Hello all, I'm having a slight issue with my Eldorada. It has a vx .18 and recently Ive been having issue with overheating. The temps are running 350-400 degrees. It doesnt matter how far out I put the HSN (I can turn it into a misquito fogger) it doesnt matter. The engine is running very strong. After about two laps around the yard I have to let it sit and idle to bring the temp down. I have checked for air leaks. Found one at the carb base, and sealed it. No change. The fuel Im running is Trinity Monster Horsepower 20% with 12% synthetic oil.

Tonight I change needle settings back to factory. Ran same temps, but bogged in mid range. Take off strong and top end strong untill heated up then lost top end till cooled down. When this started it also started burning out my plugs (mcoy mc-69) never had any problems before. I check the coil in the plug and it is not pitted or black, it still has its silverish color(the pic of the plug has a tank ran thru 1/2 of which was very rich settings and other half factory settings). I have taken carb apart to check for any debri stuck in needles, nothing. I have also noticed that the throttle arm moves in and out a little. I understand it moving in and out when opening and closing. But it also does it stationary. And when I adjusted the LSN tonight I noticed a drastic change when putting a little pressure inwards on the needle when adjusting, it was like shutting the needle almost all the way down. The rpms shot way up, and when pushed back out it settled back down. Never noticed it doing that before tonight, and I have adjusted LSN plenty of times while running.

The changes I have made are a 15 tooth bell (which I thought thats when it all started, so tonight I put stock back on-no change), and have replace the stock manifold with a header (including pics). Before putting stock manifold back on, I wanted to get more opinions on what it could be (your up Eddie and friends).

Hope this is enough info to get started. Thanks in advance.

make sure your fuel tank is holding pressure and its not leaking at the cap. sometimes the cap wont hold pressure and it will run very lean. Also check your fuel lines for a hole.

I have notice that the fuel line before the filter always has bubbles in it, but after the filter dont notice any.

blow in the line from the pipe, and take the line off the carb and put your finger over it to block it, see if you can see/hear a leak in the lines, filter or the tank.

Blew in the hose, and it held pressure in the tank for 30 secs. Wondering if you ever heard of the stand up pipe cracking in tank close to top, possibly getting air from there?

i dont know bro, does the fuel seem to flow freely to the carb, is the filter clogged. maybe the carb opening is clogged, just a few suggestion.

When I first start it, I prime the carb by holding finger over exhaust and spining engine over. It takes a little bit longer to get there then when it was new, just figured it was the addition of the filter. Took apart the filter yesterday, and nothing plugging screen. Took the HSN holder off so could check fuel intake nipple-clean.

I just thought of something thou. When I was checking for air leaks in engine with the throttle wide open I had problem pushing air past LSN. I had to open the LSN all the way up to blow into engine. Would this have been normal?

it should have a little resistance, try taking it out and flushing it clean, something has to be very wrong to run the engine that hot.

Will tear it down again. Also was just trying my vaccum tester on tank and lines. Will not hold vaccum at all. Goin through items one at a time to see which one/ones are leaking. so far have found the filter to be the worst. Is there a different style of o-ring that seals better?

depends on the filter your using. i say check the tank!!!

Ok, on the vaccum leaks the filter losing very fast, found slight larger diameter o-ring and tested again-now holds steady. The tank wouldnt hold either, found the orange o-ring in lid very spongy and weak. Again found o-ring with same ID, but very slightly bigger OD. Retested tank will now hold 15 in-mg, and will only drop half a point in 20 secs. As for the lines, just goin to replace.

if the tank couldnt hold pressure, it will let the exhuast pressure escape thru the cap and wount be able to push fuel to the carb and make it run very lean!!! also make sure there is do obstruction behind the fuel nipple in the tank preventing good fuel flow.

Will check nipples in both tank and carb, and if not raining tomorrow will give it another shot and see what happens. Will let you know.

Thanks for the help, and for letting me bounce ideas off of ya!!

Talk to you tommorow

your welcome bro, let me know how you make out!!! We will figure it out.

Edit - did it start running hot all of a sudden, or has it always done this? What's your LSN set to?

it just started running hot all of a sudden. No changes were made to either needle, usually runs 260-290. the only upgrades I did at the same time were the filter, header, and 15 tooth bell (which was replaced with the original to bring RPMs back down to no avail).

ugly duck- When setting the LSN I use the 30 sec idle test. I start of rich then slowly bring it down until it can idle for 30 secs and then take off without loading up and dying or hesitating on take off. And with those setting the truck ran strong with no problems. From how bad the filter was leaking combined with the fuel tank losing air, I'm hoping that will solve the problem. As far as I can remember thats when the problems started when I upgraded those three items listed earlier.

If this freaking rain[:@] will stop and dry up I'll be able to find out today.

