Heat issue

vectra

It is to do with my sons T-Maxx.

The usual scenario.
Fill her up..
Start her up..

Drive it for a few minutes and then you could fry an egg on the Cooling head.

(( Not down to tuning I might add :rolleyes: ))

Took the engine out today to check for air leaks

Blocked the carb and exhaust port with my fingers and blew in the fuel pipe.
Lo and Behold... A steady stream of bubbles coming from Behind the flywheel.

Can this be the cause as I have read other posts and it didnt seem to point to this being the prob.
But if someone here can say for definite that this is the problem then fine.. That will make me a happy camper.

ONLY..
What will it take to sort the problem?

tallus

mate of mine had that flywheel thing, I dont know that it effected the heatsink tho, we ran it up and down for about 10 minutes-ish on my street and it performed well enough. Ok just found the orig thread, and his Issue was not related to overheating but here's the original thread Vec.
http://www.boards.ie/vbulletin/showthread.php?t=2054867678&highlight=acme
*edit* no use to you really I suppose

coolwings

You might hava a leak while it's stopped.
But it "should" go away when it's running.

Here's why:
The piston going up and down is a pump.
And it's pumping fuel-air mix from the hollowed out crankshaft at the bottom of the crankcase, upwards into the ports leading to the compression chamber.
Now when it's pumping away, there should be high pressure ((very high) under the piston ports, waiting to go up, but there should be a vacuum at the ends of the crankshaft to suck the fuel into the lower crankcase, ready for pumping up.
Many engines hava a "barbers pole" thread scribed into them at the end behind the front bearing, and this thread acts as a pump, so theoretically air should go in while it's running, and fuel should leak out when it's stopped.

Now that's how they are supposed to work.

But I haven't opened up and worked on the particular engine you're talking about, except to say if it doesn't have these features, problems would be induced by the cost cutting that removed them, if you know what I mean.

What I mean is I can't be more specific description-wise about how your one looks inside.

But I trust this will help you spot the problem.

Things to look for:

• bent shaft due to impact
• worn shaft with micro flats on the round surface where a leak happens
• cracked inner bearing sleeve (assuming ball raced)
• bearing in crooked into casting due to "burr" of casting "flash" causes leak on outside edge
• porous bearing due to wear in the ball race and balls are smaller than should be

The above list will cause, as I said, air to get in while it's running, and that would lean your engine out extra, over and above the settings you have tuned in on the carb needles. This would make it run hotter, and possibly cut out at 100% throttle, or maybe at fast idle entering transition to main needle (=25-30% throttle) . So you would have to tune it richer to cancel this problem.

But usually when we tune, we don't count the turns of adjustment, we listen to the engine, and tune for correct response from the engine. So if these problems appear, your first observation is "That's funny - it used to be best on (e.g.) 3 turns open, but now it's better on (e.g.) 4 turns, and while it should be real rich on 4 turns, it's acting lean on 4. I wonder why is that so? "

vectra

Coolwings wrote:

cracked inner bearing sleeve (assuming ball raced)

I think that the bearing may be knackered.
I took the cooling head off and spun the engine by the flywheel and to say it was "smooth" would be totally wrong.
It felt like Bearings grinding.. :eek:

coolwings

That would be easily fixed, just a ballrace to replace, however you would need to check carefully to see if the bits of metal coming off it have eroded the piston -liner set. For no doubt those bits went in and up with the fuel-air mix.

If the compression is OK that would be a good sign.

How much oil (%-wise) is in your fuel? You're using 16% nitro, right? I seem to remember you saying a while ago 15% oil (or was it 10% as in Dynaglow) was enough! Of course - lubrication might not be relevent in this case......

Pull it apart and check all the rotating parts for scoring & wear, and also the piston & liner. Hopefully the ballrace will be the only part needing replacement.

Peeping in at the piston crown would be interesting, as if it is smooth that would help confirm no abrasive bits were present.

vectra

16% Model Technics mainly. I put some Blue Thunder 20% in there a couple of times.

I am still not certain though that it is the bearing as there seems to be no "play" in the shaft in any direction.

Piston and Liner appear to be ok as well.. Now saying that I havent removed them .. i just had a close inspection of the liner and could see no visible scores.. also... The Piston is still dame tight towards the top and the grinding That I am feeling seems to be at the exact point of where the piston passes over the inlet and outlet ports..

tallus

My HPI engines make a "click" at that point too and there's nothing wrong with them.

coolwings

Vectra - We crossed posts - I added a bit to my last one as you replied

Debris goes up the fuel ports and ideally straight out the exhaust port.

It may be that the piston caught a bit at the lip of the exhaust port, as the bit went out. If the piston got (or the liner-to-port edge ) hit you might have a notch which would catch slightly as the piston goes up past the spot.

