Re-assembly and Plastic Refurbish

With the engine finally running well it is time to get this quad looking nice. The plastics are fairly sun faded and will need to be cleaned up. I also discovered the front guard was faily bent and needed some repair.

Plastics: Many people think that the best way to fix plastic is to squirt some Krylon on thick and call it good. This is the worst thing you can do to restore plastic. The first thing to do is scrub all the oxidized plastic off. I use a power sander with 120 grit paper. Sand it until there is no fading left. Don't panic about the scratches. Once all the fading is gone switch to a grade #00 steel wool. Scrub the scuffs out, and yes this will take some muscle and time. Now change to #0000 steel wool. Once again a lot of time and muscle. Concentrate on the corners and crevices and make sure they are clean. At this point the plastic should be clean and almost shiny, but still a little dull. The final step is to apply either an Acrylic finish (easy!) or a clear resin finish (more difficult).

To apply an Acrylic finish simply get under the sink and pull out a bottle of floor finish like Future. Verify all the dust if off the plastics and then rinse them off. Take a new sponge and dampen it. Spray the Acrylic floor polish on to the sponge and apply an even coat onto the plastics. I simply pull the the sponge evenly the full length of the fender. Acrylic dries very fast so don't try to touch up anything. Simply apply another coat in twenty minutes. Don't apply more than a coat or two or you will get some flaking.

If you do have a paint gun and some clear coat you can really spray a thin coat that will last a very long time.

Mikuni Carburetor Troubleshooting

I finally got the O-ring in and I ordered a main jet in just to make sure. I removed the Carburetor from the engine and put it on the bench for dissection. I drained the bowl of gas and removed the bowl. I removed the main jet and replaced it with my new 112 jet. I inspected everything and put the bowl back on. I replaced the cracked O-ring with a new one. After reinstalling the carb and hooking everything back up, I cranked the bike up. It idles perfectly! I back it out of the garage and shift into first gear and off I go. Sputter..... sputter.... same problem. Hum...... I pull the plug and the plug is black and sooty. Running rich...... I drop the needle on the throttle valve all the way and try it again. Same result. Maybe the choke is stuck open? I check the choke to verify it is sliding in the cylinder fine. I adjust the choke cable out as far as it will go and re-install it. Same issue. I check the timing which is perfect. The carburetor seems fine. Only one problem could exist if it is a carburetor problem. The main air jet must be plugged. The air jet is a small hole that starts just under the main air intake on the carb and continues into the main jet primary. The air jet is the metering circuit between 1/4 to 3/4 throttle. With it being plugged the fuel does not atomize and the raw fuel will not burn properly.

I disassemble the entire carb and let it soak for twenty minutes in parts cleaner. After rinsing it, I use my small needle pick and insert it into the air jet primary. As expected it is plugged with gunk. I clean it well and squirt some carb cleaner through it.

I re-assemble the carb and put it back on the quad. I turn the gas on and allow the bowl to fill. It starts up as before but this time as I give it the throttle it takes off with no stutter or back fire!

Installing The Engine Back Into The Frame.

Mitch and I had a very busy weekend! After the football practice, Mitch and I stopped at Weinersnitzel and bought a couple corn dogs to hold us over, then went straight to the garage to work on the 225!

The first thing we did was load up the quad and engine into the back of the truck and headed down to the car wash. Five bucks later all the grease was off and ready for the wire brushes. After unloading everything and getting the motor brushed and the frame scrubbed and wiped clean we were ready to put the engine in the frame.

The engine is mounted in the frame on the left hand side.

Verify the driveline boot is secured on the rear end side. Lift the engine and place it into the frame drive shaft first. Line up the drive shaft and the cross joint, working the engine in and back until the drive shaft and cross joint mesh. Lift the engine into the rear motor mount and slide the long bolt in. Next, secure the mounts that attach to the head. Third attach the mounts to the front of the engine and last the rear top mount. After you have the bolts inserted in all the mounts you can tighten all the mounts and attach the drive line boot.

