• Register now! It's free and easy.
  • Show your bike to the world, upload a photo today!
  • Hi Guest, did you know we have a dark style? It might be easier on the eyes at night time! Try it out here: Style Chooser

Any engine modifiers out there?

5

5-7HEAVEN

Guest
:cool:We are all blessed with many engines to choose from, in motorizing our bicycles. The more common ones are the 48cc-80cc Chinese engines, rack-mounted HONDAS/MITSUBISHIS/ROBINS/TANAKAS and a sprinkling of pocket bike engines.

I have two of each kind.:eek:

I'm wondering how many members are modifying their engines for more power and performance, in true hottrodding style. If so, let's hear your testimonials.

I'm digging into my $100 pocket bike engine with great vigor. First, I installed an advance crank key, which easily slipped onto the crankshaft. Next, I installed a DELLORTO 14/14/replica carb.

http://www.davesmotors.com/store/product871.html

I was disappointed that I had to remove the reed induction system to facilitate the carb installation.


A few days later, I found a high-performance reed system made specifically for DELLORTO carb on pocket bike engine.

http://www.davesmotors.com/store/product172.html

It bolted on easily, and I'm happy again.

I discovered that a tuned pipe would greatly enhance the pocket bike engine's power and speed. This is especially so if I were to use a brand name and model expansion chamber that had been proven on national racing tracks. For obvious reasons, I would not be able to use a lengthy tuned pipe made specifically for a pocket bike.

Since pb engines are very similar to goped engines, I reasoned that I'd be able to find a goped tuned pipe to fit my engine and bicycle.

I found Davesdiscountmotors.com online, and realized they had a LOT of goped and pocket bike performance equipment. First, I bought a "TERMINATOR X-CAN" made specifically for pb engines.

http:www.davesmotors.com/store/product1210.html

It's the size of a pack of cigarettes, and offered some performance gain. I bought one, and it would NOT bolt onto the exhaust flange, due to incorrect bolt spacing. Darn.

Next I carefully measured the exhaust port and bolt spacing. I also read and re-read the online catalog, painstakingly looking for cross-references between pocket bike engines and goped engines. I found out that the ZENOAH G62 goped engine shared similar exhaust port size and bolt spacing as my pb engine. So I bought a SIKK flange for a pb engine and an ADA billet flange for the G62 engine. Even though the SIKK was specifically made for the pb engine, its narrow flange restricted the engine's exhaust port by over 40%.:eek: Thankfully, the ADA billet flange matched the pb's port perfectly, and just needed the bolt holes enlarged to accept larger exhaust bolts.

After much time doing "spatial visualization"(like fitting upside-down puzzle parts) between available tuned pipes for goped engines and my pb engine, I WAS going to order the G62 tuned pipe. HOWEVER, since the G62 is a 62cc engine and my pb engine has 49cc, I ordered an ADA pipe that was catalogued for a 40-something cc engine.

http:www.davesmotors.com/store/product212.html


I reasoned that my ADA billet flange SHOULD match any ADA tuned pipe.

All my guesswork paid off. The G62 billet flange for the 62cc engine bolts onto my pb engine's perfectly. The 40-something cc engine's ADA tuned pipe slips perfectly into the ADA billet flange. The semicircular expansion chamber clears all obstacles, such as engine, STATON friction drive and tire. It is a very good fit, and I expect excellent midrange-top end acceleration.

IF the engine blows up, I'll rebuild, install an oversize cylinder kit and balance everything.

Let's hear about your engine mods!

Myron
 
Last edited by a moderator:


G

Ghost0

Guest
In my opinion carb and pipe are the best for the least $ but when you want to start getting crazy I would take my engine to a reliable racing Kart shop. They do wonderful things for the 100cc Yamaha's so I don't see why they wouldn't know exactly what to do with one of our 50 -70 cc units. You can probably even give them some parameters to go by like, I want more torque or top end. Some even have dynos so you could give him your carb and pipe and they could dyno tune it. I don't know that I am going to get that crazy but my pipe and carb should be here Friday and I will let all know the results.
 
Last edited by a moderator:
5

5-7HEAVEN

Guest
:cool:Ghost0, thanks for responding.

The external mods are the easiest. I MIGHT confer with a small engine repair shop for an extended throttle cable, or dyno-tuning and dialing in. I might use their services if I get stuck, and over my capabilities.

It'd be fun for me to do my own work. Since the engine and its modified parts are relatively inexpensive when compared to car parts, I don't feel intimidated learning from my own mistakes.

Ghost0, which engine and bicycle are you using?

For the moment, my bike of choice is a year-old SCHWINN SKYLINER that I bought for $100. The engine is a generic 47cc-49cc ebay engine, with STATON friction drive and .875" spindle. I'LL probably install my gear chain drive in the future, to take advantage of the pb engine's high-rpm capabilities.

