"Like turbo" noise when accelerating and oil leak after crash

[kierownik]

Hi everyone.

I need some help fixing my nitro buggy.

It's a basic buggy with vx18 engine and 2 speed gearbox. It's my first nitro car so I'm new to the hobby but already hooked up.

I crashed it the other day. It went sideways and it hit the kerb. When it hit the kerb the engine moved a bit but enough for the gear mesh to separate from the central differential (gearbox).  A silicone exhaust coupler also got damaged (slight crack on the side).

1) I repositioned the engine and managed to start the car, It runs but.... When on the ground and accelerating it makes a noise like if it had a turbo. I thought it could be the damaged exhaust coupler but I temporarily fixed it and it still makes that noise. Doesn't seem to be making it when I rev the engine with wheels off the ground. What should I check and try to fix to get rid of that sound?

2) The oil seems to be leaking from somewhere, can't locate it. But I think it might be a rear pull start plate. Also exhaust manifold gasket probably. But when I cleaned the engine yesterday and fired it up for a moment it looked like the pull start plate. What else do I need to check?

3) When I pull my buggy backwards it makes that spinning noise, which I can't remember if it was making before the crash 🙈
4) Also when the engine starts it revs up a bit like if I'm giving it some throttle but I'm not and it starts pulling and wants to drive away on it's own. That wasn't happening before the crash.
 

I'll be very grateful for any help.

 

Edited July 2, 2021 by kierownik

[kierownik]

Ok I think I managed to fix that whistling noise. The clutch's bearing didn't sit in properly. Reassembled it and lubricated the bearing slightly and it's how it should be. One thing I noticed is that the shaft which the clutch sits on is very slightly bent when I spun the engine without the glow plug in. I'm not sure if it was like this all the time but I'd imagine so as I tried to straighten it and couldn't. It's proper tough. So I don't think that this crash could make it bend. I'll see how it behaves when I get the car running again.

I also sealed the engine properly all around and replaced all the gaskets to ensure there's no more air leaks. 

Now I'm just waiting for the exhaust coupler to arrive, hopefully tomorrow, and hopefully the car will be fixed.

 

Edited July 2, 2021 by kierownik

[Nitroholic]

The shaft is part of hte crankshaft, and if it's bent that's a serious issue for your engine. You clutch will be wobbling as it sits on it, and the mesh will vary as it rotates. If the bend is enough to be noticable....it's almost certainly had it.

 

On the other issues...pulling the car back should make a spinny noise. The clutch bell is spinning freely on the bearings when you do that. That's normal

 

 

[kierownik]

7 hours ago, Nitroholic said:

The shaft is part of hte crankshaft, and if it's bent that's a serious issue for your engine. You clutch will be wobbling as it sits on it, and the mesh will vary as it rotates. If the bend is enough to be noticable....it's almost certainly had it.

 

On the other issues...pulling the car back should make a spinny noise. The clutch bell is spinning freely on the bearings when you do that. That's normal

 

 

What would you suggest me to do then? Replace the crankshaft? I'm trying to find them online but they're hard to get.
Do you think it bent when I crashed the car? Or was it like this from new but I never noticed?

[Nitroholic]

Dont know how bad the bend is...but if you are seeing it with the naked eye...

 

Its possible the crash damaged it, but if it has always been bent, then the vibration from the motor must have been pretty harsh. These little motors spin up to around 30,000 rpm .... and a bent crank would mean the clutch/flywheel assembly would not spin true. That would set up vibrations that would be noticabnle.

 

Can you put a picture up of the motor/crankshaft. curious to see how out of true it actually is. I have heard of engiens suffering damage this way...and also getting damaged when being shipped etc. if not properly packed and protected.

 

[kierownik]

14 hours ago, Nitroholic said:

Dont know how bad the bend is...but if you are seeing it with the naked eye...

 

Its possible the crash damaged it, but if it has always been bent, then the vibration from the motor must have been pretty harsh. These little motors spin up to around 30,000 rpm .... and a bent crank would mean the clutch/flywheel assembly would not spin true. That would set up vibrations that would be noticabnle.

 

Can you put a picture up of the motor/crankshaft. curious to see how out of true it actually is. I have heard of engiens suffering damage this way...and also getting damaged when being shipped etc. if not properly packed and protected.

 

I think it must've always been there. Mostly because when I repaired my car and fired it up it behaved and sounded just like before the crash. Either way I won't be driving it any more. I've managed to find a new crankshaft for 18 pound so I will order it and replace it asap.

[kierownik]

Just one thing....

Might be a stupid question but it's better to ask than be sorry afterwards... When I replace the crankshaft and crankshaft only will I have to go through the engine break-in procedure again?

[Nitroholic]

no. The break in is to allow the piston and liner to seal properly. They are a tight fit at the compression end of the stroke as they seal with no piston ring ( which you would get in a larger engine) They need to bed in to avoid damage.

 

The crank runs in bearings, so should be fine. I would take a bit of nitro fuel ( which contains oil too ) and give the crank a coating where it runs in the bearings and where the conrod sits. Just so it has some lubrication for first start

[kierownik]

1 hour ago, Nitroholic said:

no. The break in is to allow the piston and liner to seal properly. They are a tight fit at the compression end of the stroke as they seal with no piston ring ( which you would get in a larger engine) They need to bed in to avoid damage.

 

The crank runs in bearings, so should be fine. I would take a bit of nitro fuel ( which contains oil too ) and give the crank a coating where it runs in the bearings and where the conrod sits. Just so it has some lubrication for first start

Yeah I was gonna do exactly that. 

Thank you very much!