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Old 12-26-2009, 07:42 PM   #1
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Default Engine Flaming Out

I know it's difficult to determine an engine problem on the internet, but maybe someone has had a problem similar to mine.

At the track today i installed a fresh conrod in my Caster Grenade. It ran fine during practice, but then starting to flame out during the heats. We thought it was a clutch spring problem so we changed those. That didn't help. In the main it was apparent the coming out of the straightaway when i let off the throttle, the engine would die. We kept adjusting the tune, but the same problem occurred. Sometimes i could barely get off pit lane. So when i let off the throttle the engine acted like it would just load up with fuel, and stall when i gave it throttle. One person said it was lack of compression, however the engine does have some flywheel resistance when hot. Others said it was rod/crank slop. Which would have to be the crank since the rod is new.

If you having any suggestion/ideas please feel free to post them.

Thanks
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Old 12-26-2009, 07:51 PM   #2
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thats usually a sign of low compression and or crankpin wear,i would lean to the crankpin wear.
also is it running hot? if so rear bearing is about to drop.
me personally i would pull it out and strip it down to inspect.
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Old 12-26-2009, 07:53 PM   #3
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Originally Posted by helivaguy View Post
thats usually a sign of low compression and or crankpin wear,i would lean to the crankpin wear.
also is it running hot? if so rear bearing is about to drop.
me personally i would pull it out and strip it down to inspect.
No it wasn't running hot. I'm going to strip it down tomorrow and do a detailed check over the crank pin.
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Old 12-26-2009, 07:58 PM   #4
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cool let us know..
also measure all the way around the pin.
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Old 12-26-2009, 08:34 PM   #5
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I just took the backplate off and checked the slop. I can see where the crank pin moves inside the rod, and squishes fluid around in between the two. The rod is brand new, so wouldn't that mean the crank pin is worn since it has some slop between it and the rod?
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Old 12-26-2009, 08:40 PM   #6
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Quote:
Originally Posted by Cory Kerber View Post
I just took the backplate off and checked the slop. I can see where the crank pin moves inside the rod, and squishes fluid around in between the two. The rod is brand new, so wouldn't that mean the crank pin is worn since it has some slop between it and the rod?
yep

so the rod you took out of there may just be fine

cory the go techs tend to have a soft crank...

the grenade is a gen4 gotech

massive mods might have a crank instock

or talk to single2372 on the CVRC forum he might sell his grenade pretty cheap!
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Old 12-26-2009, 08:49 PM   #7
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Thanks Marcus, i'll see what i can do. Worst comes to worst i'll get a new crank and fresh pinch!
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Old 12-27-2009, 09:29 AM   #8
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I had the same symptoms with my engines, it turned out to be the high speed needles o rings. they were worn out and the needle was spinning out from the vibration of the engine. I was able to put the buggy up on the bump box give it throttle and watch the needle turn all the way out. a new set of o-rings and i was good to go. i run a OD ss .21.
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Old 12-27-2009, 11:15 AM   #9
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Quote:
Originally Posted by Cory Kerber View Post
Thanks Marcus, i'll see what i can do. Worst comes to worst i'll get a new crank and fresh pinch!
If the crank/rod fit is very loose it will go through glow plugs rapidly . Tell tale sign

Crank measurement to look for and be within tolerance is 4.92mm or better , measure in many different spots on the crankpin .

Hope this helps ,
Monty



And btw , the crank/rod fit has to have a little play so oil can get in there :-)
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Old 12-27-2009, 12:23 PM   #10
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Honestly, the rod/crank feels the same as it always has, if not better since i installed the new rod. I think the problem is the lsn because it's extremely easy to turn. I read in an rc car action magazine to put a light bit of blue loctite on the threads. But i don't trust putting locktite on my engine. I'm going to get some new o-rings and give it another shot.
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Old 12-27-2009, 12:42 PM   #11
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Quote:
Originally Posted by Cory Kerber View Post
Honestly, the rod/crank feels the same as it always has, if not better since i installed the new rod. I think the problem is the lsn because it's extremely easy to turn. I read in an rc car action magazine to put a light bit of blue loctite on the threads. But i don't trust putting locktite on my engine. I'm going to get some new o-rings and give it another shot.
if its a go tech , you should replace the carb anyway . i would suggest putting a novarossi carb

pm me if you need one ,
monty
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Old 12-27-2009, 12:47 PM   #12
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Quote:
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if its a go tech , you should replace the carb anyway . i would suggest putting a novarossi carb

pm me if you need one ,
monty
that was one of the best most accurate advice on a go tech motor!

the nova carb makes all the difference in the world!
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Old 12-27-2009, 02:28 PM   #13
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would a O.S. carb work as well?
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Old 12-27-2009, 04:05 PM   #14
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I guess I'll look into a different carb. I took my motor apart today and found that the rod can be wobbled up and down on the crank pin. I'll have a vid up shortly.
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Old 12-27-2009, 04:20 PM   #15
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you will see the rod slop more at TDC when rotating the crank back and forth,
agree you cant beat a novarossi carb.
btw the 14mm novarossi crank will work in there also.
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