help! weird acceleration somethings not right

[Kbecker3]

'81 gs750L, when i am riding it normal all seems good. but when i really try to accellerate, say near 7,000 rpm or so, it seems like (for lack of a better way to describe it) a turbo will kick in.(doesn't matter what gear but usually around 2nd, and 3rd) dont think the clutch is slipping, because it wants to accellerate alot more w/ the rpms.

-I dont think the clutch is slipping, I just replaced the plates, and the springs.
-I have rotella 15W40 running in there currently.
-seems like it is running on all 4 when it is at idle. (all 4 get warm right away)
-it does have an inline fuel filter from the P.O. but i took a good look at it when i was sitting on center stand, reving engine. and it doesn't look like it is restricting flow.
-just replaced the petcock 3 months ago.

it almost doesn't feel like it has the power it should in the low rpms. any way to start looking for a problem.. so i would know where to start looking.

my only guess is when i get home (currently at work) i can check the plugs. any other ideas?

[focus frenzy]

are you saying that when you open the throttle wide open it builds up to around 7K rpm then starts pulling allot stronger?

if so, then welcome to the meat of the power band, also known as coming on the cam/s.
the power delivery of pretty much all GS is tuned towards the top end and the harmonics of the porting, cams and rest of the engine hits its balance in the 6-7K rpm range and there is a pretty big spike in the power curve.

it's pretty much all in the cams, a yamaha XS1100 falls flat on it's face at 6K rpm, below that it is a torque monster, my 1000G is nice and sweet and behaves below 6K rpm, above that it is a screaming demon, the whole caricature, sound, and response changes like Jekyll and Hyde.
the larger 16 valve engine are not as abrupt in the cross over as the older 8 valve engines but they still do change personality.

[t3rmin]

In my experience the 16v motors have more of a dramatic "hit" at the 6k powerband, and below that they're less torquey than the 8v. My 700, for instance, is downright bland below 5k. I'm not sure whether the '81 750L is 16v or 8v...

And yes, I've often thought it felt like a turbo kicking in. Quite normal as long as you don't have any other "symptoms" (checked the plugs lately?).

[Kbecker3]

i replaced them (plugs) when i first got the bike in april. it had the typical problems (RR and stator) P.O. tried to re-wind stator w/o replacing the melted wire(we wont even go there) anyway. changed the oil. and all has been good since. but never really started to take the rpms up that high till the recant.

i would think it is the 16 valve... not sure though. any way i can tell easily? it says TSCC on the motor case...

but anyway, no i have not pulled the plugs since.

forgot to add that it has a stock air filter (replaced filter in april) and airbox.

[t3rmin]

i replaced them (plugs) when i first got the bike in april. it had the typical problems (RR and stator) P.O. tried to re-wind stator w/o replacing the melted wire(we wont even go there) anyway. changed the oil. and all has been good since. but never really started to take the rpms up that high till the recant.

i would think it is the 16 valve... not sure though. any way i can tell easily? it says TSCC on the motor case...

but anyway, no i have not pulled the plugs since.

forgot to add that it has a stock air filter (replaced filter in april) and airbox.

It's 16v then. 16v motors say TSCC and have squarish cam end caps (or none). If you're just starting out and these are your first forays into high RPMs, it would be somewhat surprising to feel that kick. I suspect your bike is running fine. The 16v motors like to rev, when you want power, you've got to get the RPMs up.

[focus frenzy]

In my experience the 16v motors have more of a dramatic "hit" at the 6k powerband, and below that they're less torquey than the 8v. My 700, for instance, is downright bland below 5k. I'm not sure whether the '81 750L is 16v or 8v...

And yes, I've often thought it felt like a turbo kicking in. Quite normal as long as you don't have any other "symptoms" (checked the plugs lately?).

Suzuki used more radical cams in the 700 to keep the peak power in the same range as the 83 750 and the 84 and 85 750 sold else were in the world.
they hotter cams gave the 700 a big hit when it came on the cams.
a good performance booster for 83 750E's is to put in cams from a 85 700 as the 700 cams have more lift and duration, the draw back is it takes away from the bottom end.

[t3rmin]

Suzuki used more radical cams in the 700 to keep the peak power in the same range as the 83 750 and the 84 and 85 750 sold else were in the world.
they hotter cams gave the 700 a big hit when it came on the cams.
a good performance booster for 83 750E's is to put in cams from a 85 700 as the 700 cams have more lift and duration, the draw back is it takes away from the bottom end.

Yup. I guess the 700 wasn't the best example, but my 16v 750 is similar in that it's less torquey and likes to rev more than the 8 valvers I've ridden. Overall much faster and more fun, but more peaky.

[Kbecker3]

well, ok... sounds good to me.. if it sounds like that is normal... my last bike was a 1983 yamaha Virago XV500k (shaft drive). smooth all the way up to redline, never had a jump like that. so just seemed weird to me.

also wanted to ask there is a small hole in my airbox(was there when i bought it) is it good to patch it up? or is it fine as is (hole is about the size of a dime or nickel. looks like from removing the air box (rubbing against the frame)?

[t3rmin]

You want that airbox as airtight as possible!