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Cen GST 7.7 Problems. Need Help :(

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Old 10-21-2006, 04:37 PM
  #1  
Ghaligan
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Default Cen GST 7.7 Problems. Need Help :(

Ok i don't understand this. This engine is totally different from the Cen Genesis Limited Edition Truck. After i broke it in the 6 tanks, and changed it to the prefered settings, it's overheating rapidly. If it's too rich, i got a problem. If it's too lean, THAT's worse. If i run it lean, the temp climes over 400 degrees in less than 10 seconds. Even with the High Speed Needle out. If i try leaning out the Low Speed needle with the High Speed Needle in too, same thing. It goes over 400 degrees immedately. If i richen the High Speed Needle and bring IN the Low Speed Needle, it does it AGAIN. If i Richen the High Speed Needle and, the Low Speed Needle, she won't start. If i mess with the Idle, well it idles fine no matter what. Here's another problem. The Fuel that goes into the Carb does NOT stay in the Carb. As soon as i give it a pull, just ONE pull, the fuel immediately escapes the Carb and back into the fuel tank. This happens rather the Low Speed Needle is in, or out. I can't seem to find that setting for the best proformance without climing over 400, like my Cen Genesis LE is. You know what's the worse part? I've been doing this now without the Body on. So i'd only imagine the situation much much worse once i start placing that on. If anyone could reply for help, that would be great. Thanks everyone. I've been at this for 2 days now, and the bones in my hand are ready to snap from pulling and pulling. Not saying i hate the pull start, in fact i rather deal with pull start than Roto Start.
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Old 10-22-2006, 12:17 PM
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Default RE: Cen GST 7.7 Problems. Need Help :(

Ghaligan, Have you drove it when it seems to run ok but high temps?? does it seem to run fine with alot of power?? How are you checking Temprature?? This might one of those times that you will need to tune for power not temprature!! Try tuning for power not temp. and see what kind of power you can tune for. Maybe the black ead is not giving you an accurate reading the traditional temp gage, just guessing. but tune for power and see, if it seems to still get hot enough to melt plastic(Lexan) then you could have a problem, but try my way first..

Good luck!!

BTW I'm Jelous you bought a GST!! I have to pressure the wife abit more or tell her it is for her, yeah thats the ticket!!


Have Fun!!
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Old 10-22-2006, 02:23 PM
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Default RE: Cen GST 7.7 Problems. Need Help :(

Hey Dogman, I don't know what's the deal. I'm using one of those Duratrax Temp Readers. They're blue. I think you know what it is, but, it fits right into the Black Cooling head on the GST. When it reaches 400 Degrees, it starts making little jump sounds as if it's saying "Hey, i'm tooo hot shut me off". I tried turning the 2nd and third speed shift points 15 minutes turned OUT. To see if maybe it was because CEN had that tranny to shift toooo later. Maybe that was why? I'm not sure lol. Here's a picture of my trucks. I'll continue this again today and see what happens.
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Old 10-22-2006, 11:05 PM
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Default RE: Cen GST 7.7 Problems. Need Help :(

I don't know. The GST has almost finished a whole gallion of fuel and i'm still getting this overheating issue. I haven't been able to have fun with this truck at all. This wouldn't be the first time i land on a bad truck either. I've had so many Genesis trucks in the past that carry defects on them, i end up reselling them and lose money because you can't return them. I'm not saying i want to do that to the GST. And i don't want to even think that with the GST. I wish people would come around and help me out but they're all too busy on other boards posting every so and so. I just don't get this at all. By the way, i think the new AM Radio is better than the MX-3 radio. It seems to have quicker response. I tried putting the MX-3 Radio on the GST, and it SUCKED really bad. When i put the Skyion DSX back on, everything was quicker. Such as turning.
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Old 10-23-2006, 01:41 AM
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Default RE: Cen GST 7.7 Problems. Need Help :(

try to call cen, their Tech Support is First Rate. Gabe or one of the crew should be able to get you straitened out. the Duratrax gauge has settings you can change that will give different temps depending on the setting you have it on... anodized aluminum needs to be read on a different setting than plain brushed aluminum. maybe you need to adjust those. but 400 is WAY TO HOT.
how were the temps during the breakin tanks? did you heat cycle the motor for breakin, or run teh standard procedure?
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Old 10-23-2006, 11:14 AM
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Default RE: Cen GST 7.7 Problems. Need Help :(

