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OS 12CV Repair Parts

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Old 05-21-2018, 04:45 PM
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Mr.Alvaro
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Question OS 12CV Repair Parts

Hi everybody, me again .

Here is my current situation. I managed to restore my HPI NITRO RS4, Is up and running, just waiting for the back muffler so it will be entire original. The engine runs great, buy when restoring it, I found that the front and rear bearing are a little worn out, they are not as smooth as they are supposed to. I went through amazon and found the 2 bearings but the combined price is a little over $50. Also checking for other parts (piston, cylinder, connecting rod, crankshaft) the price goes up to nearly $180. So now here is my question, it is really worth to buy those parts to replace pretty much the whole engine when the time come or better forget about it use it until die and get another one, maybe a .15/.18? If the best option is the number 2, which engine do you guys recommend. I am planning on do some changes on the car and probably add a 2 speed transmission.

For extra info, I am using Torco Fuel Air 20% Oil, 25% Nitro. I didn't use the one for cars because on the engine manual it says fuel with at least 18% Oil. Also using new but old time stored Hobbypower Glow Plug N4.

Thanks for the help.
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Old 05-23-2018, 04:30 PM
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Originally Posted by Mr.Alvaro View Post
Hi everybody, me again .

Here is my current situation. I managed to restore my HPI NITRO RS4, Is up and running, just waiting for the back muffler so it will be entire original. The engine runs great, buy when restoring it, I found that the front and rear bearing are a little worn out, they are not as smooth as they are supposed to. I went through amazon and found the 2 bearings but the combined price is a little over $50. Also checking for other parts (piston, cylinder, connecting rod, crankshaft) the price goes up to nearly $180. So now here is my question, it is really worth to buy those parts to replace pretty much the whole engine when the time come or better forget about it use it until die and get another one, maybe a .15/.18? If the best option is the number 2, which engine do you guys recommend. I am planning on do some changes on the car and probably add a 2 speed transmission.

For extra info, I am using Torco Fuel Air 20% Oil, 25% Nitro. I didn't use the one for cars because on the engine manual it says fuel with at least 18% Oil. Also using new but old time stored Hobbypower Glow Plug N4.

Thanks for the help.
I’ve been busy and didn’t get to look for the parts we discussed via PM awhile back. I no longer have the parts; sorry.

As for your engine - its nowhere near worth restoring it. Parts are hard to find and usually expensive then too. Junk the engine when the time comes and replace it. I recommend Novarossi engines as they’re better quality than the “cheapies” and more competitively prices than they used to be, but you’d have to see what engine will fit your car. Most come with slide carbs and IIRC your RS4 engine will have a rotary carb.

As for your fuel - absolutely, without a doubt, DO NOT use fuel with 18-20% oil! It will cause you more grief with engine behavior and tuning than I can begin to describe. Use a fuel with 15-25% Nitro and 10-12% oil - of which is a castor/synthetic blend. This combined with a medium heat range glow plug gives good reliability, throttling, and performance.
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Old 05-23-2018, 07:47 PM
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Hi again 1QwkSport2.5r, sorry to hear that you don't have the parts anymore.

Yea I have been reading the forums and everybody mentions Novarossi as a pretty good engine but they don't offer rotary carbs :S. If I get one of those probably I will have to modified the car a little and use one of those cables (I don't know the exact name but I mean like the ones used on bicicles to operate brakes check the attached image) but probably is going to be a pain to make it reliable, maybe making some parts in Nylon with a 3D printer but mine doesn't arrive until late july.



Other option will be to install another of those servo arm against the top part of the chassis (next to the tank) and link it to the carb and the arm to the servo arm.



Regarding the fuel I managed to tune the engine, I was scared with the temps (trying to keep it under 250º F) and that made me waste a lot of time because of the car stalling etc, finally after I forgot about the temps and concentrate in the sound + smoke + amount of oil pouring out of the muffler I got it to work flawless (2 tanks one after the other, and just opening the throttle a little while turning the engine on after the first tank). Then the little devil on the shoulder asking for the engine temp, it was 308º F and the engine was still rich.

Just for the last question, what will be your second best choice of engine preferably with rotary carb?

Thanks for your time.
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Old 05-24-2018, 06:40 AM
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Rotary carb engines aren’t really made anymore, so I don’t have an answer on that.

As for fuel - high oil fuel will cause the engine to run hotter because it has to be run so lean to get clean performance. Regardless of what the manual says, do not use more than 12% oil for regular running. It will run much better and be much easier to tune. I guarantee that.

FWIW: OS specs to use 18% oil in their car engines, but it’s their scapegoat to get it if warranty claims. Racers use as low as 8% oil and don’t have engine failures due to the fuel.
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Old 05-24-2018, 09:34 AM
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Last night I stayed late looking for engines, I found that some SH engines have a rotary carb but the reviews are so splitted that I guess I will be modding my car when the time comes to replace the engine with the novarossi.

Thanks a lot for your time.
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Old 06-10-2018, 09:08 PM
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Hey 1QwkSport2.5r. Thanks a lot for your fuel recommendation. I took my Torco 22% Oil / 25% Nitro oil and got some methanol from them and mixed down to 12% Oil / 13.6% Nitro and it did wonders, temps went down. No more 20 minutes tunning, runing amazing.
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Old 06-11-2018, 07:10 PM
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Amen brother!!
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Old 07-10-2018, 07:27 AM
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Originally Posted by Mr.Alvaro View Post
Last night I stayed late looking for engines, I found that some SH engines have a rotary carb but the reviews are so splitted that I guess I will be modding my car when the time comes to replace the engine with the novarossi.

Thanks a lot for your time.
Don't disregard SH engines so fast. While it is true that the engines that come in cheap redcat rtrs are SH, the engines that come in Losi rtrs(dynamite) are SH as well. The very well respected LRP engines? SH. The fairly well regarded Mach series engines? SH. The big red, nosrams, sportwerks, all SH. I will not argue that SH are better than the more popular/expensive engines, but I will stand by my opinion of SH engines as easy to tune and a good value for the money. Yes I am a fan of SH engines. I say that as someone who owns over twenty of them, as well as a comparable about of novas, os, and pretty much everything else.
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Old 07-10-2018, 07:37 AM
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Btw, if you want I'll sell you another 12/15cv in good running condition with rotary carb and a rotostart backplate for $45 shipped.
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