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Old 07-14-2009, 08:14 PM   #16
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Originally Posted by PTP Racing View Post
Have you tried everything and completely eliminated anything but the engine itself from being the problem? ie. replace fuel line, tank, exhaust couplers, glow plug. Have you thoroughly inspected it for air leaks? Does it have a zip tie on the carb boot?

Also does the engine run or does it stall constantly? You said its constantly rich or lean. Does it do it randomly? Are you tuning it and it goes right from one extreme to the other.

My first V-Spec I bought used. I got it in the winter and was running indoors on a small track and it ran perfectly. Then when I went outdoors to bigger tracks it seemed to be too lean but as soon as I richened the high speed even a hair it would fall right on its face. The problem turned out to be the midrange needle being set wrong. It was flush but about 4 oclock moving it to 2 oclock totally changed the engine. I was then able to lean the top end considerably and the engine powerband was much more linear.

I have to agree with isolating the problem if you haven't done so already. I'd even go as far as find someone you trust with the same vehicle if possible and ask them to hook up your motor to their vehicle and run it. I'd also return the carb settings back to stock and try and run it. I've seen a couple of people have issues with the fuel tanks and try to tune around only to really mess up the carb settings. If there is something wrong in the fuel delivery system, it can really throw you off base as far as trying to find the right tune. Also, check your exhaust pressure line too. Sometimes the pressure nipple on the exhaust pipe can get clogged with oil/dirt and that will affect the level of pressure the tank gets. Good luck and let us know if you were able to figure it out. It takes time, but once you do it once you'll be able to solve it again more easily next time something like this happens.
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Old 07-14-2009, 09:54 PM   #17
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I would DEFINITELY send your motor to Mark at PowerHouse R/C, he is a great guy to deal with and has ALL the answers.
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Old 07-14-2009, 11:38 PM   #18
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I have to aggree as well i ahve seen many motors with abbrassive texture around the crank inline with the induction port of the crank, this is from dirt coming in at some point, and the block flexing. another spot to check is ther front bearing, the best wat to isolate a bad front bearing is to pull the crank and internal's and look threw the back of the motor up to the front, if you see even a small pinhole of light showing threw the seal, it will pull dirt and cause a tuning nightmare, it starts off rich, you lean to compensate then it leans to much, and by that point the motor is saturated with heat and you trying to find the sweet spot but the leak is keeping it from staying consistant.

It's a good idea to have the ziptie on the carb boot, but also a small hole in the boot can cause tuning problems.

Any dried cracking header and pipe seals will also cause inconsistant tuning, so be sure those are in good shape, you can also pull the HSN out and check for any trash in the housing, if it is cloged or something stopping fuel from getting in this will cause prolems and lack of cooling the motor.

Any out of tolerence issues can be caused by overheating=to lean, lack of fuel, or an air leak, and the other is pulling in dirt, I have had several os motors come into the shop withh less than tight head bolts out of the box, it's always a good practice to disassemble the motor and clean it anyway, and it forces you to check back plate screw and headbolts.

If the motor has pulled in dirt, it can eat away at the rod bushing, this will cause tuning problems once the motor has come up in temps, the motor is set to be run at certain head clearence and once wear begins it throws those settings off, I think the cheapest fix to start off with is some new TKO front and rear bearings. there's alot of good info on here, if none of the remedy's help, i would contact the dist, or OS and see what they may be able to offer as far as getting you back to the track and racing. if i can help with anything else feel free to PM me or send me an email. Good luck


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Old 07-14-2009, 11:41 PM   #19
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I have to aggree as well i ahve seen many motors with abbrassive texture around the crank inline with the induction port of the crank, this is from dirt coming in at some point, and the block flexing. another spot to check is ther front bearing, the best wat to isolate a bad front bearing is to pull the crank and internal's and look threw the back of the motor up to the front, if you see even a small pinhole of light showing threw the seal, it will pull dirt and cause a tuning nightmare, it starts off rich, you lean to compensate then it leans to much, and by that point the motor is saturated with heat and you trying to find the sweet spot but the leak is keeping it from staying consistant.

It's a good idea to have the ziptie on the carb boot, but also a small hole in the boot can cause tuning problems.

