my way around a high temp 2.5 motor

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1mtx1

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So i been reading thread after thread about over heating 2.5 motors. I guess its the norm to see these motors run well over 270. I found some good info looks like the stock low end setting is to lean when you set it flush. I was running yesterday it was around 41 deg out side and i was sure enough running super hot. I seen temps over 250 (280+) and i had good smoke and it drove ok but i kept getting hotter . I know a air leak is not uncommon for these motors so i was up late going over the motor. I might have to seal the carb but what i did was i backed off the low end a full turn then what the stock setting was. I even think my carb opening from yesterday was on the smaller side so i set the idle a tad higher. I have my high end around 5- 5 and half turns out from closed. All this is not un heard of. I did a test tank to day around the same temps today. I ran around 200 deg after some on off throttle runs. I was not seeing lower temps as i would idle yesterday today i could hear the idle come down a tad and the temps would drop ever 3 or so seconds just a few degs. I did see a lot of fuel build up as i was idling. I had to lean the high end i was stalling after i started then gave it some throttle. I really did not do much with my high end, i know the rule is high first, then low then idle. In my case i was so close to messing up a new motor i had to dial in the low end and idle. I was damn near 8 turns out yesterday and i was still over 260 deg and i had a few flame outs. I plan to do more testing from where i left off. My next investment is a new air filter and i need a can of wd-40 to check my carb/ needle's for leaks. I know the back plate is prone to leaks as well. I really am blown away how so many people have the same issue i do. It can be a simple to high low end and not enough idle gap or it could be a air leak. I am running 20 percent fuel with a new hot plug and i think i am on the right path. I just want to see if anyone has came across the stock settings to be to lean? I know my out side temps are on the colder side so a richer setting would be a good idea.
 
as a general rule of thumb with a trx engine ,seal everything!.best thing to do is get some hi temp rtv the copper one and seal the backplate and the carb throat.
I also go as far as to take all needles out and get some green slime and coat the o rings and set to factory then start again the next day just to give things a bit of time to cure.
I had a 3.3 once that for the life of me would never run cool , fresh rebuild the works I tested all the seals on the carb still no joy in the end I got a carb rebuild kit and did the carb after that it was sweet no probs at all ,maybe look into that for the sake of 5 bucks
 
as a general rule of thumb with a trx engine ,seal everything!.best thing to do is get some hi temp rtv the copper one and seal the backplate and the carb throat.
I also go as far as to take all needles out and get some green slime and coat the o rings and set to factory then start again the next day just to give things a bit of time to cure.
I had a 3.3 once that for the life of me would never run cool , fresh rebuild the works I tested all the seals on the carb still no joy in the end I got a carb rebuild kit and did the carb after that it was sweet no probs at all ,maybe look into that for the sake of 5 bucks

100 percent what i am doing, i did the soap/water test last night as i wanted to reset my gear mesh etc. I did not see anything to bad but for the hell of me going out any way to get a can of wd-40 i will get the hi temp stuff i might have a hard time getting the green slime local. Is there anything i can use instead? I know i want to test my new needle settings , i really need a open parking lot. i been working on the brakes and ya know i might just go upgrade servos as well. I got new proline tires the other day so i feel as much i put in to a used truck i might as well go 100 percent in and do it right. I got new shock towers new battery/ receiver box that should be here tomorrow. I did see the motor load up pretty fast as it did not punch off the line after i let it idle for some time. i know i am still on the rich side, i go for 3 or so seconds on the pinch but i heard a few people say even traxxas said to aim for 5 or 6 seconds. I feel i can lean the low end and even start to lean the high end but who knows i could be less then a 1/4 turn lean on both ends then back to 290 deg. I did see with my rich setting the second gear come in to play. I really need some space to do some speed runs to really dial things in. North east this time of the year is tricky. You can have 41 and a lot of wind, you can have 20 deg with lots of sun. Then you can have neg temps/snow/wind, I threw around the idea to cut ties with the maxx and move on. I will not deal with flame outs and not being able to run a tank. I did see a few shut downs, that was do to being to rich i had to bump my idle up a tad and lean the low end. I was towards the last 1/4 of the tank . Sucks its 9 pm as i want to go work on another tank. I been taking it slow and just not going by the temp gun . It did help today as i was only 140 deg and had a bad idle.
 
