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Noob with an old 2.5 revo

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TK5310

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Brief story, I've always wanted a nitro RC truck since I was a kid (like, 30 years ago LOL), never got around to getting one.
Now serveral old bastards I know have been buying & fiddling with nitro stuff a bit lately - I had a play with one a couple of weeks ago.
Nothing like what I remember seeing as a kid!!
Cool as, gotta have one!

So I made a bit of an impulse purchase - an old 2.5 revo with a nearly new motor in decent nick.

Spent some time, stripped it down to bare chassis, cleaned everything up, read the manual & set up all the suspension as it should be.
Got it running, climbed a steep learning curve to get it tuned 1/2 decent, adjusted up the clutch to where it seems right (it was waaaaay slow on the take up), got it to actually shift right (adjuster was wound in hard & it stayed in 1st gear).

Many grinns ensued with a sweet running car, still got a bit of fiddling to do, methinks the clutch could still be a little tighter & I gotta chase the tune a little etc.

Anyway, enough of the rambling on, the one & only thing I'm not completely stoked about with this thing is it really doesn't launch all that hard, once it gets moving it boogies, but getting off the line a bit faster would be nice - gotta be able to drag race friends 2wd smaller things that wheelstand & just F*ck off outta there.

So, looking for a few simple mods to get it off the line faster, but with one preface - the motor is sweet, got plenty of life left in it, but when it does get a bit sad I'll pop a 3.3 in it, so anything I do has to keep that in mind.

Thniking maybe lower gearing (don't care much for top speed, just acceleration), but not sure if that's a good idea for when the 3.3 goes in - may be too much for the stock driveline?
Also thinking a new air cleaner (something that flow better than the stocker) & maybe a pipe would liven it up a little?

Right now it's 100% stock & all in good nick.
 
A pipe will definately liven up your engine. I like THS myself, but they all seem to work better than the stocker.

As far as gearing goes, you don't have a lot of options;

Clutch bell (14-tooth)(15-tooth)(16-tooth)(17-tooth)
Spur gear, 34-tooth 36-tooth 38-tooth 40-tooth

Gear set, 2-speed close ratio (2nd speed gear 40T,)
Gear set, 2-speed standard ratio (2nd speed gear 39T)

You may need to go with the 14/40 set up to get where you want. However I doubt a Revo can ever beat a T-Maxx in a drag race because of the gearing. Different story if you want to race 5 laps at the local track.
 
make sure your LSN is tuned, try making it a tad more lean and see if it pops, if not try tighten the slipper a bit more. i have my slipper tight so i can move it with my hands and needs a bit of pressure to do so, if its not tight it will just slip (as its suppose to do) and waist the energy that u could be using putting the front wheels up.

i have 14/40 setup on my revo and it use to do wheelies when ever i wanted, having some motor problems i think now, its getting a bit old and needs a rebuild i think.

if you find ur motor is loosing compression, parts look a bit **** house then upgrading to the trx3.3 might be a good idea. you just have to sus out the engine mount etc you may need.
 
The LSR (low speed needle?) is pretty good I think, any leaner & the idle starts to climb, doing the pinch test the idle just climbs slightly & the motor dies after about 3 seconds.
By the sounds of it the clutch needs to be tighter.

14/40 gearing sounds good - I assume gears for a revo 3.3 will fit?

I like THS myself, but they all seem to work better than the stocker.
Click to expand...

I think maybe there was supposed to be a link in there? - what pipes should I be looking at on the budget side of things? - can I use the pipe with the 3.3 motor down the track? - what about side pipes?

Those 'motor saver' air cleaner things, are they any good? - going to need a new intake soon anyway, rubber has started to split on the stocker, it's not right through yet & I glued it up to be safe, but I can't see it lasting real long.

I'll mostly be using the car on dirt/grass & concrete, nothing real rough - is it worth putting the heavier springs that come in the longer travel kit that I got with the car?
Car already has red springs in it, not sure if they're all red or if it already has heavier springs - it dives hard under brakes & squats quite a lot under power.

1 last question - the glow plug heater on the ezy start is borked, the wiring on the car is good & the starter part works, but it won't heat the plug. I've just been using a plug heater hooked to a 6V lantern battery, but having the ezy start plug heater working would be nice. Can I just hard wire the plug heater part in the hand unit to give the plug battery voltage as soon as I plug it in?, from what I've read the ezy start plug heater is a bit underwhelming, should be better if it starts heating the plug as soon as I plug it in with full battery voltage.

Sorry for all the questions, new to this & it's quite a learning curve (fun one tho).
 
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Doing some searching, looks like it may already have a resonator pipe on it, or is this the stocker:

P3250616.webp


P3250617.webp


P3250618.webp
 
TK5310 said:
The LSR (low speed needle?) is pretty good I think, any leaner & the idle starts to climb, doing the pinch test the idle just climbs slightly & the motor dies after about 3 seconds.
By the sounds of it the clutch needs to be tighter.

