OWB Busted...For Good!

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THE JUDGE

THE JUDGE

Well-Known Member
Messages
470
Location
Colorado
This weekend, while attempting to beat on my Savage, the OWB started slipping to the point where the rotostart would just spin and the one-way wouldn't grab at all. Cleaning was no use either, the rollers were getting loose. So I looked on Ebay for a replacement, and found this kit to eliminate the OWB entirely:

http://cgi.ebay.com/hpi-4-6-oneway-...ryZ44028QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

I also noticed that when I turned the flywheel with the rotostart gear removed from the engine, the shaft coming out the back didn't rotate, probably due to the friction of the o-ring behind the backplate. Which means the OWB does nothing while the engine is running anyway. I figure for the extra 5 bucks or so, this should be a strong and permanent solution....

However, I have been wrong more than (many more times than) once...Does anyone have this, or know why it would be a bad idea? (I ordered one anyway...$20 isn't too big a cash gamble)

Thanks
Greg
 
look and sound like a big hasle for a small fix lol, sounds like it should work though!!!

i hate my roto start wanna trade for a pullstart??? or anyone else for that matter
 
stang_racer said:
look and sound like a big hasle for a small fix lol, sounds like it should work though!!!

i hate my roto start wanna trade for a pullstart??? or anyone else for that matter
Click to expand...

Big hassle? Nah...it's only 4 more screws than replacing the OWB. :)

And I love my rotostart...Power tools FTW!
 
oh ok kool!!! hope it turns out well for you!!! i second that^^
 
I'm fairly sure there have been threads on this before and it has been tested. Not too sure what the out cone was but I think they went back to a one way.
 
MTBikerTim said:
I'm fairly sure there have been threads on this before and it has been tested. Not too sure what the out cone was but I think they went back to a one way.
Click to expand...

Really? I tried searching, maybe I used the wrong search terms. Now you've got me wondering...I better keep searching to find out what the problem was. From what I have witnessed, I can see no use for the one-way bearing-on the F4.6, the shaft the bearing sits on actually serves as a one-way. Perhaps I'm missing something...

Tim, you don't happen to remember who else ran one of these?
 
i wouldnt use that a one way is a one way for a reason, these engines backfire. i know my pullstart yanks itself inside the housing. id jsut stick to one ways, they make a grease specifically for one ways i picked up like 5 years ago, havnt seen it sinc tho. stuff is good tho even fi the bearing doesnt grab nemore u spread this stuff on the rollers and the bearings works like new again
 
Hey drivefast. I have that on my engine and it works great. I broke 4 OWB's before I found this. Like you said the starting shaft only turns when you are starting the engine, thats what the spring and pin in the con rod is for. The only thing you have to be careful with is that the OWB is the weak point. This eliminates that so the stress is transferred to the roto start plate. I also switched to a pull start and its been much better for me. With the roto start you cant feel if the engine is flooded like you can with the pull start.
I had emailed HPI customer support before I bought it and they didnt have a problem with it and even told me to let them know how it worked out.
If you keep breaking OWB's I would recommend this. The worse that can happen is you just remove it and put the old shaft back in, no harm done.
Hope this was helpful
 
I can see how the one way could be useful with a pull-start, because it would help it rewind, and for the reason stated above. With a rotostart however, there is nothing to get wound/bound up. Just two gears.

Regardless, anyone who has an external OWB can check this themselves...Turn the flywheel by hand with the rotostart cover off. If the O-ring sealing the rear shaft is at all snug, the shaft will just sit there while the crank spins. The spring-loaded pin at the crank acts as the one-way.

Either way, I'll tell you all about how it does after it gets here, for better or worse. I'm not trying to start anything, just going off of what I saw on my motor. If I'm way off base, so be it...I can always go back to the OWB, or worst(best?)-case scenario...a new motor!
Cheers :beer:
 
I was typing while you posted that, Keith...whoops.

Thanks for replying, you confirmed my suspicions! :resp: Not that I wasn't going to do it anyway, but I feel a lot better about it now.

Thanks for everyone's input, I'll post pics and whatnot when it arrives!

Greg
 
Drivefast just be careful with this if you stick with the rotostart. Like I said the OWB is the weak point. With this, is the engine floods or binds for any reason you will crack the roto start case..I switched over to the pull start with this replacement and so far so good.
Anytime bud. Let us know how it works out.
 
Keithv said:
Drivefast just be careful with this if you stick with the rotostart. Like I said the OWB is the weak point. With this, is the engine floods or binds for any reason you will crack the roto start case..I switched over to the pull start with this replacement and so far so good.
Click to expand...

Understood. I'll keep that in mind, thanks! I may not have a choice if I ever get better TVPs in the future.

Perhaps it would be wise to loosen the glowplug when I start it, huh?
 
My kit showed up today in the mail...

owbkit002je4.jpg

owbkit003ut8.jpg


Here is the end if it, compared to the stock shaft on the left. The new one has a more gradual ramp where the little pin engages, that's a good thing!
owbkit005lx9.jpg


There's nothing to the installation. In fact, the only paperwork simply said to make sure and Loctite the set screw. I sure did that! I also eyeballed the depth of the nut on the shaft so it engaged the rotostart gear the same as the OWB did.
owbkit001vp3.jpg

owbkit006it6.jpg

owbkit004su2.jpg


I'm going to try and run the truck this weekend, weather/time permitting. If this gives me any trouble, I'll be sure to report it.

