How To: Ofna 250cc Mid Tank Mod

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Divey1130

RCTalk Rookie
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Location
San Diego
RC Driving Style
  1. Bashing
  2. Racing
I notice a lot of people always have questions about the "half tank lean" on the savage and I wanted to share with you what I did to resolve this problem. I myself had the same issue on my XL and hated to have to either run rich at the begining or keep filling up the tank. It's easy to do any of these but in my case I wanted to be able to drive with a whole tank and not worry about the leaing issue as well as longer run time. With the 250cc tank you get about 8-12 minutes more of run time (depending on driving conditions) versus the stock 160cc tank. I am aware that new era makes a tank for the half tank lean but now you just sacrificed your run time by a lot and that's what I did not want to do. So I will show you how to do a Ofna 250cc mid tank lean mod on a regular tvp. I have the XL but it is the same on the others. I have already posted this on a savage forum so I'll copy and paste here and update whats needed. I'm going to try to give as much detail as I can for future reference for other members so sorry if this is long.
Ofna Mid Tank Mod Parts:Ofna Fuel Tank 1/7 Scale OFN19504
Ofna 250cc Fuel Tank Mounts 87504
FLM Servo Mounts FLM46000
FLM Servo Plate FLM45500
RPM Receiver Box 80052
HPI Nitro Rush Bumper Set A349
HPI Shock Parts/ Rod End Set 85050
Robitronic Alum Servo Arm R17003
Ofna Linkage Sliders OFN10704
Ofna Linkage Kit OFN10724
Ofna Alum Servo Arm OFN 10733

The very first thing I had to do was make a platform out of pvc to work off of.
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Now it's time for the build. I first started by mounting the servo plate.
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Then I had to fugure a way out to mount the tank using the mounts made for that tank. This was the tricky part because the tank mounts were on the very front and back and when fitted on the plate it extended past any point to mount it. I used some 2mm alum and make some extensions to be able to mount the mounting post. I then bolted it down in existing holes in the servo plate. As you can see I had to notch the rear plate to fit in between the shock tower.
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Then fitted the tank on the mounts and what a perfect fit it was.
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Then I had to figure a way out to mount the steering servo. I tried various locations for it and ended up making a plate (2mm alum) for it so I could mount the servo mounts to. While I had this apart I put in bearings in place of the plastic bushing in the steering post. I then mounted the servo and tried to hook up the steering but noticed that the servo arm was to short. I was unaware of this so a trip to the hobby shop and picked up one. (This one was the only longest one they had) Then the darn link from the arm to the steering post was to short and I noticed that there was a lot a flex in it. So I used some shock rod ends and cut a long screw in half and whola, I had a stronger adjustable link. This setup worked great and I’m very happy with it. Here are some pictures of this.
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Now time to relocate the throttle/brake servo. Again I made a plate and mounted the servo mounts with the servo. I was initially only going to make a plate for half of the way but then decided to go all the way just because the tvp was cut down on this side for the stock fuel tank. I left the whole piece more for protection and I liked the way it looked. I’m still waiting for the linkage and alum servo arm so that will be installed later. Here are a couple pictures.
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Next page


Now time for the battery box and receiver box. Pretty easy on these. Drilled a hole in the center of both boxes and shock towers and mounted the boxes. The only thing I did not like was the battery box. The battery fit but it is a very tight fit. Barely had enough room to mount the on/off switch and the excess wire. Here are a couple pictures.
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I still have some finishing up to do so I will post the final product when finished. Here are a couple things I added while doing the mod: Wheelie Bar
Big Joe’s mounted on Axial 8 Spoke
All new bearings entire truck
Hex screws entire truck
17mm hex hubs
Skid plate (waiting for FLM mounts)
Lowered shocks ¾” for stability plus 30wt front/rear
14 tooth CB for larger wheels
Bulletproof diffs front/rear with 30,000wt
FLM Motor mount
Here are some pictures of them.
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This is what my work area looks like after a couple days.
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Well I got the throttle/brake linkage together which took some thinking. What a pain in the butt that was to figure out. Apart then take apart and over and over until I got this. I am still waiting for the skid plate mounts and the alum servo arm for the t/b servo. Other than running the wires and fabbing a plate for the motor guard it should be done. Probaly by tomorrow I should be able to get it going and post a vid. Suggestions or comments and the linkage is welcome. Thanks for looking. Terry
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Well finally got my mounts for the skid plate and my alum servo arm for the t/b servo. I am all done now. What a fun project it was. I think for christmas I will be getting the FLM tvp's and a couple other little things. The only thing left that I would want is a 2.4 radio and a new motor. But with my wife not working the motor will have to come in time. I will run the 5.9 til it blows. Here are the rest of the pictures finished.

