Pocket Bike Engine Project II

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lowracer

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Oct 17, 2008
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I removed the banana seat since it was uncomfortable & sat too far rearward.
Back to a conventional bicycle saddle.
My favorite saddle is a leather beach cruiser seat I bought off eBay made by Gyes for $70 (similar to a Brooks only wider)
 

lowracer

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Oct 17, 2008
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Dont know why I went & bought that jet kit???
I was 'tuning' my carb & replaced the stock jet with a #70 jet.
Been riding around short little rides & all seemed well.
Today I went for a long ride to go show some people this motorbike & noticed it wanted to die at idle. I adjusted the idle adjustment screw & this seemed to work out.
Got to both destinations & showed the bike.
On my way home, it started to bog out & die. Got it to start back up but had to pedal assist the engine to get it going (no power). Then nothing...No more start...Nothing.
I removed the v-belt from the large pulley & wrapped it around the handlebars to avoid rubbing anything moving & proceeded to pedal home.
Once I got home, I replaced the stock jet into the carb & tried to start it...Nothing...
I removed the exhaust system & took off the head & low & behold, the piston has a nice hole in the dome & the top of the cylinder wall is fried. The spark plug reveals a very light gray color so I am guessing it was running way too lean using that #70 jet.
Now I gotta decide if I want to buy a new cylinder & piston or a Tanaka engine to replace this one?
-Lowracer-
 

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gera229

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Sep 4, 2011
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I'm sorry to hear that. I've been reading through the pocket bike forum and learned a lot. Going to make sure I don't do the same as what happened to you.

A new cylinder and piston is fairly cheap for these engines.
What kind of oil were you using? Was it synthetic?

How far did you ride it that day in miles before it started dying?

And as far as Tanka goes, they are reliable but not near as powerful and fast as these engines are. Correct me if I am wrong.

Also report the total miles on your cylinder before it died.
Most china girls die at about 1000-3000 miles based on what I have read.
 

lowracer

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Thanks Gera,
I use Yamalube 2R (good stuff)
I rode it around 25 miles.
The only reason this happened was due to my jet kit experimenting (leave the stock jet)
The tanaka's are only 1.6 hp stock but I bought one today for $89 (new & free shipping)
I got about 1000 miles on the blown engine. It would still be ok if I didnt lean it out.
The plug was a real light gray so it was running real lean & burned a hole in the piston.
At least it didnt explode into shrapnel...lol
I can get a new cylinder & piston for about $30.
Not bad
-Lowracer-
 

gera229

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I will be using Amsoil dominator because people reported it being the best in preventing piston wear. Amsoil makes the best synthetic oils, although they are not cheap, the ratios for Amsoil do not need to be like super low. With that oil an 80:1 ratio is considered good.

I imagine your engine was smoking.

Why is the Tanka so cheap on amazon?

By the way I did not find it on amazon.

Does the pocket bike engine Carburetor and exhaust work with the Tanka?
Hopefully extra money won't need to be spent on that, because for the tanka carbs and exhaust are probably expensive. Or does it come with it already?
Also a gearbox for reduction. Or does it have one built in? So a clutch is still needed if it does not come with one.

Most of the money I spent went on accessories such as cable, throttle, sprockets, fuel etc.
Making mounts for the Tanka shouldn't be hard if it fits inframe.

Let me know how strong your tanka runs when you mount it on and how fast you will go. Also how loud it will be.
Reason I ask to let me know is because I want to know if power is worth sacrificing for reliability.
Both engines can be reliable and both can fail (Although Tanka is probably a little bit more reliable), but only one (Tanka) has less power and the other has more power.
 
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lowracer

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Oct 17, 2008
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The oil wasn't the problem for my burned up piston, it was the fuel mixture.
The engine didnt smoke at all. Just started losing power & compression (hole in piston).
The seller on Amazon sold out last night. They were liquidating their last remaining stock.
I wish I could have bought a truckload at that price & sell them myself.
The Tanaka comes complete with clutch, fuel tank, carb & exhaust. It doesnt need further reduction using my pulley drive system.
The Tanaka from what I read is alot quieter than a Pocket bike engine w/expansion chamber. Will do a write-up once I put a few miles on it.
If my other Cag fails, I'll stay away from Pocket bike engines, but I still believe the problem I incurred was due to me messing with the carb jetting without a clue about what I was doing.
-Lowracer-
 

5-7HEAVEN

Well-Known Member
Aug 2, 2008
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Oooh, sorry to hear about the piston. Don't fret it, though. It's a very cheap lesson. Live and learn more, all in the name of research and development, and pushing the envelopment.xct2
 

gera229

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Hey were you going WOT when it happened?

That's one good deal if it comes with everything.

Normally a refurbished motor JUST THE MOTOR is $200.
 

lowracer

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5-7,
Yeah, I'm ok with the expense of what I learned playing Jet-I-Master...lol

Gera,
I wasn't going WOT with this bike (never go WOT on this bike since its a no-suspension bike & these engines are super speedy).
The Tanaka engine is brand new (not refurbished) for $89 w/free ship
They got sold out quickly.
-lowracer-
 
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gera229

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Sep 4, 2011
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Lowracer that is cheap. And it came with everything for that price? Not just the engine right? Amazing deal.

Hey also, do you think that, what happened to your pocket bike engine, could happen to the China girls 66cc/ 69cc? Would the China girls handle it better or break a lot sooner if using the wrong jetting?

Isn't this pocket bike engine supposed to be more reliable than the China girls? Would you get it over the China girls?

And the stock jetting was like the right jetting and nearly perfect? Smaller jets than stock would make it too rich and larger jets than stock would make it too lean?

What's the stock jet number?
 
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lowracer

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Oct 17, 2008
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Gera,
You got it all mixed up. The jet has nothing to do with your oil & gas mixture (you do that in a gas can). The jet changes the air to fuel mixture. Bigger jet hole=richer more fuel to air mixture, Smaller jet hole=leaner less fuel to air.
-Lowracer-
 

gera229

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Oh so you were running a smaller jet than stock right?


So
Lean. Smaller jet:
too little fuel too much air

Rich. Larger jet:
Too much fuel too little air

Right?
 

lowracer

New Member
Oct 17, 2008
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Ok,
I went & pulled the trigger today on a Stage 2 kit from Big Motor Sport for $69 & free shipping to repair the damage I did to my 2nd Pocket Bike engine by running a different jet tat was too small. This kit will give me what I need to repair my Pocket Bike engine with a bunch of spare parts to boot. I needed just the piston, rings & cylinder block.
I also ordered a Brand New Tanaka PF-3300 33cc engine off Amazon for a killer deal @ $89 & free shipping that will be arriving Monday. I originally thought of not repairing this 2nd pocket bike engine but after riding 'The Beast' around I changed my mind. It is so much more powerful than either my Subaru Robin EH035 or the Tanaka 33cc that I dont think I can live without that power...
Call it addiction!
-Lowracer-
 

5-7HEAVEN

Well-Known Member
Aug 2, 2008
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lowracer, I think twin Tanaka 33cc engines would work VERY well. dance1

It'd be very dependable, but not as fast as your pb engine.xct2
 

lowracer

New Member
Oct 17, 2008
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Charleston, SC
Not sure yet what I'm going to do with that Tanaka engine?
I am definitely repairing the Pocket Bike engine (love its power).
-Lowracer-