80cc Bicycle Motor Kit 

Model H2-80 (this is the latest, more robust version)
Has roller bearings including top and bottom of the con rod.

A  Homemade 12 volt LED headlight
B  DIY gas gage
C  Needle valve gas shut-of
D  DIY paper element air filter
E  Cork sheet glued inside to reduce noise

Assembly
The first thing I did was poke a small wad of paper towel into the intake and exhaust ports to keep out any dust I may stir up while working, and especially grinding or sanding dust.

Rear Sprocket

The instructions say to begin with the rear sprocket. It was a little worrisome that trying to slip the sprocket onto the rear hub revealed the first problem with the kit. There was flash in the hole from where it was forged. A Dremel tool with a small grinding wheel made short work of removing it, but it still would not go on. My dial caliper showed the hole was about .005 out of round. Again, the Dremel tool with grinding wheel made short work of it.

The instructions show the sprocket bolts inserted from the outside. I elected to insert them from the inside to make it easier to put the nuts and lock washers on since I am not as nimble as I once was. Besides, I may want to change the sprocket for a larger (more teeth) one later. This may have been a mistake as all 9 of the bolts had to be shortened so they would not hit the frame. An abrasive cutoff wheel on the Dremel was used. Nothing to it.

But getting the holes lined up with three inner plates, the two rubber discs, and the sprocket proved to be a challenge. A philips screwdriver about the diameter of the bolts was a big help.

Somewhere on the 'net I found dimensions for the minimum diamond size for this motor that claims >11" for the distance from top of the bracket for the pedals to the bottom of the top frame bar near the seat. NOT SO! After I finally got installed, a tape measure tells me >13". Note: I have seen these motors on girl's bikes by mounting the motor high, but that looks like I could easily damage parts of my body I might want to use again some day.

This is a really hard one to convert. Better use the older type with horizontal bar. It is the one I used, it looks nice and is light and I can lower the gear ratio enough for my tired old legs, but I would not try to do another one. Also, make sure the rear wheel has 36 spokes.

I had chosen a cheap ($66) 18 speed bike from Walmart, mostly because I wanted to keep the weight down in case I wanted to put the bike in the trunk of my car, and ease of pedaling to get the motor started. However, these bikes have the top bar dropped lower near the seat (for looks I guess). This makes the bike sort of in between a boy's bike and a girl's bike. I dubbed this design the "hermaphrobike". You would be FAR better off spending a few bucks more for the old fashioned style cruiser boy's bike type frame with ROUND tubes. These have the upper tube parallel with the ground.

To make the motor fit the frame I had to grind a little from the lower oval bar, and remove quite a bit of aluminum from the front motor mount. I highly advise NOT doing this, but I had already purchased the bike. A little plastic had to be removed from the air cleaner housing. Anyhow, it fits great and gives the lowest center of gravity possible.

I swapped the studs from the rear engine mount with the front engine mount. This made the longer studs match the oval tube, and short studs match the round (seat) tube.

I used some inner tube rubber held on with vinyl electrical tape to cushion the motor mounts, gas tank, and ignition module.

Cheap and easy DIY chain breaker.

This was a Bell brand for under $5 at Walmart. The #415 chain is too big for it. I used a large screwdriver to work the lower protrusion until it broke, and a small vise-grip on the upper one. Finish the removal with a file. Now the #415 chain is perfectly centered under the punch pin.

Fuel Valve/Strainer (petcock)

I added an in-line paper element fuel filter with 1/4-5/16" barbed nipples. The fuel pet-cock came with a red fiber washer. I replaced this with a neoprene O-ring. After I checked later I found the valve was not holding. I added an in-line needle valve and replaced the original petcock with a nylon barbed nipple and Teflon tape.

Ignition module

The ignition module has two ears that are meant to accept small, long bolts. I saw the ears were starting to bend before it was held in place tight enough for me, so I replaced the bolts with a nylon cable tie with inner tube rubber between the module and frame.

Ready to go!  OOPS. Fuel is running out from near the fuel valve. After I determined the leak was not the valve, I discover a flaw in the brazing they did on the fuel outlet from the tank. I ground through the paint and cleaned the area with acetone. A very large soldering iron made a permanent repair in minutes. Don't use a propane torch! While we are at it, the new tank should be rinsed out with a little gasoline which is then discarded.

Off we go!  The engine started after pedaling a short distance. The idle was way off. The little spring loaded adjustment screw sticking out the left side is NOT the idle mixture; it is the idle stop screw. Between that and the cable length adjustments you should have a nice idle.

