teluan

I have the back plate off my 4.6 AE (AKA .28 Pro) engine and giving it a good cleaning. I put WD40 in the crankcase from the open back plate end and it started to drip out the other side at the crankshaft/flywheel area. I take it that this means my bearings are bad or something as this would suggest no matter how well I seal the backplate I will have an air leak from the flywheel end.

Does everyone agree?

absolutemayhem

the front bearing is always going to leak. and unless it bad while your driving it, replace it.

teluan

Then why do people seal the back plate if the front bearing leaks anyways?

teluan

I found this tonight on You Tube. This guy talks like this is really bad but does not state what it should be like. No bubbles at all?

http://www.youtube.com/watch?v=KEYdy...eature=related

teluan

Then I found this on a bearing website. Click on the link and read the second paragraph

http://www.bocabearings.com/Issue5.aspx


If you cannot see it this is what is says:

HP ENGINE BEARINGS - HIGH PERFORMANCE!

It is normal for fuel to slightly leak out of the front bearing from the crankcase of a nitro engine because it is not a perfect seal there and the inside of the crankcase is pressurized. Other than that fuel should not leak out of your engine in any other place. So, not only must you have good seals in the top part of the cylinder - around the head gasket, the glow plug, and, of course, the piston itself - but you must also have good sealing in the lower part of the crankcase. This involves the seal on the backplate, on the front bearing housing and at the front bearing area of the crankshaft.

The solution is Boca Bearings High Performance Engine Bearing series. Designed with our exclusive 2RU rubber seal technology. The High Performance Series were created specifically to eliminate fuel leakage problems and to provide better compression in your engine. If you are experiencing the dreaded spray out of the front of your engine, HP bearings will substantially increase your over-all performance.

chookman46

Unless there is an issue with the performance of the engine I wouldn't worry about the bearing. It doesnt matter if you have the best seals in the world the bearing is still a slip fit on the crank and will leak anyway. Using Wd40 is just compounding the problem because it is very thin and actually a penetrant, if anything will leak out it will. A lot of onroad engines dont run any front bearing seals and only run metal shields, these engines run fine and have no problems.

teluan

Thanks chookman46! I am going to run the cleaned up engine tonight and will post results!

SLAYERDUDE

I agree, I wouldn't worry about what you are describing.
Keep an eye on the flywheel area after you run and if it's slinging fuel off the flywheel then I might start getting concerned.

automan_1954

You will find many opinions here, but if you want so profesional advice... REPLACE THE FRONT BEARING. Any time fuel leaks from the bearings the seal is shot, if wd40 leaked passed the front bearing seal with the engine apart it has to be pushing out fuel while running or sucking air in. If you want your engine to run right and not by ruined by an air leak that will make it run very lean when at more than half throttle you have to replace the bearing. While you have the crankshaft out, slide out the sleeve and put fangs on the side ports, put the V shaped cuts on the bottom of the port at the rear of the port that way the air and fuel will go toward the front of the engine and make the air/fuel mixture swirl giving you more power

Snook Man

I personaly have never seen a slightly used front bearing that did not leak to some extent.
Rule of thumb: if the bearing is leaking enough (a line of fuel slung around the inside of the chassis/body) to affect the tune it's time to replace the bearing.

absolutemayhem

the back plate doesnt really need to be sealed..just the carb does..

and the only bearing that i have that hasent leaked to this day..is the stock bearing on my GRP NINJA...it on gallon #5 with zero leaks anywhere.

teluan

I feel good!!! After a steep learning curve / nitro engine crash course I got my 4.6/.28 Pro installed in my MGT and it started first pull. I only ran it for about 15 seconds as it was late at night so I ran it in my garage to keep the sound down (fumes were strong). I am so thrilled with myself that I took apart my engine, cleaned it, sealed it, reinstalled it and ran it again after all this. I was worried that it would not work at all after all the fiddling I did. I am going to tune it tomorrow and see if I can get it to idle for half a tank. If it does, then I am going to see if i can run it around for a full tank. I have yet to get through a full tank. It usually runs great for 5 mins or so and then stalls. When this happens it is very hard to start again unless it sits for a while. This apparently means it is running too hot. I found my point and click temp gun so now I can actually measure the temperatures when I tune it tomorrow. The manual says it should run between 220 and 260. I will post another update letting you know.

In some ways I am hoping I can continue to use my 4.6 engine for a while longer and take back the .32 to save some money as the cost to repair my used MGT if including the new engine is as much as buying one brand new. No regrets as I have enjoyed learning how to repair and am more comfortable than ever with RC Nitro. On the other hand everything I hear about the .32 Axial suggests it is WAY more powerful than stock which is tempting to install even if I get the 4.6 totally up and running reliably. Would be a shame though to do this and come away being disappointed with the performance gain as I am already impressed with the 4.6 (I really hauls and I am having a hard time imagining even more power).

I will be in touch with an update.



BTW...I had a HELL of a time getting one of the engine mount screws out tonight. 3 trips to the hobby shop and 2 to the hardware store to drill the bugger out took well over 2 hours. Good news is I have all the tools to get stripped nut, bolts and screws in the future. I picked up a cheap gear puller to as I know I will need it to pull off the flywheel one day.

calvino

Side note, dont always tune from temp... it can be nice if you know your engine runs in a certain temp zone and its running hotter... you either have a leak or you are running lean. Other than that... just have fun with the thing really. If the engine you have now is enough power... stick with it until you get real good with it so you dont end up breaking more parts..... due to it. [8D] Hey I put after run oil into my engine sometimes if its sat for a *LONG* time to lube the parts up and if it sits in there it will slowly oooooze out of the bearing but thats to be expected because it cant seal itself 100%. Sure some seal better than others, but its not going to kill your engine at all

teluan

Thanks calvino for the reply!