I agree, the Suzuki doesn't like to 'lug down.' It would be interesting to find out what rpm the engine is at when it 'bogs and complains.' Mine certainly does that, too, but, my guess is we're below 2500 rpm. I think the rev-limiter on our quads is 9000(?)...

For reference purposes, I like to break an engine's rev band into fourths. The first fourth is the lug-zone, where long-stroke, mildly-tuned engines can generally operate satisfactorily. For the Z400, that's idle to 2250rpm, and they don't like heavy throttle in that band.

The second fourth is what I call bottom-end, i.e., the bottom end of the actual power band. For us, 2250-4500 rpm. Here, we're rolling into good, usable power, although the engine isn't really happy, yet.

The third fourth (mid-range) is where most of the work happens: 4500-6750. LOTS of throttle response/torque, our very trick cylinder head coming into its own. This is where the Hondas run out of talent.

And, of course, 6750-9000. The engine is shrieking with glee, although the power is beginning to taper off. Of course, it's still stock...

 

Check out the dyno for the Titanium 4 and PowerBomb on FMF's web site (www.fmfracing.com). Stock the bike makes max hp at about 6,800 RPM. With the FMF setup it makes max power at something like 8,400 RPM. It's going to be bumping up against the rev limiter at near max hp. This is a ride I am looking forward to!!!

 

That bumping the rev limit deal is no joke. I drilled out both the pea shooter end on my silencer as well as putting a 1 3/8 inch hole in the plate inside the silencer and now whenever you run through the gears hard you will hit the rev limiter in 1st and 2nd pretty quick. And I left the spark arrester intact. It made a seat of the pants difference but I still intend on replacing the pipe with a White Bros at a later date.

 

<< I make a distinction between &quot;low end power&quot; and &quot;throtle response&quot;. Throtle response is pretty good on the Z, it's low end power that I feel is lacking. The bike just doesn't like to lug down. You can't just punch the throtle coming out of a turn. The engine will bog and complain (and sounds like a lawnmower!!), A DOWNSHIFT IS MANDITORY, LIKE ON A 2-STROKE. >>



I agree. I guess I am just looking for a way to keep the motor from &quot;lugging down&quot;. I am not the best rider in the world and sometimes I miss the downshift. The other time I notice it is trying to cut doughnuts in wet sand, or powerslides in wet sand. I know if I get better at shifting and clutching, some of these preoblems will go away. I really think I would be happier with slightly lower gearing.

On another note, throttle response is awesome. The power comes on smooth and quick. I just do a lot of riding in second gear.

 

I was talking about low end pull not throttle response when I said this bike will PULL taller gears AFTER you invest in exhaust. It pulls great right off the bottom grunt and downshifting is NOT as necessary as you would think after you install your exaust. Exhaust really does wonders for the Z. I've got cams, piston, and FCR 40mm carb on the way and will post on how it peforms.

 

<< I drilled out both the pea shooter end on my silencer as well as putting a 1 3/8 inch hole in the plate inside the silencer >>



Could you describe where you put the 2nd 1 3/8 inch hole? How about pictures or a sketch? thanks.

 

You say no one posts gains about torque. The Trinity Racing pipe gains 6 ftlb of torque

 

So where can we see the Trinity torque curve??? Just a single number isn't very informative. The SHAPE of the curve is important also. If it increases by 6, where does it increase, on the top , on the bottom, everywhere????

 

Here:

http://www.trinityracing.com/news/index.html#3

Click on the first line of red type.

 

Thanks for the link, but how come they didn't show us anything below 35 mph??? (And, I would really prefer to see them use RPM rather than MPH.) 35 mph is about max for tight trail riding, so most tight trail work will be done below that speed. So, it's TO BAD THIS DOESN'T REALLY TELL US ANYTHING ABOUT THE LOW END!!! Guess I'll have to do my own dyno if I ever want an answer.

It looks like about 6 more ft lbs at around 45 mph, and maybe 3.5 at the higher speed. From what I can see, this motor makes its best torque in the mid range. Also, note that the SHAPE of the stock hp curve is almost identical to the SHAPE of the moded curve. This just serves to emphasize that a hp curve without a torque curve isn't good for much!