When I 1st started to build my 1st gas powered bicycle, I never imaged the struggles I would have with a build. The biggest mistake in building a 2 stroke gas bike is not having the correct and quality components.
You have been riding bicycles since you were a little child, imagine not having to pedal and cruising along faster than you can pedal! OR if you want to experience riding a motorcycle but not sure if you want to invest a lot of money. Welcome to the world of a gas powered bicycles.
I greatly enjoyed the build process for the 1st few hours, it’s been years since I worked on a bicycle and since I am into the IT industry, I do not work on mechanical objects daily. According to the directions with my kit, I just had a few bolts and brackets to add to my bike and I would be complete. My 1st test ride was 1am in the morning I did not care how late it was and if I woke my family or neighbors. I wanted to test out if my bike would roll. It did in fact roll, but will all sorts of clicking and rubbing sounds. Not knowing anything, I assumed this was normaly….NO
From all the YouTube videos, it looked like a 2-3 hour build. Initially it did only take 3 hours to build, but nothing was straight, the chain kept falling off, and it was difficult to stop. After weeks of tinkering every night, I realized I kept making the same mistakes every part of this build. The biggest mistake in building a gas bike is not having the correct and quality components.
There are hundreds of YouTube videos on how to build a 2 stroke gas bike, most of which are edited and make it look very easy, in fact, some videos estimate the build should be 2-3 hours, but they never account the problems with the incomplete kits. Some steps are completely omitted or never go into depth leaving you stuck at a critical point. None of the gas bike build videos I watched discussed any issue I had with my build. So I compiled the 5 top build upgrades you should purchase before you even begin your build.
These upgrades are not performance upgrades, these gas bike upgrades are almost essential for the 1st time gas bike builder. These upgrades are to speed up the process and for your safety. There are many reports that bikers at top speeds had mechanical failures causing major accidents. But do not let that discourage you, a few simple upgrades you can make your build quick, enjoyable, and produce a quality safe 2 stroke bike.
1. Bicycle Frame too small to Fit a motor.
The best bike to convert to a gas 2 stroke gas powered bicycle is a 1 speed 26 inch beach cruiser. You can pick these up on Amazon for about $100. There are several reasons why we want this particular bike,
2 stroke engines regardless how well balanced have a lot of vibrations and over time will cause cracks on cheap bike frames. I found the Huffy Cranbrook (after modifications) be a great starting bike. The bike is fairly cheap and by some accounts made of quality metals, but like with anything you will need to check out the quality of the welds on your bike before you ride.
The 1 speed allows for a much simpler chain adjustment and sprocket installation. With the gas bike conversion, we still have the chain from the pedals, but now we are adding the chain from the motor to the rear wheel and having 1 speed on the pedals makes for a process for the 1st time builder to easily figure out.
The 26 inch beach cruiser has a wide open frame with ample room for just about any 2 stroke gas motor on the market. Most 2 stroke gas kits have all the engine mounts designed specifically for a beach cruiser style bike. Most mountain bikes and other street bikes have a narrow bike frame which requires lots of additional mounts and sometimes custom metal fabrication. The 26 inch cruiser style bike does not require any modifications and the motor will slide right into the frame.
After a few rides, I did discover the mud guards to develop cracks. After I discovered these, I immediately removed them entirely from my build to eliminate any sort of accident while cruising along at top speed.