Hey Timmahh, I have been sorta thinking the same thing about the temps from that corny duratrax thing too. I wonder if it was playing games with me. But then again, once it read back to me around 415, and said OK MAYBE THIS THING IS BULLING ME. So i went ahead and drove it. And like just a minute later, it wasn't making the sound anymore where the piston is was moving. It sounded flat, and started to smell like fire! During that setting i had the High Speed Needle about 1/2 turn out from flush. And i know for a fact if i go in, the tempertures will raise even faster. But sometimes when the needle is OUT like that, during a high speed pass, she'll go really fast for a few seconds, then RPM starts to die slowly, even if you're holding the throttle all the way down, and just shut down. But if i have it Leaned out, i'll get great results however......i get them numbers climing over my head even idling. It's like i said before, i'm just about done with a whole gallion of fuel with the truck doing this. Sometimes, i wish it was the same engine from the LE version, because after break in, i did exactly what i did to the LE, and BOOM, i had NOOO problems at all. I did the same to the GST, and whoooop...there it is. Over heating issues. And as for the other question, during break in, i was getting something like 250 - 340 degrees. I didn't move the needles at the time since i was instructed not to. The only thing i did was lower the idle 15 minutes out. Which i had done to the LE too. I do NOT have Idling issues. I just have over heating issues. If i could, i would trade this GST engine for a LE engine. This is just rediculious. I know if i call CEN today, which i will, they are going to tell something i already did to the truck.
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Old 10-23-2006, 04:52 PM
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Default RE: Cen GST 7.7 Problems. Need Help :(

Just curious because of your last post, How many turns out are you on the HSN? High speed is generally not thought of in turns from flush.
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Old 10-23-2006, 04:58 PM
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Default RE: Cen GST 7.7 Problems. Need Help :(

those on board temp things that wrap around the head read very inacurate try a regular temp gun that you can aim directly at the glow plug
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Old 10-23-2006, 05:51 PM
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Default RE: Cen GST 7.7 Problems. Need Help :(

Hey guys. Here's the deal with the High Speed Needle though, if i run it IN from Flush, it'll give me pretty good performance, but raises temps fast. Now if the High Speed Needle in OUT from Flush, which is how it's suppose to be, holding the trigger on the transmitter makes it dash out, but the RPM starts to die, and shut down immediately. If the Low Speed Needle is in too much, it'll over heat too. If having both needles OUT, the truck will not start. So there's always something in the ways i have tried. Currently, i gave up, put a drop of After Run in the engine and put it away for tomorrow to see what the hobby shop says, and if they can give me a hand. If they can't, Ken from Cen Racing says to send it in.
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Old 10-23-2006, 07:47 PM
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Default RE: Cen GST 7.7 Problems. Need Help :(

ORIGINAL: Ghaligan

Ok i don't understand this. This engine is totally different from the Cen Genesis Limited Edition Truck. After i broke it in the 6 tanks, and changed it to the prefered settings, it's overheating rapidly. If it's too rich, i got a problem. If it's too lean, THAT's worse. If i run it lean, the temp climes over 400 degrees in less than 10 seconds. Even with the High Speed Needle out. If i try leaning out the Low Speed needle with the High Speed Needle in too, same thing. It goes over 400 degrees immedately. If i richen the High Speed Needle and bring IN the Low Speed Needle, it does it AGAIN. If i Richen the High Speed Needle and, the Low Speed Needle, she won't start. If i mess with the Idle, well it idles fine no matter what. Here's another problem. The Fuel that goes into the Carb does NOT stay in the Carb. As soon as i give it a pull, just ONE pull, the fuel immediately escapes the Carb and back into the fuel tank. This happens rather the Low Speed Needle is in, or out. I can't seem to find that setting for the best proformance without climing over 400, like my Cen Genesis LE is. You know what's the worse part? I've been doing this now without the Body on. So i'd only imagine the situation much much worse once i start placing that on. If anyone could reply for help, that would be great. Thanks everyone. I've been at this for 2 days now, and the bones in my hand are ready to snap from pulling and pulling. Not saying i hate the pull start, in fact i rather deal with pull start than Roto Start.
Dude, you have some kind of air leak...look into the tank or the fuel line and check the head bolts...you are sucking in air somewhere.
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Old 10-23-2006, 08:10 PM
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Default RE: Cen GST 7.7 Problems. Need Help :(

You might even have some crud in the HSN passage or jet, as well as possibly sucking air into the engine somewhere causing leaning..
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Old 10-23-2006, 08:16 PM
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Default RE: Cen GST 7.7 Problems. Need Help :(