Insert the starter motor and secure it. Attach the reverse indicator wire, neutral wire, and any other breather hoses and wires. This is a good time to install the carburetor and airbox. Verify all your cables are in the correct location and install your gas tank. Install the front fenders, and top cover. Install the handlebars and plug everything in. Install your battery, and verify everything lights up appropriately. Install the rear fenders and put the seat on.

Put 1.5 liters of oil in the engine. I like to pull the spark plug on a dry engine and then crank it for thirty seconds to allow the oil pump to fill the journals full of oil before I start it the first time. Install the spark plug and fill the gas tank. Turn on the fuel cock and allow the bowl of the carburetor to fill. Crank it over and wallah! Mine started right up. I had to adjust the clutch a little and off I went for a test drive. The gears feel good! No noise or strange sounds coming from the transmission! The only problem is that when accelerating the quad cuts out quite bad. My guess is the o-ring on the carburetor that I decided not to change out. I imagine it is sucking air under load. I guess I will get that ordered tonight.

Sub-Transmission Fixed!

The gears finally arrived from Canada yesterday and everything looks good! (Thanks eBay). It took me a while to remove the damaged circlip from the end of the Counter axle but finally was able to remove the circlip and the damaged gear. I cleaned and lubricated the new High wheel gear and placed it on the axle and secured it with a new circlip. With a few taps I was able to synch the new gear in with the High pinion gear and drive gear. I started assembling the other gears into the sub-transmission and noticed the reverse gear had also sustained damage. Luckily that gear had come with my Canada package.
I applied a thin layer of gasket maker and tapped the cover into place. I turned the drive shaft and everything felt smooth as silk. Problem fixed!

Waiting.....

Still waiting for those Canadian gears.... While waiting I decided to put the case back together from checking everything out. It took me a while to put the segment back on the shift cam. I had messed up the pins and had to figure that out by running through the gears a couple times. With the segment installed I was able to install the shift shaft and oil pump. I installed the oil pump gear on the crank and with the new gasket, installed the crankcase spacer. I was able to install the clutches quite easily and buttoned everything up with new lock washers. Just as I was about to put the engine cover on I noticed the compression spring for the clutch was missing. After looking for thirty minutes the spring could not be found and so the cover could not go on, grrrrr! the spring has been ordered and I am back to waiting......

More Trouble

I went down to the Yamaha shop a couple of days ago and picked up a new set of bearings. I was excited to get the transmission buckled back up so I put the new seals in and tapped the bearings into the holes and put the pinion and gears back in the sub-transmission. As I turned the drive shaft it feels tight but it does not sound too good. I looked everything over and tapped the cover back onto the gears. I turned the drive shaft and.... yuck. It won't turn and when I force it it sounds like I am grinding coffee. So what is the problem? Taking a closer look at the main high speed gear. There is just enough damage so that the gears don't mesh, and of course I did not mark the gears when I pulled them out so the damaged teeth are not matched to the damaged teeth on the other two gears. Well $@#$..... I guess it is time to buy new gears.

I searched the internet high and low and finally found gears for sale from a dealer back East. I clicked the "checkout" and got the gears on the way, I thought. The dealership called me on Monday and told me "the gear is not made anymore and we will refund your money".

On to Ebay. I found a scrap yard up in Canada that was selling the guts to the sub-transmission for $100. After some negotiation I was able to get them for $50. They should be here in a couple days, I hope.

The Diagnosis

Tonight I decided to see what was keeping the YFM225 from shifting correctly. If you will remember the former owner claimed the YFM stopped shifting after trying to pull start it. With the engine on the bench I pulled the crankcase cover and inspected the shifting shaft and shift cam. This all looked good so I decided to open the sub-transmission cover. As I cracked the cover I noticed the remains of a bearing sitting in the lowspot of the sub-transmission where the shift cam comes through. I pulled the middle set of gears out and found the bad bearing. Luckily the outside race was still whole and the structure around the race, although beat up, was not damaged to a point that if could not be used. The inside race was almost completely destroyed but surprisingly the shaft had no damage. I was able to slide the damaged race off the shaft and with a little work, pull the outside race out of the case. I was very lucky that there was not more damage done to the sub-transmission with a gear jumping around inside. I split the case and inspected the primary gears, shift cam, and shift forks, which all looked good. With the debris not impeding the movement of the primary shift cam, the gear movement worked well and slipped into all five gears. I put the two halves of the case back together and called it a night.
I will not only order the bearing that came apart but will replace corresponding bearing on the other end of the shaft.

