Nitro engine running backwards?

[bigblockmaverick]

My buddy just swapped the sirio .18 into his t-maxx and it has had about 10 tanks through it. Last night i was helping him get it started and it fired up funny. Now i was skeptical at first but i was throttling it up to let her war up and noticed the spur gear was spinning right along with the engine. Thinking the tranny was messed up , we shut the engine down. rotated the spur gear and nothing was wrong. Fired the engine back up and everything was fine. I swear beyond the shadow of a doubt the engine was running backwards. Is This Possible? Sorry for the long thread.

 

[visioneer_one]

Its certainly possible. That's usually a sign of too much compression or too hot a glowplug - on startup the engine fires early (before TDC) and runs backward, albeit poorly.

Try a cooler plug. You can also try shimming the existing glow plug up with an extra washer to lower the compression.

 

[bigboystoysguy]

theroreticaly, its impossible to start up backwards just cause of the porting and the way the fuel is delivered to the combustion chamber. now if there is fuel in the chamber all ready it may pop in the oppisite direction but it would never run backwards, now if you can prove me wrong ill definately listen to your argument!!:thumbup:

 

[Error401]

2 stroke nitro engines will run backwards, sort of. They run like crap, but the will run. The problem with car engines running backwards is the pull start, or on traxxas motors the EZ-start, or roto on the other engines. When the engine runs backwards, it tries to engage the 1 way and the PS will stop it, dead. The roto and EZ will put enough strain on it to kill the engine too.

In the case of an engine without any of these starting options, they will burble a little at idle, but as soon as you give it throttle, it'll die.

 

[bigboystoysguy]

hmm.. that does make sense but I've never seen it happen, at idle i geusse it would run ok but the timing on the intake port of the crankshaft just makes it seem impossible, thats all:smart:

 

[Error401]

They will, but alot of fuel gets ejected out of the carb. Yes, the timing is all wrong and they will only run backwards at idle. Used to be a minor pain when I flew planes, they did it all the time.

Point is, they won't run backwards at anything above an idle, and only if the engine has no onboard starting system (pull start, ez, or roto start).

 

[chevyguy80]

The engine has the stock ez start and the one way bearing, its almost dead but it still engages. I am not trying to blow smoke up anyones butt , but i am not totally new to the nitro scene, and i swear i saw it with my own eyes. We were running the truck at night in a lighted parking lot. So it was a little dark. The only reason i even looked at the spur gear it due to the fact i was giving a little gas and it was bogging out, but not even trying to lurch forward. I thought at first the motor had vibrated loose and the clutch bell was not engaging the spur. I thank you for all your posts but if it could happen i am hear to say it did.

Oh by the way its my truck in case you guys are wondering why i posted the deatails on my posesed engine.

 

[Error401]

Cool.

 

[mickmack]

This reply is 6 years on, however I purchased a second hand tmax.

It appears it is running in reverse, the g'box was minced, so put it back together with a forward only kit, thinking that there may have been other issues so this was the easy solution.
ran it and it went backwards!
The ez start had been converted to a pull start.
I put it back together with the backwards and forwards gears.
It is running forward off the backwards gears, and using a heck load of fuel, throwing out heaps out the carby.
but apart from that seems to run okay!
I am yet to take apart the pull start to check.

From the front of the car the motor spins anticlockwise.

Mike.

 

[Metalhead Matt]

The only way an engine could run backwards is if the ez start was wired backwards and the one way bearing was installed the wrong way. A pull start will only turn the engine over in the right direction. If the owb was installed backwards in a pull start, the rope would pull out with out spinning the engine, and then the owb would engage, making the rope not want to recoil. Your engine is spinning the right direction.

 

[olds97_lss]

This reply is 6 years on, however I purchased a second hand tmax.

It appears it is running in reverse, the g'box was minced, so put it back together with a forward only kit, thinking that there may have been other issues so this was the easy solution.
ran it and it went backwards!
The ez start had been converted to a pull start.
I put it back together with the backwards and forwards gears.
It is running forward off the backwards gears, and using a heck load of fuel, throwing out heaps out the carby.
but apart from that seems to run okay!
I am yet to take apart the pull start to check.

From the front of the car the motor spins anticlockwise.

