Jets vs Exhaust

[tkent02]

Typo?
2.5%?

[renegadmonk]

Typo?
2.5%?

awww man...i was dreaming of the big 25% gain.....

[Graham]

Typo?
2.5%?

No typo. About 25% over stock on a mid 70s to early 80s Japanese 4 cylinder motorcycle. Good header, open-air intake (pods or stacks) and the proper jetting. A good header will scavenge the exhaust gasses, increase compression and have a strong power band. If you can’t feel the HP increase then you should work on your jetting.

[blowerbike]

do you copy and paste from notepad?

shhhhhhhhh

[renegadmonk]

No typo. About 25% over stock on a mid 70s to early 80s Japanese 4 cylinder motorcycle. Good header, open-air intake (pods or stacks) and the proper jetting. A good header will scavenge the exhaust gasses, increase compression and have a strong power band. If you can’t feel the HP increase then you should work on your jetting.

wow now that is interesting. Guess its time to get working on this mod...i may was well since my exhaust is rusting out anyway...so what the heck.

[mlinder]

Graham is absolutely correct. In order to meet EPA standards, these GS's were seriously lean from factory and extremely restricted.
My butt dyno says 10 to 15 HP increase on the 550's from pipes, derestriction and proper jetting. Possibly more.

The later 650's may not have the same percentage, but may have similar gains, i.e. another 10+HP. The early 750's, also.

I haven't had the pleasure of rejetting the 1000's or bigger, so I can't give an honest answer as to their gains.

[mlinder]

wow now that is interesting. Guess its time to get working on this mod...i may was well since my exhaust is rusting out anyway...so what the heck.

Try just removing the airbox lid on your 650, and increasing main jet size (stock is 110, right?) to say, 117.5. May as well get 115's and 120's while you are at it, just to be able to fine tune.
Enrichen your idle circuit by 1/8th or so of a turn on on your air screw.

Pods in general are not my favorites on CV carbs, though as people have said, the cheap ones are completely useless on CV carbs more often than not. Velocity stacks seem to work well enough on CV carbs.

I don't have a 650 airbox, but my guess is that there are velocity stacks already in there. Little hard rubber guys. Work great, a friend has those on his 750, I love being able to hear all the engine noise when I'm behind him. Those are on VM carbs, but same thing applies.

[renegadmonk]

more interesting info...you guys are great ...very glad to be a part of this site. Will note all of this.

[Blaqjak3]

This an awesome site!! All of you guys are great, I really appreciate your willingness to share from your trails and errors. Thank You!

[tkent02]

No typo. About 25% over stock on a mid 70s to early 80s Japanese 4 cylinder motorcycle. Good header, open-air intake (pods or stacks) and the proper jetting. A good header will scavenge the exhaust gasses, increase compression and have a strong power band. If you can’t feel the HP increase then you should work on your jetting.

Show me some proof that a pipe gives this kind of performance gain over a properly jetted bike with stock pipes and intake? 6-8 % is about it.
25% is huge, it's not going to happen without some engine mods. 25% would make a 750 about as fast as a 1000, that kind of improvement is just not there.
I've run a lot of pipes and pods on lots of bikes, and spent a lot of time perfecting jetting, on both stock systems and with pipes/pods. None of them got that much faster, a little bit on top, but not anywhere near 25%. They sound faster, and they feel faster, because they have less torque before the power hits, so the increase feels bigger.
Only some two strokes have that much to gain from a pipe, but that's a whole different science lesson...

[posplayr]

Show me some proof that a pipe gives this kind of performance gain over a properly jetted bike with stock pipes and intake? 6-8 % is about it.
25% is huge, it's not going to happen without some engine mods. 25% would make a 750 about as fast as a 1000, that kind of improvement is just not there.
I've run a lot of pipes and pods on lots of bikes, and spent a lot of time perfecting jetting, on both stock systems and with pipes/pods. None of them got that much faster, a little bit on top, but not anywhere near 25%. They sound faster, and they feel faster, because they have less torque before the power hits, so the increase feels bigger.
Only some two strokes have that much to gain from a pipe, but that's a whole different science lesson...

we clearly have a variety of posters (or posers) here at GSR.

I never realized how dangerous it was to add pods and pipe. With an 1166 I must be at a 50% hp increase. I'm glad I stopped there.

[mlinder]

Show me some proof that a pipe gives this kind of performance gain over a properly jetted bike with stock pipes and intake? 6-8 % is about it.
25% is huge, it's not going to happen without some engine mods. 25% would make a 750 about as fast as a 1000, that kind of improvement is just not there.
I've run a lot of pipes and pods on lots of bikes, and spent a lot of time perfecting jetting, on both stock systems and with pipes/pods. None of them got that much faster, a little bit on top, but not anywhere near 25%. They sound faster, and they feel faster, because they have less torque before the power hits, so the increase feels bigger.
Only some two strokes have that much to gain from a pipe, but that's a whole different science lesson...

The smaller bikes do. Again, the increase is not a % across the board as you go larger. I don't know if it's 25%, but I do know doing so will put you ahead of bikes that I KNOW are putting 65 HP out.

And it's not so much the pipe, as the intake de-restriction and fixing the from-factory lean condition with proper jetting.

[chef1366]

we clearly have a variety of posters (or posers) here at GSR.

I never realized how dangerous it was to add pods and pipe. With an 1166 I must be at a 50% hp increase. I'm glad I stopped there.

Freak'n jet engine.

[Graham]

Show me some proof that a pipe gives this kind of performance gain over a properly jetted bike with stock pipes and intake? 6-8 % is about it.
25% is huge, it's not going to happen without some engine mods. 25% would make a 750 about as fast as a 1000, that kind of improvement is just not there.
I've run a lot of pipes and pods on lots of bikes, and spent a lot of time perfecting jetting, on both stock systems and with pipes/pods. None of them got that much faster, a little bit on top, but not anywhere near 25%. They sound faster, and they feel faster, because they have less torque before the power hits, so the increase feels bigger.
Only some two strokes have that much to gain from a pipe, but that's a whole different science lesson...

I’ll admit I’m being generous by giving the pod filters a 5% increase. But header companies have been advertising for years 15% to 25% for just the add on of a header system. You can find the tests in old cycle magazines. A 750 with a good header system and jetting could out run a stock 1000. Back in the day, I had a KZ650 that would eat Z1s for lunch. Bikes in the late 70s and early 80s had very restricted exhaust system and air boxes. Don’t take my word for it, do your own research. Here is a little help to start you out.
http://www.motorsports-network.com/akrapovic/info.htm
http://www.exhaust-notes.com/glossar...-exhausts.html
http://www.superstreetbike.com/howto...ons/index.html

[Graham]

we clearly have a variety of posters (or posers) here at GSR.

I never realized how dangerous it was to add pods and pipe. With an 1166 I must be at a 50% hp increase. I'm glad I stopped there.

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