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Well that was all of it done with the stock tvp’s. Now here are a couple pictures with the FLM LCG tvp’s. I did change a couple things around as you can see in the pictures. Mine has changed by getting FLM LCG TVP's which make the 250cc ofna tank mod easier and the servo relocation easier because the tvp's are set up for this. And here is a picture of it now:
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The first picture is the relocation of the reciever box using a rpm boc mounted on the side, the next picture is the relocation of the battery box using a hellfire battery box, the next picture is the relocation of the throttle/brake servo (hitech 5645mg) which has the ofna throttle/brake mod but with the execption of the throttle linkage is directly attached the the carb slide with no other linkages like in the normal one, it produes less drag and a super fast response even with that servo, the next picture is the ofna 250cc tank mounted, and the last picture is the relocation of the steering servo (hitech 5955tg) with a killer robtronic alum servo arm.
Now on these pictures is with the new tvps so mounting everything was alot easier. Anyone of you here can do the same thing if not better. You get nothing but good results from this mod. Longer runs times, no more tank leaning out, safer location for the gas tank, better throttle/brake setup, and a whole lot more. Any questions feel free to ask. It's a working progress and it's almost done. Thanks Terry



Here is a short video of the new throttle/brake linkage setup and what I did to eliminate the steering slop. I take no credit for idea on the steering mod as I found some info on this site. All I did diffrent was make a new alum plate and a single cam setup. Thanks for looking. Terry

 
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Your fuel pickup is in the front of the tank. You're going to grab airbubbles when you get past 1/2 tank. Just my thoughts, But nice work;)
 
^^ There's a tube inside the tank that goes to the bottom with a stone filter on it. Also the tank leans towards the front. Terry
 
^^ There's a tube inside the tank that goes to the bottom with a stone filter on it. Also the tank leans towards the front. Terry

The filter goes to the front of the tank though. When all the fuel goes to the back of the tank when you crack it, and your gonna get air in your fuel line regardless if it at the bottom of the tank or not. Not trying to seem like an ***hole by butchering what you did, just giving my .02.

Check out Pope's build at HPISF, he's running the same tank.
 
The filter goes to the front of the tank though. When all the fuel goes to the back of the tank when you crack it, and your gonna get air in your fuel line regardless if it at the bottom of the tank or not. Not trying to seem like an ***hole by butchering what you did, just giving my .02.

Check out Pope's build at HPISF, he's running the same tank.

I have seen his build that's where I originally posted this. So your saying when I'm going up hill all the fuel will go to the back thus sucking air. I can see that happening but what if your going downhill. It's going to do the same as well. Or am I not seeing this correctly. Terry
 
I have seen his build that's where I originally posted this. So your saying when I'm going up hill all the fuel will go to the back thus sucking air. I can see that happening but what if your going downhill. It's going to do the same as well. Or am I not seeing this correctly. Terry
Yes going up a hill, accelerating or doing wheelies the fuel will go to the back of your tank potentially sucking air. There is not real way to completely fix the problem but with the pic-up in the back I do think it would be better. However what you have now regardless is still better than stock. Oh yeah....NICE Diffs!
 
