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-   -   HPI RS4 3 engine rebuild problems (https://www.rcuniverse.com/forum/rc-car-engines-272/11677833-hpi-rs4-3-engine-rebuild-problems.html)

Ksred 04-23-2020 10:28 PM

HPI RS4 3 engine rebuild problems
 
I have neglected my RS4 3 for a long time, and the engine is frozen. So I took it apart to see what was up. There was some gunk in there, but not a lot. For the most part the inside of the engine was pretty clean.

But it still won't turn. I pulled the cylinder and piston out and that seems to be the problem. The piston is very tight and simply will not go above the halfway point, more or less. I managed to get it removed from the cylinder and there is no obvious issue. The sides of the piston and the cylinder walls are shiny and smooth, no gunk in there, nothing I can feel on either surface. But even after cleaning them up real good and wiping everything down, piston gets stuck halfway up. Only thing I can think of is the piston and/or cylinder is slightly warped. If so I can't feel it, and aside from sitting in my closet for a long time it was never abused. It was running fine the last time I played with it.

I looked for replacement parts and that's a laugh. Been out of production for quite some time of course.

The engine I have is the nitro star 15fe. The one with the purple heat sink. Does anyone have a suggestion on what else I can try to get it working? And if not, what options are there to replace the whole engine? It looks like the current nitro star T3.0 is the same type of engine, but I couldn't find anyone who had those in stock either.

Thanks for any advice you guys can give.

tl671 04-24-2020 10:44 AM

SH makes the HPI engines, maybe you can check them for parts.

Otherwise any .12 or .15 engine from any manufacturer (OS, Novarossi, Picco, SH, Traxxas, etc) is a drop in solution.
I have a Picco .12 in my RS4 2 kit.
And is a MUCH stronger performer than the original motor.
But then just about anything would be.

Ksred 04-24-2020 11:18 AM


Originally Posted by tl671 (Post 12599581)
SH makes the HPI engines, maybe you can check them for parts.

Otherwise any .12 or .15 engine from any manufacturer (OS, Novarossi, Picco, SH, Traxxas, etc) is a drop in solution.
I have a Picco .12 in my RS4 2 kit.
And is a MUCH stronger performer than the original motor.
But then just about anything would be.

Ok, thank you. I wondered about the other brands out there, it looked like they all made a similar type of engine. I just assumed they were proprietary in some way and I had to get an HPI engine.

tl671 04-24-2020 11:33 AM

You're welcome.
They all use the same mounting dimensions.
Otherwise, they would only be able to sell engines to owners of one brand of vehicle.
Most R/C vehicle manufacturers don't make their own engines anyway.
Any "small block" will fit. I've been out of the game a while myself, and went down a rabbit hole since I answered you.
There are now engines in the .12 - .20 (3.3 Traxxas) range that will bolt right in.
If you're looking for utmost performance, I recommend something non-pull start.
But then you have to buy a starter box too.
If you're just bashing/tearing around parking lots, pull start is fine.

1QwkSport2.5r 04-24-2020 12:29 PM

SH doesn’t make the 15FE as far as I am aware. To my knowledge they were made by Toki in Japan. I have a .15FE and it’s got “Made in Japan” cast into the case. SH engines have never been made in Japan.

That said, the 15FE is not worth putting any effort into fixing. Replace it. The kicker is if the RS4 engine mounts from under the chassis or not. If it does, you’ll need to change the engine mount to fit an engine with a standard mounting using the side mounting lugs.

Ksred 04-24-2020 01:36 PM


Originally Posted by 1QwkSport2.5r (Post 12599602)
SH doesn’t make the 15FE as far as I am aware. To my knowledge they were made by Toki in Japan. I have a .15FE and it’s got “Made in Japan” cast into the case. SH engines have never been made in Japan.

That said, the 15FE is not worth putting any effort into fixing. Replace it. The kicker is if the RS4 engine mounts from under the chassis or not. If it does, you’ll need to change the engine mount to fit an engine with a standard mounting using the side mounting lugs.

It does mount from under the chassis. Four little screws into the bottom of the engine, no separate mount. I assume mounting kits are out there to adapt to a side mount.

And yeah, engine does have made in Japan stamped on it.

Ksred 04-24-2020 05:50 PM

I'm thinking maybe something like this.

-- Ack, can't post URLs yet. Looked at the Novarossi engines on their US website. The Legend .12S is on sale for $179, looks like a nice engine.

I'll check out the Picco line as well. I did find a few adapters that should fit my chassis so I can mount a normal engine.

My exhaust comes out the front right side, pipe sticks out in front of the engine and engine was side exhaust. I assume there's a way to adapt a rear exhaust engine to work in that configuration?

D3MON 04-27-2020 10:27 PM

is your flywheel keyed? or is it the collet type? if its the collet type really any SG type engine should fit, even something like the G3.0, (these were used on the later version of the RS4-3) or a long threaded crank engine. (short threaded wont work as there isnt enough threads to engage the pilot shaft/nut because of how thick the flywheel is.)
the main issue with the 15FE is that they are single needle carbs, unless yours was swapped out for the O.S. 10E carb.
they are pretty decent engines, but i wouldnt sink alot of money into one unless you have a reason.
engine mounts are probably going to be a pain to find, but doable.
and you are positive its not pinch that is causing the issue? i dont think i have ever heard of a sleeve/piston warping except for very extraneous circumstances, like overheating way past 300F. or mechanical failure.
if you pre-heat the engine to 200F with a heat gun, will it turn over then?

Ksred 04-28-2020 04:54 PM


Originally Posted by D3MON (Post 12600367)
is your flywheel keyed? or is it the collet type? if its the collet type really any SG type engine should fit, even something like the G3.0, (these were used on the later version of the RS4-3) or a long threaded crank engine. (short threaded wont work as there isnt enough threads to engage the pilot shaft/nut because of how thick the flywheel is.)

It uses a collet, so all good there.


engine mounts are probably going to be a pain to find, but doable.
I found a couple I think will work. The simplest are just a pair of spacers with longer screws. My chassis has a bunch of different spaced holes drilled around the engine mount area, so I believe just about any type of mount will fit.


and you are positive its not pinch that is causing the issue? i dont think i have ever heard of a sleeve/piston warping except for very extraneous circumstances, like overheating way past 300F. or mechanical failure.
if you pre-heat the engine to 200F with a heat gun, will it turn over then?
I'll try heating it up first, but should that be necessary just to get it to move? Before I tore it apart you could not pull the starting cord at all. Once I had the back of the engine off and could see the connecting rod, I could spin the shaft by hand the wrong way, pulling the rod down, but as soon as it got to the halfway point going back up the piston would bind up. Once I took the heatsink and plug off I could spin the shaft all the way around, but only because the sleeve could move up as well.

With the sleeve and piston removed and cleaned up, I can insert the piston from the bottom but it's very tight even there. When the top of the piston gets maybe a bit past the halfway point of the sleeve it's stuck fast. No way will it go anywhere near high enough to let the crankshaft turn a complete revolution when it's all assembled. No obvious damage to the sleeve or piston, and it was never abused. I only ran it maybe a dozen times, and none of that was racing. Just messing around in a parking lot, hardly any WOT to speak of.


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