ORIGINAL: Ghaligan

Ok i don't understand this. This engine is totally different from the Cen Genesis Limited Edition Truck. After i broke it in the 6 tanks, and changed it to the prefered settings, it's overheating rapidly. If it's too rich, i got a problem. If it's too lean, THAT's worse. If i run it lean, the temp climes over 400 degrees in less than 10 seconds. Even with the High Speed Needle out. If i try leaning out the Low Speed needle with the High Speed Needle in too, same thing. It goes over 400 degrees immedately. If i richen the High Speed Needle and bring IN the Low Speed Needle, it does it AGAIN. If i Richen the High Speed Needle and, the Low Speed Needle, she won't start. If i mess with the Idle, well it idles fine no matter what. Here's another problem. The Fuel that goes into the Carb does NOT stay in the Carb. As soon as i give it a pull, just ONE pull, the fuel immediately escapes the Carb and back into the fuel tank. This happens rather the Low Speed Needle is in, or out. I can't seem to find that setting for the best proformance without climing over 400, like my Cen Genesis LE is. You know what's the worse part? I've been doing this now without the Body on. So i'd only imagine the situation much much worse once i start placing that on. If anyone could reply for help, that would be great. Thanks everyone. I've been at this for 2 days now, and the bones in my hand are ready to snap from pulling and pulling. Not saying i hate the pull start, in fact i rather deal with pull start than Roto Start.
Maybe this will help I had an over heating problem with my ofna GTP 1/8 scale over heating after the break in process. The owner at the LHS told me to stop using that blue T fuel because of the blue gummy residue it was leaving on the piston, and to try O d fuel but none was in stock at the percentage that I was using ( 30%). So I bought a bottle of 30% Trin fuel readjusted the carb a little bit and the over heating was no more available. I also used a cold plug thru break in & for fun about 3 gallons of fun.
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Old 10-24-2006, 11:01 AM
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Default RE: Cen GST 7.7 Problems. Need Help :(

Definitely sounds like an air leak, but also, on your High Speed Needle, How many turns out are you? Not in relation to flush as that doesn't mean much, but as in how many turns out from bottom are you on that needle?
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Old 10-24-2006, 11:33 AM
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Default RE: Cen GST 7.7 Problems. Need Help :(

Hey everyone. Thanks for helping me out. I just came home with another Gallon of Byron's Fuel 20% Nitro since that engine's already eaten an entire gallon of it. Umm, what are those factory settings on the needles? Was it something like 4 1/2 turns out on High Speed Needle and 1 turn out from Flush on Low Speed? Air Leaks, As a matter afact, it would seem that alot of Air Bubbles do enter the Carb and sometimes, makes the Fuel escape back into the Fuel Tank. I've already tested the Fuel tank itself by putting it in water and checking to see if there's any small holes on it. The tank was fine. Then, i checked out the O-ring under the Carb to see if that was busted, it was fine as well, and reinstalled the Carb back on the Engine tight. What other areas could there be an Air Leak? Also, i've checked the Black Cooling head, and all 6 screws are tight on there too. GKCONTRA, it's like i said before, if i bring that High Speed Needle OUT like it's really suppose to (That's how my Genesis LE is) it won't let me keep the RPM like it's suppose to. It will lower down and die immediately even when you're holding the Throttle down all the way. Once you let it go, it shuts down. I check the Glow almost every so and so, and that thing is still igniting like a champ. I have a strong glow igniter too so those are surely not the cause. Aluminum Crusher, i don't know, the fuel i have is fresh, and was the one fuel recommanded by CEN. It's the same fuel my Genesis LE uses too. I wonder guys...Do you all think it might have to do with that new Black Cooling head? I'm just guessing. I might be entirely wrong.
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Old 10-24-2006, 08:18 PM
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Default RE: Cen GST 7.7 Problems. Need Help :(

I dont think the head has anything to do with overheating..It might have more to do with the reading your temp sensor is giving..have tried to completley disassemble the carb to be sure there was no debri caught in the jets??? Air can be drawn into the engine thru the front bearing if the seal is bad, air can leak past the rear engine plate behind the pull-start recoil. In fact, there are two places in that area air could get by. 1) where the starter shaft passes thru the back plate there is an O-ring. 2) around the back plate there is another O-ring that could leak.. Just remember, When you re-assemble these parts, use a thin coating of grease to help the O-ring to slide in without binding or getting caught by an edge..If you search the forum for sealing a nitro engine you will also find that there is a mod that requires a thin coating of silicone gasket sealer on the mating surfaces of the engine parts, to seal air leaks of imperfect part machinig/mating,,Check it out!!