2. Incorrect rear wheel Sprocket Installation
The biggest issue I had in my gas bike build with the rear sprocket gear which installs on the rear wheel on the beach cruiser. A wobble in rear sprocket will always derail your gas bike chain. This is also known as a rag joint sprocket. Special attention is required on this installation part of the process, each of the 20 bolts, some sort of rubber gasket, and 20 nuts with lock washer. All of this has to have the exact tension otherwise the sprocket will wobble in and out causing the chain will wobble and fall right off the gear which could cause bodily harm if riding or simple frustration in my experience. Can the stock rag joint work, absolutely if you have a ton of building experience, but I tried several times, and could never get the sprocket to even out. Regardless of what I loosen or tighten, I would have that little wobble causing a clicking sound. This sound I was hearing was the chain nearly coming off the sprocket every time the chain would reach the out of balanced sprocket. I spent days tinkering with the sprocket, eventually I took the entire stock sprocket off the bike and reinstalled. Any off set or lateral alignment chain and sprocket issues will always lead to chain derailments. At this time, the coaster brake came loose, then I had a real mess on my hands. A warped sprocket and no working coaster brake. I was on the very of a total disaster. The best way to address the issues with the rear rag joint rear sprocket is to purchase an upgrade CNC version clam shell. This CNC sprocket simple bolts around the hub of the rear wheel making for a perfectly centered sprocket every time. This 1 component will keep your drive chain very straight, but will save your hours on the build as the rag joint sprocket is extremely difficult to install. From my personal experience, I was never able to get the rag joint style sprocket installed correctly after days had 100s of hours trying, but the CNC sprocket installed in about 15 minutes and was perfectly straight right from the beginning.
3. Loose Chain on the Gas Powered Bicycle
Now we have installed the rear clamshell sprocket, we need to make sure the chain is very tight. A loose chain on a gas bike will cause jams inside the engine sprocket and will eventually derail. Talk to anyone who has already built a bike and it’s almost 100% agreed the stock chain tension is hated by everyone. Why do they include this cheap useless and potentially dangerous part…simple put, price? Again most kits chain tension is a basic component, but will fail over time, causing bodily harm and frustration. The stock chain tensioner is a clamp on style and over time I see a potential of the chain tensioner moving into the spokes causing an instant rear lock up.
There are 2 ways to address the loose chain. My experience, I was able to get the chain lengths to a perfect size while adjusting the motor ever so slightly provided enough tension where I did not need a chain tensioner. This by some experts is the best method. This is the best method since there are less moving parts in the entire gas bike drivetrain. In addition, not every frame will have a space to mount a chain tensioner.
The 2nd and most common is an upgraded chain tension. I did purchase a quality chain tension and attempted to install, unfortunately I still had issues because my chain length was 1 link too long causing about 2 inches of slack. The aftermarket chain tensioners now have springs which keep a constant steady tension on the chain. These chain tensioner only work if you have a marginal amount of play, 1- 1.5 inches of play should be your goal, but I still but found the stock spring was still not up to the task. So you will need to purchase a high quality chain tension with an upgraded spring, otherwise with a weak spring, the chain will jam up in the motor housing causing bodily harm if riding or simple frustration in my experience. The chain tensioner mounts right onto your existing 2 cycle clutch cover and assures your chain rides straight to your sprocket without any adjustments. This chain tensioner is much safer because the chain cannot be pulled into the spokes at high speeds
What are the benefits of mounting the chain tensioner to your bicycle engine?
When I installed installed the stock chain tensioner, I had to bend it to try to get your chain to ride even to the rear sprocket. After upgrading to the chain tensioners, the engine mounted designs assures that me the chain will ride perfectly straight to the drive sprocket without any bending or modification. Even in the end, I did not need one, I never had to worry about chain tensioner getting pulled into your spokes.
4. Using a weak Chain on a 2 stroke engine
The stock chain that comes with most kits will work for experience builders, but there lots of side to side flex and which will cause the chain to keep derailing over time if not installed perfectly straight. During the build I was fortunate enough to have my son’s 4 wheeler nearby and just happened to look at the chain on that 4 wheeler. I applied the same principle on the gas bike as on the 4 wheeler a number #41 heavy duty chain. This #41 chain along with the proper sized master link comes in lengths long enough were you can make 2 useable chains for your gas bike.
