nitrotec

ok, today was actually a good day for me considering it only took me a good month to get this truck to run right. it starts nice and it goes through all gears. i was thrilled. little disappointed with speed though and i guess i understand why. the engine is only 3 ports and 29000 rpm. ok i get it more power less speed. I can proudly say this truck is a tank very solid very stable. i did some off roading today and i was impressed. I couldnt pick up wheelies for the life of the truck. But i still have a problem. why is the tuning a nightmare?it was running so good at the normal temp and i get this high pitch sound like it is running lean and i know i am not. i am always running slightly rich and then the engine starts to smoke i shut it off rightaway. what is this high pitch sound. you will only hear it when truck slows down. sometimes the sound goes away when i rev it a little and then it gets stuck on this high pitch sound till i shut it off and let cool. what i am doing wrong here and what is it that i am missing? I set it back to manf settings hsn 4.5 turn out and lsn 2 turn from flush and i retune. then the high pitch sound. somebody help please this is ridiculous!!! it is like i cant have any fun with this truck for one good full tank???!!!!!

dustin7837

My Feedback: (1)

OK, I think we need a bit more info first.

Do you have any way of taking a video so we can hear the noise?

Have you put a check valve in yet?

Do the engine temps get high?

You say you only hear the sound when you slow down... I know on mine, I had a clutch spring let loose and it would make a high pitched "metal on metal" sound anytime I slowed/stopped and there was a burning smell from the clutch bell. Check your clutch if this sound plausible?

PS: if you want to do wheelies, remove the center diff gears and put in the locker (looks like this, should have come with the GST http://www.cenracingdirect.com/index...OD&ProdID=3071 )

nitrotec

ok! you can listen to the sound at this end of this video. you will only hear it after runing half way through the tank when the truck slows down to a complete stop. http://www.youtube.com/watch?v=kK9PJgSI&feature=related

as far as check valve is concerned. i got the ofna valve you recommended. according to the instructions it goes on the fuel line. is that true?? if not where does it go and in what direction????

also what glow plug do you recommend??

dustin7837

My Feedback: (1)

You're link just goes to the Youtube most watched page.

The Check valve does not go on the "fuel" line. First, unscrew the blue "lid" from the one end of the check valve and remove the filter as you do not need it. Then put the check valve in the line that goes from the EXHAUST to the Fuel TANK, making sure the arrow is going towards the TANK.

Also, when the truck starts to act poorly around 1/2 tank, have you tried filling the tank to the top again? Reading your last post the phrase ( halfway though the tank) just clicked something in my head. Pretty much anyone with a Genesis/Nemesis/GST has had this problem, but generally it results in the truck stalling completely rather than just making a high pitched noise.

Anyway, I bet if you install the check valve as I have specified and then retune, It'll run.

I've always run OS #8 in my nitro RCs and have always had good luck with them.

nitrotec

i will try it tomorrow
try this again (copy and paste)dont click on it directly)
http://www.youtube.com/watch?v=kK9PJgSI&feature=related
thanks

dustin7837

My Feedback: (1)

Even copy paste into the address bar of firefox or IE won't work. Just click the share button below the video and post the URL listed there. It should be like http://www.youtube.com/watch?v=xxxxxxxxxxxx

nitrotec

Ok, Igot you a good video of the truck. how do i upload the video for you to watch??

dustin7837

My Feedback: (1)

Just upload to Youtube, then click on the "share" Button below the video and copy the link.

Come back to RCU, click the "Youtube" button and paste the link Between the Youtube "brackets" eg: [yo

nitrotec

[youtube]http://www.youtube.com/watch?v=48CeUtvmBlw[/youtube]
check this out and tell me what you think. the video is on you tube anyway. on you tube search for "cen gst 7.7 high pitch" in the search box. it is the first video by "pkarnak" let me know

The Real Dogman

Looks to me like your tune needs to be leaned out a bit more. You would be surprised how lean the tune needs to be with the ofna valve installed..

nitrotec

I honestly dont know how lean i need to be. are we talking about the lsn or the hsn. When you saw the video and when the truck was making that sound if you noticed i turned the lsn counterclockwise to calm it down. what are we saying here??the engine was smoking it must have been too lean actually. I am very lost!!!

nitrotec

Just to add on theprevious post. the video shows clearly that the truck is running fine. at one point and i dont know how the sound started again. something is triggering this high pitch idle. the truck was going through all three gears clearly. something is causing this and i dont know what it is!!!!