The tear down

I got home tonight and decided to start tearing down the quad to make it easier to work on. I started with the racks and the front guard. I noticed it had been damaged fairly bad in a collision and could probably not be repaired easily. I was able to find a good used replacement on ebay for $35 with shipping and so I purchased it as a replacement. After all the racks were off I uninstalled the rear fenders. This gave me good access to the left hand side of the engine where the clutch and shifting mechanism is located. I drained the oil and pulled the left cover. I removed the clutches and started inspecting the shift rod and cam. I did not see any physical damage but while manipulating the gear I noticed I could shift out on neutral into first and second gear. I could shift back into first gear but not back to neutral with out a lot of messing around, and could never get the quad into third gear at all. This has lead me to believe that either the shift forks are damaged or the shift cam grooves are damaged. Not the best news considering it means I will have to split the case to get at the damaged equipment.I pulled the front fenders, which meant pulling the handlebars and unhooked all the cables and tubes from the engine and carburetor. I removed all the mounting bolts and with a little muscle I was able to pull the motor and get it onto the bench.

I am again impressed with how well this quad is put together. Everything is heavy duty and well thought out. Although the frame is dirty the powder coat has protected the metal very well.

The pick-up

Well here is how it all happened:

Last Saturday I was looking through the classifieds and spotted the quad, a 1986 YFM225 Moto4. I have a weak spot for these old quads, not only because they are bullet proof, but because you can get them for rather cheap. I called up the owner and made arrangements to stop by on Sunday before the Vikings playoff game to take a look.
Like many wives with husbands that have to have a greasy project, my wife does not share my love of old quads and bikes and so whenever I start itching to start one of these projects she starts figuring out a way to deter my ambitions. I had schemed in my little brain on how we could take the truck to my sister in laws to watch the playoff game without making it obvious that I had already slipped the 300 bucks into my pants pocket and planned to bring my project home. Like most wives, my wife is also much smarter and craftier than me, and as I tried to announce we would be taking the truck, she had already loaded up the Sequoia with the veggy pizza and bruschetta we would consume later that day.
After stuffing myself with enough chicken wings and buffalo burgers to keep Tyson in business for another month. I grabbed my brothers in law and out the door we went.

The quad was parked by the side of the owner's house and after some small talk I found out that Clark was the original owner! The fenders have a little sunburn on them from sitting outside the last couple years, but all in all the quad is in great shape. I looked under and inspected the swing arm boot to avoid the nightmare and expense of rebuilding the rear-end like in last years project. Clark explained that the last time he had been out riding it was a little cold and it was not starting. He tried pull starting it and when he popped it into gear it stayed in gear and would not come out..... hum. After thinking of the many things that could have bent and broken, I figured it was a project and had fixed worse. I gave Clark my money and told him I would be back on Monday evening to pick it up.

Monday came quick and I stopped by, got my bill of sale signed, and title in hand. I had Vern (brother in law) help me lift the old quad into the truck. After tying it in and dropping Vern off I headed home.

A little history of the YFM225 Moto4

Yamaha first introduced the YFM225s Moto4 in 1986. This was an upgrade model from the YFM200DXS. The 225 not only had more power but also a dual range transmission, dual headlights, speedometer, trip meter, and was a larger machine all the way around.
The cylinder and head used the same basic overhead cam configuration that Yamaha introduced into the 200cc four stroke motorcycles starting in 1980. Below is listed the model numbers and corresponding years.

1986 YFM225S
1987 YFM225T
1988 YFM225U