Rough day for my jato...

[olds97_lss]

If you want to see a bit of damage, scroll on through my storyline. Photo's at the end.

Just a few photo's of the results from my annoying day. Apparently, when traxxas was designing the jato, they decided having the engine head sticking up above the roll bar and rear tower shouldn't cause any problems.

I beg to differ. This is the second engine I've trashed in this rig the exact same way. The first one was a OS18TM which really sucked to break. The second is a month old TRX 2.5R that was just starting to run really good and consistent.

I ran the crap out of it last weekend and ended the day thinking all was well. Then I rinsed the entire chassis off with a hose (forgot about a non-water proofed servo) and hit it with canned air, then threw it on a shelf.

Took it out today with the new body I just got, get to the bash site, turn everything on, find out my throttle servo is now dead. My fault completely. So, then I broke out the savage, which I banged up pretty good (will go in a savage thread).

Got home, futsed around replacing the servo in the jato, realized my rear tower was also cracked, checked things out a bit, didn't see anything out of the ordinary. So I took it out this afternoon. Got it running and all seemed good, wheelies, smoke, decent idle, then as it warmed up, it started running like crap. I tweaked it, swore at it, threatened it with a hammer... none of my usual stuff worked. I messed with it for over an hour, then I was having erratic loss of receiver power for no reason... Finally I just gave up and went home (didn't take out the savage this time as well).

Give the chassis a once over, check my fuel lines, check all the obvious stuff for tuning problems... didn't see anything. So, I found a new switch and replaced the one on it to try to remedy the power problem. I knew the switch was a bit buggy from the recent past, but today was especially bad.

As I'm sitting there holding it up to route the switch wires, I notice oil running down the chassis... then I look at the engine and realize one whole side is coated with nice clean oil...

Pulled the engine and this is what I got:

So, I take the 2.5 I replaced with this new 2.5R and start tearing it apart to use the crank case. Then I remember, one of the backplate screws is stripped... I'm sure that will cause problems. I made sure to RTV the crap out of it, so hopefully it will run ok and not suck air. Seemed to seal ok.

Then, once I have the engine all back together and installed, I sit there trying to think of a way to avoid busting a 3rd crank case in this truck. Lately, it has been my "go to" truck just when I get the mood to run something. Nice, light, fuel efficient, not too loud... just good all around fun.

(hammer is there to show the line between the tower and roll bar as I was thinking...)

So, knowing that I drive it more than my others, I know I have to figure out something to avoid the head making contact with the ground. Regardless how good I drive, it will inevitably end up on it's roof at some point.

Out comes the hacksaw:

Now I have a bit more room between the head and the line between the tower and roll-bar:

The only reasons I thought to do this is that the original 2.5 had the old cast head on it. Which I believe is shorter than the 2.5R head. I don't have an old head anymore as I used it for the ERP with a trashed 2.5 I had that had seen another owner who stripped out pretty much every screw in it. The other reason is I can't think of a way to mount one of my "one off" roll bars on it to avoid this issue.

Hopefully cutting the head by 3 fins doesn't trash my temps and hopefully it helps avoid yet another busted crank case.

 

[sweetdiesel]

Simple yet ingenious solution. Very nice.

 

[Racer 1966]

Innovation - I love it! I bet it won't hurt you temp wise but let us know how it does :thumbup:

 

[olds97_lss]

Well, I ran it today. The crank case I had as a spare had a carb installed/sealed already, so I didn't mess with it. And I was unable to get the rear bearing out of it, so I left it in. Other than that, I replaced everything with the parts from the busted crankcase engine.

My electronics problem was not resolved... I think it was just a bad connection on my receiver. After unballooning and replugging everything in, it worked fine.

As for the temps, the carb in that crank case was way out of whack. So, after a few tanks worth of tuning, it was running ok at 230F. I lost quite a bit of snap out of the engine though and i"m not sure why. Used to pull easy wheelies on pavement, but not anymore... could have something to do with the 320F temp I had hit with the cracked crankcase yesterday. It still has good compression, but is a bit more sluggish than it was the last time it ran good. Still ran about 500cc's through it today, then my trans grenaded. One of the pins in the two speed apparently fell out and turned the gears in the trans into confetti.

I'm contemplating throwing my 18TM in it... or at the very least, put the carb from the busted crank case on it. Guess I have a week to figure it out since I just ordered parts for the trans.

 

[Racer 1966]

If I read right, your power difference may be from using a 2.5 block instead of a 2.5R. Some of the porting is in the block.

 

[olds97_lss]

Well... that sucks! I thought the only diff between the 2.5 and 2.5R was the head.

I'm also bidding on a new crank case on ebay... for the 2.5. I'm having a hard time finding anything relating to the old 2.5 on traxxas website. I downloaded the manual for the 2.5R and it's part # for the crank case is 5222R. Which I can't find on tower. I can find 5222 though.

 

[olds97_lss]

Well... lasted 2 whole bashings:

Now I know I did not hit the head on anything. So, my only guess is it's from impact of the chassis hitting the ground from decent air. Not sure what to do now... this is the 3rd cracked so far. All 3 were the engine mount tab on the rear.

The only thing I can think to try now is to put some piece of rubber between the tabs and the engine mount and also between the bolt heads and tabs. Or, put silly heavy oil in the shocks so it can handle air. Which sucks, because I have it setup now where I really like how it handles. But, apparently 5 feet of air under it is just too stinking much.

I'll probably try the rubber under the tabs, but my main concerns will be keeping the bolts tight and the loosing the cooling that the chassis had as it wicked away heat.

