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Old 03-30-2004, 09:35 PM
  #1  
quadzila99
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Default Tuning question

I have a smartech magic wheel(I know I have heard please stop laughing it was free) I have about 10 or 11 tanks through it. It should be broke in. I m having problems fine tuning the mixture. Its set were it runs great top end but overheats, about 240 to 250. If I richen it up to run cooler its very blubbery and horrible throttle response. I changed the glow plug cuz it was still the original, thinking it would make a difference, it didnt. I m using Trinity Monster fuel 20% nitro 18% oil. I m thinking its just choking on oil. Could it be too much nitro? I bought some more fuel that is 20% nitro but 12% oil. I havent run it yet. I just wanted to get some opinions first. Also it has never shifted. Everyone I have talked to said it will shift when you start to lean it out and get more power or rpm. I ve leaned it out so much it cuts out before and still has never shifted. Any opinions or input would be helpful. Thanks
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Old 03-30-2004, 09:40 PM
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Default RE: Tuning question

250 isn't overheating. 280 on up is overheating.

Where did you find trinity MHP 20% with 18% oil in it? All I've seen is 12%oil. The extra oil might be causing your blubbering. You could try a hotter plug. Like a McCoy mc-59 or an OS A3.
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Old 03-30-2004, 11:54 PM
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Default RE: Tuning question

I am running pretty much the same fuel you are and it could be that the high oil content in your engine is bogging it down. When you lean it out is it up around 250? and does it get bogged down at idle or when you are running it? If it is only at idle your low end needle (if equiped) needs to be leaned out. If its not equiped you could open up your idle screw a tiny bit. Be careful to monitor temps at idle so the engine doesn't overheat. It is probably not shifting because of a slightly off tune engine and a mis adjusted shifter. There should be some sort of adjustment on the transmission to change what RPM it shifts at. Good luck with it.
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Old 03-31-2004, 12:22 AM
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Default RE: Tuning question

My vote is for the high oil content. Trinity Monster Horsepower with 18% oil? That has to be a break-in fuel, in which case it is too much oil for the engine to get any performance out of. That's the reason it won't reach high enough rpm to hit 2nd gear, and when you lean it any more it becomes air lean which increases the temps.
I'd say try the new (lower oil) fuel and try to retune it. You should be able to lean it out enough to hit 2nd while still keeping a good temp.

EDIT: Don't mess with the shift point in the tranny until you try the new fuel and retune.
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Old 03-31-2004, 10:07 AM
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mecky33
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Default RE: Tuning question

jefx, its not a break in fuel. It is just a standard fuel made by wildcat and sold as Trinity. Wildcat eliminator is the same fuel, and that is what I run. In my MT2 with the 18% and temps around 240-250 I can run up and wind out second. Its all a matter of getting the tune right for the fuel. The only ill effect that I have seen from the 18% oil is a tendency to flood easily when restarting it.
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Old 03-31-2004, 10:11 AM
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Default RE: Tuning question

250 degrees F is not overheating. You are fine running it at this temperature. I run 18-20% oil in all of my engines (car and airplane) with NO problems. Its a myth that engines run poorly at higher oil levels. They run just fine with a little fine tuning.
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Old 03-31-2004, 11:07 AM
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Default RE: Tuning question

Thanks for the input guys. I thought it was too hot. When it gets to those temps it generally will stall if I let it get anywere near idle and its very hard to restart until it cools down. Its not due to low idle it actually idles too fast right now. Just trying to keep it running to set top end first. The fuel is a breakin blend. I ll try the new stuff today.
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Old 03-31-2004, 11:31 AM
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Default RE: Tuning question

Trinity Monster Horse Power is 12% oil. They have a TMHP fuel with a high oil content, but it's for break-in, it says so on their site.

While oil is needed for a 2-stroke engine to provide lubrication, too much oil is indeed bad for a 2-stroke. The proper amount is just enough to provide adequate lubrication, no more, no less. TMHP comes in a 12% mixture, I would stick with that. Running 18% oil is for when you're breaking-in an engine and the fuel mixture is intended to be rich anyhow. I'll explain why.

