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Old 11-17-2010, 12:04 PM
crazyman crazyman is offline
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Hi. This is going to take me awhile as I am self employed and money is like non-existant, but here goes. I have fab skills and an imagination. I have a duraforce lawn boy (yes, Russ's twin kart is what led me here). I have ported the exhaust and boost port, ordered an HL227, (thanks Russ!) and am contemplating cutting out the bridge in the reed cage and having the inside milled to run one wide reed. The coil was bad, so I baked it in the oven (again, thanks Russ.) I have a Hoosier 32x14.5x15 drag slick that will be my rear tire, and will use a wheel barrel tire up front. Of course it will be lawn boy green! It will be geared to go about 35mph, so the sprocket in the drawing I know is way too small.

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Old 11-17-2010, 01:05 PM
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I wonder if a wide, square profile tire in the back would keep you from leaning while turning.
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Old 11-17-2010, 03:09 PM
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If I run the pressure low enough, it should compress the sidewall on the "turn in" side. It should also lend itself to a soft ride.
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Old 11-17-2010, 08:19 PM
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How do you plan on powering a tire of that size? What kind of ratios will you use?
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Old 11-17-2010, 08:41 PM
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Yeah, I second that... Is it even possible for that engine to power that tire to that top speed?

And what's this about baking a coil?
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Old 11-17-2010, 08:53 PM
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well the dura force is 6.5hp @4000rpm stock (according to google), with a 32" tire, and some mods to the engine he is prob looking at something like a 10t clutch 20t js sprocket, 10t js sprocket with 60t rear, or a 12:1. yeah, kinda bored.
that should get him to 30+ with decent acceleration depending on the mods and weight.
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Old 11-17-2010, 09:45 PM
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Quote:
well the dura force is 6.5hp @4000rpm stock
With small mods I get about 8.5hp (x2) at well over 6k rpm (stock flywheels). Translates to low 50's mph.
17 tooth clutch and 70 tooth driven with 11" diameter tires.
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Old 11-17-2010, 09:53 PM
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Quote:
Originally Posted by Russ2251 View Post
With small mods I get about 8.5hp (x2) at well over 6k rpm (stock flywheels). Translates to low 50's mph.
17 tooth clutch and 70 tooth driven with 11" diameter tires.
sounds nice, what about running a 2 speed for the bike with the drag slick?
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Old 11-18-2010, 07:58 PM
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in that case you should have no problems hitting 30.
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Old 11-20-2010, 07:49 PM
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Quote:
I have ported the exhaust and boost port
Why?
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Old 11-21-2010, 03:53 PM
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Quote:
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Why?
The same reason you put two on your cart..

Really just to see how far one of these engines can be tinkered with.
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Old 11-21-2010, 07:17 PM
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Quote:
The same reason you put two on your cart..
No irreversible modifications were made other than keyway and blade taper removal.

Please post the before and after numbers. I am very interested in seeing them.
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Old 11-22-2010, 01:12 AM
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7-8 Degrees or so more exhaust port timing isn't hugely radical, nor is 2-3 degrees more boost port duration. I followed A. Graham Bell's two stroke tuning book almost to a T.

I'll probably run two pulleys on each the jackshaft and the crankshaft. One for low speed yard fun, one for strip/top speed fun with a spring loaded tensioner on the slack side of the belt. Figure the sizes so it uses the same belt for both speeds. Just a simple swap over. By doing this, I can use a smaller diameter bore clutch (cheaper, as crank is 1") on the jackshaft. Low speed would rev the engine to go, race would stall the clutch and use the entire rpm band for acceleration. Since the clutch would be mounted on the jackshaft after the pulley setup, the clutch engagement rpm would be goverened by the belt setting.

That setup would also make starting and warm up easier, as you could pop the belt off until it was warm.
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Old 11-24-2010, 11:06 PM
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How's that for irreversible? It'll never ever touch a mower ever again either way. Opened up, if you tilt your head to the left, it kind of looks like an african tribal mask..... Ouga shaka, ouga shaka. LOL

I was going to use a plunge bit and a router to mill off the ridge to make a new reed seal, and found that the bit was a half inch or so too short. So I have to order a 1/4" x 2 1/2" end mill bit. $4.50 shipped off eBay..



The wait goes on... And thank you r97 for the preliminary ratio calculations..

Happy Thanksgiving!!!!

(Russ, the three thanks in this post were from my first post, just spread out so you can have the credit.)
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Old 11-24-2010, 11:50 PM
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u should use a truck inner tube sum how
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Old 11-25-2010, 12:16 AM
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I have the inner tube that goes with the slick..
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Old 11-25-2010, 09:01 AM
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cool, have you started making the frame?
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Old 11-25-2010, 09:39 AM
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Its Kinda Like A Tractor . . ? Big Massive Wheel At The Back And Tiny Wheel At The Front And Will Struggle To Reach 35mph !!
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Old 11-25-2010, 11:55 AM
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They build drag racers the same way. It's all in the gearing and the total power available.
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Old 11-25-2010, 06:54 PM
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Am curious as to why you went with a single reed petal configuration when it is well known that high performance engine builders opt for multiple petals.
I have restored many Clinton 2 cycle engines which were equipped with 2 large reeds (stock) as are all Lawn-Boys.
I recently purchased a high performance Clinton reed cage (Palmini Engineering) that consists of 6 small petals.
Difference in power throughout power curve is quite noticeable...especially on the low end where it is needed most.
There is a Clinton chainsaw conversion that is up for auction (Ebay) at this very moment that features the very same high performance Palmini reed cage.
I might also add that with multiple petals, high speed flutter is virtually eliminated.
More reeds = less work/each total. Could be compared to multi-valve 4 cycle engines.
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