The Spectra Mountain Fury 4 Stroke
When this thread started I didn't own a 4 stroke bike so I didn't plan on participating. Recently I put together a nice 4 stroke kit so I thought that it would be worth contributing. I originally pulled this bike out of a bike recycle bin and it was in pretty sorry shape when I got it. The poor Mississippi-built Murray Spectra had seen much better days. All of the bearings were dry and filled with sand and both wheels were pretty severely rusted. The rear deraileur was bent and all of the pull cables were rusted. The chain was so rusted that it wouldn't bend at all.
Anyway, this bike was a journey! I repacked all of the bearings and derusted the wheels. I then replaced the rear derailer with a Shimano unit and bought a new pedal chain. I picked up a relatively stiff but comfortable seat at my local bike shop and replaced all of the pull cables and cable housings. I then installed new tubes and Kenda 1.5" tires. After the tires, I ordered a quality speedometer with a backlight and 5" raised handlebars for a more laid-back ride. Finally, the bike was back in adequate working condition.
After getting the bike so that it would finally roll as a pedal bike, I decided to move onto the next step. I ordered the Huasheng 4G kit from bicycle-engines.com and with my dad mounted the engine. A 3 piece wide crankshaft had to be used so that the pedals would clear the engine. One issue was that the bike had originally used a 1 piece crank and some tubes that were protruding into the bottom bracket had to be ground down before the 3 piece adapter would press in. The hardest part however was the rag drive sprocket which would align horizontally but not vertically. A combination of JB Weld and paper clips kept the rag drive in place. Surprisingly though, in just 2 days the bike was up and running.
There were several issues that plagued this bike from the start however. The rust on the stock steel wheels was almost all of the way though the rims. Also, the steel rims kept getting bent out of true whenever I would hit a bump at cruising speed. After truing both wheels once I did not want to spend anymore time on them. Another issue with the bike was that the stock exhaust kept dumping exhaust fumes out right below me so unless I was moving I was constantly inhaling exhaust. A third issue was that the included motor drive chain was not standard 415 chain so it would not accept a half link in order to achieve a good chain length.
Frustrated with these issues, I bought two new rhinolite wheels with Shimano hubs, new presta tubes, and a disc brake mount rear drive sprocket from Firebelly cycles. I mounted the drive sprocket to the rear wheel and mounted the tires to the new wheels. I was going to drop the new wheels into the hangers on the bicycle when I noticed that the new wheels were wider than the original steel wheels. Using a car jack, I then spread the front fork enough for the wheel to slide in. The rear hangers just needed a small amount of spread to accept their new wheel. In total, the new wheels and lighter drive sprocket removed 7+ pounds of weight from the bicycle.
I then attached a new section of heavy duty #41 chain to the drive system. Made in the USA, this $20 piece of chain showed almost zero side to side flex compared to the old Chinese 415 chain. My dad and I worked out the spacing fairly well with a half link so that there was a reasonable amount of slack in the chain.
I then called up EZM and ordered their flex pipe in order to move the exhaust fumes back a couple feet. Installation was fairly easy. The most annoying part was that I had to order a regular 2 stroke exhaust in order to use its header to mount the flex pipe to the engine. I hack-sawed off the header and attached it to the flex pipe with a seat tube clamp. Then I screwed on the header piece and clamped the end of the flex pipe onto the rear part of the frame. Not only does this exhaust look sweet, it moves the exhaust fumes away from my face, makes the bike sound like a Harley Davidson, and added a ton of mid-range acceleration and about 5 mph to my top end. Props to EZM for such a simple yet amazing exhaust.
Aside from some smaller details that I have not mentioned in this lengthy article, this is where my bike is at the moment. A suspension 1" threaded front fork along with a new front V-brake was ordered in and will be installed when I return to my house from college for fall break. I am also considering installing a new v brake in the rear along with a caliper to V brake adapter.
The paint on the bike frame could use a little work, but overall this bike seems to be very solid. I've put around 100 miles on the bike so far and I can get it to about 35 mph. Cruising at roughly 31 mph is possible. I get roughly 120-130 miles per gallon of gas.
Here are a couple of pictures of the bike as it sits now. They are blurry because they were taken with a camera phone but I will try to get better pictures in the future. If you have any questions, please let me know. Ride safely.
