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Old 01-22-2009, 07:17 AM   #1
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Arrow TRX 2.5 Nitro Engine

I have a TRX 2.5 engine that I took apart, previously used by someone else, and I took some photos of the piston. I think theirs something wrong with it. The colour of it doesn't look so good. What do you think?

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Old 01-22-2009, 10:04 AM   #2
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It's hard to tell in the photos but it looks like it has carbon build up from being used. Does it run?
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Old 01-22-2009, 10:51 AM   #3
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It's hard to tell in the photos but it looks like it has carbon build up from being used. Does it run?
+1 this engine has a lot of hours on it using a high oil content fuel on a rich needle. What I like about the photos is you can see some interesting things going on. The sleeve has a consistant color, so I know it's never been over heated. @ 7 o'clock the pistion face there is pretty clean area under the squish band. I bet there's a trasfer port there & it has a lower timing than the other trans-ports. On the block next to the sleeve from 12 -1 and 5-6 o'clock you can see the dark burnt oil residue. I think if you did some really careful measuring, you'll find that this sleeve's been pinched at least once.

I'd be curious to see what the inside of the sleeve looks like above the exhaust port. Is it whitish or gold "brassy" in appearance.

Cleaning the engine will remove the built up carbon and sludge, that also means tolerances will be opened up (loss of compression). If the engine ran good before you lifted the head, I'd say only wipe the piston face (w/o removeing from the sleeve) and wipe out the head, then run that little fella' til the cows come home. A good thorough cleaining will mess up the fit between the P/S on a heavily used engine like this one.
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Old 01-22-2009, 10:57 AM   #4
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Chunk I am forwarding all my engines questions to you from now on!
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Old 01-22-2009, 11:19 AM   #5
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Would you recommend replacing anything?
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Old 01-22-2009, 04:48 PM   #6
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Would you recommend replacing anything?
Depends on your objective? If you're just looking for a basher. I wouldn't do a thing to it if it runs OK. If you have to rely on it as your primary engine for racing & practice... new bearings are always a safe bet, if the sleeve hasn't worn through the nickle plating, a pinch wouldn't hurt and a replacement con-rod. but you never really know what needs/should be done until the engine is totally disassembled, cleaned and measured. If you are going to end up spending a lot of repair money in the engine, consider Traxxas engine swap program. that may be the most economical way to get a reliable new engine w/o buying the farm.
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Old 01-22-2009, 05:00 PM   #7
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I just have one last question, would it do any harm if I painted my nitro head with some VHT Flameproof Coating? hehe
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Old 01-22-2009, 05:32 PM   #8
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Yes! Dont paint it with anything. Chunk T will yell at you
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Old 01-22-2009, 07:01 PM   #9
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from the views of the first picture, if you look at about the 9-11 oclock positons you will see wome light. I dont know i i am seeing things but it sure looks like some light shinning through. If it is light it seems to be worn pretty good, but over all the piston and sleeve look in pretty good condition.
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Old 01-22-2009, 07:37 PM   #10
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Yes! Dont paint it with anything. Chunk T will yell at you
Don't listen to me. Listen to Jaz

Paint will act as an insulator and help hold in the heat. The anodizing that the MFGr uses is actually a dye (pigment) added to the metal. So it's a completely different thing from painting or any type of coating you may want to apply.

Jaz... careful how much faith you put in what you think I know. You have NO IDEA the trouble I've been able to get myself in
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Old 01-23-2009, 04:12 AM   #11
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Thanks, you guys are great help.
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