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Old 07-28-2008, 04:19 PM   #1
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Unhappy Chronic Flame outs again... and again...

Hi All,

Trying to get a feeling from everyone as to what is wrong with my O.S. 21VZ-B V-Spec. Running 30% sidewinder and no changes to shims or other.

Issue Description
Recently in previous runs the engine has flamed out two times before this issue became chronic, but after starting up it seem fine the rest of the time. Prior to the two recent times this engine has never flamed out. Last Saturday engine flamed out constantly.

First race, went about 5 minutes then landed a jump and flamed out. Restarted... flamed out after about a lap on flat spot, restarted... flamed out going down the pit ramp.
Troubleshooting: Checked glow plug. Appeared perfect, but swapped out for new plug anyway. Ran on side and checked engine temp, running 210... target I usually go for is 220-230.
Second race, ran for about 3 minutes, flamed out at end of straight, restarted... flamed out at 1/2 a lap, restarted... again flame out at end of pit lane.
Troubleshooting: Re-tuned engine and bench ran engine. Ran for about nine minutes with no issues. Checked engine temp, 215.
Third race, ran for about 1 minutes, flamed out at end of straight, restarted... flamed out at 1/2 a lap, restarted... again flame out at end of pit lane.

Potential Diagnosis
Speaking to others at the track I got two potential issues.

Discounted issues verified by others
Very confident engine is tuned properly
No tank or line leaks
Carburetor and case cover seals appear good
Possible Issue #1: Dirt in a needle valve is causing the flameouts. I keep my car pretty clean, but I do recall seeing some dirt in the high mix value and using a can of air to clear some dirt.
Possible Issue #2: Upon inspection there is oil/fuel coming out around the seal to the exhaust manifold. The seal does appear worn and the fit is loose. Does not have that snug feel. Could this cause flameouts?
Someone Else?: Asking you, is there something I/we have not thought of?
Thanks to all those who post. I'm in the process of learning nitro engines and the people here offer some great feedback for learning.
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Old 07-28-2008, 04:21 PM   #2
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How much fuel have you ran through the motor?
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Old 07-28-2008, 04:34 PM   #3
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Dang Don that sounds frustrating. Even though the seals look good I'd seal the carb, pinch bolt and back plate with some motor sealant. You'll probably have the carb off to run some cleaner through the needles, might as well seal it up when you put it back on. Maybe others know of something else as well to look at.

good luck,
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Old 07-28-2008, 04:38 PM   #4
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possibly the clutch bearings, clutch spring broke.
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Old 07-28-2008, 04:43 PM   #5
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Quote:
Originally Posted by t hatcher View Post
possibly the clutch bearings, clutch spring broke.
+1
If the clutch has a problem, it will reak havok on tunning.... I'm running the same engine and fuel, and I don't remember when my last flame out was. I think it happined once to me last year. Now to be fair I don't count running out of fuel as a flame out.
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Old 07-28-2008, 05:04 PM   #6
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I had the same issue at a pro series race last month. I'd go with possible problem #1. I cleaned all the needle in the carb real well, and replced the seals. now it's fine.
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Old 07-28-2008, 05:15 PM   #7
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It may seem silly, but I had a buggy one time where the flywheel hung down just a microscopic amount too low, and if I even cased it or effed up a jumped and slammed it hard, the car would bottom out, hit the flywheel and stall the motor. Like I said, may seem silly, and probably isnt your problem, but it caused me a lot of headache until I got it figured out
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Old 07-28-2008, 06:37 PM   #8
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Thanks for the replies so far.

I've ran a gallon though the engine thus far.

The flywheel appears to be in the clear, plus it flamed out just going down the pit lane... no bottom outs there.

Thats right, someone did say clutch. I have yet to check it. I just put a new one in two races ago so this weekend was only the second run on it.

Keep the ideas coming... I'll check them all out and let you know what it was. Maybe a week or two but I will post and let everyone know what the problem was.
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Old 07-28-2008, 06:44 PM   #9
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Quote:
Originally Posted by Don Duct View Post
Thanks for the replies so far.

I've ran a gallon though the engine thus far.

The flywheel appears to be in the clear, plus it flamed out just going down the pit lane... no bottom outs there.

Thats right, someone did say clutch. I have yet to check it. I just put a new one in two races ago so this weekend was only the second run on it.

Keep the ideas coming... I'll check them all out and let you know what it was. Maybe a week or two but I will post and let everyone know what the problem was.

My first thought was "con rod." Check the con rod bushing for slop, even though you only have a gallon on it. (Break in is hard on them!) They're only like $25-30 for the V-SPEC, so it isn't a huge cost to replace if that IS the issue.

Also, it sounds like it happens when you have something that jars things... could be a fuel line with a tiny split, probably where it goes on the nipple for the carb or the fuel filter or tank.
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Old 07-28-2008, 07:12 PM   #10
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If it has always ran well for you thus far and assuming there were no major changes in the weather in your area which would be totally screwing up the tune .....................It has to be a broken clutch spring ........or clutch bearings . I have seen bearings lock up and shut a motor off after a little heat in them . For a buck a bearing at least you will know what it is not .
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Old 07-28-2008, 07:28 PM   #11
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have you replaced the front bearing yet? 9 times out of 10 when my motors have started running funny or flamming out for no reason the front bearing has been the problem actually I've been told replacing it after each gallon of runtime on the motor is regular maintanence..
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Old 07-28-2008, 07:28 PM   #12
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Funny how you describe your problems with your VSpec... Mine gave me the same issues and all at pretty bad times. I tried a new tank, fuel line, plug, pipe and exhaust gaskets and still had the same problems.

Found a hairline crack in the engine case above the motor mounting tab on the side. Very visible on the inside of the engine but hard to see on the outside. Problems started at the 1 gallon mark, but I spent the entire next half gallon trying to diagnose the problem.

Problem #2 is that O.S. doesn't seem to want to stand behind the issue. I've heard that they have a new updated engine case now and carb. Mine is the previous (with the longer backplate screws).

Leaves me a little disturbed, now I've got a brand new Vspec that is useless without a new $100 case... But check that, I almost needed a magnifying glass to see mine...
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Old 07-28-2008, 08:28 PM   #13
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Quote:
Originally Posted by cwalters View Post
Funny how you describe your problems with your VSpec... Mine gave me the same issues and all at pretty bad times. I tried a new tank, fuel line, plug, pipe and exhaust gaskets and still had the same problems.

Found a hairline crack in the engine case above the motor mounting tab on the side. Very visible on the inside of the engine but hard to see on the outside. Problems started at the 1 gallon mark, but I spent the entire next half gallon trying to diagnose the problem.

Problem #2 is that O.S. doesn't seem to want to stand behind the issue. I've heard that they have a new updated engine case now and carb. Mine is the previous (with the longer backplate screws).

Leaves me a little disturbed, now I've got a brand new Vspec that is useless without a new $100 case... But check that, I almost needed a magnifying glass to see mine...
+1 this is a common problem with the v spec..
What plug are you running?, What state are you in?, What pipe?, What carb stack? If theres no leaks, it's either your setup/tune
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Old 07-28-2008, 08:44 PM   #14
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Quote:
Originally Posted by t hatcher View Post
possibly the clutch bearings, clutch spring broke.
hey travis, didn't you have this problem, and it turned out to be your pipe?
Try a different pipe, yours may have a problem!
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Old 07-28-2008, 09:05 PM   #15
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Another thing I have heard is carbon buildup on top of the piston and head button chamber can cause early detonation due to the lesser clearance at TDC...
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