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Nickel80

RC Newbie
Messages
6
Reaction score
1
Location
New york
RC Driving Style
  1. Bashing
  2. Racing
Hi everyone, I’m new to the forum and new to nitro but not new to RC cars; I have a few electric cars that I mess with.

I recently bought a pre-owned HPI Savage X 4.6 for my son. It started and ran great until recently. The other day the brakes failed and it rolled quickly into a parked car tire, loosening the exhaust and all...loud. Further inspection showed it took some teeth out of the spur gear but still drivable. I adjusted the brakes to be more firm.

Then, I felt it was running too rich because I was going through a tank every 6-7 min. I adjusted the tune and drove around. It felt sluggish and the brakes failed again and noticed a broken brake plate on the ground; put it away for the night.

Just today I tried starting it and wouldn’t turn over with the roto start gun. So I used my deWalt cordless driver (bad idea). It still wasn’t starting but heard a clanging noise. Then suddenly the ball at the end of the roto start shaft broke off! The engine seemed fine to turn over (but not start) I don’t understand what happened. I was able to cut that piece off and file down the hex end to fit back into the roto start in the truck. It started right up. It died shortly after because my idle was too low from messing with the tune. I tried starting again and the roto start in the truck just kept spinning; a different sound than before. It appears there is a small crack in a copper/brass piece on the shaft just before the clutch bell.

What did I do to this poor truck? So upset. Did I strip my gears in the roto start system? Did I ruin my clutch bell? I’m not sure what to fix or what to replace. Can a bad tune affect starting? As in, make it so hard to crank over that it sheered off the roto start shaft end? Please help, I’m so lost.

This is a terrible opening post but hoping someone can share some advice. Feel bad since it’s my 10yr old son’s truck and just haven’t had any luck with it. Thanks
 
id recommend posting pictures about the objects in question. and may need some dissasembly to inspect and determine what is going on.
 
Welcome to RCT!

Getting into nitro at first can be very frustrating and has a fairly big learning curve. Hang in there, it's worth it in my opinion. I'm not on here as much as I used to be but I will try to help you out as much as I can. Now lets see if we decipher few of the issues.

First off let's talk about the tune. On a nitro, the tune is everything. If it's off it won't start easy, run well and pretty much ruin your experience. We used to have a good "this problem - do that" tuning chart here but my link to it doesn't work any more. You can do some research on tuning then when you get running again you can ask about a specific problem if you have one.

Next, the roto start. Most usually the problem with the roto-start system is a the one-way bearing inside the back plate gets oily and it sticks and won't grab to turn the motor over like it is supposed to. The tune can affect this too, especially running rich. You can remove the back plate, clean the bearing with nitro cleaner or I use brake cleaner. There are some gears in there too and I have broken them so you can check them out while it's apart. The sheared end of your starter wand indicates you probably hydro-locked the motor.

Finally let's talk brakes. It's been a long time since I looked at this truck but from my memory there are a couple of issues. One is linkage and the other is the servo. The factory servo for the throttle/brakes is very weak. I suggest upgrading it. I upgraded my steering servo then used the old steering servo for the brakes first then later a new one. The linkage needs a few mods that eliminates the spring loaded servo arm and re-routes the linkage more directly. also a spring dampner/adjuster that I eliminated and replaced with piece of fuel line. I had a post on that too but it's another post that my link doesn't work for. Does your truck have the dual disc brake set up? My truck is an older Savage 25 and still only has the single disc. With the mods it stops incredibly well. You can research a bit and find the info or if you need more help I will find/get more details to help you.

What part fell off? Some pics for some of this tuff helps a lot too. Hopefully this helps some. If you have more questions post them in the appropriate forums

Found a pic of the completed linkage mod.
 
Last edited:
mod-installed.JPG
 
Welcome to RCT! Not much to add to what Racer said. Need pics/video :)
 
Thank you so much Racer and everyone else! It’s nice to see this support.

My savage is a 2 disc setup, 1 of my discs broke in half which is what I found on the ground. I didn’t realize at first which is why it didn’t stop when I needed it to...created too much slack in the system. The brake issue is all on me as stock, it stopped ok but wanted it to stop better. I too read online about the fuel line mod. My issue is I replaced the spring completely with the fuel line. Stopped on a dime but I guess it put way too much pressure on the braking system and pads.

In terms of the other issues, I will post pics and/or vids later today. I was thinking the same about hydro locking however I don’t think I damaged the motor because if I spin the clutch bell gear by hand I can still feel the compression in the engine. Hopefully it’s ok.
 
