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Where should I apply RTV sealant?

Where should I apply RTV sealant?

Old 07-18-2015, 03:17 PM
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Default Where should I apply RTV sealant?

I have a tube of ULTRA COPPER RTV Gasket Maker. I'm wondering if that is OK for sealing engine and where I should apply it? I know the backplate near the pullstart, around where the carb attaches and in the needles? Should I take apart each needle and put some on there? Even around the where the throttle slides?

I've taken my backplate off before, which revealed no bearings. There was just a metal tube which slid through the backplate and that's where the one way bearing attaches too. Should I put some around that? Thanks


I noticed today after fixing many other issues with this engine, I was running it real rich to the point where I could hear it bog a little, yet the engine reached 300F running on grass. Currently 32C outside. No it was not too lean, leaning it increased power by a lot. There was a lot of smoke coming out. Power was also kinda all over the place. If I held half throttle it would be slow then speed up kinda oddly which leads me to believe there is an air leak.
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Old 07-18-2015, 06:03 PM
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There is an air leak. Most likely the front bearing You only need to seal where the fuel line meets the carb on the banjo fitting, backplate, and where the carb goes in to motor. DO NOT apply it to the needles. Also do the carb pinch bolt.
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Old 07-18-2015, 06:32 PM
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Originally Posted by Hoese37
There is an air leak. Most likely the front bearing You only need to seal where the fuel line meets the carb on the banjo fitting, backplate, and where the carb goes in to motor. DO NOT apply it to the needles. Also do the carb pinch bolt.
Dammit, I knew I saw fuel coming from the bearing. Thought that was normal because the fuel is suppose to like help seal the bearing? Would it be possible for me to apply RTV to the bearing or do I need a whole new bearing? Thanks

Also I did apply it to the LSN before reading your post. I only used a little near the head and none on the inside. Hopefully that won't cause issues otherwise I can remove it.
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Old 07-18-2015, 06:48 PM
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Originally Posted by leureece
Dammit, I knew I saw fuel coming from the bearing. Thought that was normal because the fuel is suppose to like help seal the bearing? Would it be possible for me to apply RTV to the bearing or do I need a whole new bearing? Thanks

Also I did apply it to the LSN before reading your post. I only used a little near the head and none on the inside. Hopefully that won't cause issues otherwise I can remove it.
normal for bearings to leak.... most times its not needed to silicone these engines, mostly just makes a mess.... if you do wish to use silicone remove the o-rings first, the clean the area and use the silicone to replace the o-rings...do not goop the silicone all over the o-rings, it just makes a mess of them...allow the sealant to cure for at least 12 hours.... but in the end it is almost never needed, most cases of air leaks are improperly set idle gaps and linkages......
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Old 07-20-2015, 11:31 AM
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Ultra copper is made for exhaust sealing.
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Old 07-26-2015, 11:11 PM
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Originally Posted by Maximo
normal for bearings to leak.... most times its not needed to silicone these engines, mostly just makes a mess.... if you do wish to use silicone remove the o-rings first, the clean the area and use the silicone to replace the o-rings...do not goop the silicone all over the o-rings, it just makes a mess of them...allow the sealant to cure for at least 12 hours.... but in the end it is almost never needed, most cases of air leaks are improperly set idle gaps and linkages......
I agree i used to do this all the time back in the day when i ran those ofna rtr motors. Some of those motors needed it. Hahaha. Most desent engines these days,(there are a lot out there at good prices) i dont believe this is nesscesary. However, a bearing is a bearing so it will develope a leak from the front bearing sooner or later. One of my best investments ive made to remedy this are those buku bearing caps. Those caps breathed life back into one of my ify engines. It has been so reliable it is now my race engine. Idle solid. Tune solid. Im still using the first one i installed and honestly its not showing much wear. I would say maybe 5 gallons on it. Only hassel is greasing it but i didnt pay attention to where the ports were when i installed it so i have to take my motor out to grease it. Grease it every other race day. Well worth the money. I dont know if they still make them though.
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