As far as the leaking head goes, check under the shims that should be under the head button. Look for any burrs, debri or even scratches on the mating surfaces. no mater how small the defect is it could be enough to cause air to ge by,,, Believe it!!!


good luck and congratulations on your enduring persistance to tryt another gallon of fuel before you give up..

If all else fails send the engine to me and I will find and fix the leak..I promise.. [8D]
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Old 10-25-2006, 12:14 AM
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Default RE: Cen GST 7.7 Problems. Need Help :(

air leaks, period. i have absoutely no problem with overheating on my GST. I have about 1 gallon now...
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Old 11-21-2006, 11:34 AM
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Default RE: Cen GST 7.7 Problems. Need Help :(

I heard that the cen racing genesis is faster than the gst 7.7
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Old 11-27-2006, 02:30 AM
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Default RE: Cen GST 7.7 Problems. Need Help :(

check your head screws the 7.7 tends too shake them loose make sure all screws are loc-tighted cause that big motor will shake them all loose
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Old 11-28-2006, 03:56 AM
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Default RE: Cen GST 7.7 Problems. Need Help :(

The most common overheating issues with this trucks motor will be stemmed from air leaks or in proper tuning/fuel choice...
I always run that motor 1.2mm out from flush on the bottom end and .7mm in from flush on the Hi speed needle....

I recommend byron race 3000 11% lube- 245 after ten minutes
This isnt a fuel choice issue though....

Change the fuel and pressure lines
tighten the heat sink head screws
check the exhaust gasket (most likely the problem)
make sure the pipe is tight at the baffle seam
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Old 07-13-2007, 05:42 AM
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Default RE: Cen GST 7.7 Problems. Need Help :(

I am considering to purchase a GST 7.7 but am still battling to decide if there is anything else better out there
Have also been looking at Traxxas Revo 3.3 and Savage X4.6
Are there any others to consider or is the GST the best out of this bunch?

Thanks
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Old 07-13-2007, 10:12 AM
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Default RE: Cen GST 7.7 Problems. Need Help :(

Do you realize that this topic is 5 months old? Start a new topic if you need help. Not trying to be mean

But the GST is a great truck from what I have heard from the members such as TRD. But I just bought one this week and it will be here on the 18th, Im so happy.
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Old 07-13-2007, 10:19 AM
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Default RE: Cen GST 7.7 Problems. Need Help :(

I was in your position a few weeks ago, searching for the biggest, baddest 1/8th scale I could find. I searched high and low, the big names and the no names, and honestly I wasn't too impressed with all the 1/8th scale stadium and/or monster trucks I found, they were all so similar and close to the same designs and/or specs.

I wanted something more but couldn't afford a Baja 5b, then I found the GST, and it stands out on it's own in a big way. In my opinion it's better and probably faster then the Baja 5b 1/5 scale buggy, has the largest diameter tires I've ever seen at 3.75"x7.5" and is probably faster then the Baja 5b as well, compare the specs to the others and the only thing that comes close is the brand new XTM Mammoth, which in my opinion is a plastic toy. Setting my GST on top of the Mammoth box at Hobby People it's bigger then the box that XTM toy comes in. Although spec-wise I guess it's 1-1/2" longer and has a fractionally larger wheel base, and fuel tank, at the cost of a narrower width (probably less stable in turns too).

I'd love to see a head to head of a GST vs. Mammoth, just so I can point and laugh as the .46 GST smokes the puny .28 motor in the XTM, lol.

Get a GST you'll be happy you did, not to mention whenever you take it anywhere you'll get a crowd forming..
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Old 02-01-2010, 08:38 AM
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Default RE: Cen GST 7.7 Problems. Need Help :(

Hi,
Do any of you who have a Genesis GST 7.7 have lost Rear Traction?
Also broken Wheel Hex Pin several of time on the same point?
Please let me know.
I will open the Rear Diff and see wat happen first.
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Old 02-01-2010, 10:13 AM
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Default RE: Cen GST 7.7 Problems. Need Help :(

Hold the rear drive shaft and one rear wheel and spin the other. If the diff is fine the other wheel or driveshaft would want to move. Hold the driveshaft and spin each wheel on its own - the opposite wheel should turn in the opposite direction. If not the diff is doinked.
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Old 02-01-2010, 11:34 AM
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Default RE: Cen GST 7.7 Problems. Need Help :(

Thanks for your reply,
i think i found the problem,smothing went in the rear brake system and is holding it.
I'm just busy at the moment with maintenace after bashing and some hill climb yesterday.
You can see the video's on YouTube By rvk62 channel.
I will see wats the story with the the brake system and also i will do wat you said and see.

Kind Regard.
Robert.
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