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Old 06-05-2011, 04:04 PM   #1
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Default Time to Trash This OS .12TR?

I have a OS .12 TR turbo head that I got second hand. It has good compression and the piston looks good. I have only taken the head off so far and I this thing is driving me nuts.

First, it's a real pain in the #%& to tune. It is super touchy and I have to adjust and adjust and adjust until I finally get it running well. Then it will run great! Temps are good, great response, the thing screams and all is well!!!

Let it cool, new tank, start it up, won't run worth crap. Dies on acceleration. Or for no reason while I take it off the box and set it on the ground. Over and over.

Eventually I adjust the HS just a TINY bit and it will run great again. Or maybe not. I never know with this thing. It idles fine, I don't suspect an air leak, but who knows. It is so inconsistent (and they don't even make them anymore) I am thinking just chuck it and get something else, non-pull-start that's inexpensive but more consistent than this thing. Having an engine run like this takes the fun right out of it.

Any ideas? It it worth cleaning the carb or anything else before this OS .12tr meets it's maker in my vise?

Or any ideas for a reasonable replacement, non pull-start with pilot shaft to drop into a NTC3? Thanks!
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Old 06-05-2011, 07:57 PM   #2
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Well I decided to take the thing completely apart and clean and inspect everything. It looks great inside, like new! I also took the carb apart and cleaned it and blew it out with compressed air - if there was anything in there it is gone now for sure! The seals on the needles looked good as did the carb neck seal.

I might be crazy but it seemed to me one of the head screws was loose and came out way too easy. In fact all of them were not as tight as every other engine I have taken apart. Also, the fuel intake/hsn housing was loose enough that I was able to remove it by hand.

Just for fun I sealed the whole thing up with Lucky 7 sealer when I was done. Too late to try it out but hopefully there will be some improvement, or this thing gets the vice treatment! LOL
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Old 06-06-2011, 02:02 AM   #3
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That loose bolt could have been the reason it was giving you a headache - i remember trying to tune an engine but could not get it good, till I later realised some oil was bubbling out the side of the head. Checked all the bolts and made sure it was seated correctly (it was an oooooold engine) and then it was running fine till the very end. And also the carb was full of crap, so cleaning that out also helped a lot.
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Old 06-06-2011, 05:07 AM   #4
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Originally Posted by DJ_Shakespear View Post
That loose bolt could have been the reason it was giving you a headache - i remember trying to tune an engine but could not get it good, till I later realised some oil was bubbling out the side of the head. Checked all the bolts and made sure it was seated correctly (it was an oooooold engine) and then it was running fine till the very end. And also the carb was full of crap, so cleaning that out also helped a lot.
Thanks for that, frankly if it doesn't work well now I am out of ideas. I will give it a test run and post what happens. I'm also thinking maybe that one loose bolt might have screwed with the compression as soon as it got warm. If it was the carb it seems to me that it wouldn't run fine and then bad, but I guess that's possible also if it wasn't allowing a consistent flow of fuel due to blockage. It sat unused for a very long time so that could be a culprit too I guess.
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Old 06-20-2011, 05:14 AM   #5
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Default Updates please

Any updates? Saw a thread you started that you managed to get the tune right on your engine.. A need a little help because I may have been experiencing the same issue on an O.S. 12TZ 5 port with an RP6 or P6 plug, with NO carb reducer/restrictor. Tried tuning with Cosmo 20% and Tornado 25% with both shims on. No air leaks since I've sealed the carb and the crank.
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Old 06-20-2011, 09:29 AM   #6
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Any updates? Saw a thread you started that you managed to get the tune right on your engine.. A need a little help because I may have been experiencing the same issue on an O.S. 12TZ 5 port with an RP6 or P6 plug, with NO carb reducer/restrictor. Tried tuning with Cosmo 20% and Tornado 25% with both shims on. No air leaks since I've sealed the carb and the crank.
Yes I am indeed finally getting good results with this engine. As you know I took everything apart, cleaned and sealed it. That helped, but it was still giving me some problems and flaming out. As I continued to inspect everything I found the K Factory low CG tank was bubbling/foaming fuel and it turned out there was not enough cushion for the tank vibration. I added extra o-rings and loosened up the mounting screws and that also helped a lot.

As you may have seen in my other posts I got the thing screaming - it was running awesome, but hot. Turns out the cooling head needed to be rotated 90 degrees for better airflow, I never even noticed that the cooling fins flowed through in only one direction.

I am only running the one stock shim and 20% Byrons and that seems to work very well. I also just ordered some cooler plugs (RP7) and I will see how they do - they are supposed to be good for all temps.

If you are having similar problems I would check the tank for leaks and also make sure it is not bubbling like mine was. The inconsistent fuel flow was really screwing with my ability to get it tuned! It is still very sensitive to tune but much more consistent now. Now it is a matter of very tiny adjustments from one day to the next to adjust for temperature and humidity variations.

What specific problems are you having?
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Old 06-20-2011, 07:03 PM   #7
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Default tank

No leaks on the fuel tank.. checked it under water and blew unto the pressure line.. I also loosened the mounting screws because of the 1st gen v-one rrr tank issues with the upper plate.

Basically it is very inconsistent to tune.. I had lost the factory defaults for the needles and very well out of the ballpark for the settings. So I started flush on the medium speed and low speed needles and started to tune the high speed needle. But when I get I thought that I got a good tune on the HSN (good response and good smoke) after a while it suddenly richens itself. Maybe because it was loading fuel at idle due to very rich LSN? hmmmm.. Will try again to tune..

Thanks!
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Old 06-20-2011, 07:18 PM   #8
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No leaks on the fuel tank.. checked it under water and blew unto the pressure line.. I also loosened the mounting screws because of the 1st gen v-one rrr tank issues with the upper plate.

Basically it is very inconsistent to tune.. I had lost the factory defaults for the needles and very well out of the ballpark for the settings. So I started flush on the medium speed and low speed needles and started to tune the high speed needle. But when I get I thought that I got a good tune on the HSN (good response and good smoke) after a while it suddenly richens itself. Maybe because it was loading fuel at idle due to very rich LSN? hmmmm.. Will try again to tune..

Thanks!
Well for what it's worth even when I get mine tuned great, and my LSN set so that it dies in 3-4 seconds with the pinch test and has good throttle response, it still will start to load up in about 10 seconds if I don't keep blipping the throttle. But that is just sitting idling. And once it is running it never idles for more than a few seconds before I am back on the throttle.

It sounds like you have a very touchy one to tune as well. The only other thing I would suggest, and you probably already know this, is to make VERY small changes and keep trying it out. Like no more than one hour change at a time. That is what it took for me to finally get this one. Anyway good luck and let us know how it goes!
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