Tanaka 40cc PF-4000... now what?

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motorizemyride

New Member
Jan 14, 2013
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Green Bay, WI
I managed to snag a Tanaka 40cc PF-4000 for $100 on ebay... I'm pretty pumped since these normally run $400 and to my understanding are one of the better engines to throw into a motorized bicycle. It has a 78mm centrifugal clutch with good pad life left. Also comes with a Walbro 167 high performance tunable carb, billet velocity stack, and chrome high performance air filter.

So what next? I'm pretty much set on a chain drive. I'd like to do a frame mount if the bike I get will accommodate it (and the engine isn't prohibitively wide) but odds are I'm going to get something with ridiculous struts and will need to rear mount. This is the very first bike I'm going to motorize, and while I don't need a step-by-step assembly guide I'd certainly like some pointers and advice.

Is anyone familiar with these engines? I'm curious if I will need a jackshaft with this setup. Am I going to need to weld a sprocket onto this thing? Since this isn't a kit, how do I do the nifty handlebar throttle/clutch/killswitch controls? Alternatively, are there kits that come with everything EXCEPT the engine?
 
scotto-

scotto-

Custom 4-Stroke Bike Builder
Jun 3, 2010
6,505
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38
Ridin' inSane Diego, CA.
I've run Tanaka 40's and 47R's on stand-up BladeZ scooters and they are very well made Japanese 2-stroke engines. Adapting this engine to an in-frame build is not easy unless you are very mechanical and have good fabrication skills.

You are better off going with the Staton or Golden Eagle type rack mount set-up for ease of a reliable installation. Just my opinion of course.
 
d_gizzle

d_gizzle

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May 29, 2012
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I bought this gearbox to use with a tanaka 40cc engine. I haven't even took it apart yet but the mount is the real reason I bought this one. It would be great for a rack mount. And if your slick,you could make it shift gears too.
 
Otero

Otero

Member
Feb 1, 2010
782
17
18
wa
I don't know about that video. The tank arrangement"s
a real... 'jury' rig. You cant pedal it if you need to, and,
since you can't pedal off, your clutch just got a half life
in urban traffic. I'm sure it goes like a bat, but with your
feet on the rear axle pegs, any sudden stop's gonna
look like a handstand on the bars. I give a big thumbs
down.
I totally stand with MBlack & Scotto on this'n. Go
with the Staton or GEBE kit for a first build. They're
not totally bomb-proof, but they're the closest thing
to it if your starting out. Tanaka's a great engine, but
I'da bin suspicious of one for $100.
 
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M

motorizemyride

New Member
Jan 14, 2013
12
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0
Green Bay, WI
Otero said:
...
I totally stand with MBlack & Scotto on this'n. Go
with the Staton or GEBE kit for a first build. They're
not totally bomb-proof, but they're the closest thing
to it if your starting out. Tanaka's a great engine, but
I'da bin suspicious of one for $100.
Click to expand...
I bench tested the engine and it's running great, even under load. Tore down and rebuilt it to inspect for any unusual wear/damage and aside from having a bit of normal usage filth it's in tip top condition. Truly an amazing bargain.

I HAVE decided to go with a chinagirl kit though. For a first build I figured that ease is indeed the way to go. In the meantime the Tanaka is going to sit on the workbench and wait for either my experience to reach an appropriate level or a motivated buyer.
 
5

5-7HEAVEN

Well-Known Member
Aug 2, 2008
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motorizemyride said:
I bench tested the engine and it's running great, even under load. Tore down and rebuilt it to inspect for any unusual wear/damage and aside from having a bit of normal usage filth it's in tip top condition. Truly an amazing bargain.

