• Required reading for all forum users!!!

    Welcome!
    Register to access the full functionality of the GSResources forum. Until you register and activate your account you will not have full forum access, nor will you be able to post or reply to messages.

    A note to new registrants...
    All new forum registrations must be activated via email before you have full access to the forum.

    A Special Note about Email accounts!
    DO NOT SIGN UP USING hotmail, outlook, gmx, sbcglobal, att, bellsouth or email.com. They delete our forum signup emails.

    A note to old forum members...
    I receive numerous requests from people who can no longer log in because their accounts were deleted. As mentioned in the forum FAQ, user accounts are deleted if you haven't logged in for the past 6 months. If you can't log in, then create a new forum account. If you don't get an error message, then check your email account for an activation message. If you get a message stating that the email address is already in use, then your account still exists so follow the instructions in the forum FAQ for resetting your password.

    Have you forgotten your password or have a new email address? Then read the forum FAQ for details on how to reset it.

    Any email requests for "can't log in anymore" problems or "lost my password" problems will be deleted. Read the forum FAQ and follow the instructions there - that's what we have one for...

  • Returning Visitors

    If you are a returning visitor who never received your confirmation email, then odds are your email provider is blockinig emails from our server. The only thing that can be done to get around this is you will have to try creating another forum account using an email address from another domain.

    If you are a returning visitor to the forum and can't log in using your old forum name and password but used to be able to then chances are your account is deleted. Purges of the databases are done regularly. You will have to create a new forum account and you should be all set.

Jets vs Exhaust

  • Thread starter Thread starter Blaqjak3
  • Start date Start date
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.
 
renegadmonk said:
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.
Click to expand...
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.
 
more interesting info...you guys are great ...very glad to be a part of this site. Will note all of this.
 
This an awesome site!! All of you guys are great, I really appreciate your willingness to share from your trails and errors. Thank You!
 
Graham said:
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.
Click to expand...

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...
 
tkent02 said:
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...
Click to expand...

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. :rolleyes:
 
tkent02 said:
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...
Click to expand...

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.
 
Last edited:
posplayr said:
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. :rolleyes:
Click to expand...
Freak'n jet engine. :-\\\
 
tkent02 said:
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...
Click to expand...

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/glossary-motorcycle-exhausts.html
http://www.superstreetbike.com/howtos/030_0309_motorcycle_effective_modifications/index.html
 
posplayr said:
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. :rolleyes:
Click to expand...

If you research exhaust systems like you did regulators you could know what kind of HP you should have.:p
 
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.
 
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.
:twistedevil:
 
tkent02 said:
PT Barnum was a smart man.
Click to expand...
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?
 
mlinder said:
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?
Click to expand...

Nothing, but if it gets more gain than my 650 conversion, I'll be impressed.
 
tkent02 said:
Nothing, but if it gets more gain than my 650 conversion, I'll be impressed.
Click to expand...
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.
 
You must log in or register to reply here.
Back
Top