My sons intro to horsepower

ThunderKart79

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A few months back my wife and I bought a Coleman CT200U for our children. When we got the bike it was barely used and was a great introduction to mini bikes for our children. Me being the kind of person who believes there is never enough power well I have been building my son a Tillotson hemi. I started with a 70 mm Tillotson racing block which I bought ceramic bearings than polished the crankshaft and installed a stock length ARC rod with a predictor .570 compression height flat top which brings the piston flush with the top of the block. Then I got a NR mongoose camshaft .272 lift .246 duration then I put true Honda gx160 lifters with a Tillotson hemi head with a 3way valve job polished valves 27 mm intake 25mm exhaust. Ported and polished Bowles and runners. .050 milled off of head and they are 5 mm valve stems. Then the carburetor is a 26mm flat slide nibbi. A header from NR which I took a Footpeg from a bicycle that I bored out a little and welded on the end off header. Believe it or not that made the engine quite down more than an RLV muffler that I have kicking around. Mainly I wanted some kind of muffler to help with tourqe. Also it has a PVL flywheel and a Tillotson coil which is much beefier than the Coleman one with Tailor 8mm wire and NGK boot. Then it has an Inferno fury bully conversion 10 tooth clutch and sprocket 420 chain. I also had to buy a valve notching kit from NR to cut valve reliefs in the piston. According to the compression calculator I used with the stock .045 head gasket it has 10.24:1 and with the .010 head gasket that I will be running it has 11.8:1 compression ratio and I am running 101 octane gas. My wife is scared to death but when I.was 12 I had a brand new KX 80.
 

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madprofessor

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How thick is that piston face? Those are some deep valve reliefs in a flattop, bet that's why it's getting 101 octane, premature detonation might hole it out through the thin parts.
 

Hellion

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Your 101 octane gas is likely overkill. The octane level in gasoline is not a measure of the fuel's intrinsic power but of the fuel's ability to resist detonation; or fuel prematurely combusting before the spark plug ignites it.

If you can run regular pump 87, 89, 91 octane without knocking/pinging/detonation, then do so.
 

Denny

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In my opinion on an air cooled engine the 101 is not needed yet but it is nice to have. Air cooling is not as efficient or as even as a water cooled system. Once he hits that 11.8 he will though.
 

ThunderKart79

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Ya I basically wanted to run the 101 to break in the engine . I put playdo on the piston and I have .020 clearance between the valves and piston before I cut the reliefs the valves hit the piston. Believe it or not the top of the piston is thick. After I change the break in oil I am going to try 93 octane but I plan on researching what octane level is advised for 11.8:1 compression
 

ThunderKart79

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From what I have read anything with 11.1 to 12.1 needs 95 octane 101 is the closest I can buy to 95 93 might be ok but I can afford 101 for my son to rip around the neighborhood
 

karl

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I have used the royal purple booster from the typical suspects,
but try to avoid it.

During the warmer seasons the station in town sells CAM2 leaded 110 octane at the pump
for $10.99 a gallon. I just mix some of that with 93 octane pump fuel.

So one part CAM2 to four parts premium should put you in the 96 octane zone,
and last quite a while.
 

ThunderKart79

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A store near my house sells 89 real gas they claim it is ethanol free so if I mix that 50/50 with 101 that figures to 95 I also have a fuel additive from VP that raises the octane by 9 honestly it will be cheaper to mix the gas with 89 and 101 than it will be to buy the VP and I run slide type carburetors on all of our engines that will be getting this fuel ethanol tears up stock type carburetors I am not sure if the 101 has ethanol or not
 

ThunderKart79

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Ethanol eats any rubber or plastic part it makes contact with and I have had much better luck with slide carbs than stock style carbs which I have forgotten what a stock type carb is called but anyhow I run a flat slide on the Tillotson and a D slide on my big block 452 and once I have a chance to fab a intake so I can try out the 44 BN carburetor I have for it
 

Hellion

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I didn't really mean it's likely overkill, it IS overkill. That estimated compression ratio isn't really in the realm of high compression. It's getting there though.

You're just wasting money and you could probably get by on 89 or 91, if not 87. Try it and see if you get preignition.

What does air cooling have to do with 101 octane gasoline, Denny? I don't follow you. The cooling of these engines is via the cooling fins and the lubrication oil, actually. However, if he were running alcohol in his engine then it would aid cooling (at least on the intake side of the equation) as it burns cooler, not to mention the cooling effect of vaporization in the inlet track. Maybe that's what you were thinking of? Alcohol (ethanol, methanol) has less heat energy than gasoline so you need to burn more of it, but I digress.
 