Thanks again for the caution, Keith-I got an extra one of those little spring-loaded pins just in case.

-Greg
 
Keithv said:
Good luck with it.
Whats that sticking out of the exhaust port?
Click to expand...

Oh, that's my super-top-end shorty outlaw exhaust system!:drunk:








J/K...It's a vacuum cap I flipped around to seal up the port. I didn't even think about that until you mentioned it.
 
Well, I took the truck out today and ran a couple of tanks through it. Things didn't end too well...

After I was done running it, i noticed the rotostart backplate was hanging off of the motor my the lower right screw. I looked closer, and the top right screw was missing, and the lower left corner of the aluminum backplate was broken off at the screw hole. I think this was actually my fault-the whole plastic rotostart plate looks perfect, as does the upper right screw hole. Looks like I forgot to Loctite those screws last night and two backed out after the first time I started the engine, the upper right one all the way. Sigh...:duh:

One other thing though, the OWB kit's nut was sliding back and forth on the shaft. I had cranked down that screw pretty well, and the set screw was still Loctited and had not really backed off. It still even spun the motor no problem. I have an easy fix for this-I'll just grind a tiny divot on the flat of the shaft and that'll be that.

Even though I don't really blame the rotostart for this, I would have noticed the screws backing out if I had a pull-start. Score one for Keithv, I'm considering ditching the roto at this point.

First I need a new backplate...
And my front bearing is starting to leak...
And my cheap-a$$ XTM Ebay steering servo is starting to crap out...
And my fiber disc brakes are chunking off...
:$broke: :$broke: :$broke:

Today's bash session really put a hurting on the Savy. Funny thing though, not a single part that took any impacts was damaged at all. I still love this thing!
 
Well at least you had a good bash day!
I remember seeing a roto-start back plate that was made out of metal and also was attached with 4 bolts instead of 3 but for the life of me I cant find where I saw it! Darn Internet! I will keep looking for it as I did want to try it myself because I never liked the plastic 3 bolt design.
Dave
 
Pineapple said:
Well at least you had a good bash day!
I remember seeing a roto-start back plate that was made out of metal and also was attached with 4 bolts instead of 3 but for the life of me I cant find where I saw it! Darn Internet! I will keep looking for it as I did want to try it myself because I never liked the plastic 3 bolt design.
Dave
Click to expand...

Reeeeally...I like the idea of that. I may search for one myself.

Believe it or not, though, the rotostart plate is still mint...The plate behind it is busted. I hope it's the same as the one on the F4.1, that should make it easier to find.
 
Sorry to heat that drivefast. I've cracked the screw holes on 3 back plates. Thats why I switched to the pull start. I've spoken to HPI about it too and suggested making the backplate larger so the screws arent so close to the edge. Changing the position of the roto start to allow it to use all 4 screws to mount would help too, Hopefully someone over at HPI is listening.
I'm not sure why the nut would be moving on the shaft. Mine hasn't budged since I set it.
I cant believe your front bearing is leaking already. How many gallons do you have on that engine?
Yes, the F4.1 backplate fits the F4.6
I think TigerDrive might make a roto start that would use 4 screws, I'm trying to look it up now. Ill let you know what I find.
 
Thanks for the condolences, Keith. I'm looking at F4.1 coverplates on Ebay right now. Once that's located, I'll re-consider my options. I've heard nothing but good things about the TigerDrives.

I don't know what to say about the nut moving on the shaft-there was a lot of fuel/oil in there after 2 tanks, & although it was sliding in and out, the set screw was still Loctited to the point where it took some effort to remove the screw. I already put a divot on the shaft where the setscrew goes with my Dremel, so I'm not concerned about that anymore.

My F4.6 only has about 2 gallons through it, and after closer inspection, the carb appears to be leaking right in the front, and running straight down the nose to the bearing and then onto the engine mount, which confused me (obviously). I'll see about sealing that up, but if this motor gives me anymore trouble, I'll have to start thinking about an LRP or somethin'...As it is, I have enough to order, considering I already blew the dough for a bunch of FLM stuff yesterday. :nutshot:
 
Well good luck. I just got my LRP today from Slapmafro!. I cant wait to get it installed and running.
 
^^^Yep, I saw that one too today. I hope I never have to buy any roto parts again, but if I do, that's the next cover for me.

Dude, thanks for thinking of me though! :resp:

Funny how this thread came back up today...I just got my new backplate ($3.50 on Fleabay!), and as I'm reading this, I'm putting it together so I can bash the stock TVPs one more time.
 
Last edited by a moderator:
big worm said:
the roto plate from an ofna force 21/28/32...will work on the s-25/f4.1/f4.6 and it has 4 screws
Click to expand...

Nice find there big worm! :resp:

This must be it, Ofna#50010:
st-ss-50010.jpg


I'll have to remember this if I break another backplate...assuming the rotostart will clear. So far though, things have been trouble-free with the new backplate. Time will tell...

Thanks for the info! :motorcycle:
 
In Lucy voice from Charlie Brown-"THATS IT!!!".
Thanks Worm that was the other one I saw.
Dave
 
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