Well just remember that your LSN affects the high speed running as well. The HSN is designed to limit the ultimate fuel flow at top speed, provided your LSN isn't the actual limiting factor. I had my LSN set so that it idled and launched well, but at high speeds I could screw the HSN out all the way and it didn't do a thing to the smoke or temps. I cranked out the LSN so that it idles a bit splashy and is a bit sluggish on takeoff, but now it runs a whole lot cooler and I can actually see the HSN doing stuff now. I've got a header and a pipe, too.

I'm thinking that the VX18 LSN needle isn't tapered enough for really high RPM or the additional flow of some modifications.

I had a 2" long crack in my tank and I thought that it might be causing some of the leanness, but after I replaced the tank and checked for leaks, it didn't change until I screwed out the LSN some more.

In your case, it might be a chunk of dirt still stuck in the carb even after you tried cleaning it out. Or it could be the LSN - try it flush and see how that affects things.

Well, I got to run it today max temp got to 310 and that was after about 5 or 6 full speed laps. Thanks ugly duck I cranked out my LSN and could tell the difference, had a hard time getting it just right without it dying right away from load up. But finally got it.

Unfortunatly I only got about an hour and a half run time. I guess I need to step away from the mccoy mc-59 because I went thru 3 of them in the 1 and half hour I ran, hence why I had to stop, when I pulled them out the coils were still shiny (and yes my ignitor is charged). I could see a very small gap in the coil. Weird thing was they didnt go out till it shut down, then I refueled went to start and no glow. Thats how all 3 went. Goin to get some OS A-3 plugs and try them, unless any other suggested good plugs.

the a3 is a good plug but i think your running to lean, 310 is on the hot side, you want max temps of like 280

Yeah I still need to do some tuning, but the plugs didnt agree (but the temps are alot better than 400 degrees). I found a couple other things while it was running also, #1 the slipper was slipping to much letting engine wind out full rpms while running. When tightened that it helped temps a little. #2 where the header and goes into rubber connector wasnt getting solid seal. The header pipe is just a bit smaller than stock exhaust manifold, so sealed it better. #3 fuel tank is still not completly sealed (one time after refueling and made a lap saw smoke wisping out of cap, pushed down on it and stopped for the time being), probably need to get another stock o-ring, unless himoto has come out with total aluminum tank like I have seen for traxxas.

It is Possible that a Tank that Passes a Vacuum leak test, MAY NOT pass a Pressure Leak test.....Nitro engines don't Use vacuum anyway....
Your Fuel System and Engine must be Pressure Tight to at least 6 to 8 PSI. (A bit Higher is better).
Your 1/10 Engine will produce this amount of pressure from the Exhaust, and use it to Pressurize the Gas Tank.....
If there is an Air Pressure leak ANYWHERE in the system, you will have Overheating problems, and you will NEVER get a Consistent Tune...

It sounds to me like you may have PARTIALLY fixed your Problem......
But ,,,,,310 degrees is still WAY too hot.....
You are either running too Lean, or you still have an Air Leak, OR BOTH....

Keep workin at it Bro.....And keep us informed.....Mebbe we can help you Solve the Problem....

ok i had the same problam but i was runing in the 250's-350's range... becouse i was runing it hard! low 13T clutch bell in my syclone, and man it has Torque! but it was just screaming like realy high! i righened up so much so it was bogging on take off and still i was runing in to 250's or higher becouse i used the spit test and it sizzeled and went away rightaway! ware are you suposto put the water, on the plug or on the top of the head... becouse i may be runing it properly!

but on a frends he had a bad tune and realy rich! i took it apart (for a fee Duh) and looked inside and all of the seals were ither missing or cracked. so i went to my LHS and told him that i had a hpi rs4 3+ evo and he gave me the seals and i fixed it and now it runs great! so it could be just a seal. around the base of the carb, use sencor safe gasket maker. you can find it at your auto parts store!

hopefully that works!


Edit: i also had that problam with my buggy and i found out that i had a cracked tank! so check that too. and if it is use some seal-all on it that stuff works great!

Ok, Ok. I stopped and got a couple of OS A3 plugs and tuned carb some more and ran for another hour and a half, and what do you know 270-280 running temp. Turns out I was running the LSN too far in (reason why HSN and no affect, thanks ugly duck). she was running good.

Now I still have problem with plugs, on last tank of fuel when it ran out I got truck carried it to porch, and tried to start to run what was left of fuel in lines out. But the plug had a broken coil. I cant be from lean mixture now, because she running good temps and has steady stream of smoke at any throttle position. When I pulled out burnt plug it still had a bit of fuel left on it. Used to I could run several weeks on a plug at an hour to 2 hours at a time. Now I get and hour to hour and a half. At this rate the plugs are goin to run me into the ground.

what kind of fuel are you running?

Fuel=Infinity Monster Power 20% with 12% synthetic oil