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Old 03-25-2006, 12:39 PM   #1
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Default How often do you disassemble your engine and inspect it?

I've read quite a bit about disassembling engines, but found no real guide as to when to do it.

1. How many hours/race days do you think an engine can run before it needs to be disassembled?

2. Are there any indicators that the engine should be disassembled?

3. What's the worse thing you've seen happen to an engine that was never disassembled and inspected? How long (hours/race days) was it running before it happened?

4. If properly maintained, about how long (hours/race days) will an engine last before it needs to be replaced?

5. When an engine starts to show signs of wear, do most people rebuild it or just get a new one?

I have an OS .12TZ that has about 4 hours on it, including break-in. It's only going to be run approximately 48 hours per year tops. If you've got the same engine, let me know how it's doing!

Thanks!
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Old 03-25-2006, 01:14 PM   #2
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Quote:
Originally Posted by rmdhawaii
I've read quite a bit about disassembling engines, but found no real guide as to when to do it.

1. How many hours/race days do you think an engine can run before it needs to be disassembled?

2. Are there any indicators that the engine should be disassembled?

3. What's the worse thing you've seen happen to an engine that was never disassembled and inspected? How long (hours/race days) was it running before it happened?

4. If properly maintained, about how long (hours/race days) will an engine last before it needs to be replaced?

5. When an engine starts to show signs of wear, do most people rebuild it or just get a new one?

I have an OS .12TZ that has about 4 hours on it, including break-in. It's only going to be run approximately 48 hours per year tops. If you've got the same engine, let me know how it's doing!

Thanks!
1) I believe an engine has to be disassembled after each time it sees fuel.

2) Usually, there are no indicators of when an engine should be dissassembled other than having a hard time trying to start it again.

3) I have seen pretty nasty rusted engines from people who had never used after-run oil and kept fuel inside their stored engines.

4) I usually measure an engines life by the quantity of fuel ran. I usually replace conrods on my engines at 2 gallons just to be sure.

5) Since I also have a TZ, and since the conrod is only $25, I'll be replacing it each 2 gallons and probably exchange the bearings at 3 gallons. I also have an extra Piston/sleeve for when I feel the current one has lost all compression. I have been very meticulous with this engine, and have always disassembled it and cleaned it each time it sees fuel (unless I will be racing the next day). After every race, I take apart the engine, clean it, relube it with after-run oil then put it away in a zip-lock bag with the clutch already set for the next race.
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Old 03-25-2006, 01:15 PM   #3
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On another note, I never disassembled the carburator nor mess with the needles since I don't want to lose any of the factory needle settings. I made this mistake with my old Mega Picco and never found the same setup again...
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Old 03-25-2006, 01:31 PM   #4
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The TZ is an engine that you DEFINATELY DO need to treat this way. The rear bearing rusts easily because of the way the fuel flows in the combustion chamber and collects right behind the bearing. The TZ engines also start to significantly loose compression around 1.5-2 gallons, but the upside is parts are VERY cheap so it's not a big problem......

Anyway, back to the topic.....
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Old 03-25-2006, 02:24 PM   #5
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In my experience...(3yrs off road monster trucks & 1yr onroad touring cars)
I have takeen an engine apart for the following reasons.

1. New engine, prior to break-in, to inspect the inside and verify no loose parts or "flash"
2. An engine that doesn't seem to be running well. I will inspect the fit of the piston and sleeve, look for scratches in the sleeve, inspect bearings and reseal the back plate and carburator.
3, The nitro season is over, and I will dissasmble, clean, oil and replace parts as needed.

Other than that, I do not beleive you need to take your engines apart. When I am done running for the day, I will disconnect the fuel line from the carburator and run the engine to burn off any excess full in the engine. I will then use about 6-10 drops of aftrun oil (fantom or hobbico), turn the engine over with out the glow plug and put the glow plug back in. I have done this on every engine I have ever owned, and I have never had rust in the engine or any of its parts.

I have owned a fantom 18, traxxas 2.5, sirio evo2 and picco engines. I have never broken a rod or crank. The only thing I have had happen to ruin an engine is inproper tune or a hi rpm runaway causing premature wear at the piston and sleeve.

I will say however, if you have the time, there is probably nothing wrong with dissasembling your engine to inspect regardless of duration. I would be careful, because each time you dissasmble your engine you can introduce dust and debris, gauge a sleeve, break a carburator or install the rod backwards.

I am posting this only so you have two contrasting views on the subject. Utilmatly the choice is yours, based on time restraints and how particular you are regarding your gear.

Finally with proper tune I would say most engines will last three gallons of fuel before loosing significant power, it really all depends on use and tune.

Doug
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Old 03-25-2006, 02:53 PM   #6
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you should disassemble your engine, inspect it, and rebuild it after every 1-2 gallons of fuel through the engine
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Old 03-25-2006, 03:11 PM   #7
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I agree with flack. I only take it apart if it is not running well. I will take it apart after every two gallons when I put a new connecting rod in it.
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Old 03-25-2006, 06:46 PM   #8
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definitely before you start it. you should see the loose flashing inside these sometimes! check around the wrist pin clips for flashing.

I check the head clearance as well at this time. for 30% fuel I always make sure .12's have about 0.018"- 0.024" and 0.025"- 0.030" for .21's. I have found one NIB REX 321P to be missing a 0.2mm shim. That would not have been good to run it that way.

i disassemble after break in and every race day. if I blow a plug i may pull the head real quick. if you lose a two speed or one way bearing I'd pull the backplate and check the rod play. i never go more than two gallons on a rod.
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Old 03-26-2006, 08:56 AM   #9
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Assuming you've broken the engine in properly.... After i'm done running for the day, I start by running all of the fuel out of the engine. This usually takes a few cranks to get it all burned out (the engine will start, run for a few secs, then die). After this, I pull the glow plug and air filter and spray WD40 in both ends. I then give it a few blips on the starter box to wash the inside of the engine with the stuff (make sure you have a rag over the carb and glow plug hole or prepare to get sprayed). Some people remove the rear cover and wash out the rear bearing as well. After that I do the same thing with after run oil. Even if the engine will only sit for a day, I still go through this process. The whole thing will take about ten minutes, (minus cleaning the engine of course!)

As far as taking the engine apart after every run, i've only seen this done by National or World Champ level drivers running heavily modified engines. If you take off the rear cover periodically you will be able to see any crank pin/conrod wear. The conrod is usually the first thing you would need to replace anyway. You can inspect the rear bearing at this time as well.

Or, you could make it easy and contact the Mfgr. and see what they recommend.

Regards,
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Old 03-26-2006, 09:23 AM   #10
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WD-40 is not recommended if the crank has silicon/epoxy. It also swells the O-rings on the backplate and carb.

Use Marvel Mystery Oil. A lot of after run oils are just MMO in a different container.
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Old 03-26-2006, 09:49 AM   #11
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How can you see that the conrod is worn?
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Old 03-26-2006, 10:31 AM   #12
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take the backplate off and rotate the engine through TDC.... you will see the rod move on the crankpin if it is worn.

Putting a drop of oil on the crankpin will allow you to see a bubble form if the rod is too loose.
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Old 03-26-2006, 11:50 AM   #13
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Thanks, this means that the conrod of my Sirio EVO 3 should be replaced. I only ran 1,5 liters (0,4 gallons) trough it, isn't this a bit soon?
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Old 03-27-2006, 01:46 AM   #14
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Thanks everyone! I never would have thought disassembly would be based on gallons! 1.3 gallons to go before it's my turn. I'm really anxious to see what I'll find. I'll let you know if I find something worth mentioning.
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