After you have put a few miles on the bike you will have to re-adjust the idle stop again because the engine turns easier as it begins to break in. On the chain tensioner there is a nylon (I think) wheel mounted on two fairly large ball bearing races; a vast improvement over the original steel pin that had to be kept greased and was a frequent source of failure. After the second test ride I noticed the wheel was frozen. Apparently the lock nut moved enough to make it bind. The fix is simply a washer (or two) between the bearings and the mounting bracket.

Spark plug gap 

Some say theirs works better with the gap set at .020, others .040, others, .030. I left mine at the original .032. My guess as to why it varies is the type of gas (some has ethanol) or type of oil. The motor was shipped with a Weixing Z4C plug. You can use (and it is recommended for better performance):

NGK B6HS

Autolite 425

Champion L86C

A finished bike conversion. Note how much clearance there is in the diamond with this type frame.  My engine was a very tight squeeze in the bike I chose.

Air filter element  10-24-08

This is an FF4425 (G6) filter from Autozone for about $3.
I made the adapter to offset it of plywood. UPDATE: My house is on a gravel road and the paper element filter is picking up dust at an alarming rate. So far, all I have had to do is blow it off.

10-24-08

I had my first part break today. I had the bolt that clamps the clutch lever a bit tighter than it should have been. It broke such that the broken part acts as sort of a spacer, so I simply drilled for a #10 screw and put a nyloc nut on it. The brake lever the brake lever was designed with a built-in nut. The new air filter works fine and seems quieter.


10-26-08

I got brave enough to venture to Walmart on the bike for the first time (5 miles). Just pulled into their parking lot and picked up a shiny new horse shoe nail in the rear tire. It went through the top and bottom of the tube. And not a barefoot horse in sight. Went into the store and bought a small hand pump. Tire would inflate a little then Pffft go down again. Tube was damaged enough that even the green slime sealant would not work. Back to store for a new heavy duty self sealing tube. Spent a total of $27 I had not planned on, but now have a pump that can be attached to the frame, hidden under the saddle bags. It feels like I am in the 1900's during the early days of the horseless carriage. Speaking of which... ever wonder how people could travel cross-country when there were no gas stations yet? They stopped at dry cleaning establishments that used gasoline for dry cleaning. Gas was a useless byproduct from kerosene production. Must have been a lot of dry cleaners blow up!

I had enough tools with me to repair it, but with two chains to deal with it was not easy. I figure about an hour and a half total (including standing in line in the store 3 times during the Saturday rush).

Made it back bloody, bruised , tired, and sunburned, but I have learned a lot. Please note that I am not trying to discourage anyone from these swell little engines. Murphy's law applies to everything. UPDATE: after that experience I now know that I could patch a rear tube on the road without removing the rear wheel. Should be much easier. How you ask? Pull one side of the tire off the rim, pull the tube out. Determine where the leak is (not difficult if you picked up a horseshoe nail). Patch it and reassemble the wheel.

11-4-08

I reasoned that because I have the derailer which has a tensioner built in that I probably could remove the chain tensioner that comes with the kit and adjust the motor chain as if it were a motorcycle. After about 15 miles it seems ok and is quieter and smoother. I am well into my second gallon of gas now.

Using a suggestion from the Motoredbikes.com forum, I glued 1/16" cork sheet inside the clutch cover to reduce gear noise. Update 23 May 09  The noise is even less now. Suspect the two gears are wearing in together. I am delighted.

11-15-08
I am replacing most of the engine screws with socket head hex cap screws and blue Loctite. In the magneto, all the screws were loose and all were bent a little. I figure they tapped on the sides of the magneto to align it with the magnet. New socket head cap screws with Loctite now gives me better peace of mind.

The new screws for the sprocket cover have heads .015 wider than the hole. A Dremel tool with a tiny sanding drum corrected that in seconds. The counter sunk holes for the clutch cover heads were okay.

11-23-08

I tried a small amount of acetone in the gas. Car people claim it can increase mileage by making the gasoline vaporize easier. They use 3-4 ounces per 10 gallons. Some engines like 3 ounces, others prefer 4. This works out to .2 ounces per tank on my bike, or 1 1/2 teaspoons. Works great! Smoother, less 4 cycling, and starts easier. I am convinced.

11-24-06

I made a crude but effective gas gauge from clear plastic tubing Teed into the main line. The upper end is attached to the filler neck with a nylon cable tie. (visible in photo below)

12-09-08

I discovered my cap was dripping gas from where the domed top was crimped on. Gas would slosh into the 4 holes in the bottom and the two rectangular holes for the latch, then work its way around the crimp.