14/40 gearing sounds good - I assume gears for a revo 3.3 will fit?



I think maybe there was supposed to be a link in there? - what pipes should I be looking at on the budget side of things? - can I use the pipe with the 3.3 motor down the track? - what about side pipes?

Those 'motor saver' air cleaner things, are they any good? - going to need a new intake soon anyway, rubber has started to split on the stocker, it's not right through yet & I glued it up to be safe, but I can't see it lasting real long.

I'll mostly be using the car on dirt/grass & concrete, nothing real rough - is it worth putting the heavier springs that come in the longer travel kit that I got with the car?
Car already has red springs in it, not sure if they're all red or if it already has heavier springs - it dives hard under brakes & squats quite a lot under power.

1 last question - the glow plug heater on the ezy start is borked, the wiring on the car is good & the starter part works, but it won't heat the plug. I've just been using a plug heater hooked to a 6V lantern battery, but having the ezy start plug heater working would be nice. Can I just hard wire the plug heater part in the hand unit to give the plug battery voltage as soon as I plug it in?, from what I've read the ezy start plug heater is a bit underwhelming, should be better if it starts heating the plug as soon as I plug it in with full battery voltage.

Sorry for all the questions, new to this & it's quite a learning curve (fun one tho).
Click to expand...

ok well the exhaust looks like the resonator pipe on my revo, just blue, not sure exactly but i think the earlier models came out with the blue ones, not sure if theres a difference.

if i were you id remove the ez start and put pullstart on, there will be no more problems.

and the motor saver air filters look good. but i think the newer revos have a good enough filter on them already. not sure if they would make much of a difference.

if you dont want it bottoming out as much might be an idea to rebuild the shocks and use smaller pistons. (allows less oil to pass through and wont drop as hard) i had the long travel springs on it and it was still as hell. i put the factory green and orange springs back on and seems to be pretty good. i have #3 piston in rear and #2 in front.

---------- Post added at 1:30 PM ---------- Previous post was at 1:27 PM ----------

my revo as it sits, looking into putting a big block in it, .26 or .28 picco motor.

ff106526.webp
 
Ok, plan of attack:

THS pipe - didn't realise how cheap this stuff is!
Motor saver filter
Switch to 20% nitro (been running on 16%)
16/40 gears (seems to be the most commonly available)

Pop in the heavier springs from the long travel kit & stick some 65wt oil in the shocks.
Get a sway bar kit & maybe a set of those rpm rear arms with the pin instead of the ball at the bottom (forget what they're called).

Also gotta grab some alloy wheel hex thingys (one of my plastic ones is a little sad).

Sound like a decent plan?
 
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Don't actually want wheelies, just a harder launch - which will most likely involve wheelies!

Don't reckon I'm gonna need 14/40 tho, I threw in the stiffer springs & took it out for a quick blast to chase the tune a little.
Tightened up the clutch a tad more, dropped the idle speed & leaned out the low speed needle.
Can go WOT from idle now, didn't like that before.
With less squat from the stiffer springs it picks up the fronts -just- clear of the deck on concrete, not a wheelie, but pretty close. Pretty chuffed with that.
With the stiffer springs in it'll turn a lot harder without flipping over & doesn't dive as hard under brakes so it pulls up quicker.

Can't wait to get it out into some decent room on the weekend & let it rip, the lane here is dark & narrow, only really good for blasting up & down.

Reckon the motor has an air leak tho, at idle it's behaving leanish, but get it moving & it's crisp with a nice trail of smoke & no dribble from the pipe.
So a slightly lean idle but ok off idle says air leak (spent some time in my earlier years playing with 2 stroke bikes), guess it's time to go over the motor & seal it up tight.
 
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Mmmhmm, try keeping it low too, unless ur jumping it. Will help a lot with cornering. And sealing it up won't hurt at all. Check all ur Motor bearings while ur at it
 
To get better launches and keeping all 4 planted, look at the center diff kit. On the 3.3 that I have, I also run the rear brake kit. You'd have to change over to the 3.3 transmission case to do this on a 2.5.
 
Thanks, those threads are very helpfull, I was kinda starting to go down a similar path learning to tune it, but that'll speed the process up immensly.
From reading that my idle gap is too big & my low speed needle is too rich, but my high speed needle is about right.
I'll seal the engine properly tomorow night & take it out for a good blast to tune it right now that I've read those threads.

The other thing I've picked up is that a good pipe is likely to make it less sensitive to tune with a wider tuning window (as well as more powah), so that & a new air cleaner will be first on the list to get done.

I'm happy with how it launches now, getting the tune nailed down is only gonna make it better, so yeah I'll leave the stock gearing in it for now - massive wheelspin on dirt/grass will just make it harder to learn to drive well.
I'll withhold judgement on handling untill I get a chance to run it properly, but seems a lot better with just the spring change - may end up leaving it alone for a bit & just spend time driving it & learning!
 
Nitro-X 16%, 5% castor, 10% synth.