With 10t/16t drive/driven sprocket, I'm anticipating 4,000rpm/8,000rpm/11,000rpm speeds of 10.6mph/21.2mph/29.2mph.

Acceleration should be brutal and mind-numbing.

Myron
 
Last edited by a moderator:
5

5-7HEAVEN

Guest
:cool:JMO, I compare 47cc-49cc pocket bike engines to the ubiquitous high-winding CHEVROLET small-block V8 engines. Maximum hp and torque have yet to be realized with pb engines. These engines are lighter and shorter in height than most frame-mount engines. Performance parts are plentiful and relatively inexpensive.

The CORVETTE-versions(more expensive, higher quality, higher winding with more hp potential) are the exotic POLINI 40cc-50cc engines.

I'm surprised that not too many enthusiasts are tweaking any of their engines for more hp/torque.

Myron
 
S

sunofjustice

Guest
5-7, choice topic........as an alternative engine source.......... th' 47cc cagillari ("cag"for short), IS th' most bang for the buck bar none. When I first saw one on a bicycle on myfrapper.com......I was hooked. Th' over all design is just so clean and compact.......everything is so easy to get at or work with. Upgrades are where th' 47cc (actually 40cc)......REALLY shine. My spoiler (zeus zangitsu), presently has these mods: 14/14 dellorto sha carb knock-off (#90 jet),........ aluminum spigot manifold,............... black widow, triple stage reeds,...........E3 diamond -fire spark plug (.10 gap).............gasket-matched , ported exhaust manifold,............third stage, 47 cc expansion pipe, and............upgraded 3rd bearing support housing,.......hi-po clutch shoes and springs.:) Future up grades: Dellorto 16mm phbg carb,.........inferno ignition,............49cc upgrade kit, .......jet-pro hi rev pipe. I could put in a rocket key.........but they work better on a stock engine. Would like to try a 33cc water-cooled engine on a different bike though(8-11 hp!) :D
 
S

sunofjustice

Guest
My 70cc schwinn, ranger mtb (shinobi sinner) .......runs a K&N filter.......a 20mm carb, home made 20mm manifold , NGK pocket bike spark plug, gasket matched, ported exhaust...........mated to long pipe......mated to third stage ,47cc cag expansion chamber...........with #81 chain......turning 36t sprocket......running armidillo hemisphere tire. Although th' engine on my other 70cc schwinn, suntour mtb ( blue oni) gave up th' ghost due to a crappy upper roller bearing...........I still plan to use an opened up homemade glasspack exhaust and DUAL CARBS. Which WAS gonna be a near future surprise.........Currently piece-mealing a franken engine from some old parts and bits of retired engine. Will be posting a thread soon with more detail. Peace.
 
5

5-7HEAVEN

Guest
:cool:Brian, thanks a bunch for responding. You are right up my alley.

Nice mods. Are you frame mounted or rackmounted? What's your final drive ratio? If it's just your 6t/36t drive/driven sprocket, you haven't reached the engine's full potential yet.

I saw your "franken" engine and posted my remarks.

Excellent tip on using dual exhaust pipe for dual carb setup.

Myron
 
S

sunofjustice

Guest
myron, all bikes are frame mounted...........final drive combo on spoiler: engine sprocket 6t........final drive sprocket 98t. I also agree that there ARE better sprockets.......a 7tooth or 8tooth engine sprocket........ should net even better results. (Besides, I like to give myself a handicap to see how creative I can get):cool: The 98t final drive..........I prefer for easier take offs. Th' spoilers HEAVY front end....... and drive train make for a very cumbersome bike. Th' shinobi sinner bike has a 36t, and th' blue oni has th' el cheapo 44t which I drilled out to shave weight from it. Th' plan was to upgrade to a high gear aluminum sprocket once th' engine was broken in. :rolleyes: 5-7, when are you gonna post some cool pics dangit!?!:confused:
 
A

andyinchville1

Guest
Yes I love tinkering....So far have retrofitted a tuned pipe onto a dax 70....next plan is to modify the intake manifold for ram induction, then will mod the air intake itself....probably an open air K&N style open element air filter inside some sort of forward facing trumpet to "ram" in additional air at speed....Oh...of course the boost bottle....than maybe upping the compression a bit. I like the pocket bike engines but to be more practical have to get a good gear reduction going tho
Andrew
 
5

5-7HEAVEN

Guest
:cool:Brian, a 6t yields a better final drive than 7t or 8t. Nevertheless, pocket bike engines need even lower gear ratios to show their stuff.

Love your tinkering, Andy.

Myron
 
Top