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Old 08-17-2014, 10:58 PM   #1
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Default OFNA JL Tuned .12 Tuning Issue

I put a new OFNA JL Tuned .12 PART #51128 in an MTX5 and I am having issues with it. I am running it with a Picco P6TC plug, RD Logics Turbo III Pipe, Motorsaver big block filter, 20% O'Donnell fuel, and 1 shim removed from under the head button. I've run about 1.5 quarts through it.

The motor starts right up, holds a smooth and low idle, revs properly, hits second gear, pulls hard, blows plenty of smoke from the pipe, and gets up to about 205 degrees when I run it on a track.

The problem is after about 2.5 minutes of hard laps at the track the motor just stalls, usually when I'm giving it throttle like down the back straight. I can hear it start to bog out and then it just dies. After it dies it is a little more difficult to start than normal, but I can usually get it running again after about 5 seconds of cranking. I assumed it was an air leak so I sealed up the carb neck and the back plate with RTV. That didn't help at all. My tank and fuel lines are not leaking air and I don't see any signs of oil or leakage around the lines or the motor. I blew into the carb line while covering up the carb mouth and exhaust pipe and I could not hear any air leaking out of the motor. The same holds true for the tank and the tank lid, no leaks when I blew into the lines.

It kind of sounds like a lean issue or maybe vapor lock. My fuel line is running around the front of the air cleaner so it is not too close to the motor and my temps are well within reason. I've tried to richen up both the low side needle and the main needle but I have yet to solve the problem. If I make it too rich the motor runs poorly. When I lean it out for decent power and RPM the problem returns.

It runs perfectly when I drive it in front of my house. I have enough room to hit second by my house, but I cannot wind it out in second like I do at the track. The clutch and 2-speed both seem to be working properly so I don't think they are stalling the motor. I had a few guys take a look at it at the track, but the issue remains. Does anyone have any ideas I can try?
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Old 08-19-2014, 05:06 PM   #2
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Originally Posted by rossb View Post
I put a new OFNA JL Tuned .12 PART #51128 in an MTX5 and I am having issues with it. I am running it with a Picco P6TC plug, RD Logics Turbo III Pipe, Motorsaver big block filter, 20% O'Donnell fuel, and 1 shim removed from under the head button. I've run about 1.5 quarts through it.

The motor starts right up, holds a smooth and low idle, revs properly, hits second gear, pulls hard, blows plenty of smoke from the pipe, and gets up to about 205 degrees when I run it on a track.

The problem is after about 2.5 minutes of hard laps at the track the motor just stalls, usually when I'm giving it throttle like down the back straight. I can hear it start to bog out and then it just dies. After it dies it is a little more difficult to start than normal, but I can usually get it running again after about 5 seconds of cranking. I assumed it was an air leak so I sealed up the carb neck and the back plate with RTV. That didn't help at all. My tank and fuel lines are not leaking air and I don't see any signs of oil or leakage around the lines or the motor. I blew into the carb line while covering up the carb mouth and exhaust pipe and I could not hear any air leaking out of the motor. The same holds true for the tank and the tank lid, no leaks when I blew into the lines.

It kind of sounds like a lean issue or maybe vapor lock. My fuel line is running around the front of the air cleaner so it is not too close to the motor and my temps are well within reason. I've tried to richen up both the low side needle and the main needle but I have yet to solve the problem. If I make it too rich the motor runs poorly. When I lean it out for decent power and RPM the problem returns.

It runs perfectly when I drive it in front of my house. I have enough room to hit second by my house, but I cannot wind it out in second like I do at the track. The clutch and 2-speed both seem to be working properly so I don't think they are stalling the motor. I had a few guys take a look at it at the track, but the issue remains. Does anyone have any ideas I can try?
Did you break it in? I have had issues when trying to push a new motor without enough break in time. Put the shim back in especially if you are running 20%.
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Old 08-19-2014, 10:08 PM   #3
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I think it is broken in after 1.5 quarts. The motor comes shimmed for 30%, that is why I removed one shim for use with 20% fuel.