I'm sure you can use dielectric grease in place of the green slime.
If you still having issues I would maybe wait till your outside temps are a bit warmer and try again.
What plug and fuel are you using
 
I'm sure you can use dielectric grease in place of the green slime.
If you still having issues I would maybe wait till your outside temps are a bit warmer and try again.
What plug and fuel are you using

20 percent top fuel, i was using the traxxas plug but changed it yesterday for one i picked up on ebay. They come stock in the redcat rc there a hot plug. I would say on the same scale as a duratrax plug or some basic run of the mill plug. Lights up bright and works as it should. I will get the grease and yeah i might wait tell spring. To be honest i have put more money in to this truck and i rather do it right and worst case is i just put it on the shelf for 2 months or so. I have a sc10gt that i broke in a few weeks back on a nice day and its been siting for a few weeks. I have a redcat buggy that i picked up last week sitting around as well. I might see if there is something around town that i can just run today that is not as picky like the trx series motors. I think i seen a savage for sale. Funny its all ways traxxas rc for sale on craigslist. Same story they want to get something new or there going to electric or straight out say they have no idea what they got in to etc etc. thanks for the help
 
the trx engines aren't bad so a rtr truck.
the main problem with the 2.5 is the cooling head is too small and at the end of the day its only got .15 cu displacement which really aint that big especially pushing around a heavy mt like a maxx.
plug wise I would suggest an os lc3 ,last much longer than the trx plugs. I have no first hand experience with top fuel as I can't get it here in oz but my understanding is the oil content is a bit high but its an ok fuel.
if you want a simple nitro, something with a big block is the way to go they are so much easier to tune and quite cheap.
 
the trx engines aren't bad so a rtr truck.
the main problem with the 2.5 is the cooling head is too small and at the end of the day its only got .15 cu displacement which really aint that big especially pushing around a heavy mt like a maxx.
plug wise I would suggest an os lc3 ,last much longer than the trx plugs. I have no first hand experience with top fuel as I can't get it here in oz but my understanding is the oil content is a bit high but its an ok fuel.
if you want a simple nitro, something with a big block is the way to go they are so much easier to tune and quite cheap.

I get it a heaver rc with a smaller motor and the lack of the cooling head was a issue.. The 2.5r kinda helped with the blue cooling head, see traxxas never wanted to come out and say yea go and use a aftermarket company head. So they just threw the blue one on lol. I have mine from the 3.3 but its a tad bent etc and to be honest i am working with a lot of new parts and at this point to put it on is dumb. I am picking up a new air filter today, wd 40 and the said stuff to seal the motor if need be. I still want to work with the truck and see if can get it right. One move i did was i got upgraded tires and i love them they look great and grip real nice. I do agree why such a small motor for a monster truck and whats funny if you look around the 2.5 up to the 3.3 is very cheap based on some other stock rtr motors out there. My .18 sc10gt motor is more then a 2.5 motor and the same price as the 3.3 and my sc10gt is like 200.00 less then lets say a jato . There fuel is ok, i never had a issue i buy what my local guy has. I asked and he said this is what he sells, i am sure many people buy on line. I see very little rtr around its all part support and the extra stuff we buy . For plugs to be honest i like what i use i have done the 8.00 glow plugs and the 2.00 plugs. I think i am fine, some people swear to buy this that and the other. I stick with works and if it happens to be a few bucks less why not? I am open to trying what ever i can to get this motor right.. I am 10 tanks in and i have to say the fine tune has been to the point i think any new person to this hobby would be at the LHS paying for a tune. I wonder i really do if i go there would they support the idea a ITEM THEY SOLD USED, would have a issue that would need a over haul? I told them the 3.3 that was on there failed one of the workers said ohhh. You brake that 2.5 in i said bro yeah i been at this for years i just am getting back on track. I been away for years and now i am starting to remember things as i no lie forgot about some things . I did seal one engine many years ago but it was not on a traxxas motor. I had help from a friend who had the supplies to do it and we just did it at his house let it dry for like a day or so and it was all good. Oh this must of been back in like 2006 or so. Anyways i will keep at it and i hate to have this just another traxxas rc for sale on craigslist.
 