This is speculation, of course, but if that happened you would see it on a close inspection.

I am discussing debris, but if the bearing is OK - what causes your air leak?
And where did debris come from? I am assuming the problems are linked, but it does not have to be so.

Is it possible that the bearing is the only thing "gone"? I think I hear your workbench calling for you! :-)

vectra

coolwings wrote:

Vectra - We crossed posts - I added a bit to my last one as you replied

Debris goes up the fuel ports and ideally straight out the exhaust port.

It may be that the piston caught a bit at the lip of the exhaust port, as the bit went out. If the piston got (or the liner-to-port edge ) hit you might have a notch which would catch slightly as the piston goes up past the spot.

This is speculation, of course, but if that happened you would see it on a close inspection.

I am discussing debris, but if the bearing is OK - what causes your air leak?
And where did debris come from? I am assuming the problems are linked, but it does not have to be so.

Is it possible that the bearing is the only thing "gone"? I think I hear your workbench calling for you! :-)

Top of the piston looks "Mint" when I say mint I mean "Not a mark on it" except for the usual discoloration"

What causes the Airleak...?? { Beats me }

What causes the Debis..?? { What debris? }

coolwings

Open it up and inspect the crankshaft and the front bearing, and it's seat in the crankcase to find the airleak.

A good test is to put a "thin" liquid such as unleaded, into the crankcase via the carb, and observe if it leaks out and where.

Don't forget to oil it up afterwards when you do this.

Debris would be any bits breaking off a worn bearing.

vectra

coolwings wrote:

Open it up and inspect the crankshaft and the front bearing, and it's seat in the crankcase to find the airleak.

A good test is to put a "thin" liquid such as unleaded, into the crankcase via the carb, and observe if it leaks out and where.

Don't forget to oil it up afterwards when you do this.

Debris would be any bits breaking off a worn bearing.

Will do that test tomorow.
And yes,
I do know what "Debris" is.. :rolleyes:


** EDIT **
I just had a thought..
Seeing as my Revo is going fine... Maybe if i take out that engine and dunk it in water to do the same test..then I could find out if these Air Bubbles are normal?

coolwings

vectra wrote:

....Seeing as my Revo is going fine... Maybe if i take out that engine and dunk it in water to do the same test..then I could find out if these Air Bubbles are normal?

Sure you could.
But that means interfering with the one working well, on acount of the problem one.
I wouldn't do it myself.
My thought would be that the problem one will consume enough time anyway without taking chances with my good one, if you see what I mean.

But I get the point - it would give you a baseline standard to compare the other one with.

vectra

Deffo a serious problem with the Maxx..
Took it out again today and it would fun for mayber 100 yards and stop with smoke rising from it and "RED HOT" :eek:

Could get no more than 2 passes with it before it would cut out..
tried 16% and 20% in it.. No difference

Took the Revo out a while ago and stuck some 25% in it

Probably was a little more "boost" in it but nothing worthwhile over the Blue Thunder 20% to be honest.

Now I am thinknig.. " Why not get some 25% Model Technics "
Would it be any good you reckon?


As for the problem with the T-Maxx..!!
Well to be honest, I am toying with the idea of buying him a New revo engine (2.5r) for him and be done with it

Cant be A*s*d messing about with it..Trying this and trying that etc..

g5hn710m4xpdwy

why only get him that... get him a bigger and faster engine

vectra

Flunked wrote:

why only get him that... get him a bigger and faster engine

Bigger faster engines eventually ( sooner rather than later) burn out Diffs etc. So, No need for that really.

Plug

vectra wrote:

Well to be honest, I am toying with the idea of buying him a New revo engine (2.5r) for him and be done with it
Cant be A*s*d messing about with it..Trying this and trying that etc..

Vectra your better off buying him a new engine, I had simuler problems and just said fu(k it a new engine is the way to go;) If you need any bearings I have a few, they should do the job:)

flunked wrote:

why only get him that... get him a bigger and faster engine

More money, more bolloxed up diffs etc any way the traxxas engines are little rocket engines:D Over 40+mph from a .15 engine, now thats good;)

coolwings

vectra wrote:

... 100 yards and stop with smoke rising from it and "RED HOT" :eek: ..... tried 16% and 20% in it.. .....Cant be A*s*d messing about with it..Trying this and trying that etc..

Well - here is one thing to try - it's quite easy to do tomorrow.

Take one tankful of the juice you're runnning it on right now (=100ml).
Put it into a bottle
Add 2 x teaspoonfuls of castor oil, three in one oil, sewing machine oil, fishing reel oil.
Shake hard until mixed in.
The liquid may go cloudy for a minute or so. That's ok if it happens.
Put it in the car.
Run it for 100yds plus.
Tell us how you get on.