Any dried cracking header and pipe seals will also cause inconsistant tuning, so be sure those are in good shape, you can also pull the HSN out and check for any trash in the housing, if it is cloged or something stopping fuel from getting in this will cause prolems and lack of cooling the motor.

Any out of tolerence issues can be caused by overheating=to lean, lack of fuel, or an air leak, and the other is pulling in dirt, I have had several os motors come into the shop withh less than tight head bolts out of the box, it's always a good practice to disassemble the motor and clean it anyway, and it forces you to check back plate screw and headbolts.

If the motor has pulled in dirt, it can eat away at the rod bushing, this will cause tuning problems once the motor has come up in temps, the motor is set to be run at certain head clearence and once wear begins it throws those settings off, I think the cheapest fix to start off with is some new TKO front and rear bearings. there's alot of good info on here, if none of the remedy's help, i would contact the dist, or OS and see what they may be able to offer as far as getting you back to the track and racing. if i can help with anything else feel free to PM me or send me an email. Good luck

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Old 07-15-2009, 01:20 AM   #20
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Hold the motor by the crank and rotate it till it comes up on compression and hold there with the head sitting a 3 o'clock position. If it has leakage, it will flop over past TDC and sit at 6 o'clock. This means the compression is too low and will need a new p/s set. On the crank, minor marks are fine, but if its completely scared full 360 and you feel them with your finger nail, either dirt entered the motor or the rear bearing is loose, allowing the crank to rub the case.
fyi

most vspecs will fail the 3oclock test. mine has 2 gallons maybe and mine fails, many others who own a vspec will say the same.

there one i read of that had 20 gallons on it, fails the 3o clock test but runs like a champ, ill try to find the article
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Old 07-15-2009, 05:44 AM   #21
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fyi

most vspecs will fail the 3oclock test. mine has 2 gallons maybe and mine fails, many others who own a vspec will say the same.

there one i read of that had 20 gallons on it, fails the 3o clock test but runs like a champ, ill try to find the article
3 oclock test is not a good test..........most engines once fully broken in fails, but they are running at the peak
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Old 07-15-2009, 05:59 AM   #22
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I'd check the case for a crack. V-spec cases have been known to crack and they can be minor and hard to see if you're not looking for them.
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Old 07-15-2009, 07:45 AM   #23
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Hi guys

thanks all for the valuable input, whether on suggesting places to send that mill to, tests to perform to understand where the failure comes from, or technical explanations.

Let me put things back in context. I am a beginner with IC motors, coming from the electric onroad world. I picked up a V-spec as my first off-raod engine as I knew it has a good reliability/ease of tune reputation. During break-in, it seemed to tick all the boxes and started acting funny at the gallon mark or so. It would then only run properly when leaned in such a manner that it would overheat and then become unstable. Richen it and it went back to stable, but a complete dog. Pressure lines, plugs, clutches, most of the peripheral items were changed in the meantime, but to no avail. The two local experienced racers that accepted to dedicate about 30mn each to me with a flat screwdriver in hand diagnosed it as "impossible to tune, hence washed out". During all this time, it never stalled unexpectedly once, though, hence my hope that there's still some life in it.

I took it off the car - it would pass TDC fairly easily, and show poor compression. I showed it to a local hotshot who "felt" the compression and said something like "well, uh, only the engines that I've ran for a whole season actually feel like this one". I can guarantee, from what I remember, than it would fail the 3 o'clock test.But then again, I read everywhere than OS's actually rarely display crazy compression, they just perform

I pulled it apart (with the little IC knowledge I have, remember). Under visual inspection, as far as I could tell, it didn't show anything funny. The piston doesnt travel any further in the sleeve than TDC height (sorry if wrong lingo), no visible scratch marks on the piston, some light sanding on the crank under the carb but as far as I remember nothing really serious. I didn't know about the front bearing inspection. I reoiled the thing with after oil, put it back in its box until further notice, and bought a plus4, which has now 7L and performs flawlessly now, after some tuning issues early on that were solved by using a different clutch (shoes were shot, live and learn).

I guess that now I know (a little) better, I will pull it apart again, and inspect the front bearing as suggested, as well as whether the crank is marked enough to feel the scratches with the fingernail, and closely look at the case.

