CincinnatiKid
Forum Mentor
hi i'm looking for more performance out of my 1981 gs1100e
ive had it for a number of years now, i'd say it runs at like an 8.5/10 now, I'm very happy with the engine performance on the street, I commute with it during the year.
here's my issue: I've had it on the track for track days twice this season, and I'm feeling very impatient during corner exit, waiting for the engine to catch up to my throttle hand. the exit drive takes way too long to build up. In both track days, I was on track with a modern ninja 400 and I couldn't pass him on the straights. I could outbrake him like crazy, and had way more corner speed than him, but in corner exit, his bike responded to his throttle input while mine just took too long to get up to speed. embarrassing!! the morning rules were "no passing in the corners" so I was kind of stuck behind him for a lap or two until i could get him on the brakes.
Just did a track day last monday and it was a Aprillia demo day and I was able to ride an RS660 for the last session of the day and it helped illustrate where the GS was lacking. I realize there are many factors at play here, so i'm not looking for a silver bullet, but mostly trying to solicit input from people who have gotten great mid throttle performance out of this engine.
a) Bike has 4 k&n pods on the intake, 4-1 hindle exhaust, stock engine and carb bodies. 47.5 pilot jet, 130 mains, needle from a dynojet stage 3 kit with the clip at the lower middle position (slot 3 of 6). Earlier this week I raised the needle up to the highest position (slot 1 of 6) to try to get a bit more out of the mid throttle, and it was practically unrideable, with off-idle response disappearing. holding steady speed was tough, power came back once i opened the throttle more.
It's difficult to tune the main jet where i live (city of chicago), no real safe places to rip this thing WOT consistently, so it sometimes feels subjective to make decisions on "is this better than it was before?"
b) could be a technical riding technique issue as well... i dont have a tach or a speedo but the engine takes time to build up speed when exiting a medium speed corner @ full throttle in third or second. obviously it's a bit better in second. generally I would try to stay in third and fourth through the track, third kept the revs up around 7k at the start of corner entry, i would guess. there's an absence of "snappy" pull in third or second, and definitely in 4th if i missed the downshift. can't imagine any midspeed corner on a track would be a first gear exit. (as an aside, that Aprillia had a quickshifter and holy shit what a cheater piece of technology that is!!)
c) clutch adjusted well. doesn't slip.
d) compression is good, i can get #'s to justify. leakdown test a month or two ago had great results (all cylinders in the 90% percentile).
e) would a new set of carburetors help inject some life into the engine? swapping the stock CV's for a non-CV type? obviously would still need to be tuned for high performance either way.
f) I might be able to find a shop in the chicago area that does dyno testing, I've thought about paying to have empirical testing confirm the best main jet size, and work the needle from there on my own. I called a few places this season already and they didn't want to deal with carburetors, would only deal with fuel injection & engine mapping. I get it.
g) through my time owning this 40 year old dinosaur, i've always wondered what the "good enough" point is, where I have to temper my expectations for performance. is this just the character of an inline 4? you gotta keep revs above 6k to make the thing pull off the corner? i know it's not a modern GSX-R and i shouldn't expect it to perform like one. I don't know how this bike rode in stock format in 1981, but I feel like I should have a lot more jump off the line and pull below 4k rpm... it's an 1100cc superbike!! but when a modern 400 is pulling a gap on me, i have to imagine that there's more power available, and I'd like to find it! i feel like i should be able to feel the front wheel getting light when smacking the throttle coming off a corner @ 40mph in 3rd gear. am i wrong?
thanks, hopefully this summer I can continue to dial it in with some forum wisdom! nobody i know has any experience tuning these machines. everyone i talk to has got their opinions, but no credibility to back it up!!!
CK
ive had it for a number of years now, i'd say it runs at like an 8.5/10 now, I'm very happy with the engine performance on the street, I commute with it during the year.
here's my issue: I've had it on the track for track days twice this season, and I'm feeling very impatient during corner exit, waiting for the engine to catch up to my throttle hand. the exit drive takes way too long to build up. In both track days, I was on track with a modern ninja 400 and I couldn't pass him on the straights. I could outbrake him like crazy, and had way more corner speed than him, but in corner exit, his bike responded to his throttle input while mine just took too long to get up to speed. embarrassing!! the morning rules were "no passing in the corners" so I was kind of stuck behind him for a lap or two until i could get him on the brakes.
Just did a track day last monday and it was a Aprillia demo day and I was able to ride an RS660 for the last session of the day and it helped illustrate where the GS was lacking. I realize there are many factors at play here, so i'm not looking for a silver bullet, but mostly trying to solicit input from people who have gotten great mid throttle performance out of this engine.
a) Bike has 4 k&n pods on the intake, 4-1 hindle exhaust, stock engine and carb bodies. 47.5 pilot jet, 130 mains, needle from a dynojet stage 3 kit with the clip at the lower middle position (slot 3 of 6). Earlier this week I raised the needle up to the highest position (slot 1 of 6) to try to get a bit more out of the mid throttle, and it was practically unrideable, with off-idle response disappearing. holding steady speed was tough, power came back once i opened the throttle more.
It's difficult to tune the main jet where i live (city of chicago), no real safe places to rip this thing WOT consistently, so it sometimes feels subjective to make decisions on "is this better than it was before?"
b) could be a technical riding technique issue as well... i dont have a tach or a speedo but the engine takes time to build up speed when exiting a medium speed corner @ full throttle in third or second. obviously it's a bit better in second. generally I would try to stay in third and fourth through the track, third kept the revs up around 7k at the start of corner entry, i would guess. there's an absence of "snappy" pull in third or second, and definitely in 4th if i missed the downshift. can't imagine any midspeed corner on a track would be a first gear exit. (as an aside, that Aprillia had a quickshifter and holy shit what a cheater piece of technology that is!!)
c) clutch adjusted well. doesn't slip.
d) compression is good, i can get #'s to justify. leakdown test a month or two ago had great results (all cylinders in the 90% percentile).
e) would a new set of carburetors help inject some life into the engine? swapping the stock CV's for a non-CV type? obviously would still need to be tuned for high performance either way.
f) I might be able to find a shop in the chicago area that does dyno testing, I've thought about paying to have empirical testing confirm the best main jet size, and work the needle from there on my own. I called a few places this season already and they didn't want to deal with carburetors, would only deal with fuel injection & engine mapping. I get it.
g) through my time owning this 40 year old dinosaur, i've always wondered what the "good enough" point is, where I have to temper my expectations for performance. is this just the character of an inline 4? you gotta keep revs above 6k to make the thing pull off the corner? i know it's not a modern GSX-R and i shouldn't expect it to perform like one. I don't know how this bike rode in stock format in 1981, but I feel like I should have a lot more jump off the line and pull below 4k rpm... it's an 1100cc superbike!! but when a modern 400 is pulling a gap on me, i have to imagine that there's more power available, and I'd like to find it! i feel like i should be able to feel the front wheel getting light when smacking the throttle coming off a corner @ 40mph in 3rd gear. am i wrong?
thanks, hopefully this summer I can continue to dial it in with some forum wisdom! nobody i know has any experience tuning these machines. everyone i talk to has got their opinions, but no credibility to back it up!!!
CK
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