View Full Version : GOOD INFO FOR NEW 400EX OWNERS

01-23-2002, 04:13 PM
I bought a used 2001 Yellow EX 400. I love it. I'm pretty much a maintenance nut when it comes to my toys. Treat 'em right, and they usually return the favor. It came with a Curtis Sparks exhaust system. I have a few questions. I appreciate any and all info you might share with me.

The oil in it appears to be a bluish/green color. It looks really clean. Is this some kind of synthetic? If so, should I stick with synthetic, or is regular Honda GN-4 good oil to use. My buddy gave me a couple gallons of GN-4, I would like to use it up, but would switch to synthetic if it would benefit the quad. So I guess I'm asking which is the best oil to run in it?

I would like a spark arrestor for the exhaust. I ride in some federal land, and they require one. Does anyone know if Curtis Sparks offers one, or another brand that will fit?

Is the CDI rev kit worth the $100, or does it threaten the quads integrity?

I'm sure I'll have more questions soon, thanks for your time.

01-23-2002, 06:24 PM
Ok, alot of questions i will try and answer them the best i can.

1. Im not sure about the oil color but i would change it and stick with a synthetic or synthetic blend ,but no car oils. Only use oils designed for motorcycles. You can use the gn4 for winter but when it gets hot out i would change it to a synthetic/ synthetic blend because it breaks down very easily.

2. I don't know if you can get a spark arrestor for it without buying a new exhaust. Your best bet would be to call or email curtis sparks and ask. His website is http://www.sparksracing.com/

3. the rev kit is not worth it and makes it impossible to start when it gets cold. Don't buy it and spend your money elsewhere.

I hope i helped.

01-23-2002, 09:27 PM
Find out for sure if the oil is a synthetic or not. Correct me if i'm wrong, but synthetics put a coating of lube on your internal parts that actually stays on there. If you use anything but a synthetic in a motor that was started on synthetic, you could do damage to the motor because a non-synthetic oil will simply run off the parts due to the residue left by your synthetic. If you're using a synthetic now, don't run anything but. Anyone sick of the word "synthetic" yet?

01-24-2002, 02:56 PM
were you in dirtwheels a while ago?

01-24-2002, 03:24 PM
I don't think I was in Dirtwheels.

On the oil subject. It seems every dealer I call and ask about the synthetic thing gives me a different answer. Most agree that you should not run a fully synthetic oil in the quad. They claim it will harm the clutch. One says run Honda GN-4, the next claims Yamalube was the best, one says run Belray, one says to use the Honda semi-synthetic blend.

I changed the oil, and put plain GN-4 in it for now.

All I know is, changing the plug on the 400EX is a pain in the butt.

01-24-2002, 06:00 PM
Heres the deal on full synthetic oils. The dealers tell you not to use it because most synthetic oils are for cars and using car oil is what will make your clutch slip and whatnot. The truth is that you can use any oil you want as long as it was designed for motorcycle usage. I ownly use maxima or klotz oil because first they sponsor atving and secnd they make a high quality oil designed for motorcycles.

01-24-2002, 07:32 PM
sounds to me like whoever had it b4 you ran kendall gt-1 oil in it,thats what i run and what curtis sparks recommends.i also run energy release additive in it.its expensive but sparks runs and recommends it.....

01-24-2002, 10:38 PM

I talked to someone at Curtis Sparks today. They told me about the Kendall oil.

Could you elaborate on the energy release additive. Where do I get it, and how much do I add? I would appreciate it.

01-24-2002, 11:57 PM
Interesting to see you here Quadfather...

Don't believe the crap about synthetics causing clutch slippage or not being able to change back and forth from synthetics to conventionals and vice versa.

I and many others here and on the 400EX e-mail list use Mobil1 15w50 Synthetic.

Personally, mine has some fairly significant power mods (for about the last year and 1/2), it's been raced cross country for almost two years - I'm still on the stock clutch.

The thing to watch for is that the oil you use is not labeled "Energy conserving" which means it has friction modifiers blended in. Mobil1 15w50 is the only Mobil1 that is not labeled as such (many lighter weight oils are "Energy Conserving").

Using Mobil1 is nice because it's a very good oil - but the best part is that it's readily available at Walmart, which comes in handy at times. If you feel that you need to have "Motorcycle" labeling, they make a "V-twin" version that will cost you $8/qt instead of $4/qt.