I'm starting to think I should either run a hotter plug, or add the shim back and run it on 30% with the P6TC plug. The P6TC is a "Medium" temp plug.
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Old 08-19-2014, 10:53 PM   #4
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Sounds like a lean bog. JLs like a rich bottom, so make sure of that. I used to run JLs, they were cheap and fast! They wouldn't last long though!
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Old 08-20-2014, 09:34 AM   #5
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Quote:
Originally Posted by rossb View Post
I put a new OFNA JL Tuned .12 PART #51128 in an MTX5 and I am having issues with it. I am running it with a Picco P6TC plug, RD Logics Turbo III Pipe, Motorsaver big block filter, 20% O'Donnell fuel, and 1 shim removed from under the head button. I've run about 1.5 quarts through it.

The motor starts right up, holds a smooth and low idle, revs properly, hits second gear, pulls hard, blows plenty of smoke from the pipe, and gets up to about 205 degrees when I run it on a track.

The problem is after about 2.5 minutes of hard laps at the track the motor just stalls, usually when I'm giving it throttle like down the back straight. I can hear it start to bog out and then it just dies. After it dies it is a little more difficult to start than normal, but I can usually get it running again after about 5 seconds of cranking. I assumed it was an air leak so I sealed up the carb neck and the back plate with RTV. That didn't help at all. My tank and fuel lines are not leaking air and I don't see any signs of oil or leakage around the lines or the motor. I blew into the carb line while covering up the carb mouth and exhaust pipe and I could not hear any air leaking out of the motor. The same holds true for the tank and the tank lid, no leaks when I blew into the lines.

It kind of sounds like a lean issue or maybe vapor lock. My fuel line is running around the front of the air cleaner so it is not too close to the motor and my temps are well within reason. I've tried to richen up both the low side needle and the main needle but I have yet to solve the problem. If I make it too rich the motor runs poorly. When I lean it out for decent power and RPM the problem returns.

It runs perfectly when I drive it in front of my house. I have enough room to hit second by my house, but I cannot wind it out in second like I do at the track. The clutch and 2-speed both seem to be working properly so I don't think they are stalling the motor. I had a few guys take a look at it at the track, but the issue remains. Does anyone have any ideas I can try?
try put the shim back and run with 20% nitro
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Old 08-20-2014, 06:47 PM   #6
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try put the shim back and run with 20% nitro
I tried that and it did not help.
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Old 08-20-2014, 07:12 PM   #7
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Does it get over run at the end of a long straight, when at the track?
200F is just warmed up, it may be a LSN bottom end tune and you may be too rich using the top needle HSN to lean it out.
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Old 08-20-2014, 07:43 PM   #8
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Does it get over run at the end of a long straight, when at the track?
200F is just warmed up, it may be a LSN bottom end tune and you may be too rich using the top needle HSN to lean it out.
Yep, that could be too, Ive done it a few times.
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Old 08-20-2014, 08:19 PM   #9
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Does it get over run at the end of a long straight
Over run?

Does anyone think that this could be caused by a plug that is too cold for 20% Nitro?
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Old 08-24-2014, 07:25 AM   #10
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I put the shim back and tried it with 20% and 30% Nitro and the problem remained. No amount of tuning would solve the issue.

I got frustrated and swapped the motor for an old (but known to be reliable) Ofna Picco 3-port standard (non-turbo) motor I had in my old HPI R40. This motor ran great for years in my R40, but after I put it in my MTX5 it had the same issues the JL Tuned did. I installed a new fuel tank and new fuel lines and the problem remained with my old motor. I then swapped the RD Logics Turbo III Pipe for an old (and dented) RD Logics Turbo II Pipe I used to run and the problem went away and my old motor ran great in my MTX5.

It looks like the problem was being caused by the RD Logics Turbo III Pipe. Strange, but true. The odd thing is I have the same model pipe on my R40 (but a different copy) and it runs fine with the old standard motor. Now I'm going to put the JL Tuned back in the car and purchase one of these pipes:

http://kevcoracing.com/12-picco-pipe...aust-kit-2679/
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Old 08-28-2014, 04:34 PM   #11
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I just tried the motor with a Picco 2679 pipe kit and the pipe made a tremendous difference. The motor now runs perfectly, sounds great, and makes huge power. Problem solved.
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Old 09-04-2014, 08:16 PM   #12
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Was the pipe leaking?

Anyway, good that it's sorted.
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Old 09-08-2014, 10:38 PM   #13
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Was the pipe leaking?
No, not at all. I'm still using the same silicon exhaust seal I was using with the RDL pipe.
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