Suzuki LTZ400 Testing

Scroll to the bottom for the latest test results. Click on the dyno links to view a graph of the test results.






All stock LT400Z dyno run.



This is a stock run vs. reverse meg. slip on silencer, rejetted, and no air box lid. Note:
Due to the long head pipe any slip on silencer needs to be reverse meg. or you will
lose a lot of top end. Also beware that removing the air box lid will make this bike run
very bad unless you make drastic jet changes. I will post the proper jet changes as
soon as I have more testing done to confirm the needed settings.

These a-arms are both caster and camber adjustable. They are extended for MX use
but are also available in standard and +1 for XC. I have the joint holders set at 25
deg.The tie rod ends on the stock Z are the same as a few other quads use and I have
seen a lot of problems with them. I installed a set of tie rods and ends from a 400ex.
The stock shocks are 17" long. These shocks are 17.5 inches long and offer a full 12
inches of travel with this a-arm / shock setup.

This is an example of a new exhaust system and an updated intake system compared
to stock. The stock air filter is fine on a stock bike and I could find no gains on the
stock setup by changing filters. However the stock intake system is very well
balanced and if you make any change to it be ready to make a lot of other changes or
you will lose power. On a modified engine the stock air filter is a serious restriction at
high rpm and causes the bike to go rich at a setting that is fine for mid range .



This graph represents a GT Intake kit, Full exhaust system, and a set of cams. This
setup will be tested at the track prior to further development. One of the next power
related issues that I plan to address is the Carb. The cams that I am using in this
engine have adjustable sprockets on them and are available. I only have a few in
stock at this time.


This dyno graph has a 40mm FCR carb kit. This is a next generation FCR from the  
39 and 41mm carbs. It has a lot of improvements over the older ones, including an
accelerater pump that works correctly for an engine this size. It is shorter and uses a
revised air box to make everything fit properly. The only other things on this dyno
run are the GT full exhaust, and cams.


Oops- On the 400ex we installed wheel spacers and raced them for a long time on
the stock axles. Yes we bent a few but they held up very well. On the Z400 the rear
axle- we  bent the axle on the second time out. First one side, than the other, next
ride it bent back some on one side. I have to bend it back in the press to be able to
run my bike on the dyno. It bends very easy and yes Suzuki may replace them at no
charge for some people but if you do any rough riding you will bend the new one too
untill they make a change. I will install an aftermarket one on mine.

I have now been able to test a +1 1/4 swingarm with a no link shock setup. I have
tested it at 12 inches of travel and at 10.5 inches of travel. This combination has
made a huge improvement for MX.

With the engine work that has been done to date on this engine, it was very easy to
hit the rev. limiter before you were ready to shift. I used a wire harness from a
DRZ400, a wire harness from a LT400Z, and a CDI for the DRZ400 from
Yoshimura to move the rev. limit to 11,000 RPM. This was very expensive but was
worth the money and time for the usable power that it added. Yoshimura is
expecting to have a Cam, CDI, and Valve spring kit available by July sometime.
Tentative price for this kit is $730.00. You will be able to buy this kit thru G T
thunder or any Yoshimura dealer.