nitro beginner needs help

[edfdave]

Hi, my son has been trying to break in his new RC nitro 'petrol' car and is in trouble. He's managed to run one tank thru' to start breaking it in. Great so far. Today he could not start it again and something has broken. It seems there is no tension in the pullcord and the you cannot see the piston moving in the cylinder. Can someone give an idea of what has most likely happened and how tricky it is to fix (& cost) please ? I have one very unhappy teenager now.

 

[darkslayor24]

pull your pullstart off (4 screws) be carefull not to pop the spring out. next, take the backplate off (4 screws behind pullstart) be extrmely carefull not to get dirt inside the engine. do a quick look over to make sure that nothing is broken (ie. connecting rod) make sure the one way bearing on the pullstart isnt slipping. does the engine turn over by hand?

 

[Foolproof]

Well I am no expert by no means but it is possible that it was ran hot/lean for to long and now the piston has no compression. Like I said it may or may not be that and could be many other things. I had a ton of issues with my Revo 3.3 during breakin because the throttle servo was not set correctly from factory and the idle screw was stripped into the carb housing so i couldnt adjust the idle. I have fixed quite a few other issues like the steering servos binding etc etc that was messed up new out of the box.
Also you may need to post what model etc that you are working with so that others may better help you. Good luck with the nitro.

 

[edfdave]

Hi, thanks for the ideas. I will ask my son for some more detail but I think the pull start is retracting back in (so the spring return is okay) but that it feels like there's no compression. This may be either because it's genuinely lost compression or because the piston is not connecting with the starter. My son seems to think it is the latter. If it is the latter is that a job a novice like me could sort out ?

Also, do I need to take the backplate off to turn the engine over by hand or is there another way of doing this without taking anything apart ?

 

[TGL]

You can turn it over by hand without having to take off the backplate.
With the pullstart in place, it should only turn one direction - so don't freak out.
Darkslayor's advice to pull the backplate would give you the best view of the internals though.

If you're shy about removing the backplate, pull the exhaust header from the exhaust port and turn the crank over.
If your connecting rod is broken, you won't see the piston moving up and down.
If the piston is moving, it means you lost compression.
Either way, you'll then be pulling the backplate to replace parts - or getting a new engine.

It's not rocket science to replace a piston/cylinder/connecting rod.
You'll need to remove the cooling head in addition to the backplate.
Before you remove the piston/cylinder/connecting rod observe the orientation of the parts and jot down some notes - sketch out (diagram) what you see.
The parts align in certain ways and the notes will help when you put it back together.

The body of the engine usually has a little pin sticking up and the cylinder usually has a matching notch which helps you orient the exhaust port.
Observe any cut-outs on the bottom of the piston or small holes drilled into the connecting rod where it connects up to the crankshaft. The holes direct lubrication and the cut-outs (if they are there) fuel air mixture.

 

[Metalhead Matt]

Check the one way bearing. It's the bearing that sits in the pull starter and slides over the crank. It grabs in one direction and free wheels in the other. This is so it grabs the crank and turns the engine over when you pull the cord, and free wheels once the engine is started. It's most likely dirty. Clean it with da, nitro cleaner, or throttle body cleaner(the automotive stuff). Make sure it's working correctly by trying it by hand. If all is good, reassemble and continue break in.

 

[edfdave]

Hi, thanks for all the really helpful advice. The car has a Team Infinity 18 cxp engine, car is a Bug Crusher Pro if that helps.

We've taken off the pull start and that looks fine but when we turn it over by hand the piston does not move. However, when we turn the drive coming out the other side from the pull start then the piston does move and it feels like there is compression. Does this mean it is most likely to be the one way bearing on the pull start side ?

We haven't managed to remove the backplate to check inside yet as the screws are so tight that all I've done is round off my allen key. I guess I need super hard allen keys ? I'm worried that I could destroy the screw heads tho' and then never get the backplate off.

I may check with the supplier to see if this might be covered under the warranty as I don't want to go any further than I have to.

 

[Metalhead Matt]

You need to use quality hex drivers. The bolts most likely rounded with the driver. Does the owb come out of the recoil? If so, clean it and slide it on the crank the way it goes and turn it. If it grabs, your golden. If not, replace. It may seem fine by hand, but it may slip when it's under the full pressure of the recoil. Check it for cracks too.

 

[edfdave]

Hi again. Just realised that the one way bearing is the thing that sits OUTSIDE the engine on the crank and fits INTO the pull start. Yes ?

So ... I've checked again. We pulled off the one-way bearing and tried to turn the engine by the crank. Piston did not move. Then we turned the big cog wheel on the other side and the piston did move up & down. I don't know what this tells me, any further ideas anyone ? It seems that crank is not connecting on the pull start side but the drive on the other side is ..?! Are there any pictures that might show me what's going o inside?

I'm very nervous about messing up the screw heads on the backplate as they are on solid.

 

[Metalhead Matt]

CLEAN OR REPLACE YOUR OWB. You shouldn't be able to grab the tiny crank and spin the engine. Compression won't allow this. By spinning the flywheel(big cog you mentioned), you have determined that everything is connected. The owb is your problem.

