I am writing this in hopes of helping someone else with a TRX90. The fuel in the tank must have been years old. It smelled prehistoric. I imagined the carburetor was going to look like it was full of rubber cement.
The neutral light did not work even with the bike was in neutral and the starter would not click or engage at all — not surprising with no neutral indication.
I took all the plastics off the bike and gave it a good pressure washing and inspection. I disassembled the fuel tank and cleaned all the old gas out. Surprisingly the in-tank strainer was still okay. I removed the carb, carefully disassembled it being careful of gaskets and o-rings as I didn’t have a rebuild kit and cleaned it out. It was full of scaly flakes – really full. The slow jet was completely clogged and could only be unclogged using a very small diameter piece of wire and a lot of solvent. The main jet wasn’t much better but it wasn’t completely clogged. After a good soaking in solvent, I cleaned and blew everything out and reassembled.
The engine oil was black and a lot more the consistency of water than oil. I changed it and added new oil. The chain was okay but bone dry.
I put a gallon of fresh fuel in the tank and one of the fuel lines broke. A quick trip to Advance Auto and new fuel lines were installed. Should have done this from the start.
I always remind myself that when a bike is running poorly that you can almost always solve that issue in less than an hour with a good carb cleaning and fuel system inspection. It is easy to think it will clear itself up with running but that is not often true.
Still no neutral indication and no starter. Push starting the bike it did fire up and ran pretty good. After about 15 minutes the bike ran strong. I adjusted the idle speed down and it would just sit there an idle perfectly.
I’ll take a look at the valves soon but the idle is so smooth and the top end feels strong enough that I did not prioritize this task.
I pulled the left rear crank case cover and discovered that the neutral contact switch was broken right where the single bolt attaches it to the case. The contact plate that bolts to the shift drum was damaged as well. Just for fun, I grounded one of the contacts of the switch and the neutral light came on and the starter engaged and started the bike! That was good news. Parts ordered. Since this switch was going to be replaced, I cut the end off, grounded the neutral switch and cut the pink wire. Now the neutral light stays on in all gears and you can start the bike in gear. This will be fixed when the new switch comes in the mail. Cutting the pink wire does seem to make a difference in how fast the engine revs. I’ll write more when I put the new switch in and reconnect the pink wire.
The bikes shifts normally most of the time. Sometimes the shifter gets hung up and needs to be downshifted and then the upshift occurs normally. Also, it has popped out of 4th at full throttle a time or two. I adjusted the tensioner several times with no change in behavior. If it doesn’t clear up by the next oil change I’ll see what there is to see.
The bike needs tires a few brake adjustments, a chain tightening and a good all-around lube and I think my 9-year-old will be happy. I do think the old 125 might be a little faster. The TRX90 is definitely a lot lighter, more nimble and a lot more comfortable. Maybe Honda did it to save weight and keep the price down but I am surprised there is no reverse or recoil starter. The ’86 has both of these features.
I don’t have any experience with other brands of quads but I do have 5 Honda quads and 1 Honda dirt bike. I continue to be impressed by the durability of these bikes and the relative ease of working on them. They are simple straightforward machines that are very honest. Hope to get another 10 years out of the TRX 90. I have a 9-month-old who will need a bike in about 5 years!
Hope that helps someone,
Hank
