Intake & Exhaust flow rate/ Compression/ Top speed

rick71454 · Post by **rick71454** » Tue May 07, 2013 11:52 pm

Hello BuddyLand:

I understand that Intake and or Exhaust flow rate has something to do with engine throughput, compression, RPMs. Then this impacts top speed.
I understand that performance air intakes and exhaust pipes can increase top speed.

Does anyone have any data to compare these flow rates, engine performance, and top speed? I mean, do I just go out and by these things, put them on, and hope my Buddy 125 gets higher top speed?

Whats your experience with just putting on a performance air intake and exhaust pipe?

Thanks
rick71454

PeteH · Post by **PeteH** » Wed May 08, 2013 12:37 am

You'd have to do some more. The CDI, for example, is a rev limiter, so without changing the final drive gearing, you're only going to go so fast. Racing CDIs can raise or remove that limitation, but then something in the engine will probably let go eventually.

The GY6 was designed to provide a reasonable amount of power along with high reliability and simplicity. There are comparable displacement racing designs (I'm thinking about the old 60s-70s Yamaha TT bikes) which were designed to put out power at 10 or 12k RPM all afternoon. Not so our humble Buddys.

Syd · Post by **Syd** » Wed May 08, 2013 1:04 am

What PeteH said. Engine upgrades in general will get you to the top end quicker, but won't significantly increase the top speed. Increasing RPMs and gearing changes are the way to more speed.

[edited twice to fix stupid errors]

Throwback7R · Post by **Throwback7R** » Wed May 08, 2013 3:17 am

Be careful with gear changes as you need the power to actually use them. The cdi is one of the easiest ways to go faster. However if you want a faster top speed start looking for another scooter.

lovemysan · Post by **lovemysan** » Wed May 08, 2013 3:27 am

The exhaust will have minimal effect. A performance air intake will kill low rev power. The cylinder head is very restrictive on a 161cc buddy. I plan to get a ncy big valve head and do some mild porting. Next would be carb and intake manifold , then camshaft. Also tuning isn't easy without a wideband o2 sensor at least not for me.

BuddyRaton · Post by **BuddyRaton** » Wed May 08, 2013 1:09 pm

I have had very good success with the 161 kit, air box mod, 26 mm carb and ncy pipe with the stock 125 head. Not much more top end but a ton more torque and acceleration. I'm not convinced that the big valve head is the way to go, I have heat concerns but they may not be justified...just not convinced it's the right way to go.

I haven't checked the compression but not a bad idea.

Right now I am VERY happy with the set up I have and have put a few thousand miles on it so I will probably leave well enough alone...for now

lovemysan · Post by **lovemysan** » Thu May 09, 2013 4:53 am

BuddyRaton wrote:I have had very good success with the 161 kit, air box mod, 26 mm carb and ncy pipe with the stock 125 head. Not much more top end but a ton more torque and acceleration. I'm not convinced that the big valve head is the way to go, I have heat concerns but they may not be justified...just not convinced it's the right way to go.

I haven't checked the compression but not a bad idea.

Right now I am VERY happy with the set up I have and have put a few thousand miles on it so I will probably leave well enough alone...for now

I have a similar setup running the stock carb. Low and mid range is strong despite me weighing 250lbs. After looking the stock head over I'm going buy a big valve head and polish it.

BuddyRaton · Post by **BuddyRaton** » Thu May 09, 2013 2:48 pm

lovemysan wrote:
BuddyRaton wrote:I have had very good success with the 161 kit, air box mod, 26 mm carb and ncy pipe with the stock 125 head. Not much more top end but a ton more torque and acceleration. I'm not convinced that the big valve head is the way to go, I have heat concerns but they may not be justified...just not convinced it's the right way to go.

I haven't checked the compression but not a bad idea.

Right now I am VERY happy with the set up I have and have put a few thousand miles on it so I will probably leave well enough alone...for now
I have a similar setup running the stock carb. Low and mid range is strong despite me weighing 250lbs. After looking the stock head over I'm going buy a big valve head and polish it.

Please keep us posted....I'm interested to see what difference it makes for you.

Rusty Shackleford · Post by **Rusty Shackleford** » Thu May 09, 2013 2:52 pm

I've yet to find a dyno chart for a Buddy 125 (aside from the semi-ambiguous one on the Scooter Works listing for the 161 kit). It would be nice to have a before and after. My understanding is the kit will add a little power to the low end; the exhaust will add a little power to the top end... but as others have stated, gear ratio, and horsepower to pull it, will be your limiting factor in top speed. If you need to go over an honest 55mph-60mph, a bigger bike is probably your best bet. That said, to reiterate, I would be very much interested in a dyno chart, even if only to help with choosing roller weights, contra springs, etc.