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7.7 running hot - 6/5/2008 9:27:30 AM   
vangsoe


 

Posts: 7
Joined: 6/5/2008
From: , DENMARK
Status: offline 		Hello,
I am new to this very nice forum but not that new to nitro cars.
I bought a used Genesis. Rebuild the engine new sleeve, piston and bearings etc.
Broke in the engine according to specs.
Engine is running hot now - like above 280 F after about 5 min.
of various speeds. Thats too hot of course.
The mixture is not too lean - i am pretty sure about that
I have set both low and high end needle to factory specs
and even riched them out from there - so much that you
can hear the engine is flotting with fuel.
Idle and low speed/revs dont seem to care much about the
position of the low end needle though ??
I am running 25 percent nitro. 13 percent synthetic and 2 percent castor oil.
Everything is TIGHT - no leaks. Everything is clean - no paint or dirt anywere.
I have tried with another carb - no change. I have tried with all kind of low- and
high end needle settings - starting from factory - having it running so fat that
the fuel is killing the engine - but it still runs too hot.
I have a thermometer fitted to the engine. Temp probe just above the cylinder -
just below the cooling head. I have also checked with a temp gun, and i have
also checked with water / fingers - its real HOT...not doubt about that - so i dare
not drive it...
Any suggestions guys ?
Tks and best regards from Denmark
       Post #: 1

RE: 7.7 running hot - 6/5/2008 11:31:11 AM   
nomobux



Posts: 1174
Joined: 2/21/2005
From: Ellensburg, WA, USA
Status: offline 		Start looking for air leaks.

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       Post #: 2

RE: 7.7 running hot - 6/5/2008 5:17:45 PM   
The Real Dogman



Posts: 1901
Joined: 5/5/2006
From: Tucson, AZ, USA
Status: offline 		Also check that your Exhaust Gasket is seated properly, having a torn or misaligned silicone here will allw air to be drawn into the cylinder when the engine is running..

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       Post #: 3

RE: 7.7 running hot - 6/5/2008 5:23:01 PM   
vangsoe


 

Posts: 7
Joined: 6/5/2008
From: , DENMARK
Status: offline 		Hi,
Tks for your input - appriciated.
Exhaust gasket is all new...all gaskets are new in fact.
I will put in a one-way valve as i have read about this
someplace else on this forum.
I´ll let you know what happens.
Tks again

(in reply to The Real Dogman)
       Post #: 4

RE: 7.7 running hot - 6/5/2008 8:17:00 PM   
burningpoo



Posts: 622
Joined: 5/4/2007
From: easton, PA, USA
Status: offline 		Did you replace the o-ring on the fuel tank? Is the one way valve going into the fuel tank? I've read that useing over 20% nitro you have to add a shim to the head. I'm running 30%, haven't done that and haven't had any problems, beside that after the last cleaning I think my exhaust seal is sitting wrong/dead since the back of my engine has fuel on it.

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       Post #: 5

RE: 7.7 running hot - 6/5/2008 8:37:54 PM   
vangsoe


 

Posts: 7
Joined: 6/5/2008
From: , DENMARK
Status: offline 		Burningpoo: yes - the one way valve is going on the exhaust to fuel tank line, as to solve the "half tank lean problem" i´v read about here in this forum.

I´v checke the o-ring at the tank - it takes like 10 psi of air-pressure before lifting..should be enough i guess...
Tks again

(in reply to burningpoo)
       Post #: 6

RE: 7.7 running hot - 6/6/2008 12:26:21 AM   
CEN Racing



Posts: 1516
Joined: 4/22/2003
From: placentia, CA, USA
Status: offline 		Try replacing the fuel tubing and make sure you are 1.5 turns out from flush on the bottom
Also check and make sure the carb is on nice and tight
as well as the heatsink head screws....
What fuel are you running????

We are happy to help....
customerservice@cenracing.com

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CEN Racing - www.cenracing.com

(in reply to vangsoe)
       Post #: 7

RE: 7.7 running hot - 6/6/2008 8:37:55 AM   
vangsoe


 

Posts: 7
Joined: 6/5/2008
From: , DENMARK
Status: offline 		Hi CEN,

First of all: nice to have a reply from an official CEN representative - appriciated.

Fuel tubing is new - why should i replace this ?
I am running an in-line fuel filter - a 2 mm Graupner i think it is.

I use a fresh air-filter with normal air-filter oil.

I will try 1,5 turn out from flush on the low end needle...have had best idle with about 1 - but will try of course

Heatsink, backplate etc. all nice and tight. Carb has a thin layer of silicone gasket, as well as the O-ring - so should be tight here too...

I am running a home-brew: 25 percent nitro ( fresh from local hobby shop ), 13 percent synthetic and 2 percent castor ( organic ) oil and then of course 60 percent methanol - also fresh from hobby-shop.

I am planning to fit a check valve ( one way valve ) into the exhaust to fuel tank line, as suggested by several in this forum. I never ran a half tank of fuel since i broke it in ( mostly idle ), cause the damn thing is running hot on me - so i dont know whether my Genesis will experience the troubles described, at half tank. But its worth a try - engine must be running lean somehow / under surtent conditions.