I HAVE decided to go with a chinagirl kit though. For a first build I figured that ease is indeed the way to go. In the meantime the Tanaka is going to sit on the workbench and wait for either my experience to reach an appropriate level or a motivated buyer.
Click to expand...
I would also recommend rear friction for starters. My first bike was friction drive w/1.4hp Subaru engine, then 2.2hp Mits engine, then 4.5hp GP460 engine. It was a good system for starters, but chewed thru lots of rear tires. Next was Staton rear chain drive, which was tail-heavy My final ride is a Tanaka 47R engine, which is Scooterguy center mounted. The bike feels balanced, not tail heavy. Power runs thru 8 speeds, freewheels and pedals too. The one-liter Happy Time fuel tank sits on the rear rack. This system gets better gas mileage than friction drive, about 125mpg My Tanaka engine is very powerful but still reliable, and I still have the original rear tire on it after 2 years.xct2
 
Otero

Otero

Member
Feb 1, 2010
782
17
18
wa
Yeah 5-7.
I remember that two headed monstrosity, 'the dragon lady'. That
vid's still out there. What were you thinkin'? I was waiting to see if
you'd put wings on it,(nyuk,nyuk).
 
5

5-7HEAVEN

Well-Known Member
Aug 2, 2008
2,661
240
63
Otero said:
Yeah 5-7.
I remember that two headed monstrosity, 'the dragon lady'. That
vid's still out there. What were you thinkin'? I was waiting to see if
you'd put wings on it,(nyuk,nyuk).
Click to expand...
I was thinking "more power", lol. I needed more power to ride in traffic, and did not find the GP460 or Tanaka 47R yet. There were times when one engine ran outa gas and I "limped" home on a single engine. Torque was awesome, though, for a 100-pound bike. The GP460's a sweetheart, but it's really tricky limping home with broken clutch springs on a 70lb. bike. When they make reliable springs, I'll take mine off the shelf. My Tanaka's never failed me, so I'll stick with that.
 
lowracer

lowracer

New Member
Oct 17, 2008
1,319
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Charleston, SC
5-7,
I've gone down similar paths as you (even the double engines).
I'm getting ready to start another project that will drive thru the rear 9 speeds.
Really appreciated all the info you've posted on this as you were fine tuning your system.
Pretty sure I can make it happen & will definitely post a new thread when it happens.
Thanks,
-lowracer-
 
5

5-7HEAVEN

Well-Known Member
Aug 2, 2008
2,661
240
63
lowracer said:
5-7,
I've gone down similar paths as you (even the double engines).
I'm getting ready to start another project that will drive thru the rear 9 speeds.
Really appreciated all the info you've posted on this as you were fine tuning your system.
Pretty sure I can make it happen & will definitely post a new thread when it happens.
Thanks,
-lowracer-
Click to expand...
Hello lowracer. Good luck with your 9-speed project. Low first gear of 46:1 and second gear of 38:1 come in real handy, especially when used with 15:1 highway gear.. There's no greater joy than shifting a motorized bike.xct2
 
Otero

Otero

Member
Feb 1, 2010
782
17
18
wa
On Friction: I think the trick to saving tires getting up some speed
pedaling off before hitting the throttle gradually. I realize this isn't all
that practical for urban riding. Just one more reason I avoid cities &
Russian women.
 
5

5-7HEAVEN

Well-Known Member
Aug 2, 2008
2,661
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63
On friction.....no longer for this rider. Too many flats, bald tires and wet weather.

On Stxxxn chain drive.....no longer building. Too tail heavy, poor access to rear wheel. But I DID rescue a Mits43/Staton/NuVinci Trek bike with flat tire for $200.

Oh yeah, Staton never returned my twin-engined gear box.:-||

On Scooterguy center-frame.....my favorite build. Changing to internal hub and moped/mc tires will make it bulletproof. Fuel tank can sit on top tube or rear rack.

On mid-frame installation.....my present build. GP460 engine's clutch is its Achilles' heel. The Tanaka 40 or 47R would fit mid-frame with pocket bike tranny, bikeengines.com mounting plate, SBP bottom bracket and freewheel crank.dance1
 
scotto-

scotto-

Custom 4-Stroke Bike Builder
Jun 3, 2010
6,505
24
38
Ridin' inSane Diego, CA.
5-7HEAVEN said:
Hello lowracer. Good luck with your 9-speed project. Low first gear of 46:1 and second gear of 38:1 come in real handy, especially when used with 15:1 highway gear.. There's no greater joy than shifting a motorized bike.xct2
Click to expand...
Oh yes there is......a single speed like this comes to mind :D



Who needs gears when you got this kinda power? laff On a beach cruiser???
 
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