I just bought my 82 GS 750 a few days ago for $1100, and it appears as if I should demand a partial refund on my money. It looks great, engine seems to run ok, and has new tires, but what was billed as "running great" is actually rust in the tank (which I didn't check), unbelieveably horrible gas mileage, and a dead spot so bad at 7,500rpm that the bike will absolutely not accelerate beyond it.
A little background: The bike sat (as indicated by the tank) but for unknown duration. The PO claimed 2 months while he owned it. It starts and runs like its brand new, but requires a lot of choke to warm it up, and a little choke to keep it going. With zero choke it'll stay lit as long as you blip the throttle every five seconds. It pulls like a monster throughout the powerband with no dead spots or seeming over rich/over lean conditions at any throttle angles or RPM positions (save 7,500). It's a very smooth bike.
The problems, broken down: The gas mileage is atrocious. I filled the tank yesterday, and 23 miles later it's almost down to halfway. I looked inside the (rusty) tank to check, and it's really that low. What's strange about this is the bike runs fine. Like I said, no high or low spots in the powerband. It starts easily, warms up acceptably when choked (and with the help of blipping the gas to keep it lit while warming up), and pulls very hard.
The power is there, but I'm guessing it could be stronger still. It pulls like a monster throughout, seemingly hitting the meat of the torque band at 3,000 and roaring with authority up to 7,500 in any gear. That problem is that at 7,500 it just stops accelerating. It hints at this as you pass 7,000, but 500rpm later it's not going anywhere. Of course since this bike's torque peak is supposed to be at 8,450 or so, that's a little shy on the power side.
The tank is a bit rusty, but the clear filter shows very little evidence of it getting into the system. This could still be contributing to the other two problems.
One more thing: It's got a Kerker 4-1, what looks like a K+N cone stuck to the outside of the airbox, and I have no idea if it's been jetted for those two mods. I've no idea if the K+N is clogged.
So, anybody have any ideas on what's causing this combination of problems? To tell the truth I could care less about it not pulling past 7,500rpm since it's already horrifically fast as is, but the gas mileage is really really bad. Coming off my GZ 250 which got 72mpg a few tanks, this 10-15mpg is insane.
Comment