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I've been wanting to try one of Tamiya's nitro's for a while now and have been been passively browsing eBay for a Terra Crusher off and on for a few years.  Never pulled the trigger.  Saw this TNX on Craigslist for $165 (with a Terra Crusher roller) and figured it's now or never.  Haven't started the tear down yet but, being this is my first nitro, wanted to get the motor situated first.

I pulled the carburetor and starting plate to get a peer inside and it looks like shiny metal.  No corrosion visible on the piston or wall from what I can see.  Can't get the head off using a moderate amount of force.  That's got me worried.  In the 1:1 world, I'd use penetrating oil and a torch on the stubborn part.  Pretty sure that would be a bad idea with this motor.  Maybe penetrating oil and heat from a heat gun?  Should I not tear down the motor at all?  It's 10+ years old.  Seems not disassembling to get a better look at stuff would be a bad idea.

Also, it needs a new filter.  Any tips on where to find one?  I've read it's a Force motor but I can't seem to find a filter specific for it.

And it didn't come with the Tamiya hand held rotor starter.  Would an electric drill work?

I have no plans on bashing it but would really love to at least run it up and down the yard.

Any tips/tricks/advice would be greatly appreciated as I'm more then a little worried about burning up the engine.  I did download the two associated Tamiya guides and plan on putting all the motor settings back to stock.

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 I've had success using a small butane soldering iron (no tip, just the flame) to loosing up grub screws where they were assembled with loctite. Can you get a flame or soldering iron tip onto the screw? 

Will follow this thread as I have often thought about getting a nitro to play around with.

 

Good buy too, if the body and tyres are original it does not look like it have done much work.

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Any 1/8 air filter assembly will work, I’d look at the racing brands like Mugen, TLR, X-ray, AE Kyosho for a complete assembly, if you do run it, ensure to use a foam filter oil also (stay away from the K&N look filters, they look cool, but do not work well in this scale).

I imagine a drill would work, additionally any rotor starter would work too.

Has the engine even been run? I would remove the glow plug, drip a couple drops of oil into the hole and try and turn the flywheel over, with the plug removed, if the engine is properly broken in, there should not be any (or at minimal very little) metal pinch left between the piston and liner. If it still feels very tight, the engine will need to be finished running in

Good luck with it, looks like a great example

 

**Edit - looking at the pics again it does look like the engine has been run based on the header pipe, I’d still do as I suggested anyway

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In regards to the engine being ran, the seller made it a point to tell me that he used after oil after each run but said it's been sitting in a closet for years.  He mentioned he lives in an apartment complex and got too many complaints when he ran it.  The piston does move freely and smooth.  There is resistance when it gets to the top of the stroke so there is compression.  I guess I should pick up a compression tester but I have no idea what the compression should be.

I'm now in the process of figuring out nitro specific stuff I'm going to need.  Glow plugs, fuel, fuel bottle, etc.

I haven't had a chance for more disassembly yet but will post pics when I finally get the head off.  I'll try my heat gun (basically an industrial strength hair dryer you absolutely wouldn't want to dry your hair with) on the low setting and see how that works.

Edit:

Looks like it uses an "N4" glow plug as 7730047 is the glow plug part number in the manual:

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I wouldn’t bother with a compression tester.

If you can hold the engine by the flywheel, and tip it to the side, the weight of the engine should not let it drop down if that makes sense? You should almost be able to bounce the engine against the compression. 

When you turn the flywheel the compression should almost “pop” through tdc, almost like there’s is a squash ball in there.

When the engine is hot, the compression will decrease due to metal expansion, so when cold it needs to have a fair bit of compression to be able to run consistently.

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Whatever the brand of glow engine, we always swear by OS #8 plugs.

 

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1 hour ago, WillyChang said:

Whatever the brand of glow engine, we always swear by OS #8 plugs.

 

Good to know!  Any recommendations on nitro fuel for this particular engine?  And after-run oil?

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Any good quality fuel with probably 25% nitro for that .32 I’d say.

For ARO there are specific oils available from Novarossi or Hudy for example, even automatic transmission fluid has been used. I currently use a high pressure bearing oil that can withstand extreme pressure, and my engines remain very clean inside, just make sure to run the engine completely out of fuel, as methanol is hydroscopic and will attract moisture resulting in rust.

