Rpm range with midly buit 212cc

#1
Hey fellas I just ordered me a tach from go power sports but would like some expert input on what possible rpm I am running with my current build.
Mod list
Predator 212 hemi
62 mph pegged out
12tooth clutch sprocket 40 tooth rear
Stage 1 go power sports kit with .038 main jet
Slipstream billet flywheel v2 34 advance timing
Flame thrower 8.0 high performance coil gapped at .050
Autolite race plug
18# valve springs lash set at 0
Fuel mixture just right not to rich not to lean. In-between
14.1 inch v tread tires
Mobile one racing 4t oil 10w40 with Lucas zinc added
92 non ethanol fuel
Gear ratio 3.33

I heard 7500 rpm is capable but I have no idea what I actually put out when doing 62mph. It gets there no problem as I'm only 120 pounds.

Anyone can chime in or have any ideas what rpm I could be putting out when hitting that speed? when I'm at half throttle exactly I do a smooth 51ish mph. Thanks.
 

SAS289

Well-Known Member
#3
With a 14 inch tire and that gearing the speed calc suggests 5000 RPM for 62 MPH.

Looks like you are doing different things and testing them. Try this test on your next oil change. Remove the 10W40 motor honey and try a good quality synthetic 5W30. In my opinion you don't need 10W40 or the extra zinc.

If you are going to run 5K RPM on the stock rod do frequent oil changes to run as clean of oil as possible. Better yet, get a billet rod and do the same. This would eliminate the concern of running too much RPM on the stock rod.
 
#4
Damn that's lower then I expected lol. And yes billet rod is next. I live in louisiana. Need the heavy weight I ride daily 5 days a week. 5w30 won't last. I change my oil every Friday evening like clock work lol and looks damn good every change. And I thought the motorcycle race oil full synthetic mobil one was pretty good? Got any suggestions
 

SAS289

Well-Known Member
#5
I wouldn't doubt that the mobil one is a good oil, I just question how thick of oil we run in these engines. But you do have a good point about running it hard in the hot temps of the deep south.

If I wanted a lot of zinc I would look at the Valvoline VR1 oils. But I would use them as is without adding more zinc.
 
#7
Have you actually hit a verified 62mph or is that all done on gearing calculators? If yes, how much space did you need?

My drag setup (fully built 212 Predator) with 20+hp and 4.33 gearing is a bit of a dog until after the 1/8 mile where it really picks up steam. It's running a little over 70mph in the 1/4 mile.

3.33 gearing and a 212 with no real power mods done to it. It's got to be slow. I also doubt that it's making enough power with that gearing to actually pull the top speed numbers the calculators so conveniently show. FWIW, my drag setup has a higher top speed when running a 15/65 combo than it did with a 15/59 setup.

One last thing, there's not a chance in hell you're seeing 7500rpm with a stock jam, jetted stock carb and 18lb springs. It's just not going to happen.
 
#8
You did not say what cam you are running or what valve sizes. to run 7500 rpm and still be making enough power to rev to that while powering a mini takes way more than whatever someone is calling a stage one. If you mean I heard I could free rev the engine and hit 7500 rpm with no load on the engine then yes you could probably do it for a few seconds before the rod exits the block. 18 lb springs with a stock cam and small valves could probably do that but would be starting to float around then. Could you give us the details of the Flame thrower 8.0 high performance coil or a picture of it? Not familiar with that coil.
 
#9
Have you actually hit a verified 62mph or is that all done on gearing calculators? If yes, how much space did you need?

My drag setup (fully built 212 Predator) with 20+hp and 4.33 gearing is a bit of a dog until after the 1/8 mile where it really picks up steam. It's running a little over 70mph in the 1/4 mile.

3.33 gearing and a 212 with no real power mods done to it. It's got to be slow. I also doubt that it's making enough power with that gearing to actually pull the top speed numbers the calculators so conveniently show. FWIW, my drag setup has a higher top speed when running a 15/65 combo than it did with a 15/59 setup.

One last thing, there's not a chance in hell you're seeing 7500rpm with a stock jam, jetted stock carb and 18lb springs. It's just not going to happen.
 

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#11
You did not say what cam you are running or what valve sizes. to run 7500 rpm and still be making enough power to rev to that while powering a mini takes way more than whatever someone is calling a stage one. If you mean I heard I could free rev the engine and hit 7500 rpm with no load on the engine then yes you could probably do it for a few seconds before the rod exits the block. 18 lb springs with a stock cam and small valves could probably do that but would be starting to float around then. Could you give us the details of the Flame thrower 8.0 high performance coil or a picture of it? Not familiar with that coil.
 

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#12
Currently adding a 75 tooth rear sprocket lol. Trying not burn my clutch out. With the 3.33 ratio I have with a 40 tooth. And mine is sluggish off the line till I hit bout 40 then she hauls ass to 62 and holds. With the 40tooth rear sprocket
 
#16
Have fun with this one guys. I'm not wasting my time. Lol
Aint nothing to waste. I just wanted to see if anyone knew my max rpm I simply gave my full build info for someone to possibly calculate or relate to my build with their input on rpm. Either way my tach comes in Friday so imma know my rpm them. Just got back from a little ride to the gas station. Pegged out at 62 again with setting lash at 0 over the .003 I had this morning when I went to work and di 58 mph. Have a good one
 
#17
Stock cam power peaks below 5000 rpm. It will rev higher but power will fall off quickly. Your gearing is more for bonnieville than accerlation. Add some teeth to the rear sprocket it will improve acceleration not sure about top speed.
Yea I got a 75 tooth sprocket imma throw on soon.
 
#18
You did not say what cam you are running or what valve sizes. to run 7500 rpm and still be making enough power to rev to that while powering a mini takes way more than whatever someone is calling a stage one. If you mean I heard I could free rev the engine and hit 7500 rpm with no load on the engine then yes you could probably do it for a few seconds before the rod exits the block. 18 lb springs with a stock cam and small valves could probably do that but would be starting to float around then. Could you give us the details of the Flame thrower 8.0 high performance coil or a picture of it? Not familiar with that coil.
Here's better pics of the could. Thing loves the gap at .050. Tried .035, .40, .045 and it. Had serious hesitation issues from mid to full throttle rolling into it. At .050 it's smooth all threw the power band.
 

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