The Real Dogman

no, more smoke means too much fuel/oil and you will need to tune both lsn and hsn.. It revs like that because it is starving, check for air in the fuel lines, might even be that when your engine heats up, it developes an air leak.

nitrotec

I checked everything. no leaks in the fuel line or the pressure line. I am perfectly tuned up the truck was running perfectly until a certain point. Now here is a new thing. I brought the truck in and i dont know why it occured to me to check the cooling head. i started taking the screws off and i noticed that the screws were very loose. the cooling head wasn't moving or anything but the screws were very loose. I disassembled it, cleaned it and reinstalled it and i tightened it back. Do you think i had an leak there somewhere. between the cooling head and crank case. I am really ready to give up. I have an hpi savage xl, revo 3.3, mgt 8.0 and never had that problem.

nomobux

My Feedback: (4)

Loose head screws = not a good thing !

The Real Dogman

Yep loose headscrews will def cause that. Get your head screwed back on and check it out to see if it still revs high.

midntpumkin

i changed the carb on mine and never had a problem again with the 7.7
http://www3.towerhobbies.com/cgi-bin...?&I=LXFUU2&P=0
unfortunatly its been discontinued , so i am not sure which carb may fit now

nitrotec

You know what, that is the most logical explanation to the problem, beleive i thought about it but i doubt it. the carb you replaced, is it a cen card or some aftermarket carb, do you remember the brand? you think i can use an HPI savage carb? let me know i am desprate here. I am ready to get rid of it....

midntpumkin

it was the associae carb from the 21 i have , it fit perfect . i will take a pic of it to show you.

nitrotec

please do!! so you are saying you used to get this high pitch sound on slow down also!! did you see the video i posted?? you will hear towards the end. They keep telling me i am lean, and i know i am not. the truck runs great clearly in the video till this this one point. and then i have to shut it down.

midntpumkin

here is what i used , i think the xtm28 carb is the same size as well or thextm 24/7 carb

midntpumkin

the other thing to try is to take the carb off the motor and try to seal it up with permetex, http://www.permatex.com/products/Aut...sket_Maker.htm
around the high speed needle , around where the carb goes into the motor , not inside the motor, check the carb to see if all the o rings are not broken , lube the orings with this stuff , i find it works and renews o rings . i also replaced my brand new tanks on mine , i think the orings from the rtr are no good or you need to relube them either way replacing the tank or checking to see if there is a restriction in the line . i found in both of mine the in tank filter was bad , so it also helped from being too lean. these things like to be lean on the high end or close to it , the low is usually rich , that may help too in setting the needles. i also needed 2 gallons of fuel before they really ran well , these things when i tryed to take them apart were super tight and after 2 gallons i ported the motor and removed the metal on the exaust port , they have 2 holes on the exaust port , i made it to one big hole , that opened up a whole new meaning of a can of worms lol
http://www.iaqsource.com/product.php?product=113281
good luck ,

nitrotec

hey thank you very much. I dont beleive i have to go through all this work on a month old truck. the first thing i will do is to swap the carb and seal it. I dont think the engine is really the problem, but if i find out that it is the case i might want to use the warranty and contact cen maybe i will get a replacement. thanks again.

midntpumkin

sorry i mis printed something , lube the orings with the turbine oil , not the permetex. if permetex gets in the motor it will need to be cleaned well or your going to have alot of problems.

The Real Dogman

I feel you should contact before you change anything on that motor, since you feel its NOT anything anyone has suggested, maybe CEN can help...And your right you should not have to deal anything on a month old toy... Contact CEN today!!

Just remember, ANY RTR should be gone thru to be sure everything is good to go. If you dont then you are asking for trouble. That's the main reason RTR has crippled this hobby, nobody thinks they should have to put any work into a new RTR RC.... I miss the kit days!! RTR only means all of the parts are there to get you running,, the rest is up to the end user..