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No speed gain at all with 48mm BBK
Posted: Mon Mar 07, 2011 11:15 pm
by amazing4
This has probably been brought up before, but I gotta ask. I've got a 1986 Spree. So for Christmas I got a 48mm BBK. It came with the bigger jet. Easy install all the way around. Added the extra recomended oil to the tank so it's intentionally rich. Lost alot of take-off which I expected, but gained NO top speed at all.
So after all that, it starts slower, still only tops out at 30 and smokes more! Bummer. So what gives? Is it possible that the exhaust is just loaded with gunk and it's not breathing? There are about 2200 miles on the scoot. I'm lost here and will take any help I can get..thanks.
Re: No speed gain at all with 48mm BBK
Posted: Mon Mar 07, 2011 11:17 pm
by spree-rider
i'm not going to touch this thread. i will just EXPLODE. but you probably didn't break it in right. and a bbk doesnt increase your topspeed. that's what gears do. a bbk increases your torgue and actull power to spin gears.
Re: No speed gain at all with 48mm BBK
Posted: Mon Mar 07, 2011 11:25 pm
by Petrock's 1984 Spree
The bbk will increase your acceleration and decrease your mpg. It does nothing for top speed. If you want higher top speed then do the front pulley mod or buy the aftermarket gears like spree-rider said.
The front pulley mod how to can be found on wikispreedia
In short, the bbk you got did exactly what it was supposed to do.
Re: No speed gain at all with 48mm BBK
Posted: Mon Mar 07, 2011 11:28 pm
by eliteguy50
The BBK may be ported to run at a higher RPM (higher top ground speed) but the 48mm BBK is still being choked down by the stock exhaust and intake. When you let it breath, it will rev higher than the stock bore.
Re: No speed gain at all with 48mm BBK
Posted: Tue Mar 08, 2011 12:03 am
by Bear45-70
amazing4 wrote:This has probably been brought up before, but I gotta ask. I've got a 1986 Spree. So for Christmas I got a 48mm BBK. It came with the bigger jet. Easy install all the way around. Added the extra recomended oil to the tank so it's intentionally rich. Lost alot of take-off which I expected, but gained NO top speed at all.
So after all that, it starts slower, still only tops out at 30 and smokes more! Bummer. So what gives? Is it possible that the exhaust is just loaded with gunk and it's not breathing? There are about 2200 miles on the scoot. I'm lost here and will take any help I can get..thanks.
If you lost take off, then something is screwed up, because the BBK, especially the 48mm, should help bottom end acceleration a lot. The no increase in top speed is not surprising as the 48 BBK needs more carb than the stock carb. The stock carb chokes the big end. It smokes more because you are stuffing more oil into the engine than the oil pump did by itself. Chances are if it reaches 30 mph the exhaust is most likely not the issue.
Do a compression test and let us know the numbers.