Engine overview help & tips talk. (Mach .15)

[Losi-HPI]

Hello there peoples, I recently pulled the Mach .15 out of my XXX-NT for the winter season to look it over but inevitabely replace it. This engine always ran great for me up until this past summer when later on in the summer the engine was constantly giving me problems. It was always performing like it was too lean AND too rich at the SAME time. It would have attributes to both areas at the same time and tuning in either direction proved most useless as it would keep on doing what it was doing or just plain not run at all. I tried getting help from all around me and tried looking up Q&A's on it and all this but in the end I was just sick and tired of trying to find a solution. I am positive there has got to be something wrong with the engine/carb set up,... I am just unsure as to what and have had no luck getting 3rd party perspective. I know how to tell when an engine is too rich and when an engine is too lean and I know how to solve the problem as far as needle tuning goes but this was just out of my league and my engine wasn't accepting any solutions. I shortly there-after also realised that I do not have the funds to replace my whole engine for another, and so I am going to have to stick with the one I have. ANYWAY, now that you know WHY I took out my engine and now have it apart and looking it over, here comes my point to it all. One of a few things now, first off what should I clean it in / what's a good method (basically how do I go about cleaning it all). Secondly should I replace my carb with some other? Third off, is it wise to change the flywheel in a triple X NT with the stock engine, if so, which is a good replacement? And finally now, what would be a good clutch to swap for the stock one? Thank you all VERY much in advance,...
- Justin

 

[Arrow]

you should be looking for pinch in the sleeve.
if the piston is going through the sleeve its most likely shot

 

[vbgagnon]

I think arrow is right, it sounds as your piston and sleeve are shot, another thing that you might want to do is seal your carb and backplate. Air leaks will cause problems like the ones you are talking about.

So, check the compression and if its no 100% lookup os rocket on ebay its about $20 to get a sleeve pinched and believe me the pinch is tight. And when you put the engine back together seal the carb and the backplate with some good rtv sealant it eliminates headaches.

 

[Losi-HPI]

What is this "get a sleeve pinched" you refer to? Also what does rtv stand for,... I've never used such a product before. Thank you.

 

[vbgagnon]

When you pinch a sleeve it takes your piston and sleeve and puts it in a press. This press squeezes the sleeve onto the piston so you get your compression back.

RTV is a sealant that you can get at your lhs or at a hardware store and it seals your carb and backplate so you can't get air leaks.

 

[Losi-HPI]

Thank you for those tips then I will look into that further.

 

[rocknbil]

There's a guy that goes by the name "OS Rocket" that has a huge machine for pinching sleeves. He'll do it for about $20. There are other machinists who claim to be able to do sleeve pinching, but he has all the right equipment and has a long history of happy owners. [email protected]

Then there's these things that have come up on eBay lately: "sleeve resizing fixtures." To make them work correctly you have to tighten it, then loosen and rotate the sleeve, then tighten again, always sliding the piston up in the sleeve after each torque to see if the pinch has returned. It's nowhere near as accurate as sending it to OS rocket, but I've seen a few people use it and it works, can't beat the price really.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=5923884251

 

[Losi-HPI]

Thank you. Alright for an update, I have recently finished tearing the engine apart and cleaning it and inspecting it. I saw no flaws to the piston or the connecting rod, no flaws in the cylinder, crank seemed fine, HOWEVER, when I took out the carb and looked into the block where the carb connects, I DID notice that at the end of this entrance-way where the airway meets the crankshaft that a portion of the edge was torn up somewhat. I am trying to aquire a picture so I can show you what exactly I am going on about, I will post as soon as I get one.

Ok,... until I can get my hands on a digital camera from my friend I can only show you this picture for temporary purposes. Sorry, I am trying to get my hands on an ACTUAL picture of my problem bear with me here.

 

[.21Rc10GT]

If the crank is rubbing the cylinder, the friction will heat up the carb, in turn, making it run way too lean and overheat.

 

[rocknbil]

.... I DID notice that at the end of this entrance-way where the airway meets the crankshaft that a portion of the edge was torn up somewhat.....

Look closely and try to determine if that's from the actual casting of the crankcase or if it's something hitting. If it's shiny like it's beat with a hammer, something is definately up. If it's rough and unfinished, it's probably just the casting. Shouldn't hurt performance so long as the O-ring gasket for the carb is in good shape.

 

[Losi-HPI]

I do not believe that is the way it was cast and as for the rubbing you know I think that might just be it,... infact that would make this all make sense now. It does rub on that, at least touch it anyways. I guess this means there is nothing I can do to fix this then eh since it is the block. :shrug: