Top Speed Woes

[Wekadog]

Whoo hoo! Lady Suz'i and I just got back from our first ride. Her first outing in close to two years. All it took was removing the carb to clean out the gum. And then removing it again to get the needle jet the right way around. We looked a bit silly with my car battery strapped to the pillion, but I couldn't wait for the mail order battery to arrive. Fresh gas and a 20 mile ride, and she's not running too bad.

There's a lot of backfiring on deceleration, I'm not sure what that's about. With only 350 miles on the clock, there shouldn't be any stretching of the timing chain.

But what concerns me more is the limited top speed. I couldn't quite make 65 mph on level gound, and it dropped to 55 on a mild hill. That's with me weighing just 190#. My Honda Rebel 250, a very mildly tuned low compression engine, easily did 75 if not 80 on the same level stretch, even when I weighed 220#. I was counting on similar performance.

What especially worrys me is that the PO mentioned he stopped riding Suz'i in the first place, when she was still new, because it couldn't top 65 on the freeway. So it's not a maintenance issue? Not some residual gum in the carb or valves from storage? Do they build bad ones?

Where would a person begin to look in a case where there's not a "failure" behind the problem?

Your guidance and wisdom are appreciated.

[alantf]

Where would a person begin to look in a case where there's not a "failure" behind the problem?

On the shelves of the store that sells carb cleaner (seafoam etc) :) Try running a coupla tankfuls, & see if that helps. Don't forget that the engine is still running in, and may be tight for a few hundred miles yet. You should be going at no more than ½ throttle for the first 500 miles (from new), then no more than ¾ throttle for the next 500 miles. I've had mine for over 5 years, & it runs fine, but until the engine loosened up, it ran like shit. When I first came across this site, & learned about the need for carb cleaner in the fuel, from the first tankful (with a fully run in engine) the bike ran 100% better. Much smoother. :2tup:

[Water Warrior 2]

First off you may need to give the bike a dose of Sea Foam. Backfiring(actually afterfiring out the exhuast) may be a sign of lean running with a Cali spec bike. Also check for an air leak at the rubber boots on the carb. Both intake and discharge sides.
Question, did you do an oil change? I would recommend fresh oil. And the bike isn't broke in yet either so you have a tight engine needing some break-in time to smoothen things out. Use regular gas, no high octane is needed and is just a waste of hard earned $$. Check your tire pressures too. I used to set Lynda's GZ for 2 up riding. Slightly higher in the rear tire for 2 up. On long rides I would exceed the manual #'s by 2 or 3 PSI for better tire wear and mileage.
Oh yeah, before you put the new battery in service make sure you fully charge it up or it's service life will be shortened.
Ah, I see Alantf is way ahead of me.

[PimpS]

Don't push it too much. Like said, she's breakin' in... Running in...

[raul10141964]

my was the same so I mod the carb an now can cruse at 75+ mi
my settings are
pilot 3 turns
main jet 140
needle mod
16T

[edison]

raul10141964
What's the nidler mod? :??: How much does it cost to do all the mods you did? If i could hit 75, I'd be set! 65 seems to be my max....

[Water Warrior 2]

raul10141964
What's the nidler mod? :??: How much does it cost to do all the mods you did? If i could hit 75, I'd be set! 65 seems to be my max....
That would be a slip of the fingers. Actually "needle mod" is likely what he meant to say.

[raul10141964]

you are right is needle mod
i mode the air filter to but do not mod the filter without change the jet
or the bike will not run

http://s9.postimage.org/eqlonjb17/IMG_20120830_110644.jpg (http://postimage.org/image/eqlonjb17/)

[Wekadog]

Thanks to all for reminding me about the break-in period. Somehow, I wasn't thinking of this '09 model as a "new" bike, but in terms of miles . . . it is! I'll schedule some easy rides through the lemon groves this weekend. Right after I change the oil. In general I'm a bit leery of snake oil . . . um, Seafoam, that is . . . but I guess it can't hurt. Just this once, I'll make an exception.

It's good to know there's a mod I can do if need be. I hear it's a real chore getting the air/fuel mixture right across the entire throttle range after a jet mod. I really prefer to benefit from the long hours of work the good Suzuki engineers spent on the issue. But if, after break-in, she still won't go on the freeway, I can see a jetting project in my future. Best to begin with a mod that's been worked out before.

"pilot 3 turns
main jet 140
needle mod
16T"

I presume "Needle mod" refer to shimming with a washer as described in the " Needle shim modification" thread. And does "16T" refer to a 15 to 16 tooth front sprocket modification. It all sounds easy enough. Thanks for that.

About how much additional difference did opening up the air filter make after rejetting?

[Water Warrior 2]

Shimming the needle is quick and easy. Years ago a friend had a Yamaha DT 200 that was just horrible at low RPM. I quickly made an adjustment and it ran much better. Much more user friendly at slow speed and manuevering in the bush. My bike at the time was a 200 KDX and rejetted after break-in. It was really a lot more confidence inspiring with the new jetting. Both of these bikes were 2 strokes but the same rules apply. You need the right mixture to be happy.

[jonathan180iq]

I presume "Needle mod" refer to shimming with a washer as described in the " Needle shim modification" thread. And does "16T" refer to a 15 to 16 tooth front sprocket modification. It all sounds easy enough. Thanks for that.



Yes. 16T is an "upgrade" to the 15. It's just one size larger. Some people love it. Some people dislike it. If you live in the flats, it's worth a shot.

[raul10141964]

if you combine the carb and filter mode you have the power to run the 16T on hills
crusin at 70 to 75 mi and on flat 80+