Prima 70cc kit review :)

Anachronism · Post by **Anachronism** » Tue Aug 04, 2009 2:40 am

Ok, so a few weeks ago, I ordered the Buddy 50 "Stage 2" kit from scooterworks, which includes the prima pipe, rollers, spring, jets and the 70cc kit.

Turns out they were backordered on the rollers and the pipe, so they shipped me out the 70CC kit by itself.

I decided to put the kit on first, mainly because its easier to track down problems if you install one piece at a time.

I'm reviewing both the kit and the ease of install, so first it is worth mentioning that I am a pretty good mechanic. I've worked on autos for years, rebuilding engines, transmissions, and differentials myself. I'm quite familiar with 2 strokes from working on jet skis.

That said, I've never taken a panel off of the Buddy. So call me a knowledgeable mechanic, but one that is doing everything for the first time while working on the scoot.

So, let me say that installing the 70CC kit is EASY. It was exactly 1 1/2 hours to install, from the point that I parked the scooter to the point that I fired it up to take for a test ride. No tools needed any more complex than a few wrenches and needle nose pliers for the c-clips.

The kit consists of everything you need to install, EXCEPT one glaring exception. The stock cylinder has studs for the exhaust pipe, the new cylinder did not. Your choice is to attempt to remove the studs, or new bolts/studs. I did a temporary fix by stealing two of the fan shroud bolts to use for the exhaust.

The prima parts look nice. The cylinder is definitely more performance oriented than stock- for one the 70cc cylinder has a full exhaust port (the stock port is a half-moon shape) and is definitely more aggressive. The machine work looked good straight from the box.

Note that to this point, the entire rest of the bike is totally stock. I have not touched the carb, and I probably need to. Do not install this without carefully checking your tuning!

That said, I was amazed to find that the scooter started IMMEDIATELY, and settled into a smooth idle, even with the untouched carb settings. I took it for a quick ten minute ride to get the rings seated, and was quite surprised to find that the stock carb settings seem reasonably close, in that there was no flat spots, hesitation, backfires, pops, etc, to indicate that the carb settings were wrong. In other words, with an untouched carb, it ran as smooth as stock.

With the stock pipe, it sounds stock as well.

The power increase is great. Again, even without it tuned at all, there was a ton more torque. I was doing 35 mph at 1/3 throttle on a street that I normally top out wide open at 35. Acceleration was much stronger. Obviously I did not try a top end run, or anything more than some varied part throttle with an occasionally momentary WOT squeeze, but the increase in power is quite nice.

For the price, I don't think there is a better modification. I can't wait for the other parts!

Anachronism · Post by **Anachronism** » Tue Aug 04, 2009 2:44 am

All that said, I'm open to pointers on where to start with carb adjustments. Obviously I need to start by checking the plug to see where I am, but if anybody has a baseline it would be helpful.

I should mention that I live at 6200 feet elevation, which will definitely impact things.

Lastyearsyou · Post by **Lastyearsyou** » Tue Aug 04, 2009 3:05 am

This makes me want to mark the day my warranty expires on my calendar! Can't wait

((The warranty was the deciding factor between the Genuine & other brands))

B02S4 · Post by **B02S4** » Tue Aug 04, 2009 3:33 am

Anachronism wrote:...I should mention that I live at 6200 feet elevation, which will definitely impact things.

That's probably why you weren't running way lean with the OEM carb & the BBK...

enzomatic · Post by **enzomatic** » Tue Aug 04, 2009 8:41 am

great post, are there any pictures? I don't even have a 50cc but I love to see the work and hear about it. Kinda why I hang around this place.

also nominated for the review section.

Anachronism · Post by **Anachronism** » Wed Aug 05, 2009 1:43 am

Ok, this is a bit odd...

Remember that the carb is box stock...

I just spent an hour checking the tune. First at idle, then 30% throttle, then WOT.

Each time I ran for about a minute, turned off the scooter while moving, coasted to a stop and checked the plug.

Plug looks a perfect light brown. WHAA?

Anybody else have this? I suspect a few things are going on.

1. 6200 feet elevation means a lower fuel requirement.
2. Stock exhaust, airfilter, etc limit power gains, so carb is still supplying adequate fuel.
3. Additional vacuum from 70CC is creating a better carb signal, so carb is supplying more fuel. I've seen this on jet skis where people have swapped in larger engines (like 650cc to 750 cc) and found they had to jet DOWN.

Still its weird, and I would like some reassurance that this is even possible.

B02S4 · Post by **B02S4** » Wed Aug 05, 2009 2:01 am

With 2T's, in plug reads I trust...

That said, the only way to know for sure (short of a dyno) is to bracket the main jets & test the bike on the same stretch of test road & see what results you get, especially at WOT.

If you upjet 1 step & performance improves, upjet again until it either: a)doesn't improve or b) degrades.

You can also shim the needle to fatten up the midrange, if necessary.

My best guess is that you need to be approx. 2 steps leaner than someone at sea level, given your elevation.

Trust the journey and you will arrive at the correct destination...

gearhead · Post by **gearhead** » Wed Aug 05, 2009 2:04 am

^yeah thats what sucks with modding. carb adjusting lol

Shane Wilson · Post by **Shane Wilson** » Wed Aug 05, 2009 2:09 am

Trust the plug.

I suspect your elevation is playing the biggest part in all of this.