ThunderKart79

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Every site I looked at clearly stated that 11.1 to 12.1 required 95 octane now ya if I had a high compression engine I would run fuel that came in 5 gallon cans however I have $1250 just in parts I have been drag racing for 30 years now I have got to be honest you are the first person I have ever heard recommend running 89 octane in an engine that is pushing close to 12.1:1 compression I had to put bigger main jets in the 26 mm carburetor I understand that this is about half of what it could be but after I change the break in oil I will mix it with 89 non ethanol and instead he’ll you know what I am sorry I mentioned what I was burning for fuel I was trying to share my latest build I promise you will never save enough money running cheap fuel to pay for the engine this thread was created to discuss really I am sorry I run pump 101 in my engine
 

ThunderKart79

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FYI something you learn from experience in the real world that is if you believe what your temp gage tells you the higher the octane the cooler your engine runs after all higher octane is maid and is needed so the fuel burns when it is supposed to it is not fun when you think you are on your fastest pass ever and at about 500ft you here that dreaded noise if your engine gets to hot it predetinates this stage 1 kit for my son once he can handle this engine our stage 2 will be bigger valves more stroke probably 4 more mm and 2 mm larger bore I love GOD I love my family and I love making massive tourqe and stupid horsepower I am getting my son ready to enjoy drag kart that is going to be powered by a 1200 cc Yamaha triple two stroke that I am going to have pro charger build me a blower for I hate buying horse power the head I put on this mini bike is the first head I bought that was already modified my beast friend is a machinist and I am crazy and more times then not I learn the hard way it is worth all the work and money when you take the trophy from all the people that are used to their money winning them races
 

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My understanding is with air cooled the better the chance of hot spots in the head. Especially near the exhaust valve. Just what different engineers have told me.
 

Hellion

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Ok, run 95 octane then. Just that extra octane in the 101 is going out your tailpipe. That's my main argument here; super high octane fuel
isn't rocket fuel and can't get you to Mach 1 or to the moon.

If it's that evil ethanol that you fear (and the 101 you're using is 0 ethanol = good) you can actually run E10, E15 safely enough but good heavens, don't leave it in the engine or the carburetor--run it all the way out and flush the system. That's what the alky racers do, post race; they flush it out with gasoline, kerosene or something at the end of the day.

I can tell you're upset because you didn't use any punctuation. No punctuation means I am less and less inclined to read you. Sorry.😦
But I got the gist of it.

My understanding is with air cooled the better the chance of hot spots in the head. Especially near the exhaust valve. Just what different engineers have told me.

That's not what you were saying. There is no doubt these air cooled engines (forced air, luckily👍) run way hotter than water cooled ones and it's hotter around the exhaust valve and ex. manifold, but high octane fuel isn't going to cool it down just because it's high octane.

The higher the octane, the harder it is for the fuel to ignite. The only time you will see a cylinder temperature drop is with a richer mixture or with a better than stock cooling system. In general terms, the more fuel you put in it, the cooler it runs, not the more octane you put in it.
 

Denny

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Nobody said anything about higher octane cooling the engine. That is just absurd. Hot spots cause preignition. Preignition causes detonation. Detonation causes pinging and piston erosion, broken lands and rings.
Octane number is the resistance to ignition of gasoline. Cetane is the ease at which diesel fuel will ignite. Anything else you need to learn about Hellion?
All I said was air cooled engines tend to run hotter.
 

madprofessor

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Speaking of forced air cooling (Predator 212), anybody ever add some more sheetmetal to the sheetmetal around the engine that guides the fan-forced air for cooling?
Have looked at my current one to possibly do that with some very thin metal, but so far haven't seen a really good way to do it.
BTW: I'm fortunate enough to have 3-4 brand new 5-gallon gas cans, but would certainly buy myself one if not. Found our local Wawa stations have a separate hose for ethanol-free gas. I'm going to get 2-3 gallons and some octane booster, and use my Sta-Bil stabilizer.
A dedicated and clearly marked can with a date card attached is one of the best investments ($6 ?) you can make. Have exactly the fuel you want, know how old it is, that it has stabilizer and when, estimated octane rating, etc., etc.............
 

Bansil

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Speaking of forced air cooling (Predator 212), anybody ever add some more sheetmetal to the sheetmetal around the engine that guides the fan-forced air for cooling?
Have looked at my current one to possibly do that with some very thin metal, but so far haven't seen a really good way to do it.
BTW: I'm fortunate enough to have 3-4 brand new 5-gallon gas cans, but would certainly buy myself one if not. Found our local Wawa stations have a separate hose for ethanol-free gas. I'm going to get 2-3 gallons and some octane booster, and use my Sta-Bil stabilizer.
A dedicated and clearly marked can with a date card attached is one of the best investments ($6 ?) you can make. Have exactly the fuel you want, know how old it is, that it has stabilizer and when, estimated octane rating, etc., etc.............
Mammoth did some stuff on his build that could be done on 212 I guess
page 2
GX390 build

Page 2
 

neener

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Ya I basically wanted to run the 101 to break in the engine.
Dafuq for?
Obviously after that idea you shouldn't be attempting to build anything.
Unless the engine needs that high octane(which you really went fubar and it shouldn't)"breaking it in" with 101 isn't going to add any benefit and may just cause you more problems.


Raname this thread "when to confused waste their time"
 

neener

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A store near my house sells 89 real gas they claim it is ethanol free so if I mix that 50/50 with 101 that figures to 95 I also have a fuel additive from VP that raises the octane by 9 honestly it will be cheaper to mix the gas with 89 and 101 than it will be to buy the VP and I run slide type carburetors on all of our engines that will be getting this fuel ethanol tears up stock type carburetors I am not sure if the 101 has ethanol or not
No it doesnt work that way just mixing the two together smh
 
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