This will drop the temps and demonstrate how much power the engine has at a lower temp than it is now.

Ah go on - give it a go - go on, go on, go on, go on, go on, go on :-)

Plug

GO ON

vectra

coolwings wrote:

Well - here is one thing to try - it's quite easy to do tomorrow.

Take one tankful of the juice you're runnning it on right now (=100ml).
Put it into a bottle
Add 2 x teaspoonfuls of castor oil, three in one oil, sewing machine oil, fishing reel oil.
Shake hard until mixed in.
The liquid may go cloudy for a minute or so. That's ok if it happens.
Put it in the car.
Run it for 100yds plus.
Tell us how you get on.

This will drop the temps and demonstrate how much power the engine has at a lower temp than it is now.

Ah go on - give it a go - go on, go on, go on, go on, go on, go on :-)

This is going to sound dumb.. But here goes..

2 Spoons of each or just 2 spoons of any one of the above oils?
:rolleyes:

vectra

Plug wrote:

GO ON

NO BOTHER..!!

BFassassin

i think he means 2 spoonfulls of one of them

coolwings

Yes - 2 x teaps of any one - 10ml of any medium viscosity oil.
An oil that can take high temp.
Any of these will be ok for one tankful.
Remember they are added to the oil already in your existing fuel, so the engine will definitely be cooler, slippier inside, and you can see what difference it makes.

vectra

OK,

In the meantime..
He is a vid clip (again done with my mobile..Too lazy to bring the vid cam along.:D )
Revo running 25% Nitro

tallus

excellent bit of video
bring the real cam along next time man, jaysus someone has a very steady hand !!!!

vectra

tallus wrote:

excellent bit of video
jaysus someone has a very steady hand !!!!

My 14yr old son

Back to the T-Maxx issue..
Just remembered that when I was re-assembling it... The twin exhaust system that I bought sometime ago has a Rubber "O" ring to seal it to the head but this looked a bit "better for wear" to be honest and i am wondering if this would contribute to the heat issue?

There is no oily residue coming out of there.
But maybe an air leak there could be the culprit?

BFassassin

its a possibility vectra and im sure it wouldnt be hard to replace.
back to the video though i once agin couldnt watch it from putfile:eek:

Plug

vectra wrote:

My 14yr old son

Back to the T-Maxx issue..
Just remembered that when I was re-assembling it... The twin exhaust system that I bought sometime ago has a Rubber "O" ring to seal it to the head but this looked a bit "better for wear" to be honest and i am wondering if this would contribute to the heat issue?

There is no oily residue coming out of there.
But maybe an air leak there could be the culprit?

I don't think its that cause theres 2 screws holding it in and they wouldn't leave out air leaks. Could even be fuel or a bad tune It could be the piston and slieve, if it is, it's time for the back burner. Good way to find out is take out the plug, make sure the piston is higher than the exahst and the intake port, fill it up with oil, put back on the plug, turn the engine and if oil comes down at the side of the slieve its pretty much bolloxed:eek:

g5hn710m4xpdwy

ahh, just put some petrol in the tank and fire it up, then it will give you a better eason to get a new engine... cmon, ebay ebay ebay...:rolleyes:

vectra

Plug wrote:

I don't think its that cause theres 2 screws holding it in and they wouldn't leave out air leaks. Could even be fuel or a bad tune It could be the piston and slieve, if it is, it's time for the back burner. Good way to find out is take out the plug, make sure the piston is higher than the exahst and the intake port, fill it up with oil, put back on the plug, turn the engine and if oil comes down at the side of the slieve its pretty much bolloxed:eek:

This header is held in place with a spring instead of the 2 screws.:(

Fuel should be fine as it ran perfect on them both before this.

Piston and sleeve is with an eductated guess 100% perfect.:cool:

Plug

vectra wrote:

This header is held in place with a spring instead of the 2 screws.:(

Yeah actually they could be a leak there then.

vectra wrote:

Fuel should be fine as it ran perfect on them both before this.

Thats one more thing to rule out.

vectra wrote:

Piston and sleeve is with an eductated guess 100% perfect.:cool:

You might want to check it anyway, just in case;)

g5hn710m4xpdwy

sorry to take over your thead but its a quick question: I just put evertyhing back together on my buggy but it was running for a few secconds then cut so I richened it and now it runs longer but still suts after about 10 secs, and it cant be too lean still cause its at factory settings and has always run form there... I am blaming the glo-plug but I just noticed fluid coming form somewhere its quite blackend to, so could there be a leak? just noticed there were bubbles in the fuel line? lean? ok now my brand new tank is... LEAKING!