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Took apart motor and found this issue

Old 08-13-2017, 11:40 AM
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dls0680
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Default Took apart motor and found this issue

I was having trouble with my sons TMaxx 3.3 Staying running and could not figure out the issue. I tried some of your suggestions today to try to get it running and I could not even get the EZ start to work at all or get the motor to start. I then noticed the clutch flywheel would not turn at all and I figured that might be why when it would run it would suddenly stop. I took apart the motor and removed the piston and casing I saw some metal on the top of the piston as well as some pitting on the cover at the top of the piston. When I try to turn the clutch flywheel after I took everything apart I saw that when I turn it it feels really rough and wants to get stuck. I then removed the piston casing and the piston and still tried to turn the flywheel and it still has the same problem so I figure that the problem is not the piston it has to do with the inside part where the clutch turns. What do I need to fix this or is the motor now no good at all? I have everything taken apart and I have the clutch flywheel removed but I dont know how to take the inner part of the clutch assembly out to see whats causing it to turn rough? Here are a few pics of what it looks like now. The part that seems to be causing the grinding is the crankshaft but I dont know how to remove it to see what the problem is?


so I just was able to remove the crankshaft and what I see is the bearing in the front side was broken and the little ball bearings were loose in the crankshaft housing.

I cleaned everything up and put the crankshaft back in but without the bearing because I need to order it but it seems to turn nice and smooth now. Do I need to lubricate anything before I put it all back together once I get the bearing? If so what type of lubricant should I use?




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piston (1024x576).jpg
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Last edited by dls0680; 08-13-2017 at 12:50 PM.
Old 08-13-2017, 01:51 PM
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1QwkSport2.5r
 
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If one or both of the bearings came apart, there likely is more damage than you noticed. I would suggest replacing the crankcase and both bearings. If the bad bearing(s) damaged he crankcase, it may compromise the seal between the crankshaft and crankcase between the two bearings. The crankcase seals via the oil film between the crank and case. If the case gets damaged, it could lose its seal and not run right. A crankcase if pretty cheap - you could get one from a chop shop with the bearings already in it brand new for very little. Try DollarHobbyz.com

An observation or two from your pictures - the piston crown is damaged from foreign objects it appears. Maybe a wristpin clip broke off or if the glow plug dropped its element. Usually a piston that looks like it was sandblasted means it was run super lean. Random dents of varying sizes and shapes screams FOD. If a wristpin clip broke off, it probably damaged the liner, so inspect it carefully. If the sleeve of piston is damaged, don't bother repairing the engine; just replace it. It's more cost effective that way IMO.
Old 08-13-2017, 05:34 PM
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dls0680
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I appreciate all of your help. I looked at the piston sleeve and it looks to be in decent shape inside and nice and smooth also the piston the only problem I see is the top has that pitting on it. It still fits nice and snug inside the sleeve and slides smooth. Could I lightly wet sand the top of the piston just to get rid of some of the pitting or is that not a good idea? I am going to look into ordering the crankcase baring combo and hopefully have it later in the week so I can put it all together and give it back to him for the weekend. I know we will have to do a new break in on the motor with changing the bottom half. Is there anything I need to oil while putting it together? Thank you agian

Last edited by dls0680; 08-13-2017 at 05:39 PM.
Old 08-13-2017, 05:59 PM
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1QwkSport2.5r
 
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Don't treat it too crazy when you run it again. Just run it a little rich for the first few tanks and don't beat the tar out of it right away. Lubricate all parts - I recommend ATF (Dexron is what I use) or air tool oil. Don't need much - lube the crank, conrod at both ends, piston, and a few drops around the rear bearing and a few down the carb. It will take a good glow driver (as in fully charged) to get the engine going and blow the assembly oil out.
Old 08-13-2017, 06:08 PM
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flyinwalenda
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That engine has a lot of damage. No sense just replacing a few things as it will not run well with that piston and the cost will increase a lot for those parts.
What condition is the truck in?

You will probably be better off just buying a new engine and using what is good on the old one(carb??) for spares.
Old 08-13-2017, 11:22 PM
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1QwkSport2.5r
 
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I have an engine that I got used from a guy (in a truck) that had a hammered piston like the OPs engine here. My engine runs just fine - and it actually has pinch too. So it's complete BS that the engine won't run well as it is with a few parts replaced. I've seen engines in much worse condition running and driving (and flying too!) and doing it quite well.
Old 08-14-2017, 12:58 PM
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dls0680
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Again I cant thank you enough for all your help. I will keep you posted once I get it all back together

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