Probably cracked the one way bearing, I would not use a power drill, the problem is when the engine gets too much fuel in it and it's hydrolocked, the piston will stop, and things will break.
 
Thanks all. Please see video attached.
 
The crack you are seeing is the collar for the fly wheel. It taper locks the flywheel in place on the crankshaft. No issues unless the flywheel came loose. I saw the engine make a couple of attempts to turn with the roto start so I think it is just the one-way bearing inside the back plate. Check the manual, page 32. https://www.rcdocuments.com/documents/HPI_Savage_X_Manual.pdf
 
I think what you show is the flywheel collet which does have the gap. I suspect, your flywheel maybe loose, but I could be wrong. It could still be your OWB. It will be better to take out the engine and check.
 
Got it! Thanks everyone! Very helpful. I’ll try to pull it apart when I have time this week and report back.

Hope you all had a nice Memorial holiday weekend. (US residents) :)
 
It sounds like the rotostart gear ,but the flywheel is loose as well ,so there for there is
no counter balance weight to help start the engine!

An abrupt stop could have caused the flywheel to loosen up ,maybe something
had jammed up the crankshaft from the starter when it was running!..:cool:
 
Hi all! Haven’t been on in a while…busy lately. I wanted to say thank you for all the advice. As Racer mentioned it seems I lucked out and there was some oil that got on the shaft and the bearing in the roto start system. I took everything apart, cleaned off the excess oil and re-tightened the 2 small screws that secure the bearing onto the shaft. Works great now and started right up!

A few things I’ve learned:
-Don’t use an impact gun on the roto start system, if the engine is flooded the impact gun will win and break engine, gears, roto startetc

-If truck is flooded when starting, loosen glow plug a bit to relieve pressure before trying to re-start motor again.

-check and re-check gear mesh with piece of folded paper method. Apparently when I put the truck back together I thought I had the right mesh, seemed tight but I didn’t. My spur gear is now shot. No big deal though as I planned to replace it anyway because I busted some teeth when I hit a parked car tire a while ago due to my brakes failing.

I know what to do now and have brakes, a muffler gasket (found it was torn) and some blue loctite on order. Thx again!
 
Hi all! Haven’t been on in a while…busy lately. I wanted to say thank you for all the advice. As Racer mentioned it seems I lucked out and there was some oil that got on the shaft and the bearing in the roto start system. I took everything apart, cleaned off the excess oil and re-tightened the 2 small screws that secure the bearing onto the shaft. Works great now and started right up!

A few things I’ve learned:
-Don’t use an impact gun on the roto start system, if the engine is flooded the impact gun will win and break engine, gears, roto startetc

-If truck is flooded when starting, loosen glow plug a bit to relieve pressure before trying to re-start motor again.

-check and re-check gear mesh with piece of folded paper method. Apparently when I put the truck back together I thought I had the right mesh, seemed tight but I didn’t. My spur gear is now shot. No big deal though as I planned to replace it anyway because I busted some teeth when I hit a parked car tire a while ago due to my brakes failing.

I know what to do now and have brakes, a muffler gasket (found it was torn) and some blue loctite on order. Thx again!
Sounds like you got it under control :)
 
All is under control and almost finished tuning.

I know there’s a lot to it but this is what I’m dealing with now.

idle
The truck still moves a bit on idle. I have the controller trim in the middle point (0) and adjusted the throttle linkage arm to ensure ~1mm of gap when I apply the brake. I did slight fine adjustments to the idle screw. Starts up perfect but rolls a bit.

Not sure what to do. If I make the throttle linkage longer, it stalls when I hit the brake. When I adjust the idle screw, it doesn’t appear to do too much more. Now, I can adjust the controller trim but that would be just applying more brake which I don’t want. Any ideas?

low throttle
Works great! Wheelies and blows just a bit of blue smoke.

high throttle
Feels like it’s accelerating but still feels held back, adjusted the transmission to see the 2nd gear shift when it should.

This is strange though. When driving under constant mid range throttle, it sounds like it’s bogging/choppy. Under full throttle it smooths out. Does this mean my high or low throttle is still too rich? Or am I getting lean?

thx all
 
Welcome to the crazy mad house of RC fun bud
 
Sound like you want to lean the low speed needle a little bit 1/8 turn at a time to improve your response. To help idle, as you already do your best so it does not die, you may want to open the high speed needle a bit to give it a bit more fuel to improve your idle.
 

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