Tuning and Mechanical problems Nitro MT w/pics.. Long!

[Zaytri]

Hello!

Been a member and been readin for a while now, and it's clear lots of you have TONS of experience, so that means you can help me out! Right?

First, the tuning problems...
Engine is a OS .18 CVRX -- I broke her in with about 6 tanks, and it MAYBE has 3/4 of a gallon on it. Lots of compression. Starts with 1-2 pulls, and runs GREAT, but only in the 200-220 range. As soon as I hit 250ish, it seems like the fuel is burning off in the carb before it gets into the engine. If I'm not going WOT (as in driving around slowly or idling) the engine will pulse in RPMs until it shuts down, at which point it will not start until it's cooled off. <Hissing sound comes from carb when i try to prime it> I think 200-220 is a good temp range, but it seems the car is underpowered and wants more, but I'm not quite sure!

Steering - Will be perfect for about 5 mins, then out of nowhere, car will constantly veer to the right. I'll change the trim, and it'll run for another 5-10 mins, at which point it'll veer to the left, and ill have to change the trim again.. :shrug:

I purchased aluminum towers as you can see in the pic, and upgraded to hard springs on all wheels, and I'm using newly rebuildt 40WT oil all around. Since the aluminun upgrade, i seem to end up on my lid ALOT more. Any kind of bumpy grass or dirt at any decent speed will send the truck flailing off the ground and onto it's top. None of the shocks are binding, and they move freely in all directions <up and down > I'm not experienced at telling when tires need to be replaced, could that be the problem?

And now, the mechanical ones! Yippee!!

Servo Horns... Who/Where can i get decent servo horns? My LHS sucks when it comes to their selection.. And the owner is a real bum for ordering stuff that isnt in demand.

Throttle Linkage... As you can CLEARLY see in the pics, my throttle/brake system is in a state of supreme ghetto rigging. Since the engine upgrade to a slide carb, I'm having trouble getting a good system in place to work the gas/brake. The linkage kit from HPI only supports rotary carbs. Anyone have experience with this? I want a throttle return spring as well, but dont know where to start in it's application and placement.

Header/Pipe... I cannot for the life of me keep the stupid pipe on the truck. BY tank 2 or 3, it vibrates off causing anyone within a 1/4 mile to know my exact location :arrr: Is there a better quality header i can purchase and put on without crazy mods? What's a good pipe for general bashing? Is there a better way to secure the pipe then the cheap plastic arm that attaches to the chassis? AHHH!

And for my own to anyone who owns this truck and wants some personal experience feedback..
The upgraded chassis RULES!! It stiffens the truck out IMMENSELY. Hi-Torque steering servo makes a GIGANTIC difference on handling. Titanium turnbuckles can bend, it's cheaper and easier to use the plastic ones or make your own. Shim the diffs if you upgrade the motor.. I learned the hard way. Slipper clutch upgrades helps control on dirt ALOT. Upgraded hinge pins and have never had a problem since! Upgrade your shock springs ASAP!!!

Final question..
Has anyone seen a roll-cage for this truck for under 100$?

Thanks in advance for any/all feedback and answers!
You guys are great!

Andrew

P.S. Could someone PM me on how to add pics to the actual message? Pics will be linked as soon as Webshots stops being grumpy.

 

[Tarant]

First off apologize for the long ass post. :jk:
Ok all engines are different and it you engie will die at 250 try to stay around 240 and it it runs good at 220 then stay their.

the steering servo may be going bad or your batteries are low. i have had a truck suddenly turn when the batteries are low that is why I run a failsafe.

you may want to drop to 30wt oil and it it is still to rough then your try going softer springs. are your tires really tweaked and have flat spots or unglued edges, if they do that will cause a lot of problems

you can get servo horn at Towerhobbies they have almost all types and brands I like Ofna.

i dont know about the throttle linkage

the plastic pices suck i would go to a hardwear or hobby store and buy some steel wire/rod and use needle nose pliers and bend a metal pipe hanger for your pipe ( this is what I do because I have like 30yrd of steel wire that i use.)

hope this helps

 

[olds97_lss]

The traxxas big bore header fits nicely instead of the crappy stock header which is really restrictive. The stock plastic pipe is also junk. I'm not sure what would run best with the 18 though. This may be whats causing your "weak" power output. To restrictive of a pipe makes you tune hot to get any power. A better flowing exhaust lets it breath better. Found that out on my savage...

I had the same engine (except with a rotary carb) on the same truck for about 8 tanks (with stock header and pipe), then I sold the truck as a roller.

I had bought a header and pipe, then sold the truck before installing it...

Here's a link for the header and pipe that I bought: http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXSP45&P=7
http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LX3419&P=7

As for the steering, I agree with Tarant. It sounds like your servo may be going out on you.

I'm not sure about your other problems though. Again, like Tarant, I'd say try lighter oil. The nitro mt doesn't weigh much at all, so heavy oil would make it very bouncy and hard to control. I had mounted 1/8 buggy shocks on mine with light springs and 30 weight oil. It was still a little rigid, but not as bad as yours sounds.

As for the upgraded chassis... I made a 3/16" steel plate for the center diff and engine to mount to. This helped keep me from eating up spurs. But I never ran a slipper. I was going to buy the one for the MT2, but on tower, it explicitly says it's not for the MT, just the MT2. Then I found out after selling it that the MT2 slipper fits fine.

I also made a 3/16" stell bumper/skid for the front. Never had a chance to use it either though.

This is how it looked when I sold it: