Research and Shopping

Shortly after the 2004 Terrible Towns 250, Team Guilty had the opportunity to acquire a big bore 330 for our 250R. The stock 250R was a bit short in the horsepower department compared to the new 4-strokes we were racing against. After purchasing the larger cc motor, I spoke to some other teams that were using this type of motor to find out the pros and cons of it.

The main issue that kept coming up was the transmission gear failure. The increase in horsepower from approximately 30hp to 55hp+, puts significant added stress on the gears. The transmission was not designed for that kind of horsepower, so we were in immediate need of some beefier gears for our motor. Doing some searching we found a number of companies do make stronger gears for this application. We went with the Yukon heavy-duty chromemoly transmission gears available exclusively from Duncan Racing or Baldwin Motorsports.

In this first article of a two-part series, we will get into the process of tearing down the motor.

Tearing it Apart

Before you try this at home, be advised that you should have some mechanical abilities, as it requires splitting the cases and a few specialty tools as well. As always, a Honda Shop manual is a good thing to have on hand. You will need torque settings and other need-to-know items that are found in there. If you are not mechanically inclined, leave it to your professional ATV technician at your local shop who will be happy to assist you.

Before you remove the engine from the frame, drain all the fluids out of the motor so it won't spill on you when you remove it from the frame. That has never happened to me but I know people it has happened to! (Even if I did, I'd never admit it...) You can also replace the top end, piston etc. Replacing the clutches is not a bad idea while you have it apart. You will need a flywheel puller and a special tool that holds the crank so it doesn't move while taking the large nut that holds the clutch basket on. It's very difficult but not impossible to do without it.

There is a special lock washer that should be replaced. It holds the nut on that secures the clutch basket assembly. Make sure you have a gasket kit that includes the water pump gaskets and it's always a good idea to replace the water pump seal. While you have the side cases off, inspect the clutch basket fingers and hearings for wear. Replace them as necessary. Pay close attention to the kick starter assembly as this can be a bear to get back together. If you have a digital camera, take a picture of it. This is where the shop manual really comes in handy.

Be sure you clean all the gasket surfaces thoroughly, trying not to scar the surfaces while you are scraping the gasket material off. When putting the cases and side covers back on, this will help keep them from leaking. The last thing you want to do is to take the engine apart again because of a small oil leak.

You should now be ready to split the cases. There is a special crankcase separator you can use to make the job easier. It's not required but is helpful. Attach the puller to the right side crankcase and tap the cases in different areas to separate them. Some residual oil will leak from the crankcase. Let the oil drain out and clean it up before moving on to the next step.

Next Month - Part II - Replacing the Gears

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