BTW - are you the same CEN as when i order parts from censtore@cenracing.com ?. If so - i must say i am impressed with your service and how fast i actually get the parts from you ! Thanks a million - if you are the same guys of course

Tks again and best regards from Denmark
Niels

(in reply to CEN Racing)
       Post #: 8

RE: 7.7 running hot - 6/9/2008 3:29:10 PM   
derrick05


 

Posts: 299
Joined: 4/20/2007
From: Brevard, NC, USA
Status: offline
quote:

ORIGINAL: vangsoe

Hi CEN,

First of all: nice to have a reply from an official CEN representative - appriciated.

Fuel tubing is new - why should i replace this ?
I am running an in-line fuel filter - a 2 mm Graupner i think it is.

I use a fresh air-filter with normal air-filter oil.

I will try 1,5 turn out from flush on the low end needle...have had best idle with about 1 - but will try of course

Heatsink, backplate etc. all nice and tight. Carb has a thin layer of silicone gasket, as well as the O-ring - so should be tight here too...

I am running a home-brew: 25 percent nitro ( fresh from local hobby shop ), 13 percent synthetic and 2 percent castor ( organic ) oil and then of course 60 percent methanol - also fresh from hobby-shop.

I am planning to fit a check valve ( one way valve ) into the exhaust to fuel tank line, as suggested by several in this forum. I never ran a half tank of fuel since i broke it in ( mostly idle ), cause the damn thing is running hot on me - so i dont know whether my Genesis will experience the troubles described, at half tank. But its worth a try - engine must be running lean somehow / under surtent conditions.

BTW - are you the same CEN as when i order parts from censtore@cenracing.com ?. If so - i must say i am impressed with your service and how fast i actually get the parts from you ! Thanks a million - if you are the same guys of course

Tks again and best regards from Denmark
Niels

Geez! Ya dont think that fuel has anything to do with it ? I guess not cause if you thought it,you would have said so .I might try some decent fuel before I go off the deep end

(in reply to vangsoe)
       Post #: 9

RE: 7.7 running hot - 6/9/2008 5:10:23 PM   
vangsoe


 

Posts: 7
Joined: 6/5/2008
From: , DENMARK
Status: offline 		Hi Derrick05

Whats decent fuel in your oppinion ?

We are running several other nitro cars on this fuel - HPI and SMT engines - no problems at all here...
The brand of nitro-methane we use is Model Technics - not the cheapest overhere i can assure you.
The methanol is off the shell at our local store for industrial chemicals.
The synthetic and organic oils we use are Castrol - which brand of oil do you prefer ?

LMK what you use !

Tks

Vangsoe

(in reply to derrick05)
       Post #: 10

RE: 7.7 running hot - 6/18/2008 1:16:41 PM   
derrick05


 

Posts: 299
Joined: 4/20/2007
From: Brevard, NC, USA
Status: offline 		I didnt mean to leave you hanging ,just havent been online in a while because the weather is good and I have enjoying the hell out of my NEMESIS ,man,I just love that thing,hold on a second,Im getting emotional okay,I would recommend,odonnel20%.Thats MY personal favorite,but I have to drive 100 miles to get it,so sometimes I run sidewinder20%.Your fuel may not be the problem,but it is my guess that it is.That stuff may burn fine in HPI or whateverelse,but you cant go off of that.CEN is in a leauge of its own.From what you say here there are no airleaks,and all else is good,and then you say HOMEBREW FUEL ,there it is,seems to me you have solved your own problem.I could be wrong,Im just telling you that if it were me ,the first thing I would do is dump that crap and run a top named brand fuel,with a good reputation with 20% nitro.I dont even have that checkvalve setup that everybody does and I have never had overheating issues

(in reply to vangsoe)
       Post #: 11

RE: 7.7 running hot - 6/19/2008 6:57:26 AM   
vangsoe


 

Posts: 7
Joined: 6/5/2008
From: , DENMARK
Status: offline 		Hi Derrick,

Well - it wont costs much to give it a try with some other fuel - so thats what i will do !

I did a run yesterday and stop several times to adjust the brakes. The engine was so hot the the fuel inside the carb boiled..

Tks again

Niels

(in reply to derrick05)
       Post #: 12

RE: 7.7 running hot - 6/19/2008 2:30:17 PM   
derrick05


 

Posts: 299
Joined: 4/20/2007
From: Brevard, NC, USA
Status: offline 		Yea,get some good fuel and let me know.I think that HOMEBREW is overheating your engine.I could be wrong though,but if Im right,lets hope you havent damaged your engine.Is the top of your piston still clean and shinny,or is it dark or black looking.If that piston is the wrong color,then the fuel is crap for sure.Get some good fuel,go back to factory settings and go from there.Good luck

(in reply to vangsoe)
       Post #: 13

RE: 7.7 running hot - 6/19/2008 3:01:09 PM   
vangsoe


 

Posts: 7
Joined: 6/5/2008
From: , DENMARK
Status: offline 		Hi,

Piston is still nice, clean and shiny. Compression still feels the same - its good as it should be with new piston, sleeve etc.
Mind you - i run a 15 cpx SMT engine and a 41 cpx HPI on the same fuel with absolutely no problems at all. These
engines are performing at least as well as others running "factory" Sidewinder, Tornado, Model Technic, Jet etc....

Will let you know regarding fuel in my CEN 7.7. I might consider going down to 20 percent nitro though since i have heard that CEN engines dont
like to run higher nitro percentage than 20...

Tks again - all your info is much appriciated - and best regards from Denmark

Niels



< Message edited by vangsoe -- 6/19/2008 3:03:35 PM >

(in reply to derrick05)