Ya I assumed either way it's better than stock. I will be selling a bnip set of the bullet proof diffs if you are interested. Thanks for the compliment. Terry
 
Yeah I might be interested. I am sure my current diffs will only last so long. Despite proper shimming they still shell out.
 
you could turn the tank around, might be a pain to rout the fuel lines, but then youd only have to worry about downhill and stoppies, and from most savage driving I've seen most people dont use the breaks that hard, and its usualy airborn on the down hill
 
Ya I'm in the process of doing this. I guess I never saw it that way until the earlier post. Terry
 
Well Terry we are for to help each other out. Normally we have good intentions even. But still it was a pretty good mod you did. Here is another bit of advise I have picked-up over the years......never cook bacon while naked. Hey just say'n. ;)
 
Thanks for the compliment and I love the smell of bacon. :D Terry
 
where did you buy all the parts to do the mid tank mod?

thanks for the help
 
Take the fuel line off the throttle linkage if possible. You need a 1mm gap between the stop collar and the throttle slide. This helps keep a stable idle. Makes tuning the bottom end much easier, because your idle is the same all the time.
Savage Basher, those linkage kits are everywhere. towerhobbies, E-Bay. Pick up 2 so you will have enough to build it. A set of "Z" bend pliers is a good idea as well.
 
@ Savage Basher
The parts can be found at most of the online stores. If you search "ofna mid tank mod" you get alot of info on it. Also if you read the beginning of my post I listed part numbers. There is no one specific site to buy from. But a good site is SMF Store. Hope this helps. Terry

@ Scrogg
The tube is on the brake linkage. I have a spring on the throttle linkage but it's not enough to fully close the carb. I need to figure a way to use the return spring or some setup to pull the carb back. Any suggestions? Terry
 
Would you mind posting up or Pming me the dimensions of the Alum plate that helped extend the plate to secure the tank. I'm doing a very similar build as you.
 
Great build!

Just an FYI, I run a tank (losi 8T tanks) in a similar wrong fashion on my savage (side mounted vs center), but it seems to do ok except for the very last bit of fuel. Even then, if I'm not constantly hammering the gas, it does fine.
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I have it angled forward to help combat the problem. With mine, I can't flip it because then it won't be very easy to access with the body on.

With yours, how do you fill it? Or just due to the size of the tank, you deal with taking the body off to fill since you get pretty good run time?
 
Would you mind posting up or Pming me the dimensions of the Alum plate that helped extend the plate to secure the tank. I'm doing a very similar build as you.

Hey there, Its exactly what the flm servo plate is. I just made them a little longer so I could attatch it to the existing holes in the servo plate. For the notch part in the rear, all the way back to the bulk. That Ofna 250 tank fits in there exactly perfect from end to end. Hope this helps. If not then I will draw you up the dim. and emaiil them to you. Terry
 
Hey there, Its exactly what the flm servo plate is. I just made them a little longer so I could attatch it to the existing holes in the servo plate. For the notch part in the rear, all the way back to the bulk. That Ofna 250 tank fits in there exactly perfect from end to end. Hope this helps. If not then I will draw you up the dim. and emaiil them to you. Terry

Yeah, I have the FLM Servo Plate as well and I was wondering about that extra piece you made. If you could draw it up that would be great and also how you mounted it on there as well. Thank you!

-Alex
 
Great build!

Just an FYI, I run a tank (losi 8T tanks) in a similar wrong fashion on my savage (side mounted vs center), but it seems to do ok except for the very last bit of fuel. Even then, if I'm not constantly hammering the gas, it does fine.
2009-0918-SavageLosi8TTankSide.jpg

2009-0918-SavageLosi8TTankRear.jpg


I have it angled forward to help combat the problem. With mine, I can't flip it because then it won't be very easy to access with the body on.

With yours, how do you fill it? Or just due to the size of the tank, you deal with taking the body off to fill since you get pretty good run time?

Thank you very much olds. I will be turning the tank around so I don't suck fuel when throttling it. I never even noticed that until someone here pointed it out. Even posted on 2 savage forums and know one pointed it out. No biggy, just move the mounts a hair and blam, all done. I usually tank the body off to fill it but I'm getting a new body soon (SC10 body) and will cut an opening in it. As of now I still run the stock XL body which will be my basher body. Thanks Terry
 
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