 

[edfdave]

Hi, sorry but I don't understand ... total newbie! When I turn the owb one way it seems to turn the crank and it free wheels the other way. Likewise if I pull off the owb I can definitely turn the crank by hand (both ways). But either way the piston does not move. Not sure what you mean about 'compression'.

I've found a diagram and had started to think it was a problem with something called the "Clutch Rolling Set" which seems to be turned by the pull start and which should then then turn the main engine crank/piston (and I guess disconnect once it is running).

 

[Metalhead Matt]

"Clutch rolling set" is the one way bearing.

 

[edfdave]

Thanks for your patience and bearing with me ... I'll tell you what I can see. After I take off the pull start there is a crank and on it is a hexagonal shaped thing that I assume is the owb and this fits into a hexangonal indent on the pull start. When I twist the hexangonal owb it seems to turn the crank but the piston does not move. However, when I turn the the crank sticking out the other side then the piston goes up & down.

On the 18cxp engine diagram that came with the car the "Clutch Rolling Set" is shown as the crank itself that goes inside the engine backplate and on the end there is a disk with a notch cut out of it that looks like it is supposed to connect to a pin coming out of another disk connected to the crank shaft.

Can you picture that ? If the owb is the hexagonal thing then I guess the he picture has nothing to do with my engine !?

So seem pretty sure that the owb is the problem ? I'm confused because on the face of it it feels like it is turning the crank tho'. Maybe it is turning a bit bit and slipping a bit ..?

 

[Metalhead Matt]

Ah, I know what setup you mean now. You could try soaking the engine in some fresh fuel. Maybe overnight. Just make sure that the backplate is covered by the fuel. You could also get some nitro cleaner, blast the heck out of the bearing, put the shaft in and turn it a few times, and repeat until it works again.

 

[edfdave]

Sp do you reckon the diagram I've got is definitely wrong then ?

So ... just to confirm ... I leave the backplate on and do as you say ... give the whole engine a good soak (leave out the glow plug ?), get the owb good and clean and then put it all back together and give it another go ?

Thanks again. I'm learning some stuff !



PS: I've emailed the company I bought it off as well but I guess they'll say it's not covered by a warranty.

 

[Metalhead Matt]

Well, that's what you would do if you can't get the back plate off. If you removed the backplate, you could just soak and clean the roller clutch that is attached to it or whatever. Every engine I've had to deal with has had an external owb. So it's as easy as taking the recoil off, removing the owb from the recoil, clean it, and reassemble. 4 bolts. Others should chime in with some more advice.

 

[edfdave]

My son has made a little youtube video showing the little *!&*! which may help those of you in the know who are trying to work out what i'm on about.

[ame="http://www.youtube.com/watch?v=hD3CHXgIHV4"]YouTube- THE DAMN ENGINE!!![/ame]

:\

 

[Macguyver]

looks like the part of the crankshaft where the OWB goes is not conecting with the piston.....take the backplate off and check it ...that part of the shaft should have a knotch inside that conects where the conecting rod goes on the other half of the shaft ...something may be broken inside

hope this helps ... i dont think you have a choice but to take it appart ...and when you do that ...seal the engine good when you put it back together

 

[TGL]

The owb is meant to grip in one direction and spin freely going the other direction. That way it will grip to turn the engine over (like when you pull on the pullstart) and then when the engine is under it's own power, the owb can spin separate of the shaft (or vice versa) and not tear up the pullstart.

Sounds like Metalhead's got you going on the right track.
Have you tried removing the "hexagonal thing" from the engine by pulling it out?
Like Metalhead mentioned, clean it with some nitro cleaner, or denatured alcohol or fuel if you have nothing else.

I think you'll eventually want to pull the backplate, but until then if simply cleaning the owb gets it to grip and turn over the crank you're on your way.

Wait a second, I just now saw the video...
Is that the engine in question?
If so - that hex thing is the OWB.
You mentioned that when you turn the flywheel, the piston goes up and down.
When you turn the shaft on the other end, does the piston go up and down?
I can't really tell from the video.
If it does move, try cleaning the hex thing - or buy a new one - and make sure you install it so it catches in the right direction.
You'll want it to catch when you turn the owb clockwise and spin free going counter-clockwise.

 

[Metalhead Matt]

I did have an engine like that at one time. It was out of a Megatech touring car. The hex and the shaft are one piece, and you kinda twist it and it slides out of the engine. The shaft was totally round and smooth. I think that the roller clutches on the inside, behind the backplate, could benefit from soaking in fuel/cleaner. I'm willing to bet the rollers are gummed up with fuel. It would be best to take the backplate off, and visually inspect everything, and also to keep whatever is gumming up the rollers out of the engine. Kinda covering some old ground here, but I wanna make sure TGL knows where I'm coming from. Being light years ahead of me with nitro experience, this cat can get you going. Edit: I just re-read that this is a new engine. Something could be broken. Possibly from trying to start the engine flooded. It's easy to do, especially on a new engine. Fuel isn't as likely to gum up a owb when it's new fuel. Possible though.