You have done it now !!!!!!!!!!
Spent all day fitting the GS tubes to my S model. I wanted to try this ages ago but I heard they didnt fit the S model, only the RS.
I thought if they work on one bike they must also work on mine, but i just never got around to trying it.
I read this post and immediately ordered a pair of second hand ones from Motorworks. No point buying new as you are going to butcher them, and you cannot see them anyway.
quite easy really! had to remove the big K&N and refit the standard filter, but never mind.
I bought a second hand hydraulic type cam chain tensioner for the left side too. Figured if I was messing with the inlet tubes I may as well whip off the throttle body and do the chain tensioner at the same time.
not ridden it yet, but yes the induction noise sounds louder.
If this mods adds even more grunt to the mid-range (I already have Lennies cam sprockets and a booster-plug) I will be pulling out tree stumps with it lol.
GS intake runners fitted to my 1100S: WOW !!! Pics added.
Moderators: Gromit, Paul, slparry
Looking at your photo's again. My tubes ended up in a different position to yours, not that it matters. My right side curves slightly to the left and sits directly under the left side.
When I removed the original runners I was quite supprised too. Yes, they are bellmouths BUT, it is my understanding that the shape at the end is very important. It looks like they were designed outside the airbox, then they found that due to the shape of the airbox, they needed to cut a couple of sections off the bell. Which I would have thought would have spoiled them.
I measured internal length of the GS runners, approx 9 1/2 inches. and cut them down in small bites so that when they were pushed tighly into the S runners I would retain the tuned length and both match each other.
I put a bit of silicone sealant around the joint so it HAS to breath down the new tubes.
A bit of a fiddle to get them into the airbox, and I had to fit the righthand side first or they would not have gone in.
I refitted my new standard airfilter, and it just kisses the end of the left hand tube. But no problems there.
I would suggest to anyone trying this. BEFORE messing about with the tubes (they will go in and out a few times before you are happy with the fit) carefully remove the rubber O ring around the throttle body so you don't damage it. Then on final fitment put the rubber O rings back on. Really you should use new ones, as old O rings always seem to be too big LOL. Anyway if you spray the end of your throttle body and the inside of the induct runner with WD40 it will help it slide back on, however the O ring will probably appear to be too big and keep trying to pop out. Use a small flat end screwdriver or similar tool to just keep pushing it back under the runner and back into it's slot, it will go back if you dont rush and take your time.
When I removed the original runners I was quite supprised too. Yes, they are bellmouths BUT, it is my understanding that the shape at the end is very important. It looks like they were designed outside the airbox, then they found that due to the shape of the airbox, they needed to cut a couple of sections off the bell. Which I would have thought would have spoiled them.
I measured internal length of the GS runners, approx 9 1/2 inches. and cut them down in small bites so that when they were pushed tighly into the S runners I would retain the tuned length and both match each other.
I put a bit of silicone sealant around the joint so it HAS to breath down the new tubes.
A bit of a fiddle to get them into the airbox, and I had to fit the righthand side first or they would not have gone in.
I refitted my new standard airfilter, and it just kisses the end of the left hand tube. But no problems there.
I would suggest to anyone trying this. BEFORE messing about with the tubes (they will go in and out a few times before you are happy with the fit) carefully remove the rubber O ring around the throttle body so you don't damage it. Then on final fitment put the rubber O rings back on. Really you should use new ones, as old O rings always seem to be too big LOL. Anyway if you spray the end of your throttle body and the inside of the induct runner with WD40 it will help it slide back on, however the O ring will probably appear to be too big and keep trying to pop out. Use a small flat end screwdriver or similar tool to just keep pushing it back under the runner and back into it's slot, it will go back if you dont rush and take your time.
There are only two things in life that are "Priceless"
Time & Health
Everything else can be bought or stolen.
Time & Health
Everything else can be bought or stolen.
Mike B wrote:
...I put a bit of silicone sealant around the joint so it HAS to breath down the new tubes ....
I cut mine at a about a 30 degree angle towards the curve of the runner. They fitted snugly into the 'bellmouth' and I then used longer self-tapping screws (the pair with the heads showing on the outside of the collar) to bite into the now-inner GS tube to lock it into place.
All else you described is just how it went for me. Not difficult. Slightly fiddly.
Real torque curves don't have a first derivative. :-^)
Mike - I'm particularly interested in the result on your machine since you're using the Rocket Sprocket as well.
I drew a valve timing diagram to compare the Rocket Sprocket timing vs the stock timing to try to get some idea of why the R.S. does what it does. It only changes the openings/closings relative to piston position / speed but not being a hands-on cam designer I can but surmise. However the R.S. performance clearly shows the effect of these timing changes.
Waiting ... waiting ...
I drew a valve timing diagram to compare the Rocket Sprocket timing vs the stock timing to try to get some idea of why the R.S. does what it does. It only changes the openings/closings relative to piston position / speed but not being a hands-on cam designer I can but surmise. However the R.S. performance clearly shows the effect of these timing changes.
Waiting ... waiting ...
Real torque curves don't have a first derivative. :-^)
WOW!
Well the sun was shinning this morning so I got the bike out for the first test ride with the GS tubes. Wow! there was certainly a difference. As soon as I started it I could tell it sounded different. The exhaust note is louder and much sharper sounding when you rev it. The rush of power that it normally gives in the last couple of thousand revs, now comes in much sooner. I would say about 4000 rpm. The low down power is definately stronger but more importantly it's much smoother. But as the revs climb passed about 3000 revs all hell breaks loose and it really takes off. between about 4 to 6k I found myself having to lean forward and hang on. The induction noise is much louder at those revs too. On a few occasions I actually thought I was in a gear lower than I was, simply because it was pulling too strong
Tuning the inlet lengths to work lower down the rev range has has made it noticably smoother when slowing down and blipping the throttle for downward changes. Now I consider my 1100S to be really well set up, and I thought it was smooth before, but it's better now.
