much as thin CA wicks into glue joints. There is still a tiny leak from the seal but the 20 now holds some pressure for 30 seconds or so. Enough so that I will return it to service w/o worrying about it. Overall the results were much better than I expected, especially on the old 30 that has 10 seasons on it and the bearings are all original. The 30 tested better than the newer engines! I hadn't pressure tested an engine in some time and I probably wouldn't again soon unless I suspected a leak problem. No doubt about it, leaks in a 2 stroke gas engine can seriously affect performance but these three engines seem to be in pretty good condition in that area.

Regarding main bearing seals and especially on DLE engines, they use the NSK 600XDU bearings sourced from China and Japan. I had never seen that DU designation before so did some research. I see that is a propitiatory marking from NSK that designates a Buna rubber sealed, deep notch bearing. I couldn't find much in the way of technical info about them other than that. The seals do seem tighter than on the typical 2RS sealed bearings that we commonly use in RC applications.

Being bored, off to clean out my socks and underwear drawers now. The wife will be so pleased!

ahicks

My Feedback: (2)

It's not been an issue to date on my DLE engines, some of which are getting pretty old by DLE standards.