Nicholas Fluhart

December 2, 2010

Project: Yamaha 350 Moto-4

Filed under: Project: Moto-4 — Nicholas Fluhart @ 6:16 pm

I completed an interesting project a while back. It is a 1989 Yamaha 350 Moto-4. I love old machines! These bikes were the predecessor to the 2WD version of the Big Bear. This was a very heavy-duty machine, and as such there were some very interesting industrial variations of it that were groundbreaking in the industry. One of these was the Terrapro which had, to my knowledge, the only Power Take Off (PTO) available on a four wheeler. It had a variety of very functional attachments available from Yamaha, such as a rough cut mower, finish mower, tiller, etc. The other innovative spin-off was the Pro Hauler, which utilized what is considered the first ATV cargo bed. In contrast, the 350 Moto-4, while industrial at heart with it’s Hi/Lo 10-Speed transmission, is more of a general purpose utility ATV.

I stumbled into it almost unintentionally. I purchased a group of ATV’s in south east Arkansas and this one was in the lot. I essentially got it for free. It looked fairly junky and I didn’t have any specific interest in it at the time, so it was unloaded and hauled around back where it stayed for a few months. Here’s a video clip of me unloading it at my shop:

When I bought this quad, I never intended to do anything but scrap it. My initial thought was to either sell a few easy parts, such as the carb, CDI, etc., and scrap the rest, or perhaps sell it whole as-is for parts or a project bike. However, upon closer inspection, I noticed a few things that grabbed my attention: The bike still had the factory original tires on it, which were in good shape. All the wheel bearings and seals were in good condition. Although the cosmetic condition was very weathered, the bike was remarkably untouched and noticeably sound overall.

So what does all this mean? It means that the bike probably didn’t have any real hours on it, and thus the mechanical condition was likely in decent shape requiring only minor restoration. My theory was that the bike was adult owned and ridden for most of its life and perhaps was later passed down to a kid who promptly broke it and left it out in the weather for a couple of years. With this in mind, I decided to see what it might take to get it running. If it could be repaired easily, I could fix it up and it would be worth around $1200 to $1500. So I pulled it up in the shop…

As I looked it over, I made a few notes. The one thing I knew it needed immediately was a carburetor and a hot battery. I already knew the chassis was in good shape, so if the engine ran good, all it would need was a quick cosmetic restoration. The good thing about being in the parts business is that I usually have a few spare parts laying around. While I didn’t have a carburetor for a 350 Moto-4, I did have one for a 350 Warrior so I decided to make it work. I cleaned it thoroughly and found an intake boot. I then installed the assembly using the Warrior throttle cable (P.S. The aftermarket intake boot is ridiculously fragile. They split easily. I went through two of them on this project).



Warrior Carb on the Moto-4 Intake Boot




Well, good news and bad news. The good news is that the engine ran. The bad news is that it was a total travesty. The jets in the Warrior carb were too rich for a stock setup, so it ran poorly and smoked. Also, the cam chain in the engine was rattling and the starter clutch was going out. Decision time: Do I scrap the project or order some parts? For me to make any money on this thing, I need my total investment to be $500 or less. So I needed to guesstimate my total parts bill if I fixed this thing from one end to the other in order to sell it for a good price. It’s always a bit of a gamble, but I ran some loose numbers and given my access to used parts and my discounts on new parts, my figures indicated I should be OK. Theoretically.

So I went for it. I ordered a carburetor kit for around $20 and a D.I.D. cam chain for $25. For the starter clutch, I went used. I got on eBay and won an auction for a Warrior flywheel, starter clutch, stator assembly, and stator case, all for $55 (the Warrior and Moto-4 starter clutches are interchangeable). I only needed the starter clutch, so I kept that and resold the bare flywheel for $35, and the stator w/case for $85. So that puts my total parts bill thus far at -$20. I’ve already made 20 bucks and I haven’t even done anything! I love eBay! Moving on…

So I pulled the carb back out and installed the kit:



Using the stock jets seemed to fix my rich burn problem. The engine ran pretty good, albeit noisily. I jumped on it to test drive it and check the clutch and transmission. It actually drove pretty good and had a lot of power, but unfortunately it revealed a few other problems. The engine smoke didn’t clear up and the centrifugal clutch wouldn’t disengage. This project, like most, was rapidly snowballing.

Oh well…in for a penny, in for a pound. I decided to disassemble the engine and assess the damage. If my hunch was right, all it would need is a set of rings, and since I already had to partially disassemble the engine to replace the cam chain and starter clutch, it would only take a few more steps to install a set of piston rings.

First I addressed the centrifugal clutch issue. It turns out that the shoe springs had fallen off somehow and were digested by the transmission. Hmm….I’ve never quite seen that happen before, but there’s a first time for everything. After ordering and receiving the wrong springs twice, I decided to replace the entire centrifugal clutch assembly with one I had on the shelf which was out of a 1995 Kodiak 400. Success!