Mike.

They will run backwards, even with a pull-starter or Ez-start. I've had it happen on more than one occasion with my OS21 RG, which is a pull-start engine.

Sounds really weird and blubbers, but I could rev it up, which caused the spur on the savage to just sing. Both times, it would back fire out of the carb, then start running in reverse.

The OWB was almost shot and slipped very easily and it was around 50F outside both times it happened. Too cold, too rich and a weak OWB were my causes.

I killed the engine and fired it up again, then it started in the right direction. Was really weird to hear it though.

 

[mickmack]

Is my engine running backwards?

Okay I dissambled the pull starter (it has had the ez start system removed),
I have found that the pull starter can only be assembled one way, meaning that I can't start it the other way anyway. The others on the net seem to turn in the same direction (clockwise from the rear of the engine) (Incidentally I did try to assemble the pull starter the other way however it came unsprung after working a few times because of the hitch point will no longer make a u bend therefore would come out, at the same time I changed the one way bearing to go the other way.)

From the front of the engine when starting it runs anti-clockwise, is this correct.
Now if this is correct and this is the direction the engine is supposed to run then why is my t-maxx running on the reverse gear when it is going forward, (so far it has stripped two reverse gears! because it is running on them to go forward when the gear is designed for only occasional use).

As mentioned I had put the forward only conversion kit in because I was annoyed at replacing reverse gears only to find that the Tmaxxx would only go backwards with the forward conversion kit in!!!!!!!!!!!!!

I am not sure whether it is related but to run the truck I had to slow the acceleration from neutral otherwise would cut out, and run higher rev's than I would otherwise expect.

I have no idea what is goint on:\

>Mickmack, the diffs are probably installed wrong. Also another
>common mistake. Done it myself ....once

Thanks for the reply man, it must be just the g'box assembly, didn't know it could do that!

Mike.

Should the engine run counter clockwise from the front of the engine just to confirm?

 

[olds97_lss]

CCW from front, yes.

The problem you may have been having was that you were in fact driving in reverse all this time and didn't know it. If your diffs are both upside down, it causes the truck to run backwards with the FOC installed. So, if your trans works now and it goes backwards, pull the diffs and flip them and your problem should be solved.

It does seem stupid, I admit, but once you have a diff in your hand, spin the input shaft and note which way the output shafts turn. Twist the diff and spin the input shaft the same and your output shafts will spin in the opposite direction as before.

I've screwed up installing maxx diffs before. Once, I got both backwards causing your problem. The other time, I got one backwards and one right. That one really threw me at first (as it was the first mixup I did). I'd hold the truck in the air, rev the gas and the wheels would spin (not paying attention to the direction of the spin). Put it on the ground, rev the gas and it would just grunt snort smoke and sit there doing nothing. Then I picked it up and rev'd slowly... and realized what I had done.

 

[mickmack]

Thanks for the advise Man, you sorted me out.

Mike.

 

[mikegigabyte]

I've had a diesel powered whacker run in reverse, exhaust was coming out of the air box

 

[bigjay]

I've had a diesel powered whacker run in reverse, exhaust was coming out of the air box

Diesel engines run strictly off of compression.

You can take an old diesel truck and role start them backwards. Backwards meaning the transmission in the opposite gear to the way you are moving. They run like crap, but you will then have 1 forward gear and several reverse gears.

 

[Nathan44]

But still why would the exhaust be coming out of the air box???

I am so confused on that!!! Was it because the piston was spinning the other way causing gas and exhaust to shoot out the air box?

 

[2revo1maxx]

I put one diff in backwords and my maxx played tug 'o war with it's bad self!

But still why would the exhaust be coming out of the air box???

I am so confused on that!!! Was it because the piston was spinning the other way causing gas and exhaust to shoot out the air box?

Because it's breathing air through the exhaust, and blowing spent gasses out the intake. It would have to be direct injected to do this. I think most big diesels are.

 

[Nathan44]

Ohh okay... I got ya now!

 

[jsnone1]

Okay guys, I have Nitro Stampede that I just put a newer engine on and the engine is running BACKWARDS!!!!

Here is a video:

How do I fix this???? I have let it sit and tried again, several times, with the same results!!!

Could it have anything to do with the clutch???