I've been having problems with the engine that came with the inferno 7.5 RTR buggy. Well not like new issues, more like ever since I purchased the car. The engine would never tune right, and before you ask yes it was broke in...right. I recently found that the carb was suction air though the slide throttle. I seemed to have fixed it, and I can kind of tune it, but once the engine gets hot it wont run or start, It has to cool off before I can getting it running again. I'd also like to add that I had taken it to leisure hours and while running it around, the air filter fell off! I don't think it sucked anything in, but I did take the carb off and the heat sink and I didn't see anything out of the ordinary. Now I was told by another guy that He's heard that the kyosho RTR engine had issue to begin with, and he's the one to point out the leaky carb. I'm new so I thought what it was doing was normal. He's also mentioned that he had an engine once that did the same thing and the engine turned out to be junk, it would get hot and lose compression. I'd just like a second opinion. I'm probably just going to buy another engine. But I'll like to work all the options out of this one.

Get a new engine...

If the air cleaner fell off(did you oil it?) you sucked dirt in the motor. Did you see any dirt in the carb throat before putting the air cleaner back on? The motor runs good when its cold because it hasnt reached the right temps to run at, and when it does get up to temp it expands and the sleeve expands to the point that the piston no longer holds compression so it just doesnt run. That dirt that got in there acts like sand paper and wears out the internals fast. Once you suck dirt its pretty much over.

yeah just buy a new engine

Yeah I didn't see any dirt in the carb, and I pulled off the heat sink and nothing in the cylinder, though I did notice some very small scratching. I couldn't even feel the scratchs though so I thought maybe I got away with it. Obviously not. See I work on engine overhaul for a living, but these little ass things are nothing like there much larger counterparts. No piston rings, and no cross hatching on the liner...in my mind it doesn't compute. But the sh** runs. Simply amazing.



Sorry had a newb moment.

lol

Was the the air leaking back into the lines through the idle screw adjustment last week sunday? No o-rings in that setup at all. Either way, yeah that motor isn't very good, about as bad as the force .26 I originally got from OFNA on my Ultra comp2. Pulled the head off to check the combustion chamber and found metal flakes in the chamber and a score on the sleeve that I could see but not feel with the edge of my nail. Sent it back to OFNA and they sent me a new one.

pick up an OSRG, around a $100 and it's better than the stock motor.

How about this.

Since its still under warrenty, take it back to where you bought it (Al's I think) see if they'll swap the motor for you). Take fresh rtr motor and decide, either sell it on ebay, or use it.

I'm pretty sure the warranty doesn't cover running without an air filter. It might be too late for that option.

I had a Kyosho Mad Force about 3 years ago and it came with the Kyosho .21 motor. That motor started everytime on the 2nd pull and ran forever with no flame outs, idled perfect too and had good power. ANY motor that sucks dirt is pretty much done wether you see dirt in there or not. If there are scratches on the sleeve, piston and the induction on the crank, inner and outer part where the carb sucks air, also the bearings prolly feel notchy too. The motor is not that bad, its just not a top of the line engine, but if a filter falls off a big money motor its over for it too.

any motor in a mad force looks fast, thing pops wheelies like no tomorrow

Mad force had a compeltely different motor.. those where the old GS21's. Kyosho is using a new Engine MFG (reported to be OS) on all their new RTR's. The new engines make a good deal more power than the old GS21's but they have been known to be quite a pain to tune. If its stalling when it heats up I'm thinking the little bit of dirt probably did it in.

if you get a Box for it I'd go with a Novarossi 21BF. that gets my vote got a good inexpensive all round engine.

yeah its like a light switch, I run it cold and as soon as it gets hot its died, just like a flame out, but you can't get it to start until it cools off.

it's worn out prematurely it sounds like. I would just get a new motor, don't try to fix that one.

tinkered with it alittle yesterday, it seems as though, the glue plug is by far the hot for the engine, the engine overhaets and dies. Gonna try a colder plug and see what happens.