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Old 01-18-2009, 03:00 PM   #1
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Default HPI 5.9K Rotostart Issue

I got an HPI Savage XL with the 5.9K engine for Christmas. The engine has the Rotostart 2 assembly to start it. I broke the engine in, and have run about 12 tanks (including break in which took 10 tanks) through it. The engine was never run too lean, and always stayed below 250 degrees F for the two post-break-in tanks.

This afternoon, I attempted to start the engine with the Rotostart. The rotostart assembly would spin, but the engine would turn over once and then the assembly would keep spinning but the engine wouldn't engage again. I took off the exhaust pipe and watched the piston move once in the sleeve and then stop moving. If I took the glow plug out, the engine would turn over with the Rotostart as normal. There is no issue with the piston/sleeve, and the engine is not binding or flooding - the Rotostart assembly on the backplate simply spins but the engine does not.

Things I checked -
- engine not flooded
- glow plug is good
- rotostart battery fully charged and spinning powerfully
- took apart rotostart assembly on back of engine - the gears look brand new and are not stripped

Everything seems to be in working order. Could something else be slipping (does the engine with the rotostart have a one-way bearing)? I'm not sure what to look for. Any thoughts would be welcome. Thank you!
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Old 01-18-2009, 03:13 PM   #2
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seems to have something to do with the rotostart part on the engine. i would start by taking it off and cleaning the one way bearing. then go from there. it was the one way bearing in my lst2 that would always cause a problem like this.
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Old 01-18-2009, 03:18 PM   #3
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one-way bearing is cause of most problems with rotostart/pullstart
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Old 01-18-2009, 03:21 PM   #4
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Sounds like a one-way issue.
Roto starts eat those faster than the battery thats plugged into it.
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Old 01-18-2009, 03:21 PM   #5
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Quote:
Originally Posted by franklucas View Post
seems to have something to do with the rotostart part on the engine. i would start by taking it off and cleaning the one way bearing. then go from there. it was the one way bearing in my lst2 that would always cause a problem like this.
OK - I'm going to show my ignorance here but I don't have tons of experience with nitro cars just yet. Is the one-way bearing on the starting shaft, or do I have to get deeper into the engine to get to it? The instructions don't make that clear at all, and I can't find a part number associated with it. Thanks...
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Old 01-18-2009, 03:21 PM   #6
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Running rich leaves lots of oil inside the motor and to much oil in the one way bearing lets it slip and wont engage the shaft. Store your truck on a 45 degree angle with the rear end being higher. This lets the excess oil in the one way bearing drain, and it will work as it should. I am breaking in a 4.6 right now, 3 tanks and so far so good. Hope this helps.
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Old 01-18-2009, 03:30 PM   #7
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oneway bearing goes into the crankshaft so you have to remove the backplate.
it is part number 15294 so see yourself in the manual
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Old 01-18-2009, 03:33 PM   #8
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take the black plastic peice off of the engine and the back plate off of the engine i beleive the one way is on the metal shaft that goes through the back plate into the engine.
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Old 01-18-2009, 03:35 PM   #9
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this is a picture of it

http://www.hobbiesr.com/hpi/hpi-505/hpi1669.htm
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Old 01-18-2009, 03:53 PM   #10
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Thanks guys - I found it. It's inside of part 15294, the one-way is surrounded by the actual piece that mates with the rod and turns the engine over. I'll spray it out with some nitro cleaner and see if that de-greases it enough to get me back in business. If not, I will have to order a spare (or two).
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Old 01-18-2009, 04:46 PM   #11
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Cleaning it off really well with motor spray and reinstalling the piece seems to have done the trick. Got her started and did a few passes before calling it a night (since it's dark and the neighbors probably don't appreciate the noise on a Sunday evening). I'll run a few tanks through tomorrow, but looks like your tips did the trick.

Thanks! And I am storing it with the rear end raised so the oil doesn't collect again on the bearing.
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Old 03-27-2010, 03:30 PM   #12
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I'm having the same problem but my OWB looks very diff in the 5.9 no matter how clean I get the bearing it still slips. When i use a drill connected to a socket that fits the nut it turns over fine when i put the plastic part that the rotostart fits in it slips again. I have checked the gears in the plate nothing seems wrong..I am at a loss here.
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Old 03-28-2010, 08:08 PM   #13
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Only thread I have found about the OWB issue so can anyone give a suggestion or should I call HPI to have them help me thru it?
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