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Old 05-24-2010, 07:57 PM   #1
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Default Tune problems, need opinions

Ok i consider myself a decent tuner, i dont have flame out, My engines last usually 10+ gallons, but this engine has me at a loss.

Its always been picky on tune. Well last saturday i went to tune the engine because it hasnt been ran in a couple weeks and its warmed up. I took it around the track a few laps brought it in and tried tuning it, unless i kept it rich my idle was high, if i lowered the idle it would die, ive tried everything possible, even took it back to little out from flush and tuned again, tried an OD 97T instead of the nova c6tgc. nothing. So last night, i tore the engine apart, bearings feel great, piston was dark but it wiped off. I flushed the needles out, actually flushed the whole engine out with fuel. Inspected all the orings, all good, oiled everything while putting back together. Today i put in in my buggy, at first acted great, started running it at 1/2 a tank, almost ran out of fuel, put more fuel in, got to half a tank and my problems started again. Only thing i can think of is the front bearing is bad, i dont see excess fuel tho. This engine has good compression, not Huge but normal for an engine with 5-6 gallons on it.btw ive tried a new tank, all new lines, new exhaust gasket, new springs, and a new gallon of fuel as well. any tips or opinions would be appreciated
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Old 05-24-2010, 08:01 PM   #2
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oops... IDK
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Old 05-24-2010, 08:03 PM   #3
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oops... IDK
wtf frank? lol
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Old 05-24-2010, 08:07 PM   #4
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Originally Posted by losi_racer View Post
Ok i consider myself a decent tuner, i dont have flame out, My engines last usually 10+ gallons, but this engine has me at a loss.

Its always been picky on tune. Well last saturday i went to tune the engine because it hasnt been ran in a couple weeks and its warmed up. I took it around the track a few laps brought it in and tried tuning it, unless i kept it rich my idle was high, if i lowered the idle it would die, ive tried everything possible, even took it back to little out from flush and tuned again, tried an OD 97T instead of the nova c6tgc. nothing. So last night, i tore the engine apart, bearings feel great, piston was dark but it wiped off. I flushed the needles out, actually flushed the whole engine out with fuel. Inspected all the orings, all good, oiled everything while putting back together. Today i put in in my buggy, at first acted great, started running it at 1/2 a tank, almost ran out of fuel, put more fuel in, got to half a tank and my problems started again. Only thing i can think of is the front bearing is bad, i dont see excess fuel tho. This engine has good compression, not Huge but normal for an engine with 5-6 gallons on it.btw ive tried a new tank, all new lines, new exhaust gasket, new springs, and a new gallon of fuel as well. any tips or opinions would be appreciated
Does it have an air leak?
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Old 05-24-2010, 08:10 PM   #5
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Does it have an air leak?
Thats the only thing i cant think of. only sign is the idle tho. All my orings are good tho, thats why i was pointing towards the front bearing
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Old 05-24-2010, 08:17 PM   #6
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Just a thought, have you pulled the motor and checked the block for cracks?
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Old 05-24-2010, 08:18 PM   #7
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Just a thought, have you pulled the motor and checked the block for cracks?
yes, inspected every part, had every part disassembled and inspected while i flushed
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Old 05-24-2010, 08:25 PM   #8
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are you on the original bearings? Do you have a unusual amount of oil around the front bearing?

that would be my guess on your airleak. I actually had a problem with the pressure nipple on my pipe getting clogged. Took forever to figure that one out.
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Old 05-24-2010, 08:25 PM   #9
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Check for air leaks. Then I would lean the lsn, that should raise the idle. Then as go adjust the idle as it gets to high. That will give a lean hsn so you will want to richen it up a little.
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Old 05-24-2010, 08:26 PM   #10
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are you on the original bearings? Do you have a unusual amount of oil around the front bearing?

that would be my guess on your airleak. I actually had a problem with the pressure nipple on my pipe getting clogged. Took forever to figure that one out.
Tried a different pipe to

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Originally Posted by losi guy View Post
Check for air leaks. Then I would lean the lsn, that should raise the idle. Then as go adjust the idle as it gets to high. That will give a lean hsn so you will want to richen it up a little.
tried that.
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Old 05-24-2010, 08:38 PM   #11
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Are you sure the slide is closing all the way? Is your throtle trim set right? Sounds to me like it is running with a high idle and a richer setting which means to me, for what ever reason, when you lean it out on the low and lower the idle it is closing more then you would like it too.

I know it sounds elementary but you never know. If that is not it, i would start at the clutch and work back. I get a cup full of real soapy water, get a brush and wipe it on any part of the engine i am checking a leak at. Then i blow into a piece of fuel tubing that is connected to the carburator. Who knows, might be a carb boot or pinch bolt. You know alot of front bearings leak "a little", but if it is really blowing bubbles that is probably your leak.
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Old 05-24-2010, 08:42 PM   #12
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Originally Posted by dreaux View Post
Are you sure the slide is closing all the way? Is your throtle trim set right? Sounds to me like it is running with a high idle and a richer setting which means to me, for what ever reason, when you lean it out on the low and lower the idle it is closing more then you would like it too.

I know it sounds elementary but you never know. If that is not it, i would start at the clutch and work back. I get a cup full of real soapy water, get a brush and wipe it on any part of the engine i am checking a leak at. Then i blow into a piece of fuel tubing that is connected to the carburator. Who knows, might be a carb boot or pinch bolt. You know alot of front bearings leak "a little", but if it is really blowing bubbles that is probably your leak.
Not rich bottom,thought of that too. Put brand new clutch. i seal the pinch bolt, inspected the boot. All my orings are fine so every thing is sealed, thats one good thing about a nova. I ordered new bearings we will see
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Old 05-26-2010, 06:49 AM   #13
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Originally Posted by losi_racer View Post
Not rich bottom,thought of that too. Put brand new clutch. i seal the pinch bolt, inspected the boot. All my orings are fine so every thing is sealed, thats one good thing about a nova. I ordered new bearings we will see
Even though you think your o-rings are ok, I suggest sealing the carb. A person on YouTube that calls himself Squirrel (his username is Squirrelod) says that even though the o-ring on the carb seems ok, he recommends removing it and sealing with gasket material.

You can find this video here: http://www.youtube.com/watch?v=6xwDy-I0Z4I

He mentions that some gasket material might not be strong enough. Get gasket material that can withstand over 350F for sealing with just in case.

EDIT: Notice that Squirrel also mentions Team Associated's green slime. It's used for sealing the HSN and LSN.
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Old 05-26-2010, 10:21 AM   #14
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This sounds identical to the issues I was having with my DBX. 2 changes that I made at the same time helped significantly. First was a new o-ring on the gas cap. Second was a new glow plug. I am curious to hear if your new bearings help.
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Old 05-26-2010, 10:41 AM   #15
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You do mention you checked everything... and I realize this is an obvious one to check... but...

How much play does your conrod have? That sounds JUST like the symptoms of a sloppy conrod.

Also the obvious airleak questions that everyone has covered...
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