Lets face it, I was not an expert starting this process and using a #41 chain would allow a bit more left and right on the sprocket alignment while giving the chain more strength and flexibility. The upgraded #41 chain is actually wider than the stock #415 chain and has less sideways flexing. When installing the #41 chain on your gas bike be sure to use some mechanic gloves as any high quality chain comes pre greased for proper use and that is a pain to get off your hands.
Installing the #41 chain if not difficult and requires no modifications. It’s the exact replacement for the stock 415# chain that comes with most 2 stroke engine kits. Another advantage of upgrading to the #415 chain is that the chain will not stretch. The stock #415 chain over time will stretch and if not caught in time could come off your sprockets and jam inside your motor. With absolutely no disadvantages of upgrading to a #41 chain, the chain alignment and tension are still need to be in check, but with the #41 chain, the alignment can be off a bit (still not recommended) I personally was able to break the stock chain without the tool, but for the #41 I did purchase a chain break tool, I did not want to break or damage the high quality chain. In case you cannot tell, there is no reason NOT to move to a #41 chain
5. Low Quality Rear Wheel on a motorized bicycle
The Rear wheel on a 2 stroke gas kits is where all the action happens. The weakest point on stock beach cruiser bikes is the coaster brake and spoke thickness or strength.
Most 26 inch cruiser bikes do only have a coaster brake (brakes when you pedal backwards). The stock coaster brakes are the weakest point in most stock cruiser bikes. Stopping is very important and should not be overlooked. The stock coaster brakes on most cruiser bikes are not designed for high speeds such as you will achieve on a gas bicycle. There are a few options on decrease stopping distance on a rear coaster. You can repack the coaster bearings with high temperature grease, this is somewhat difficult and if you are new to bikes in general, this is not suggested. Another difficult option is replacing the rear hu entirely. If you were to repack the hub, you might as well replace the hub. How do you do this? I have no idea lol, after reading the manual and watching YouTube videos, I came to the conclusion, repacking a coaster brake bearing is out of my league and required special tools. The easiest and best overall option is to purchase and upgraded rear wheel with a quality coaster brake and thicker wheel spokes.
Coaster brakes are typically designed for speeds up to 11mph, at speeds achieved by a 2 stroke engine, the stock coaster brake will overheat and become useless and you will have no stopping power. Long term solution is to add a 2nd backup handbrake – more on that later, but by upgrading to a quality rear wheel, with a quality coaster is a quick multi purpose best long term solution.
Another weak point on the stock cruiser bikes is the wheel spoke thickness. Most stock wheels are have a thickness of 14 gauge, however, we want a wheel thickness of 12 gauge. The thicker the steel the lower the number. We want this thicker steel on our rear wheel as it provides more strength. Even though we upgraded to a clam shell style sprocket, (step 1) there is always some pressure on the bike wheel spokes and having that extra tensile strength will greatly reduce any breaks to the spokes. I learned after a few miles on my bike that a loose spoke on any bike will eventually break off and get stuck into the drive chain causing the chain to immediately stick causing the rear tire to lock. This was a very scary movement, but luckily I had was riding slow enough I was able to control the skid. Any breaks on the spoke could fly into the drive chain… causing bodily harm if riding or simple frustration in my experience
Why do the 2 stroke gas kits that come with parts that are difficult to assemble and build?
If you are a master gas bike builder you can successfully build a gas bike with the provided parts provide with most engine kits but lets face it, I am not a master gas bicycle builder and is why I had such difficulty with the stock parts in the kit. Keeping the price low is the only reason why these cheaper parts are included with the kits. Even if the price is just a few $ per part us consumers can save a lot of our hard earned cash for the engine kit. With so many different options and upgrades available, it will be hard for the vendor to understand the builder’s skill level so they include these cheaper parts in the kits. There is a trade off from quality vs price, you know that old saying you get what you pay for.
My advice after spending about 1 month to tweak and tune my gas bike build, spend the extra $$ and get the recommended parts before you begin your build.