Did your bike feel too rich before the kit?

rajron · Post by **rajron** » Wed Aug 05, 2009 2:10 am

I had a similar experience after I kitted my 125 4 stroke – it was only after I opened up the air box, already had the less restrictive exhaust, did I need to re-jet; +5000 feet here. I hear about how it was necessary to re-jet after adding the pipe, but up here it was not necessary, maybe a little lean, but still the plug looked very good – it was the final combination of kit, exhaust, and intake that the jet adjustments were needed.
Open up the intake, install the new pipe, then the re-jetting fun starts, along with even more power; incidentally, my scooter is getter better with age, as the newer parts seat in.

Anachronism · Post by **Anachronism** » Wed Aug 05, 2009 2:56 am

Plug looked a little blacker than it does now, but the Cylinder wash pattern looked perfect on the old cylinder. So, it was probably rich, but not by much.

I opened up the fuel mix screw by about 3/16 of a turn just to play it safe. After a test drive, I found that the bike felt about the same, but the exhaust stunk BAD of unburnt fuel. I'll try it tomorrow and probably move it back.

Anachronism · Post by **Anachronism** » Fri Aug 07, 2009 8:07 pm

So after about 100 miles on the kit, I'm getting a pretty good feel for performance. The bike is still getting faster every time I ride it.

Right now, it is able to run about 10 miles faster all throughout the range. Hills that used to slow me down to 25 it now climbs at 35. My top speed on flat ground used to be 40, not its an easy 50. Top end is improving as the cylinder breaks in.

Some of the problems with the stock CVT are still present- most notably, once the scooter is in "high gear", it doesn't like to move off of that, even if RPMS go way down. I have rollers and a spring on order to fix that, along with the pipe.

I'm going to try the prima rollers to get a feel on what weight rollers I really want, then I will probabl buy the Dr. pulley rollers.

Only changes I made to the carb were opening up the mix screw 3/16". I'm amazed that the stock jetting is so close. Still, and I can't stress this enough, if you put the kit on, CHECK FOR YOURSELF. Don't blow up a scooter because the stock jetting happened to work for me...

Anachronism · Post by **Anachronism** » Sun Aug 16, 2009 5:59 am

Kit is pretty close to broken in, although the cold idle is pretty ragged, indicating that it could still do to loosen up a bit.

I've also changed the rollers to help the engine a bit, and have starting doing some WOT runs to get a feel for performance.

Running a variator with half stock and half 5 gram rollers, I'm running 52-53 MPH (indicated) on the new setup on flat ground. Stock, I was getting 40 MPH.

Hills are greatly improved. Hills I would wheeze up at 20 MPH I am now climbing at 40. Simply amazing. It is well worth the money for the 70 CC kit.

black sunshine · Post by **black sunshine** » Wed Oct 21, 2009 9:14 pm

hey, is this whole review with the 70cc kit only? or did you get the pipe put on there at some point too? i have the prima pipe myself now and i'm about to get the 70cc kit . . . EXCITEMENT!

KS Power Nick · Post by **KS Power Nick** » Thu Oct 22, 2009 4:45 pm

WE have installed a bunch of the 70cc iron kits. If you are running with the stock air box and exhaust the stock jetting in the carb is close. Now if you open up the air box and exhaust LOOK OUT!!!! You will have to at least go up one step on the pilot jet and on the main you will have to go up 4-5 jets.

Example. Ported 50cc with dual stage boysen reeds and uni filter (stock exhaust) went from a 80 main to a 110 main. With an exhaust it would be more. Those 70cc kits REALLY like bigger carbs. Look at a 19 or 21mm carb.

Also If you can afford it. I recommend an Aluminum cylinder over the iron ones. The alum cylinders will run cooler and because they will run cooler they will usually have more aggressive of a port timing for more power.

black sunshine · Post by **black sunshine** » Wed Oct 28, 2009 7:33 pm

sitting in the coffee shop across the alley from Twist N Scoot, anxiously awaiting my kit install. quivering with excitement.

Kaos · Post by **Kaos** » Wed Oct 28, 2009 8:58 pm

black sunshine wrote:sitting in the coffee shop across the alley from Twist N Scoot, anxiously awaiting my kit install. quivering with excitement.

Woo! Way to go! Not that I've got a 50, but kits are fun stuff

black sunshine · Post by **black sunshine** » Wed Oct 28, 2009 10:43 pm

Kaos wrote:
black sunshine wrote:sitting in the coffee shop across the alley from Twist N Scoot, anxiously awaiting my kit install. quivering with excitement.
Woo! Way to go! Not that I've got a 50, but kits are fun stuff

hooooly crap this is AWESOME!!! i can feel the wide-eyed stares of the cagers as i leave them in the DUST at the light . . . and hills? screw you, hills! hahaha!

okay, some hills still slow me down a LITTLE. but dammmn . . . this is awesome!!

(jeez wait till i get a Blackjack

)

Lil Buddy · Post by **Lil Buddy** » Thu Oct 29, 2009 2:15 pm

black sunshine wrote:jeez wait till i get a Blackjack

<-- <--- <----

jasong222 · Post by **jasong222** » Mon Nov 07, 2016 2:12 am

Just out of curiosity- What will be the performance changes with this mod?

I have a Buddy 50, and recently I've been thinking about changing it to something bigger. Generally I have two things that come up with my ride currently: Speed out the gate and a 2nd passenger.

So my questions-

How does this mod affect the ability of having a second passenger? I know the weight recommendation is ~225 pounds (or something near to that.) I'm ~180 and I don't feel confident in the Buddy (50's) ability to take on a second person. Although I haven't tried it.

What would you say would be the average 'top cruising' speed of the bike now? Not the fastest you could go, but the fastest you could sustain. Like for highways and such.

I gather from the posts that 'out the gate' is pretty good.

Any thoughts?

Modern Buddy

Prima 70cc kit review :)

Prima 70cc kit review :)

Differences with a 77cc mod?