The only other thing I can think to try is to create a small dam under the engine with stuff out of the way, fill the cavity with epoxy, then bolt the engine in. The epoxy will be there as a base for the engine to sit on. Then it would be supported by the entire base of the engine and not just the tabs. If the rubber bits don't work, then I guess that will be attempt #4...

I like this truck too much to stop driving it. I can't believe I'm the only one having this problem...

 

[Rolex]

I've been trying to figure out what that gritty, oily looking brown stuff is.
Aaaaaah.......it's DIRT! There's your problem, you're running it!

 

[olds97_lss]

Yeah, it was clean and shiny before I fired it up this morning... oil makes a hell of a mess. Can't say odonnell fuel doesn't have enough oil in it!

 

[olds97_lss]

Well... I've broken crankcase #4...

Tried putting a bit of rubber sheet under the mounts and tightened the engine bolts down snug. Was a pain getting it installed since it made the mount a bit taller, but to no avail... busted the same ear yet again. Also burned a spur gear today. Haven't chewed one of those up all year!

Feels like it's time to shelve this thing. Between the time/effort and $, I can't make it a bash session without costing me a new crank case.

The only thing I can attribute this to now is slapping the ground on landings. I didn't wreck a single time today, but I did land from about 3-4 feet on concrete. I ran 3 tanks of fuel...

I surely did not go through crank cases like this when I ran revo white springs on the rear. Guess I'll have to go back to them as that seems the only possible problem now. I'm running cut UE Red SuperMaxx springs on it now which are I believe around 12lb springs. Stiff enough to not slap the ground off of a 12 inch drop, but soft enough to run over rough terrain without bouncing.

I have one more crank case... I just don't know if I have the patience to tear the stupid engine down for a 4th time.

If I do, I'm going to make a pool of epoxy under the engine mount for the bottom of the case to sit in. Hopefully to give it more support. It seems that since it's cracking on the lower side of the ear, that it's from landing and the engine is dropping. With epoxy holding the base of the crank case up... either the entire crank case will crush or it will work... or some unforeseen thing will happen. That with the stiffer springs might make me through a single bash session at least. I just hate running the stiff springs...

 

[newb]

WOW, i bash my jato 3.3 pretty hard and have yet to bust a crankcase. i run a basically stock jato with 54t integy spur and aluminum a arms, sandpaw rear paddle tires and i hit some big (7ft high and about 30-35ft long) jumps in packed sand. i do run 70weight oil in the rear shocks though

 

[olds97_lss]

Well, I ended up using JB weld long cure as a base under the engine. I lightly coated the engine and chassis area with oil, then poured in enough jb weld for the engine to rest in it. Then I let it cure. I later pulled the engine and gently pushed the engine mount a bit to break the jb weld loose so I can adjust my mesh.

I also put my hard revo springs back on. Thinking of trying some heavier oil and putting the 14lb UE springs back on that I had. What springs were you running with 70 weight? What brand of oil?

Just finished running it for about an hour at the skate park I have been busting it at. Crank case is still dry as a bone. Just stupid bouncy...

 

[Scrogg]

Give it more suspension down travel and use thicker shock oil. I assume there is sway bars on it or for it to help the handling issues. Concrete and R/C jumping is a bad combo.

 

[newb]

ya i got my rear shocks set up with the stock green springs and 70weight associate oil and running them for the most travel. looks jacked sitting on the ground compared to before. I'm having a problem with getting the transmission casing to hold up, i keep busting the ears off where the shock mount bolts on. i was gonna mention also that with the 3.3 the head sticks out alot more than the 2.5r so I'm thinking that it is more a issue of the hard landings.

 

[olds97_lss]

I know concrete is bad, but 90% of the time, I'm jumping out of the park and into grass.

I have the truck standing as tall as it will go and I have wheels/tires on it that add even more clearance before bottoming out.

If these revo springs get on my nerves too much, I'll switch back to the buggy springs and up my oil quite a bit. I believe I'm running 40 weight now in all 4 shocks.

I'm fairly confident as well that it's the hard landings. I do (on occasion) land on the concrete, but it isn't the norm. I know it only takes one good whack to bust the crank case though. I guess I should just be content with the smaller air and leave the big air to my savage.



You say you keep breaking ears that the shocks mount on on the trans case? Do you mean the two bits that stand straight up that the shock tower bolts directly to or the ears on the case where the upper turnbuckles connect?

 

[newb]

ya i keep breaking the two little ears that the shock mount bolt directly to. after the first cases busted i took off the rear aluminum shock mount that was on there when i bought the jato off my friend and put on the stock plastic one thinking it might flex enough to save it. i will be on my 4th case this week when it arrives. lucky they are only $6.

 

[newb]

oh i also forgot to mention a new problem that is happening since i jacked up my suspension. i installed a new set of 2.2 proline sandpaw tires on a set of 2.2 traxxas rims(trx3674) and they rubbed on the inside of the rim so much that it wore out the tie rod ends on rear. not sure how I'm gonna solve this problem yet.

 

[olds97_lss]

I have yet to bust that part on my trans case. I've busted off the ears that hold the upper tie-rods. I've busted many shock towers in half though.

I ran these wheels on mine without any excessive rubbing issues that I noticed:
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXJJ86&P=7

I ran the matching ones on the front:
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXJJ87&P=7

 

[newb]

i switched from a different rim, the traxxas ones dont have enough offset and are a little smaller on the inner diameter. I'm gonna have to get a new set of the hpi ones that was on it first.

 

[sandiegan]

i bash my jato 3.3 pretty hard and have yet to bust a crankcase. i run a basically stock jato with 54t integy spur and aluminum a arms, sandpaw rear paddle tires

no offense but if you running integy spur gear and integy a-arms, and they aren't broken or bent on the first run, then you don't bash your jato hard at all !!