In Search of the Lost Top End
Posted: Sat Feb 09, 2013 1:25 pm
Good Day, eh?
I've had my stock '79 for a couple of years now and have enjoyed tooling around the backroads of the Island. She starts at the touch of the button, pulls smoothly from 1500 rpm in top gear up to speeds governed by comfort (stock high bars) and the limits of my aging body. She doesn't burn oil, attracts more attention on a sunny Sunday afternoon at the coffee shop than bikes costing four times what I paid for her and apart from a clatter from the clutch - which was minimized with a decent carb sync - I was a happy camper.
Then my step-son bought an '84 VF1000 Interceptor.
I soon found that to keep up with the exuberance of youth, I was going to have to ride considerably harder than usual and to my dismay, discovered that the engine had a hard time pushing past 7500 rpm in 4th! Dropping into fifth, she'd accelerate some more but again run out of breath around 7500 rpm. By this time, Shawn was disappearing into the distance and I was more than a little concerned. What could be wrong when she runs so well in the lower gears - up to redline if asked - but has such a hard time at high revs in 4th and 5th?
The P.O. had the engine apart at one time so I initially thought a cam sprocket might be one tooth out but she runs so well at 'normal' speeds. There's a good flow of fuel from the tank with the petcock hose disconnected. He had also fitted a pair of aftermarket mufflers of unknown origin which are welded to the stock header pipes and collector. They're looking more than a little shabby (and are a touch too quiet for my taste anyway) so I sprung for a set of Sankei replicas from Six Center in Holland. I'm thinking that perhaps the cheap aftermarkets are too restrictive and are choking the engine at high rpm and wide open throttle. Could I be right? Or do you suggest I look elsewhere for the lost top-end?
Thanks
I've had my stock '79 for a couple of years now and have enjoyed tooling around the backroads of the Island. She starts at the touch of the button, pulls smoothly from 1500 rpm in top gear up to speeds governed by comfort (stock high bars) and the limits of my aging body. She doesn't burn oil, attracts more attention on a sunny Sunday afternoon at the coffee shop than bikes costing four times what I paid for her and apart from a clatter from the clutch - which was minimized with a decent carb sync - I was a happy camper.
Then my step-son bought an '84 VF1000 Interceptor.
I soon found that to keep up with the exuberance of youth, I was going to have to ride considerably harder than usual and to my dismay, discovered that the engine had a hard time pushing past 7500 rpm in 4th! Dropping into fifth, she'd accelerate some more but again run out of breath around 7500 rpm. By this time, Shawn was disappearing into the distance and I was more than a little concerned. What could be wrong when she runs so well in the lower gears - up to redline if asked - but has such a hard time at high revs in 4th and 5th?
The P.O. had the engine apart at one time so I initially thought a cam sprocket might be one tooth out but she runs so well at 'normal' speeds. There's a good flow of fuel from the tank with the petcock hose disconnected. He had also fitted a pair of aftermarket mufflers of unknown origin which are welded to the stock header pipes and collector. They're looking more than a little shabby (and are a touch too quiet for my taste anyway) so I sprung for a set of Sankei replicas from Six Center in Holland. I'm thinking that perhaps the cheap aftermarkets are too restrictive and are choking the engine at high rpm and wide open throttle. Could I be right? Or do you suggest I look elsewhere for the lost top-end?
Thanks
. She now has that surge of power starting at 6000 rpm about which I've read so much, redlines in 4th and presumably will in 5th, if I could find a road surface on PEI not strewn with potholes! What was already a great motorcycle to ride just got even better!
I'm happy you didn't just give up. Nice job!