Jets vs Exhaust

[chef1366]

If you research exhaust systems like you did regulators you could know what kind of HP you should have.

Actually he does.

[mlinder]

I'm not about to get into a ****ing contest.

All I can say, is that different bikes respond to rejeting and changes in intake and exhaust differently.

Bikes that are severely restricted and jetted lean to meet epa standards respond very well to 'corrections'. The gs550's are a very good example of this. Early gs750's are not dissimilar, though to a lesser degree. KZ650's do quite well with intake changes, as do early CB750's and later CB550's.

The less overlap in cams, the less response you get from exhaust changes, in my experience.
Most gains seem to come from intake in these instances.

[blowerbike]

in mlinders defense.......
let me ask you cough "pro's" cough cough a question.
1986 GSXR1100...
these made under 100 hp closer i believe to 90 hp stock at the rear wheel.
add a pipe and st. 3 jet kit and timing advancer..
i believe this added around 20-25 hp on this model..maybe a couple more.
say it ain't so...
i say it is and yes i bought one new in 86 and did all of thee above and seen/felt the improvements 1st hand from seat of the pants and at the track.
is this common...
i'll let the "pro's" answer that question.

[tkent02]

PT Barnum was a smart man.

[mlinder]

PT Barnum was a smart man.

tkent, I have to get to a dyno before February for my racebikes.

What will you give me if I see a 10hp increase in a gs550 from stock carbs and airbox vs rejetting and and deristriction?

[tkent02]

tkent, I have to get to a dyno before February for my racebikes.

What will you give me if I see a 10hp increase in a gs550 from stock carbs and airbox vs rejetting and and deristriction?

Nothing, but if it gets more gain than my 650 conversion, I'll be impressed.

[mlinder]

Nothing, but if it gets more gain than my 650 conversion, I'll be impressed.

It won't. As you may remember, I'm doing the same.

My guess is 62ish HP from a deristricted and properly jetted 550.

The 650 makes quite a bit more than that.

For the 550, it could just be a case of greatly increased midrange from the rejetting and such, that makes it feel like it's got more top end, when in reality, it's just much faster to near the same top speed.

I dun think so, though, since both 'worked on' 550's in my experience, are capable of about 115+.

Which requires more than 49HP.

I'll do the comparison as time and money allow.

[tkent02]

O k

[mlinder]

Kent, you have a 550?

[tkent02]

Yes .

[mlinder]

Have you done anything to it, so far?

[tkent02]

Took most of it apart, put some of it back together, derusted the tank, painted the frame, scrounged up a lot of parts, including a 650 top end, removed about 17 lbs of leaves, muck and slime. Adjusted the valves, cleaned the carbs, cussed out the PO. Fixed a few leaks. Same old stuff they all need.
It hasn't run in decades.
Yet.
And yours?

[mlinder]

Oh, runs fine after 10 years of not running. Better after rejetting, etc...
All of em, actually.

My question was to see if you had a running one. I think you'd be surprised. I was going to send you main jets and have you run your bike against them with stock jetting and airbox, and then after deristriction and rejetting. The difference really is extraordinary on the 550. Most responsive bike I have/have had to such changes.

[tkent02]

The difference really is extraordinary on the 550. Most responsive bike I have/have had to such changes.

Cool, I believe that part, and I can't wait. But I'll have to wait, doing a bit of traveling. I'll get it going in a couple months. What size jets did you end up with?

[mlinder]

You're going straight to a 650 top end. Different story for you.

I run 110's with stock airbox and filter, with the box-top removed.