khkim0102

Hi!

After running a few tanks, my HPI Savage suffers from oneway bearing's slipping. Even though I put a new bearing, it still happens.

After running a few tanks, the shaft of the engine becomes quite oily, and this causes bad slipping of the bearing. I don't run it too rich, and I am using Trinity 20% nitro fuel.

Isn't there any way to prevent oil's coming out, making the shaft oily? I am so frustrated with taking out the engine to clean up the bearing and the sahft and putting it back in so many time.

Thank you for your attention!

James

1QwkSport2.5r

First off, you'll never find an engine where the backplate bushing doesnt leak. The problem is with the starter shaft getting a glaze to it after even a single tank of fuel. The only remedy I've found to get you by for awhile is to pull the starter shaft out and lightly sand it with 400-600 grit sandpaper to break the glaze and give the bearing something to "grab" onto. I use 400 grit and hand-sand the long way of the starter shaft and after that I use a dremel with plastic bristle brush to scrub any grit grains away. Wipe down with fuel, denatured alcohol, or acetone and reinstall in the engine. Note: Only sand the shaft where the One-Way Clutch rides on. Sanding the shaft where the backplate bushing is can lead to wear on the bushing causing an air leak.

On my engines, the spin starter socket on the engine doesnt spin when the engine is running, so you have to imagine the one-way clutch is spinning around it at up to 30,000rpm+. After a short time the starter shaft gets polished so smooth the one-way cant "grab". The more scratches in the shaft, the more grip area there is.

khkim0102

Thank you very much for your tip!

I will do what you said! Hopefully, it will last for a while without slipping! I am very sick and tired of taking out the engine, cleaning out the bearing and the shaft, and putting it back so frequrntly.

Thank you again!

Foxy

Switching to a lower oil content fuel and/or leaning your tune a bit will help. A lot of people who run their engines slightly rich, supposedly in order to prolong engine life, have one-way problems due to the build up of excess unburnt fuel and oil.

1QwkSport2.5r

When I got my first Losi MT, I had all sorts of issues with the one-way clutch. I posted about it a number of years ago and a lot of replies included just what you said. Problem is, running the engine lean or on less oil didnt change the slipping problem. At that time, I was running store-bought fuel. One didnt cause more slippage than another. I went down to 8% oil and it still slipped.

At least for me, the one-way usually only slipped on first startup. After the engine ran a little, it wouldnt slip the rest of the day. Now that I mix my own fuel, I run 12% castor and dont have any slippage issues after sanding the starter shaft. To note; I have not had any one-way trouble on my smallblock engines..... only the big block engines with the internal one-way clutch.


Not to contradict you, Foxy.. I just know from my experience using less oil or leaner mixtures never cured the trouble for me. I did find the slippage was less (on the next cold start) if at the end of the day I ran the engine at a good rpm to empty the tank all the way instead of low throttle/idle to empty and kick it over with the starter until it wouldn't start. At idle and low rpm, there isnt a fast enough airflow/gas flow inside the crankcase to spew the extra oil out that collects. Running a faster rpm helped, but wasnt a "cure".

Just my experiences... no offense or bashing intended here.

The_Shark

ive had engines that NEVER had a issue with the one way, even when the backplate leaked like a sieve.
right now my t-maxx with a .15picco doesnt like to grab when i first start it, afterwords it grabs just fine. its the nature of the beast, nothing will be a 100% unless you use a bump box, but then you have to maintain the bump box.


i would start with steel wool/sandpaper, it should work for awhile atleast, just remember a well tuned and primed engine will take less time to start-reducing wear and tear on the pull start!

DaveG55

If your engine has an "external" OWB, as opposed to one inside the crankcase, then I know that some people have drilled a small access hole (the size of a "spray straw") and then use WD 40 or a cleaner of some kind to flush the OWB when it starts to slip.
Personally I've always had pretty good luck with the sanding the shaft method.

On the oil issue, sometimes it's not so much the amount of oil in the fuel so much as it's the particular oil/formulation that a fuel uses. I usually run O'Donell fuel and, even though it's oil content is not that much less than other oils, it seems to slip less.

Argess

If your engine has an external OWB, and the starter shaft has the inside disc with the tapered groove, you don't really need a OWB. You can take a nut of the same size, drill and tap for a set-screw through one of the flats, file a small flat on the starter shaft for the set-screw, and no more OWB issues.

Alternatively, you might get away with a small (thin) o-ring around the shaft, between the backplate and the OWB. Make sure it's not too tight a fit. This will only work on shafts that don't spin when the engine is running.

As far as keeping everything stock (which I do), I use the method described above. I clean the OWB with alcohol, scuff the shaft up a bit with fine emery cloth, and it seems to last a long time before I have to clean it again.

Make sure you check the OWB cage isn't cracked. Once this happens, you will have to replace it.

And I can't resist the opportunity to post my OWB pics and GIF ... LOL :

378

My Feedback: (4)

Some engines leak more oil than others. I got three gallons out of the original one-way for my 18 CV-RX before it started slipping. I'm also one of those guys who runs their engines on the rich side, and on top of that I use high oil fuels. 15-18% oil, somewhere in that area.

The_Shark

ofna force engines disengage the starter shaft from the crankshaft after the engine starts, really cool design, just a spring and peg inside the crankshaft. what a reliable engine those forces are, NEVER had a pull start issue.

yakfish

My Feedback: (27)

Yeah the Kyosho engines have a similar design. never have a PS issue with them either! One way bearing really are a pain in the butt. Thats why I run bump start engines now!

HerrSavage

I have experience with both HPI Rotostarts and Losi Spinstarts(lots), and the Losi backplate system has far, FAR fewer issues with OWB slippage. I have been running LST2's for nearly five years, and very, VERY rarely have had issues - if at all.. I think one Sportwerks .26 might have given me some issues a couple years back.. But the LRP Spec 3, Mach 427's, and Dynamite Big Red have all been flawless..

So anyway, I'm not sure if the shaft from a Losi Spinstart can reach in to the engine in a Savage - but if it does it would be worth a try IMO.. I always had headaches too with HPI Rotostart backplates..

1QwkSport2.5r

I've only had Traxxas and Losi, and the Losi's have been the problematic OWB trucks. I had one OWB crack on a pro .15 in my nitro sport, but otherwise the TRX engines have been very reliable. Losi on the other hand... Of the 3 Losi/Mach engines and 1 SH engine I've had, they all had OWB problems. From new/break-in, I'd get a gallon on them and then they'd start to slip here and there on a cold start. After the engine ran, they'd start fine.

Though it doesnt matter what brand, they all have faults at some point. Its the nature of the beast.