In cold inconsistent ambient temps like you have, I'd suggest wrapping maybe half the cooling fins with aluminum foil. Then your engine heat is retained for a more consistent tune. Wind chill can trick you into believing your engine is running cooler than it actually is. The most common solution is leaning (which is the wrong solution).

I've never heard of 5-6 second pinch test. I'd stick with the tried and true 3-4 second pinch test for now, .7mm-1mm idle gap, adjust the HSN so a smoke trail is visible. Once you reach peak performance, back the HSN adjustment off slightly.

Check over the rest of your truck for binding issues. bad wheel bearings or a brake that's misadjusted could cause excessive drag and resistance to your engine.


Also leak test your fuel tank the same way you leak test your engine.. If your fuel lid is not sealing correctly you'll get an air leak causing an inconsistent lean issue.
Try tuning your engine with less than a half tank of fuel. T Maxx fuel tanks have a high COG, piss poor design causing whats commonly called "half tank lean issue".
Lots of guys remedy this issue all together with the "Ofna Violator fuel tank mod"
 
In cold inconsistent ambient temps like you have, I'd suggest wrapping maybe half the cooling fins with aluminum foil. Then your engine heat is retained for a more consistent tune. Wind chill can trick you into believing your engine is running cooler than it actually is. The most common solution is leaning (which is the wrong solution).

I've never heard of 5-6 second pinch test. I'd stick with the tried and true 3-4 second pinch test for now, .7mm-1mm idle gap, adjust the HSN so a smoke trail is visible. Once you reach peak performance, back the HSN adjustment off slightly.

Check over the rest of your truck for binding issues. bad wheel bearings or a brake that's misadjusted could cause excessive drag and resistance to your engine.


Also leak test your fuel tank the same way you leak test your engine.. If your fuel lid is not sealing correctly you'll get an air leak causing an inconsistent lean issue.
Try tuning your engine with less than a half tank of fuel. T Maxx fuel tanks have a high COG, piss poor design causing whats commonly called "half tank lean issue".
Lots of guys remedy this issue all together with the "Ofna Violator fuel tank mod"

talked to traxxas they said i should not be over 4 turns on the high end and i have a leak. I was told to look near the tune pipe and it could be my carb and the lid to the tank. I will ahve to go back over things, i think my brake set up was not tight enough i set it up to tight but fixed that and the mesh is good for the clutch bell/spur. I was told 20 percent and a hot plug is not good i should use a med plug. And that is about it oh yea i heard to shot for a tad longer then 4 seconds and rich the low end more then factory. There is a lot of thread about this. idk i might try another motor if sealing it does not work,i thought about that last night .
 
20% byrons and an os lc 4 plug will cure that
 
I know Traxxas recommends ONLY their fuel with their engines but changing brands to Byrons or O'Donnell, etc. could help.

Is your engine new or used? If you bought it used, assume it has some mileage and the sleeve has lost some pinch. Front engine bearings tend to leak more also, both can effect consistant engine tune.
 
I know Traxxas recommends ONLY their fuel with their engines but changing brands to Byrons or O'Donnell, etc. could help.