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Slow progress but I'm getting things disassembled for cleaning and re-greasing.

I'm finding more rust than I was expecting - on the shafts, cups, bearings, and pivot balls.

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And a small metal shaving inside the diff housing (the pick is pointing at it).  One of the diff gears is a little damaged.

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Hi,

Great to see some more Tamiya nitro getting some love. I have all of these larger scale trucks in my collection and recently restored the Gold version of the TNX in the Build section. You are correct the FR32 engines were made by Force for Tamiya. They are pretty much identical to the original Force engine with only a few subtle changes like the cylinder head etc. Parts are interchangeable in general. The Tamiya part number for the TNX filter assy is 41063 but they are discontinued and hard to get like most Tamiya filters now. As mentioned you can probably use any modern 1/8 scale truck filter. Stay away from using a K&N crankcase breather sold as an RC filter, they dont filter well. 

If the inside of the engine is looking ok then I wouldn't remove the head. Not much need to unless you know the engine needs a complete overhaul. The FR32 engines do strip the glow plug thread though so bear that in mind when tightening up the plug and always use a washer. As mentioned the OS A8 is a good plug and use 20 -25% fuel. The only other issue is the clutch shoes, part number 51032. Long discontinued and hard to find. If you intend to run it a lot you will need a spare. I pick them up whenever I see them.

The rust on the cups and shafts wont be an issue, a quick wipe down with some light oil will see them ok. The rust in the bearings in the diffs might be. The bearing part number is 53065 but its just a 1260 bearing. If there is anything more than surface rust on the outer race then I would replace.

The damaged diff gear will need replacing, should be easy to get. You didn't say which one is damaged but they are probably in 9404695.

Cordless drill is fine for starting, if you have the starting rod just put it in the chuck and away you go. The rod is available as a separate part or you can use a ball ended long allen key cut down.

The manuals if you dont have them are on the Tamiya website, look forward to seeing more pictures.

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On 6/22/2019 at 3:56 AM, acprc said:

I have all of these larger scale trucks in my collection and recently restored the Gold version of the TNX in the Build section.

Yes!  I've been referring to that and another post of yours on your techniques!  That's what I love about forums like this.  The knowledge sharing.

On 6/22/2019 at 3:56 AM, acprc said:

If the inside of the engine is looking ok then I wouldn't remove the head.

It looks very clean.  The previous owner claimed he oiled it after each run and I've found nothing to indicate otherwise.  I've been hesitant on doing a complete tear-down.

 

On 6/22/2019 at 3:56 AM, acprc said:

The rust on the cups and shafts wont be an issue, a quick wipe down with some light oil will see them ok. The rust in the bearings in the diffs might be. The bearing part number is 53065 but its just a 1260 bearing. If there is anything more than surface rust on the outer race then I would replace.

The damaged diff gear will need replacing, should be easy to get. You didn't say which one is damaged but they are probably in 9404695.

Cordless drill is fine for starting, if you have the starting rod just put it in the chuck and away you go. The rod is available as a separate part or you can use a ball ended long allen key cut down.

Thanks thanks and thanks!  Exactly the info I'm looking for!

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Slow progress on the disassembly.  I ordered the wrong shock O rings.  Too small.  Looks like I needed 9804362 :blink:  The manual doesn't help much for certain specific part numbers unless you're looking for the parts bag.  I'm also going to need new oil seals (9804347) as one looks a bit deformed.  I'm electing not to take the pistons off the shafts for cleaning unless someone gives good reason to do so?  The pistons look fine.

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Only reason to worry about the piston shafts would be corrosion or burs as they could damage the red o-rings as they slide past. The manuals on the bigger 1/8 scale vehicles, especially the later ones tends to focus on the bags only however most parts are individually part numbered but take some working out.

You do need 4mm o-rings for the TNX shocks and thats the correct part number you quote for both the ring and seal.

 

Getting there though.

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FINALLY finding some time for my 5.2r restoration.  I've ordered lots of replacement parts in the meantime.

Getting the diffs rebuilt and put back together:

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More progress.  Finished up the gearbox.  Pretty neat little 2 spd.  I'm still not 100% sure how it works but amazed none-the-less at the ingenuity that goes into designing these vehicles.

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Great progress, very satisfying isnt it.

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