fixing different exhaust temperature

[tomacGTi]

Do the cylinders come back when revving the bike or up higher on the tach?

Randy, yes, it does return back to idle at a lazy pace, it takes 2-3 seconds. This was today when it was idling correct and warmed up. What does that mean?

Thanks!

Sync your carbs...

Also, usually means that you're a little lean if I remember correctly on idle. I would do 2 1/2-3 turns and see how it is. When you're happy, then sync the carbs.

[tomacGTi]

http://www.randakks.com/TechTip72.htm

Good page to read up on for the basics. Factory Pro has a good one as well.

[AlanDog]

Mixture screws out to 3, carbs are synced, idles cold (with choke) and warms up nicely, but still weak acceleration in the mid-range and top-end. When I bought it, it was stronger, but the exhaust really smelled of gas when it idled, so maybe the mixture screws were way out and maybe the fuel leaks helped the WOT performance... 

In any case, I'm wondering what the next step is. Should I invest in a Factory Pro kit? Play around with my main and pilot jet sizes? All the jets are stock... ps. the valves are adjusted and I did install a higher temp thermostat.

[tomacGTi]

Get the FP kit. Well documented and great customer service, you won't be disappointed.

[AlanDog]

I never wanted to get this good at pulling the carbs and putting it all back together... I installed the kit in a little over 2 hours. I know there are guys here who do it in 20 minutes, but for me...

A definite improvement. I just went with the 97.5 main jets since the jetting thread here it seems to be popular with stock intake/exhaust. I went with the needle set 3 down... basically the bike runs stronger on the bottom and top end. It's probably stronger in the middle (4-7k) but the flat spot is still there. I've been studying the jetting thread here and I'm thinking of going to 2nd groove on my needle. Although most setups seem to be set to 3. I've tried running WOT in the middle rpms cold versus hot and it's hard to say--weak either way. Although it seems to be stronger with the choke on thru that range. I think I need to ride it more. It's a bit hard to test dead cold, as I have to ride out of the neighborhood and I'm not going to hit WOT at any rpm on the street where I live, it's just not safe.

Go richer or leaner for the needle setting? Any input? Would going lean on the mixture screws, say bringing them from 2.25 to 1.5 turns out and seeing if the midrange is better or worse be a good way of narrowing down which way to go? (I just tried to re-read the link to the Randakk page and it looks like he took that content down). It's totally rideable now, maybe I should just keep riding it more until I'm more sure... I really don't enjoy fiddling with the bike, I just want to ride it...

[tomacGTi]

Get the warmer thermostat as well. It will make the jetting much more consistent.

Do all of your tuning with the engine at operating temperature, you're wasting your time with it cold. Also, it is neigh impossible to jet out the dead spot. All you will manage to do is move it around and compromise everything else.

[AlanDog]

As far as testing cold, I was just trying to follow the factory pro tuning instructions:

http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,high_rpm_engines.html

"If the engine pulls better or is smoother at full throttle/5k-7k in a full throttle roll-on starting at <3k when cool but soft and/or rough when at full operating temperature, it is too rich in the midrange and the needle should be lowered.
If the engine pulls better when fully warmed up but still not great between 5k-7k, try raising the needle to richen 5k-7k.
If the engine pulls equally well between 5k-7k when cooler as compared to fully warmed up, the needle height is probably properly set."

I actually did upgrade my thermostat a couple weeks ago... so you're saying other changes (to intake and exhaust?) need to be made to get rid of the midrange flat-spot, or I'm just stuck with the way this particular bike is??? Certainly there are posts on the jetting thread of people who say the engine pulls strong throughout the rev range. 

Thanks for your help Randy!

-Alan

[tomacGTi]

To go by factory pro's suggestions would be to warm up the bike and ride it till hot. This way you can accurately compare cold running and hot running and go from there.

Easiest way I've found really is to set the top end first with the main then idle when hot via the screws and then the midrange but the middle needle setting 98% of the time is perfect. You can also shim with a washer to get that 1/2 step if need be. Also remember that all circuits overlap so what may be good for one will affect the other. That's why I try to tune either end first, the middle usually follows with. Don't forget to synch the carbs after.

That flat spot is damn impossible to tune out. People that say that it has a clean pull usually pull right through it via gearing in the 1-3. Flat spots will manifest more when the engine is under load and cold so you should tune the motor for how you ride versus outright pull at high revs. Area under the curve is better than outright numbers.

As worked over as my bike is, that flat spot is still there but is certainly diminishes as it warms up. I've just learned to ride around it. Certain exhaust and airbox combos can also affect it as well: making it better or worse depending. Like I said, you compromise and move it around but it really never goes away.

Search the SV forums as well for tuning tips. Although a different bike there are more of them and the theory is the same. Just don't try their cam swap on the 400, ask me how I know...

Isn't tuning fun?

[tomacGTi]

Alan, the other thing I can tell you is that the factory pipes on this bike are restrictive. This may be your top end issue. Don't be afraid to call FP for advice as well.

When I swapped headers, my jetting went from a 105 main to a 120 with all other parameters remaining the same.

Even my ported/gutted stock headers with a Cobra F1S slip on didn't flow as well as the Vance and Hines pipe that I have now. There is a difference up top with these for sure. The Vance and Hines is also louder than hell but is no match for the growling airbox that you straddle.

These things have potential but you have to keep things in perspective: all this work will still not make it an R6 or GSXR. It'll be more fun but it's still not the same.

-Randy

[AlanDog]

I brought the mixtures screws out 1/2 turn ( to about 2 3/4 ) and it's clearly rich at idle but that pretty much fixed the midrange problem, at least enough for me. I had to dial back the idle speed screw when it warmed up but hopefully that's it. I wonder how much that mixture screw position affects gas mileage. I guess I can measure it now and dial it back and see...

I'm not into crazy high performance, and I really don't want a loud bike. I really like the idea of a small inline 4 as a move up from the ninja 250. This bike had enough power for me. I was holding off on other mods because I wasn't sure if I'd ever get the carbs sorted out. Now I want to customize and raise the seat, get new brake pads and change the fluid, and get new tires. I'll be ready for my 2nd track day this spring!

Thanks again. I would of certainly given up without this forum. Hopefully this thread will help others!