Then I began the main teardown. I removed the head, cylinder, and then the stator and case and of course the flywheel/starter clutch assembly (this requires a special tool) and I was then able to remove the cam chain.



Cylinder Head Removed



Cylinder Removed

Once removed, I saw that the piston rings were worn. I made note of the size and ordered a set for around $20. The cylinder was in decent shape for the most part, but there was a slight ring ridge at the top. Rather than risk breaking my new rings, I used a Zimmerman Ridge Reamer to remove the ring ridge. Some of you old-timers may know what that tool is. It’s a cutting tool invented by Herman W. Zimmerman in 1935 that’s designed to cut ring ridges much like a boring bar would. It worked perfectly. I then honed the cylinder and installed the new rings.



Reaming the Ring Ridge



Cylinder Installed

To install the new starter clutch sprag, I first had to remove it from the Warrior flywheel and install it on the Moto-4 flywheel. While many would mistakenly believe the two flywheels are interchangeable, they are not. If you look closely you will see the ignition pickup surface is longer on the Moto-4 and is located in a different position.

It is very difficult to get the bolts out of these because when the factory installed them, they took a punch and smacked the end of the bolt after it had threaded through. This was to swell the threads and prevent the bolt from becoming loose. Since they are Allen bolts, you can’t get much torque on them without rounding them off. So what do you do?

I took my angle grinder and gently ground off the swelled end portion of each punched bolt. I ground it down smooth with the surface as seen below.



Using the Grinder



Bolt end ground smooth.

I was then able to take my impact driver and remove the bolts manually.



Removing the bolts with an impact driver.



Once ground smooth, the bolt turns easily.

Then it was time to install everything. It worked out good. The engine started smoothly with the new starter clutch. It ran quiet with the new cam chain and did not smoke with the new rings. It also shifted perfectly with the new centrifugal clutch. So now I’ve got a good, running ATV with only about a $20 parts bill and lots upon lots of labor. Oh, and it still looks like trot-line weight. So now it’s on to cosmetics…

I pulled all the racks to straighten and paint them. The rear rack had a noticeable bend in the top bar, so I had to use my torch to heat it until the metal was glowing and soft. I then took my pry-bar and straightened it.

While I had the racks, seat, and gas tank removed, I went ahead and sent the seat to be recovered ($40) and I fixed a leak in the gas valve as seen below. It was also a good time to wet-sand the fenders to bring the color back to them. I then replaced the left rear mud flap with a New Old Stock (NOS) flap I had on the shelf. I also fixed the tail light and installed a new lens that I had on the shelf.


Repairing Gas Valve

The last little bit I had to do was fix the rear brakes. It utilizes a cable-operated mechanical disc brake. I had to replace the hand cable, but the foot cable was good. Fortunately, the pads and caliper were in good shape. All I really had to do was clean and properly adjust everything.

I pulled the right rear wheel off to assess the situation, then I disassembled the brake assembly:



I cleaned and painted everything. It worked like a new one.



After the cosmetics were cleaned, painted, polished, and whatever else needed, I began the most important part: installing my favorite accessories.

I generally utilize the same type of accessories on all of my utility ATV’s. Although I’m building this one to sell, I still may use it around the yard or as a backup until it sells, and I like to have all the features I’m used to. These include: auxiliary lighting (specifically on the rear), CB radio, and a good winch.

I started with the winch. This ATV already had a winch, but not much more. There was no auxiliary winch solenoid or wiring. The winch was an old-school 2,000 lbs Super Winch mounted to a thick steel plate on the front rack. It worked great but needed to be wired properly. First, I needed a solenoid. I had a good single-wire unit on the shelf, likely from a Polaris. I found a place to mount and ground it to the frame. Then I wired from the winch, where the main operation toggle was located, to the battery. I then wired a master On/Off switch so the solenoid would not engage and the winch could not be operated unless the main switch was in the “on” position. This is a safety feature that prevents the winch from accidentally engaging when not in use.



Winch Solenoid




Once the winch was taken care of, I proceeded to the other accessories:


Light and CB Radio

I installed the CB radio and antenna. The radio is a Cobra 19 Ultra III. It actually talks very well for a less expensive radio. The idea is to use a small, less expensive radio, not because I’m cheap, but because it will see rough service and potentially some weather, so if it breaks you do not want to be using a 29 LTD Classic. Next I installed the rear light and wired it to a toggle switch next to the master switch for the winch.



And that pretty much concludes this long ordeal of a project. I kept the quad for a few months, using it around the yard. It was a smooth riding machine with a very tight turning radius. I really enjoyed it. In fact, I would have liked to have kept it for a yard quad, but I’m limited on space so I had to make room for the next one. Here’s what it looks like now…







My total parts and supplies bill was very nominal, and after enjoying the quad for a few months, I sold it for $1300. Although the whole thing snowballed into much more than I had anticipated, it was a fun, profitable project. That’s all I can ask for. On to the next one!

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