2-stroke fuel (when combusted) is a mixture of 3 things; (combustable)fuel, oil, and air. Since air is always delivered at a full amount controled by the carb slide, we'll say that air is always delivered at 100%. We'll say that half of the fuel mixture is air and the other half is combustable fuel/oil (it's not half and half, I'm just using that to make it easy to understand). Oil is not combustable, it's there for lubrication purposes only. It will slowly sizzle away only because of the intense heat made in the engine, but does nothing for performance. By increasing the amount of oil in the fuel mixture, you are decreasing the amount of combustable fuel to air ratio, causing an air lean condition. If you are running 12% oil, you have 88% combustable fuel to mix with the air; or 6% oil, 44% combustable fuel, and 50% air when combusted. If you are running 18% oil, then you have 82% combustable fuel to mix with air; or 9% oil, 41% combustable fuel, and 50% air when combusted.
This results in an air lean condition which is not a problem when running rich for break-in, but when you try to lean it out for power, you have to overlean to get rid of the excess oil which is clogging the engine up. In order to reach a point of good power delivery with a high oil content fuel, you are decreasing the amount of combustable fuel in the fuel to air ratio, and the excess air causes higher temps.
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Old 03-31-2004, 11:37 AM
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Default RE: Tuning question

Homebrewer, if it's a myth then why is he experiencing problems that only help to prove my point?
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Old 03-31-2004, 12:37 PM
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Default RE: Tuning question

If 18% oil is a break in only mixture, why does wildcat market it as their standard Nitro fuel?
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Old 03-31-2004, 12:47 PM
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Default RE: Tuning question

It would depend on the type of oil and additives. Maybe they use a type of oil that is more easily burned and therefore doesn't effect the engine as much.
As oil technology has increased, there have been better oils introduced into the 2-stroke world, allowing you to use less oil with the same amount of protection. This is especially noticeable in the dirtbike/4-wheeler/snowmobile world, which I own all of. My statement above is of my own findings from dealing with and maintaining larger 2-strokes engines, and would still apply to the smaller (R/C) engines.

The Trinity 18% is made and recommended for break-in procedures, but can also be used for the backyard basher who doesn't care as much about performance, and who would like a higher oil content fuel.
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Old 04-01-2004, 08:54 PM
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Default RE: Tuning question

Well I tried the new fuel yesterday. It does seem to run alot better. Until I had my first break. After starting it the starter handle smacked the nipple on top the fuel tank that goes to the muffler. Snapped it clean off. Oh well. It did seem a little stronger. Had to totaly re tune though. It did gain some rpm but still never shifted. I wish they made tachs for these things, or maybe they do just dont know about them. I was reading another thread from another smartech owner he says his does wheelies on demand. Mine has never come close to a wheelie (EVER). Unless in a turn, of course it rolled after that. Well have to order a tank now.

Kurt
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Old 04-02-2004, 12:59 AM
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Default RE: Tuning question

I've never seen a tach for them. How's it running up top? Is it clearing out good? Have you tried leaning the HSN (High Speed Needle)? Usually 2-speeds are set pretty good at the factory, and you should rule out any possibility of a bad mixture before messing with the shift point. Once you mess with it, it's hard to put it back to factory spec. What are your temps like now?
You should always let the engine warm up before trying to tune it. You want to start rich on the HSN and work your way leaner 1/16 to 1/8 turn at a time, making a couple high speed runs between each adjustment to let the engine catch up to the new setting. If you reach a point where the engine cuts out up top, richen the HSN 1/4 turn. If it still doesn't shift after the HSN is in good tune, then and only then you may need to adjust the shift point. The owner's manual should (hopefully) tell you how to do it.
As far as wheelies, you probably just need to get the LSN adjusted better. But start with the HSN and get it set right before you tune the LSN. One step at a time.
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Old 04-02-2004, 09:37 PM
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Default RE: Tuning question

So, could the fact that im running 18% oil, and 15% nitro fuel in my tower hobbies nitro st-15 be why it has no low end? It seemed to have good top end, but it took it a minute to get there. Also after i shut it off, and fill up with fuel, it will just barely take off without dying, it seems so rich, and i have to use about 1/4 of the tank to get it warmed up, and running right again. I have never tried nitro with lower oil content, so maybe its the problem? Quadzila99- What kind of low end performance gain did you see? Does it run a lot better? Thanks

Eric
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Old 04-03-2004, 12:35 AM
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Default RE: Tuning question

Cummins, I would say to go up to 20 percent and keep the 18% oil. I have not seen any performance decreases in my truck with 18% oil. In fact, I am pushing more power than Cen says I should have. I have been breaking drive train components that they never see replaced because of it.
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Old 04-03-2004, 01:00 AM
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Default RE: Tuning question

It was running great top end and low, once it warmed up. Kinda sluggish and does die sometimes when its cold. I was in the middle of tuning the topend leanning it out when I broke the fuel tank. So until I get that fixed wont know how it will perform. The temps were right around 240.
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