My thoughts exactly on the engine, if I'm gonna kill an engine learning to tune I want it to be this one, not a 3.3!, probably won't kill it anyway, I'm a cautious tuner (I build competition engines for a living - drag racing, road race, speedway etc).
But a lot of what I know about tuning 4 stroke petrol engines just doesn't apply to 2 stroke nitro glow plug engines.
I'm finding it amusing that you can run them dead rich & all you'll do is drop power - do that with a 4 stroke racing engine & you'll foul plugs, wash bores, kill rings etc.
 
You have much to learn grasshoppa...:D jk

Look for fuel with about 12% total oil and 20-30% nitro, that'll make tuning easier and yield a suprising amount of extra power all by itself.
 
Will do, I'll burn what I have left of the 16% (about 1 pint) then grab some 25%.
I've noticed what seemed like an excessive amount of oil getting sprayed over the rear bumper & body, I guess the 15% oil in the fuel I'm using is contributing to that, 12% oil should reduce the mess a little.
You fatten it up with more nitro don't you? - nitro has lower chemical potential energy than meth, but you can burn a lot more of it per XX amount of oxygen.
Do I need to run a cooler plug with the 25%? - seems like not enough of a jump to require a cooler plug, but TBH I don't really know.

Untill my new pipe arrives will drilling out the tailpipe of the original pipe help with power at all? - drill to 5.5mm?
 
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You can overbore the pipe slightly, but don't compromise your fuel pressure by going too big. You're right about the fuel, and the oil only gets in the way of a good burn, if you know what I mean. 8% oil is enough for most engines, but 10-12 is playing it safe. You should always have something coming out of the pipe, because that's all part of your engine's cooling system.....you will notice a little less mess though.
The best tuning advice I can give you for a fuel change is to richen the needle 1/4-1/2 turn and tune it in from there. The 3% less oil will make it run slightly cooler, so don't tune for temperature, tune for performance.
Traxxas engines will always be fine with a med-hot or hot plug, unless it's cold outside or you exceed 35% nitro.....the hotter plugs make for better idling and throttle response.
 
So I put about 1/3 of a gallon through this on the weekend, left the pipe alone & just concentrated on learning how to tune it.
It was hard to start, would stall if I didn't leave the plug heater on for a bit after starting, bogged a little sometimes, didn't like to idle & the tune seemed to move around a lot.
Got all that sorted, she was rich on the high speed & a tad lean on the low speed, I actually had the idle gap to small as well.
Now she starts & idles cold, warmed up there is no bog & it's responsive & pulls hard right through the rev range. Running sweet as & really not that far off in performance to friends 2.8 & 3.3 powered buggies (I reckon they need some tuning time, a 2.5 in a big arse revo should get nailed by a 2.8 in a little 4wd buggy).
Having 2 gears helps I guess, but even top end it's not lacking by much, new pipe & 25% fuel will be enough to keep up or beat em for now.
A big plus is the big tyres, while they're wheelspining or wheelstanding & hard to control the revo just hooks up & goes, much easier to drive.

Pretty happy with it so far, glad I didn't get the buggy I was looking at to start with!

1 friend threw a rod in his 3.3 & busted a shock, another busted his front end tapping a gutter, being new to this I rolled the revo a bunch of times, snotted a gutter a few times & smacked it hard into a concrete barrier when I misjudged speed & braking distance winding it out.
Didn't bust anything, did manage to knock the pipe & 1/2 the electonics out with the sudden stop of hitting the barrier, put it all back together & it was fine.
Tough bastard.
 
Changed the shock oil last night, the stuff that came out had seen better days, so I'm thinking changing the diff oil as well may not be a bad idea.
Anyway, put 65wt oil in the shocks, seems a lot better but haven't run it properly yet.
Also discovered the suspension uprights were very loose on the balljoints, so tightened them up & did another wheel alignment.
Also trimmed the bump stops for a bit more steering travel.
Dropped the body mounts down a bit (they were at max height), trimmed the body a tad to get it to fit lower, pulled all the crapy old stickers off it & got out the yellow gaffa tape to fix up some cracks, it'll need a new body some time, but while I'm learning I'll stick with this one.
My new THS pipe & motor saver air cleaner should be here friday (I hope), can't wait to get them on, looks like 1/2 the problem with oil all over the rear suspension is a cracked header pipe, so new pipe & header should fix that as well as making a bunch more power.
When I get the new pipe on I'll switch to 25% fuel at the same time so I only have to retune once.

I've also scored a slightly busted 3.3 motor for nix, friends old motor, threw a rod last weekend - he's buying a complete new motor & putting a davis diesel rod in it straight away, so I'll get his old motor & the new stock rod from his new motor, just need to buy a piston & sleeve & she'll be good to go. Pulled it down last night & everything else looks pretty good. Dunno if I want to break in a fresh motor just now tho, so I'll probably rebuild it & stick it on the shelf for a few weeks.
 

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