By tuning the inlet length for lower revs it has certainly improved cylinder filling, hence the difference in the exhaust note.
Just for those that dont know what my bike is like. It has "lennies" sprockets, an opened up induct (by myself), a booster plug to richen the mixture a bit, And a "Y" pipe to replace the CAT. It did have the big K&N filter, but it had to go to squeeze in the GS pipes. It now runs the standard filter. But you wouldnt notice!
If any of you have fitted the "Lennies" cam sprocket and like like the results, you will LOVE the GS tubes. They do the same, but more. If you have both like I now have, you will be amazed! they work really well together.
Well the sun was shinning this morning so I got the bike out for the first test ride with the GS tubes. Wow! there was certainly a difference. As soon as I started it I could tell it sounded different. The exhaust note is louder and much sharper sounding when you rev it. The rush of power that it normally gives in the last couple of thousand revs, now comes in much sooner. I would say about 4000 rpm. The low down power is definately stronger but more importantly it's much smoother. But as the revs climb passed about 3000 revs all hell breaks loose and it really takes off. between about 4 to 6k I found myself having to lean forward and hang on. The induction noise is much louder at those revs too. On a few occasions I actually thought I was in a gear lower than I was, simply because it was pulling too strong
Tuning the inlet lengths to work lower down the rev range has has made it noticably smoother when slowing down and blipping the throttle for downward changes. Now I consider my 1100S to be really well set up, and I thought it was smooth before, but it's better now.
By tuning the inlet length for lower revs it has certainly improved cylinder filling, hence the difference in the exhaust note.
Just for those that dont know what my bike is like. It has "lennies" sprockets, an opened up induct (by myself), a booster plug to richen the mixture a bit, And a "Y" pipe to replace the CAT. It did have the big K&N filter, but it had to go to squeeze in the GS pipes. It now runs the standard filter. But you wouldnt notice!
If any of you have fitted the "Lennies" cam sprocket and like like the results, you will LOVE the GS tubes. They do the same, but more. If you have both like I now have, you will be amazed! they work really well together.
There are only two things in life that are "Priceless"
Time & Health
Everything else can be bought or stolen.
Time & Health
Everything else can be bought or stolen.
Mike B wrote:WOW!
Well the sun was shinning this morning so I got the bike out for the first test ride with the GS tubes. Wow! there was certainly a difference. As soon as I started it I could tell it sounded different. The exhaust note is louder and much sharper sounding when you rev it. The rush of power that it normally gives in the last couple of thousand revs, now comes in much sooner. I would say about 4000 rpm. The low down power is definately stronger but more importantly it's much smoother. But as the revs climb passed about 3000 revs all hell breaks loose and it really takes off. between about 4 to 6k I found myself having to lean forward and hang on. The induction noise is much louder at those revs too. On a few occasions I actually thought I was in a gear lower than I was, simply because it was pulling too strong
Tuning the inlet lengths to work lower down the rev range has has made it noticably smoother when slowing down and blipping the throttle for downward changes. Now I consider my 1100S to be really well set up, and I thought it was smooth before, but it's better now.
By tuning the inlet length for lower revs it has certainly improved cylinder filling, hence the difference in the exhaust note.
Just for those that dont know what my bike is like. It has "lennies" sprockets, an opened up induct (by myself), a booster plug to richen the mixture a bit, And a "Y" pipe to replace the CAT. It did have the big K&N filter, but it had to go to squeeze in the GS pipes. It now runs the standard filter. But you wouldnt notice!
If any of you have fitted the "Lennies" cam sprocket and like like the results, you will LOVE the GS tubes. They do the same, but more. If you have both like I now have, you will be amazed! they work really well together.
Mike - to use the local vernacular - no better not - but how bloody fantastic to hear!
Isn't it great 'when all hell breaks loose'. Yee haaaaa. Goes like a 1200GS above 6k.
Ppl here have looked at me a bit strangely when I described that, so thankyou.
Mine will be on the dyno this time tomorrow.
Doesn't it make you wonder how the factory could get it so wrong?
It now feels like the sports bike I expected.
Quick - start buying up all the GS choobs there. Between us we should be able corner the market before word gets out!
Mwahhh harrrr harrrrr ...
Shhhhh - don't tell Lennie until I get a pair of his sprockets.
Real torque curves don't have a first derivative. :-^)
I guess BMW were looking for a high BHP figure to sell the bike as a sports bike. Unfortunately BHP figures sells bikes. However, if it comes in very high up the rev range most of the time in normal riding you would never feel it.
What we have done may have lost a few bhp at the top of the rev range, but added it somewhere else. That somewhere else is more usable to me as I never rev it that much anyway.
What we have done may have lost a few bhp at the top of the rev range, but added it somewhere else. That somewhere else is more usable to me as I never rev it that much anyway.
There are only two things in life that are "Priceless"
Time & Health
Everything else can be bought or stolen.
Time & Health
Everything else can be bought or stolen.
Mike B wrote:I guess BMW were looking for a high BHP figure to sell the bike as a sports bike. Unfortunately BHP figures sells bikes. However, if it comes in very high up the rev range most of the time in normal riding you would never feel it.
What we have done may have lost a few bhp at the top of the rev range, but added it somewhere else. That somewhere else is more usable to me as I never rev it that much anyway.
My tach shows little sign of slowing all the way to 8000, so I'm not expecting to lose much hp, if any.
My rear tyre now has abrasion marks around its centre, so I s'pose the rear drive is next for a close look.
Real torque curves don't have a first derivative. :-^)
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