Is your engine new or used? If you bought it used, assume it has some mileage and the sleeve has lost some pinch. Front engine bearings tend to leak more also, both can effect consistant engine tune.

new motor, saved the carb,and pullstar and header/pipe from a 3.3. Ok i just ran out got a can of wd-40 and put it on everywhere. No change in idle or rpm nothing. I started after spraying after start up then i let it warm up and sprayed more. No change in nothing just made a mess. I made sure i got it on the carb and i checked the tank just about every where. See traxxas said if i am over 4 turns on the high end it is a leak. I sprayed it on the tune pipe any spots where a seal would be that COULD leak. I am kinda confused lol
 
I still recon you need to get a kit for the carb and rebuild it especially if it's a 2nd hand one and for the sake of 5 bucks
 
I still recon you need to get a kit for the carb and rebuild it especially if it's a 2nd hand one and for the sake of 5 bucks

I am going to check the seals on it and , go to the auto store and seal it up . I am working on my sc10gt now looks like i have a lose flywheel. I can not catch a brake good thing i have free time so i can get things in order. thanks for your help
 
i was on my way out late this morning. I have not had a chance to even run off road with my maxx yet. I went to a local park i did some speeds and i did some on off throttle driving and i seen pretty good temps and good smoke and good idle. I forgot my body so i ran with out it but i did not do any jumps nothing like that. I seen 230-250 range i did see 270 but that was with little fuel left and i just did a very long speed run. I was able to bring it in and let it idle and give it gas it was showing sings of the low end being a tad rich. i was getting great punch off the line but the pinch test was like 5 seconds . It was around 30 deg and i felt happy where i was at. I did not get anything to seal the motor but its going to snow tonight in to tomorrow so i might do it tomorrow. I even got to start my sc10gt but my remote batteries just about died on me ..So i had enough time to check the fly wheel it started and did not stall so i was happy. I know i am rich but i am happy with how my maxx drove. I seen temps fall well i was stopped as where i was seeing temps going real high a few days ago. I am pretty darn happy i had my girl with me and she seen me so happy this was the first day i had fun with my rc. I even used my new proline tires and they did great on the hard dirt
 
sounds like a win to me ,happy days!

yeah i got greedy. I ran my sc10gt i went in for the day. My glow plug striped the whole that it goes in. For some odd reason my traxxas glow plug remover tool did this. Sure i did but its ok i got a new one on its way it was a few bucks to bad that was my new servo money but i did get my new t maxx filter and 50 body clips i lost all mine but 2 i think there all over my house lol.
 
lets get you guys a update... I have got a new 2.5 air filter for my t maxx. I placed a order for a medium glow plug to try out as i have a few hot plugs on hand. I got 2 new fuel filters as well. I have one but its kinda to big and i do not have a good spot for it the new one's i got are smaller and a i got a good deal. I got some snow the other day so my maxx is just siting. I all so got a traxxas 2070 servo, i know its not a metal gear servo but i am not to hard on my rc trucks and i think for what i paid i did well. I think the 2055 did ok in the park but with the new servo i should be happier with how it handles. I will stick with the park its big and wide open and fenced in. It has grass/dirt and i know i can build a small jump and bring it with me. Its only a few min from house and its a great spot. I did install my 2.5 rear shock tower so now i can move my shocks around as i plan to get better shocks soon. I used my gray receiver battery box and it looks much better and i do not have to worry about screws striping out no more. I really like the look of it, i did not use the battery box i just moved my receiver hump pack up front with my on/off harness. My maxx is starting to clean up, i need new bumpers, i can use new shocks and i could use one lower rpm arm to complete my rpm full front set. I need to upgrade the whole rear as i still have the black bulk head and my lower a arms need to be upgraded. I really do not have much left to do as i can get away with the shocks so another 50.00 or so and i will be sitting real nice. Oh yea i pulled a few spacers and my maxx is sitting lower and i used those spacers on my sc10gt to raise it up as it was bottoming out well driving. My maxx is so much better sitting lower i like the lower ride hight.
 

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