J_D

Hey all, On my.18 engine, I've noticed that there is fuel accumulating on one of the lower fins of the cooling head, on the exact same fin, that has the four cap head screws, attaching it to the rest of the engine.

Also, since I've noticed this... Whenever I give my truck full throttle it just boggs down, and slows the truck right down, like engine braking sorta thing happening.

I'm not too familiar with pulling apart nitro engines, so I was looking for a little information before i pull it open...

I'm thinking that maybe the shim needs replacing or something?

thanks in advance

snowbl!nd

It could be two things...

The glow plug washer... If it becomes bent/scratched this small washer can allow fuel from the combustion chamber to escape, which would result in a residue accumuating around the glow plug and base of the cooling head. Fix - replace glow plug/washer.

OR

Loose head... If the four screws holding the cooling head onto the engine crankcase are loose, they will also allow fuel from the combustion chamber to esape. This will have similar effects as a loose glow-plug, as the combustion chamber is not "sealed" when the fuel combusts. If you have not removed the cooling head, and the engine was running OK previously, it is very unlikely that the head shim/s is/are damaged in any way. Fix - Simply ensure that the four screws are properly tightned (use "star" tightening method - tighten each screw a little at a time and work you way around by tightening one screw- then the opposite, then another, and it's opposite etc)) but DO NOT use threadlock.

J_D

yeh i think its the four screws, but i only have crappy allen keys, so I'm gunna buy a good allen wrench so i don't strip the screws, thanks for the help.

Its not the glow plug cos theeres nothing around it, and its in tight

J_D

alrighty everything is tight.. too bad its midnight right now lol... Gunna have to wait till tomz to test it :P

Wide Open

i had the same problem once and it did turn out to be a loose screw for the cooling head. hope it works out for you.

J_D

ok everythings tight, It does get any fuel on the cooling head anymore.. yay....

.. but, it still boggs down at full throttle, i can get to 3/4 and its fine, soon as i hit full it just boggs down... i first thought that it might be becuase its too rich, so i leaned it out, but still the same problem...

also, i think my HSN is changing slightly from the vibrations, should i pull it apart and replace the spring? coz its changing abuot 1/4 of a turn through out a run..

also should i replace my glow plug?

J_D

ok it doesn;t bog anymore.

The screws on the exhaust header were loose... one of them was loose by 1 and half turns!

so i tightened them and now it runs fine... YAY!

But.. can someone please explain why? how can a loose exhaust make ur engine bogg at high rpm, does it need the back pressure or something?

Wide Open

thats the entire point of the back pressure. to deliver fuel consistantly. when your muffler was loose it lost pressure and the engine had to try and suck its own fuel. so at low throttle when it didnt need much fuel it was fine, but as you brought the throttle up and it needed more fuel, it just wasnt enough.