3.8 hp

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mini bike man

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i was wondering if you think some simple mods would help my 3.8 hp 97 cc dirt bug engine i was going to port and polish shave the brow and mill the head just a thought until i blow it up its staying on the bike i have a briggs 5 hp so what do you all think thanks:2guns:
 
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mini bike man

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kool what else do you think would help i think im gonna get a different carb this one is junkie chinese
 
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Kenny_McCormic

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Carb should be fine, be aware that the eyeborw is only present on some sidevalve engines, a OHV or OHC engine does not have a place for an eyebrow to exist.
 
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yeah its a flat head i know because it really junkie and chinese and old lol
 
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mini bike man

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yeah tyler i think im capable of telling left from right
 
Jerryburger

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thay are 2.8 hp to be 97 cc it weird because its metric
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Those are impressive little motors, to be sure. My son's DoodleBug had one, (but with the older taller 5.5>1 ratio) and it'd haul my carcass up to top governed speed (about 28mph). The newer DoodleBugs have a shorter ratio of about 6>1. Supposedly the motors are governed to 4000 rpm. I have an extra one that, I'll probably bolt onto my 10 speed. I'd think if you messed with the jetting a bit on that stock carb and opened the muffler up a bit, you might get a some more power from it. If you're thinking on replacing it with the B/S 5hp, you won't be sorry. Just by sheer displacement, it'll out-perform the 2.8hp motor.
 
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oscaryu1

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JerryAssburger said:
Those are impressive little motors, to be sure. My son's DoodleBug had one, (but with the older taller 5.5>1 ratio) and it'd haul my carcass up to top governed speed (about 28mph). The newer DoodleBugs have a shorter ratio of about 6>1. Supposedly the motors are governed to 4000 rpm. I have an extra one that, I'll probably bolt onto my 10 speed. I'd think if you messed with the jetting a bit on that stock carb and opened the muffler up a bit, you might get a some more power from it. If you're thinking on replacing it with the B/S 5hp, you won't be sorry. Just by sheer displacement, it'll out-perform the 2.8hp motor.
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Those Doodlebugs do 28MPH top speed?! There's about two in our neighborhood - both riders less than 100lbs... in elementary (primary school).

All I have to say - If that's 28MPH, then I'm starting to think my electric bike goes 35+!
 
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jr dragster T

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Those stock doodlebugs hit no where near 4000 RPM. It sounds so easy revving like 2300 or a tad more. And they never hit 28 MPH. There safe enough to put a 5 year old on.
 
Jerryburger

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Those Doodlebugs do 28MPH top speed?! There's about two in our neighborhood - both riders less than 100lbs... in elementary (primary school).

All I have to say - If that's 28MPH, then I'm starting to think my electric bike goes 35+!
Those stock doodlebugs hit no where near 4000 RPM. It sounds so easy revving like 2300 or a tad more. And they never hit 28 MPH. There safe enough to put a 5 year old on.
Click to expand...
GPS'd mine at 28mph with me (200 lbs) on it. No sh_t. I was looking at HF's version yesterday in the store, and it says that it's factory limited to 15mph.... maybe that's the one(s) you're aware of? Why wouldn't an engine making almost 3hp carry a minibike to almost 30mph?

...my cheapie handheld GPS hasn't let me down yet, accuracy-wise.
 
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mini bike man

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well to day i milled the head a little bit more power i think im gonna milled it once more to a total of 30 thousands taken off that should do thanks all
 
Russ2251

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Uh ...ok.
Most of my head gaskets measure between .020 to .040".
A quick lapping (40 minutes work) and head and deck are perfectly mated. If power curve is adversely affected, replace the gasket. Reversible.
Since my sealing problems have been solved...every block/head-2/4 cycle gets the treatment sans OHC or OHV. Biggest improvement evident with 2 cycle.
Modeling clay comes in handy to make sure piston crown doesn't slam into head (or anything else).
 
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