Make sure the cap is clean.

I used Gorilla Glue (Elmers polyurethane glue should also work) once I had determined it seems gas proof and dribbled it into two of the 4 holes with the cap inverted. After a few minutes I set it on its side using a large pill bottle as sort of a stand. While watching TV I rotated it many times, a few minutes between rotations until I was sure the glue has set up enough. The next day I center punched the top and drilled a #60 hole for a vent.
  No more leak and very little labor.

1-27-09
About 400 miles are on the bike now with no problems. Now that the initial bugs are out it is a very reliable machine. The carburetor has been re jetted from .028" to .024" for this altitude. Makes it much smoother. A speedometer has been added, and I got it to 34 MPH, hit a bump, went airborne then backed off on the throttle. I am too old for that sort of thing.

I am using  a dry chain lube on the primary gears. My thinking is something that sticks of not-quite-sure-if-it-will-work is better than a lube guaranteed to come off. Several hundred miles now, and all seems well with it.

2-7-09
Twice now I have had the button that holds the clutch disengaged (mounted on the clutch lever) pop out. I was fortunate to find the button and spring. Here is the problem...

The bottom groove where the "E" clip fits was machined off-center. A knife edge needle file corrected that, and with a new "E" clip it was back in service.

27 March 09
I finally got around to miking the needles on three HT carburetors. One has been in use for 450 miles, the other two unused.

The one in use is much slimmer (more radical taper) than the other two, and came with the clip second from the top making it even richer. This was the machine I reduced the main jet from .028 to .024 inches and still is a little on the rich side. The clip is now on the top groove.

The other two needles are identical as far as I can tell and came with the clips on the very top groove.

I measured the float height on the two new carbs measuring from the gasket to the bottom of the float with the carb inverted. I got .772 and .750

Guessing, I would say it is possible for the distance to get smaller when the kit is bounced around in shipping, but can not get greater.

The two carbs with fatter needle tapers mate to needle jet hole with a #44 size, and the one with a more drastic taper a loose #45 hole. In this case, I would NOT say the needles are matched to the jets they fit into. But it does explain why it was very rich out of the box. So much for the theory the needles are matched to the jet.

3 April 09
I changed the front rim for a wider 2.125 rim. Took a while since I never did anything like that before, but it got confusing when two spokes did not fit right. Finally I figured out they were 1/4" longer from the factory. The wider tire inflated to 30# makes a big difference in this gravel road. It doesn't slither from side-to-side like it used to.

I got another rim for the back that is about 30% heavier. Not surprising, there were spokes too long... 10 of them, all on the same side. I had a mental picture of a bunch of Chinese kids and a box of assorted spokes in a factory. Some spokes were super tight. The Dremel tool was used to shorten the long ones using an abrasive cutoff wheel.

20 May 09
The bike is now a hybrid (or maybe tribrid) with the addition of a 600 watt, 36 volt electric motor.
Click here

12 June 09 Playing with the ignition timing
I expected it would be hard to remove the nut holding the magnet to the crankshaft, but it was slightly more than finger tight. The shaft measures .315" and the woodruff key .105"

The circumference of the shaft is  .315 x pi =  .989, that divided by 360 = .0027 inches/per degree.
The woodruff key width is about 39° and the HT is said to have 2° advance. To get 6° advance I need to offset the key about .011 inches. Not very much.

When I installed it I tightened the crankshaft nut finger tight, then tapped the magnet with a plastic hammer to make sure it was against the new surface of the key. Now my low end torque is better and likely the gas mileage.

3.5 Hp (some claim 5 Hp)
150 MPG (very overly optimistic)
80 cc (but who knows for sure?)
7.5 volt, .5 Amp alternator output. (Mine measures 14.2 volts with a half-wave rectifier under load)
Needle bearing crankshaft and connecting rod (both ends)
Shipping weight 22#
Gas tank 2 liters
Catalytic converter muffler. (Yeah, right)
Speeds up to 40 MPH (but limited to 20 during the break in period)
CD ignition system

My electrical circuit
Tools carried in the "trunk"
Porting and muffler mods

Links

MotoredBikes.com Lots of info. This is my favorite.

http://alttransbikes.blogspot.com/   Some inovative bike designs

Kings Motor Bikes Instructions, parts

Spooky Tooth  parts, forum

MotorBicycling.com Excellent forum

Porting and performance hints for 2 cycles  PDF file. Excellent!



More coming soon.

Copyright Bill Weller, 2008-2009 All rights reserved.