All in all, If everything looks fine, I will send it back to one of the addresses suggested above, because even if it isn't worth being fixed (in the end a v-spec can be bought for less than $250), the $30 or so these modders are charging for an inspection and the diagnosis information they will share with me will be a good investment to gather knowledge.

Thanks again,

Paul
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Old 07-15-2009, 07:55 AM   #24
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Before sending it away at least inspect the crankcase for cracks. I've seen more than one V-Spec with a crack through the bottom. If that's fine seal the engine back up using silicone, including the carb throat and give it a run.

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Old 07-15-2009, 08:34 AM   #25
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I'd check the case for a crack. V-spec cases have been known to crack and they can be minor and hard to see if you're not looking for them.
if its the OS with the black carb boot - that issue has been solved in the release of last years model
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Old 07-15-2009, 02:28 PM   #26
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Allright, back from the workshop downstairs where I disassembled and inspected the mill once more. Findings:

- it miserably fails the 3 o'clock test, as expected
- Crank has "marks" under the air intake port, like if it had been lightly wetswanded with 2000grit sandpaper, but no marks than can be "felt" and that feels any different from the surfaces where there are no marks
- No cracks anywhere (that I could see)
- Front bearing is like new. Zero slop, zero leak, zero light passing thru
- Crank pin dimensions: 4.95mm "horizontally" and 4.92mm "vertically".

All in all, time to send this motor to one of the modders mentionned above and learn from it... I also have a brand-spanking new V-spec that I'll send for break-in too I guess...

Will keep you posted about what the findings are once the autopsy results are known

Thanks all for the help,
Paul
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Old 07-15-2009, 02:34 PM   #27
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I see no need to send in your new one for break in..Start your break in while the modder has your other one..Just heat it up to 200 before you start it. Keep the temps up, and follow the Break in Bible stickied on the top of the Off road section
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Old 07-15-2009, 03:04 PM   #28
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Originally Posted by Lonestar View Post
Allright, back from the workshop downstairs where I disassembled and inspected the mill once more. Findings:

- it miserably fails the 3 o'clock test, as expected
- Crank has "marks" under the air intake port, like if it had been lightly wetswanded with 2000grit sandpaper, but no marks than can be "felt" and that feels any different from the surfaces where there are no marks
- No cracks anywhere (that I could see)
- Front bearing is like new. Zero slop, zero leak, zero light passing thru
- Crank pin dimensions: 4.95mm "horizontally" and 4.92mm "vertically".

All in all, time to send this motor to one of the modders mentionned above and learn from it... I also have a brand-spanking new V-spec that I'll send for break-in too I guess...

Will keep you posted about what the findings are once the autopsy results are known

Thanks all for the help,
Paul
What fuel are you using for break-in? Also sounds like the crank is going oval pretty quick for 1.5 gallons. How is the rear bearing also?
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Old 07-16-2009, 02:58 AM   #29
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Hi again

having it broken in by a professional is partly to ensure it is done properly, mostly to save me a huge amount of time. Breaking-in is the most frustrating part of IC RC (whether you do it properly or not is another story). It takes hours (litterally), it's expensive (you burn fuel for nada), it's cumbersome (you never know when you can lean, you have to walk down from the drivers stand all the time, you're always afraid to run dry, you never know if you're on the right temp range, you have to spend a day at the track "for nothing", and so on so forth) - if someone is willing to sell me that service for a reasonable amount ($40 typically) then I certainly am willing to purchase it, and giving them a big hug as a bonus

For info I broke the vspec in with a Fuel most of you have probably never heard about, but remember I don't live in the US. I used Labema 25% at that time, it's considered one of the best western european fuels here

Thanks

Paul
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Old 07-16-2009, 07:41 AM   #30
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Simply use 5% nitro/18% oil fuel for break-in next time. Enough oil so you can lean it enough to keep temps above 200F, but have plenty of lube. I've never had any issues with any O.S. or Nova motor using this type fuel. Also heat the motor prior to starting. I'm sitting on a VSpec that a buddy of mine ran 30% RTR fuel in fir break-in. The pinch disappeared very fast and it loss compression within 1.5 gallon and blew the rod when it was being retuned. It will be rebuilt into a Ninja soon.
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