• There has been a recent cluster of spammers accessing BARFer accounts and posting spam. To safeguard your account, please consider changing your password. It would be even better to take the additional step of enabling 2 Factor Authentication (2FA) on your BARF account. Read more here.

Unexplainable ooomph!

SD Hornet

SD Hornet

rider
Joined
Nov 4, 2008
Location
San Diego
Moto(s)
Honda CB600F, VT600CD
BARF perks
AMA #: 1102494
Riding my Shadow 600cc v-twin home from work today, I was surprised at the increased acceleration and top speed that it exhibited. While ascending a grade that usually bogs the bike down to 70-75mph, it was still accellerating hard (relative term) at 85mph. 85-90mph is typically the top speed on level ground. There was no tailwind and I gassed up with regular gas the night before.

Since the bike is completely stock, has over 60k miles, and no work has been done recently, I was wondering where the approximately 10hp boost came from? That would be about a 25% increase in overall hp.

What would cause that to happen? An airleak, great gas, or ?
Was I hallucinating, or should I just shut up and ride? :ride

Thanks!
 
Its not that it suddenly gained excess power. That's how it should be. Maybe you've had an air leak or something else causing it to run weakly. No 600cc bike should bog down to 75 MPH.
 
I'd agree. Since you didn't mention anything about recent or past work. We could assume it to be any number of problems as bunnygoat mentioned, an airleak. Or a possible blockage in a jet (even a minor blockage) that has worked loose, etc...

Any number of things could have happened. However if it's running correct NOW.. I wouldn't go messing with things. I would suggest though if you haven't stuck to your maint schedule very well. With 60k on the clock now. Perhaps it would be a good idea to start working on the PM stuff and keep her running as she is now.
 
Considering that you gassed up the night before, that being the difference seems to be the most logical conclusion. I agree that no 600 should be bogging unless it's a humongous grade you are going up (unlikely). Humbly suggest a reputable fuel system cleaning additive may be to your benefit.
 
Thanks for all of the replies!

It is a 1996 model and I have owned it for 6 years. I have put the last 40k of its 60k miles on the odometer. Performance has not degraded in that time.

I have not been disastisfied with its function. It has performed the way it was designed. The Shadow 600 ain't no 600cc inline 4 that makes 80hp or more. Off the showroom floor, it only makes 35-40 hp on a good day! Top speed on level ground really is about 90mph. The odometer scale only goes up to 105 mph. Going up that hill, going home from work, I have done hundreds of times. Historically 75mph is about all it will do up that 2 mile grade without fail. That is why I was surprised with this evenings oomph in performance. I am still dumbfounded as to why.

The bike logs about 8k miles a year and I throw some seafoam in the tank about 3 times a year.

Dan
 
Bikes always show a little more power in colder weather - do you not ride in the chilly months usually?
 
Summarizing posts so far, causes could be air leak, freeing of minor blockage of jet, gas, cold dense air, and wrist action. We'll have to see how it performs from here forward.

From your input, I tend to suspect good gas and denser air as the cause. I usually buy Chevron, Mobil, or Shell gas for the additives. I do ride in cold weather to work (in the 40's F) and sometimes in the 30's. I do wear an electric vest on weekend rides, or tours, when the temps drop below 60 F.

Thanks for the suggestions!
Dan
 
Um, maybe a tailwind?

(not really trying to be a smarty)
 
This is why I love riding in cool, humid conditions. :ride
 
I am going to chalk it up to cold moist air. Rode it 250 miles last Sunday in 80 degree temps and performance is back to normal.
 
You must log in or register to reply here.
Back
Top