Also, the air cooled engine typically places many demands on engine oil, so I highly recommend a full synthetic in a heavier weight. There is no reason to use a synthetic blend unless you are trying to save money - blends do not exist because they perform better than full synthetics in any category, they exist to meet a price point.

I tend to avoid oil additives -- most of the time additives = snake oil.

Yes, Sparks does offer a S/A.

Don't bother with the CDI box, it will only make your quad not start when cold (I've detailed why in past postings if you want to look them up), and the 400EX does not develop any appreciable power beyond the 9200 RPM rev limit. It takes a pretty heavily modified engine to require CDI modification & if you've done that, you'll need an aftermarket connecting rod as well. Goto http://www.gthunder.com/ for dyno graphs, they have one with a WB CDI vs Stock on a modified bike, note there is no difference in power below the rev limit - which seems to contradict what the aftermarket will tell you (about them advancing the timing and such) - also note the power curve of a stock engine.

Other tips:

Double check your throttle adjustment if you haven't already.

Disassemble and lube all pivot points - especially the swingarm bolt, shock linkage bearings, etc.

Loctite any bolts that attach plastic, including the fuel selector.

If you do much jumping, gusset the upper shock mount where it attaches to the frame tubes.

Be careful and always use a torque wrench on the oil reservoir drain bolt.

You'll love OEM parts prices for the 400, much better than any other ATV out there.

When changing the spark plug, make absolute sure there is no dirt caked in the head.

Jet the pilot circuit more rich for easier cold starting. A 42 seems to work well for the majority of folks with basically stock bikes.

01-25-2002, 07:56 AM

Thanks for your info. It is much appreciated.

Believe it or not, when I bought th EX, I thought to myself, this is going to blow Gabe's mind.

My quad seems to fire right up in cold weather.

Could you expand a little on a couple of your points? Such as:

throttle adjustment

lubing pivot points

also, is there a trick to changing the plug? Such as removing some plastic or something? It took me way to long to do it, and I'm pretty decent with a wrench.

Thanks again

01-25-2002, 08:36 AM
For the plug, I had to grind down the outside edges of the spark plug wrench provided by Honda to even get it to fit down in the head far enough to extract the plug.

The XR400 comes with a nicer plug wrench than the 400EX does, but I'm not sure if it fits any better (If I remember correctly, it does). Other than that - there's no plug removal tricks I know of.

Pivot points - like any other bike or quad, they come poorly lubed from the factory. Common trouble areas are the swingarm pivot bolt - it's easy to remove and lube, but will cause you severe headaches if you let it go too long. I use a good synthetic grease on the needle bearings in the arm, and anti-seize compound on the whole length of the bolt. I usually do this about every 8 or 9 months.

The rear shock linkage pivots are caged needle bearings as well, there are 4 of them if memory serves me correctly. Make sure to take them apart when you are doing the swingarm and grease with a good synthetic lube to keep them in good condition and the suspension operating properly.

On the front control arms - Honda uses spherical bearings instead of the bushings used by most of the quad makers - I lube mine every so often, but taking hits on trees usually does them in before they go bad (on the lower arms). Strangely enough, buying a complete lower arm is cheaper than buying new bearings. So... I just replace lower arms every so often at $35/ea (yep, the whole arm - bearings, seals, ball joint, and all is only $35).

Throttle adjustment -

Honda ships (or at least, they used to) 400EX's and other quads with the throttle adjustment at the thumb throttle housing screwed all the way in - which does not allow the carb to open to full throttle. This needs to be adjusted correctly (much like the clutch adjustment). The problem is that most dealers don't catch this during their PDI.

The throttle adjustment procedure is pretty much common sense stuff for the mechanically inclined - I just pulled the boot of the air cleaner side of the carb and observed when the cable was adjusted to allow full throttle, I then verified that it could close all the way to idle, then verified with the quad running that it would idle properly and wasn't affected by turning the bars lock to lock...

01-28-2002, 03:01 PM
do you have a factory plug wrench(the one in your ex tool box)thats what i use.and i found energy release on the net and called them and ordered a quart,you use like 2 oz's.per quart of oil.i think one quart bottle is what i had and it lasted all summer.thats changing oil like every other ride.

01-29-2002, 09:37 PM
Thanks for all of the replies. Your info was much appreciated and very useful.

01-30-2002, 04:39 PM
good thread.. sending a copy to the FAQ fourm.. ;)