I want my zxr 400 to have more power

[westie]

I have a zxr 400 89 and I want more power.
I am prepared to do anything to it.
Its fun as it is but noticably lost power after first track day round last weekend. Am considering pulling it down, so any useful tips on getting more power would be greatly appreciated.
Thanks

[Wheeliemonsta]

Gidday Westie,
Best bang for bucks mod you can do to the 400's is a J.E Racing 450 cc big bore kit (If you planning on running in F3 next year then forget it as the class is reverting back to a production based formula for the 08 season...)

Best man you can talk on the subject would be Andy Bolwell, he's at the other end of the country, but a phone call is cheap...

03 437-0559

Don't expect something for nothing because that just aint how it works...

If theres anything that needs doing on your bike, then make that your first priority i.e optimise what you already have before you go looking for extra power, a correctly tuned & set up bike alone can give you an extra second a lap...

Cheers

[Masterchop]

Start by checking the valve clearances, they have a history of stretching valves (then breaking) on high rev down shifts.

If all is good with the valves, stick a pipe on it or gut the standard one,they are quite restricted.
Then a set of flat slide FCR carbs help with responsiveness and helps it breathe better.
If you want to spend some more mony get some cams with slotted sprockets and get it set up by somebody that knows what they are doing.
And some porting will help as well.

Of course if it is an SP it will already have the cams and carbs and a close ratio box.

[Hoon]

Check compression and balance the carbs. That costs nothing to do.
You need to confirm whether you really are down on power (and by how much) or just imagining it.
Top speed you should see about 220 kph with standard gearing if its in good shape. Thats about 13500 RPM in top gear. 1/4 mile a standard ZXR400 is good for 12.9s.

[westie]

Thanks to all above this is the info/guidance I am looking for.
Have done compression test today cold and will do warm one tomorrow.
1:110 2:110 3:135 4:135 not too good, but could be valves or rings need warming up.
I have a carb balance kit and have done my fireblade to the point where amps said it was fine when they dyno'ed it.
Will be taking off the muffler and trying out a new one(second hand tho).
If they make no difference then I will be gutting them for sure, little by little.
I am going to make a new fibreglass air box which will connect to the ram air ducts but not have the opening under the tank. Just have the air ducts connected to the air box where they go through the tank. Will try that out too.
Where are some good places to trial a bike for top end speed appart from the track days. Might end up at puke when ever possible.

[westie]

Check compression and balance the carbs. That costs nothing to do.
You need to confirm whether you really are down on power (and by how much) or just imagining it.
Top speed you should see about 220 kph with standard gearing if its in good shape. Thats about 13500 RPM in top gear. 1/4 mile a standard ZXR400 is good for 12.9s.

I found that on the long straight(taupo) if I throttled on it would lag big time and I would have to find a throttle setting that let me accelerate.
What do you reckon?????

oh and I have a set of zxr 250 gauges so I rev limit at 15000 rpm on them.Lol

[Hoon]

Probably jetting or someones been messing with your airbox. Sounds pretty sick to me. You really need to get it sorted before you even think about doing more mods as you'll just be wasting your money. I'd start by getting rid of any "improvements" and going back to standard airbox and jets. Once you have it running right in standard form you have a solid baseline to work from and can add the mods back in one at a time to assess their effect.

A sweet running standard bike is way better than a sick worked one.

[westie]

Probably jetting or someones been messing with your airbox. Sounds pretty sick to me. You really need to get it sorted before you even think about doing more mods as you'll just be wasting your money. I'd start by getting rid of any "improvements" and going back to standard airbox and jets. Once you have it running right in standard form you have a solid baseline to work from and can add the mods back in one at a time to assess their effect.

A sweet running standard bike is way better than a sick worked one.

Yep sounds like a plan that could lead to success.
I have had the bike for only one month. I have just gotten it rideable, so now I can have some fun on it. Last weekend was the first time I've ridden it. So I know how it goes, now I can make a start at getting it running good.

Got home at 8pm this evening from work and now have no time to work on it.
There's just not enough time in the day!
Atleast I left the battery on all day and its flat now. lol

[feral1]

Hey ya westie,

Your getting some good advice here. I would work firstly on getting the thing running right. then take it from there.
Once it is running solid and sweet, feel free to PM and i can talk you through some of the things my motor has had done to it.
Cheers
Feral

PS if you want a factory race kit manaul (for the '89 H model), pm me your email address and i'll get it to you for nicks.

[westie]

Have just gotten round to checking valve clearances.
Measurements taken to fit next available thingy.(what is the tool called again?) Tickness gauge I think
EX
1 2 3 4
.203 .178 .178 .178 .203 .178 .203 .203

.127 .152 .178 .152 .152 .152 .152 .152

IN

Standard clearance is EX 0.16 - 0.21
IN 0.12 - 0.17

Looks ok. Just a couple of rougue clearances which match up with the lack of compression on the two cylinders 1&2
Any suggestions on rectifying the rougue ones?

[xwhatsit]

Well the rough clearances in 1 & 2 are larger clearances than factory recommended. This won't mean less compression; you'll lose compression when the valves are over-tight and cause them to stick out into the combustion chamber once the engine heats up.

Having loose clearances, though, will cause a loss of power (the valve remains closed for a bit longer, opens later and closes sooner); although with them being out by a small margin, I don't think the loss of power would be very noticeable. Having loose clearances will also make for a noisy top end.

Is it a normal tappet valve arrangement, or do you need to use shims? If it's just normal screw-type tappets you might as well set the clearances correctly, very easy job.

[westie]

Well the rough clearances in 1 & 2 are larger clearances than factory recommended. This won't mean less compression; you'll lose compression when the valves are over-tight and cause them to stick out into the combustion chamber once the engine heats up.

Having loose clearances, though, will cause a loss of power (the valve remains closed for a bit longer, opens later and closes sooner); although with them being out by a small margin, I don't think the loss of power would be very noticeable. Having loose clearances will also make for a noisy top end.

Is it a normal tappet valve arrangement, or do you need to use shims? If it's just normal screw-type tappets you might as well set the clearances correctly, very easy job.

On a long shot - what if it were carboned seats or valves and they were disturbed on the track from getting thrashed for 20 mins, especially if the bike hadn't been run in a long time(possibly nana rider in the past) That could explain greater than factory clearance and loss of compression? The long shot being that a small piece of the carbon had come away and left a leakage?
But then they are equal compressions(1&2) and that would be an impossibility

It was a very noticable loss of power third lap from the end of first session (20 mins)

The tappets are not adjustable as far as I saw. I think they just get replaced(says the manual)

Something else was the engine wouldn't turn over by hand on the tyre when in gear and no spark plugs in??? Felt pretty tight

Thanks for the reply.

[westie]

Hey ya westie,

Your getting some good advice here. I would work firstly on getting the thing running right. then take it from there.
Once it is running solid and sweet, feel free to PM and i can talk you through some of the things my motor has had done to it.
Cheers
Feral

PS if you want a factory race kit manaul (for the '89 H model), pm me your email address and i'll get it to you for nicks.

Thanks for the manual feral. I am starting to work on it and hopfully be ready soon(or sooner)