Primo Scooter

Performance

If you have some ideas for increasing the performance of your Primo Scooter from Primo, please contact us. This page will have tech emails from customers who are trying to increase the performance of their scooter. We do not support changing your scooter because it voids your warranty. The suspension and brakes are not designed for higher speeds. So caution should be taken before attempting to increase the performance of your scooter. Some state laws may prohibit modifying the performance and may change the classification of your scooter to a motorcycle. Please read our disclaimers. We are providing this info, but we do not warrant the information and we have not checked it for accuracy.

March 2004 - Motorcycle Tech who has a Primo Scooter Primo 21: "We ran the Primo on the Dyno, and it put out 2.2 HP. Actually a bit more than I expected, stock. That gives us a baseline to work with so we know if our changes make it better or worse. BTW, we found out that doing just about *anything* to the intake side to improve airflow (opening / removing the airbox, etc) made the HP drop! Even pulling the little rubber "snorkle" out of the airbox only made it louder and run rougher. A very delicate balance in the fuel mix with the stock WABRO carb. If anyone should ask, tell them to leave the intake tract alone if they don't know how to jet the carb for a richer mixture (Mikuni mains fit quite nicely)."

January 2004 - Customer in CO. " Got the results back from what kind of oil is used in the transmission case, 10W-30W. My friend thought that 10W fork oil would not work because it would break down under high temperatures so that’s what in the case. It takes one and a quarter quarts of 10W-30W. If their going us the scooters in the desert or lets say Las Vegas then 10W-40W would be better.

We played with the scooters yesterday and found some interesting results. The cerebration system has small metal fingers that are closed and are opened as you increase the amount of intake, located behind the copper looking spacer that you mentioned. We removed the fingers and found that the carburetor would not handle the extra flow of air (it would not start). My friend found that the manufacture developed the carburetor only to do minor adjustments to the amount of air and fuel. He then went over to his bike shop and returned with a Yamaha carb which would do true adjustments. We then installed the carburetor and removed the fingers again and were able to adjust the carb so it was stable. We tested drove it around the block and achieved 55 miles per hour. We then removed the air cleaner intake and discovered that we could go 65 mile per hour. My friend fells that we could go little faster if we modified the air cleaner and put a high performance exhaust system on. All adjustments can not be made without first changing out the carburetor. The manufacture produced the carb and the fingers as a hole unit to prevent the scooter of achieving such speeds. The carb retails for about $65.00 to $85.00 depending on what version you put on, and the adapter the replaces the copper spacer is about $28.00. We are going to do some more testing as soon as we finish on what you can or cannot do. I will send pictures and a detailed parts list and were you can get then, so you can do the modifications. Now for the draw backs.

We found that the scooters will handle the 55 mile speeds with no problems but the 65 mile speeds would be to much unless you modify the cooling system. We modified the cooling buy replacing the existing fan with on that came of a 125 Yamaha. The fan is located on the opposite side of the transmission case. You remove the plastic grill cover remove two screws and put on the new one. My friend told me that running at greater speeds you would need to replace the brakes with disk brakes at least on the front. Overall we spent the whole day yesterday until about 11PM on this. Like I said we should finish today and I let you know everything. My friend has a friend that owns a bike speed shop and muffler shop in town so he’s coming over today to look at the scooter. So it looks like the little scooter that could, dose!!!!"

February 2004 - Co. "Ok the guys just left and will return with the modified exhaust today or tomorrow I hope today. Oh ya one more thing at these speeds the scooter brakes the law. I mean a Cop just gave me a funny look as I was scooting down one of main side streets at about 55 miles per hour in a 35-mile speed limit. Well as you well know the 50cc limit on no registration, well we just broke that that speed limit. So again may want to let folks know that they have to register the scoots if they are caught. This is stuff that comes to mind. As I said, we are still playing with it. Right now, I noticed a great improvement on pickup and go, from a dead stop the bike would raise the front end slightly. So maybe just with small modifications would be enough to satisfy the folks like me that just want a little more performance instead going all out and that way keep the bikes within a safe running and mechanical speed I mean you don’t want to sell a kit that would blow the engine. I am thinking like a Carburetor, Clutch, a modified exhaust, and a cooling fan will do the trick. I could add instructions on how to remove and replace with new hardware and what tools that would be needed. You know make it simple even though I blooded my knuckles so far from doing this stuff. The bikes are easy to take a part after someone shows you. If I had instructions I could have done just about any repairs on the bike, there are do’s don’ts though. The biggest thing to remember is that the Phillips head screws can rounded out really easily, you know when you use the impact driver your customers need to take there time and hit the tool top dead center or it could damage the screws. I will eventually replace the screws with American made Allen bolts with modified heads to fit (They come in Blue, Red, or silver the ones kids are using on their cars engines (Honda Civics’). The reason for the Allen instead of Hex bolts is that they will not damage the cast aluminum casing when you torque them down. My friend recommends no more than 3 pounds of torque when you bolt the transmission casing back on in a star formation.

See little things like that an improve maintenance greatly when comes time to replace a clutch or a gear.

Ok here’s one you need to know now just with the stock bikes.

Tuning the stock carbs:

1. Warm up the for about 3-5 min.
2. After warmed up, turn the airflow screw clockwise until it is tighten. Do not force the screw too tight, it might damage it.
3. Turn the airflow screw counter clockwise 2 turns (180 degrees rotation considered 1 complete turns).
4. Now turn the fuel flow screw clockwise until tightened. Again, do not force the screw too tight.
5. Turn the fuel flow screw counter clockwise 2 turns.
6. Then start the scooter. (Make sure the scooter is on the center stand before you start the scoot, and squeeze the rear brake when you start.)
7. Adjust the fuel screw (turn counter clockwise) until the RMP drops. As soon as RPM drops turn the fuel ½ turn counter clockwise again.
8. Now adjust the airflow screw either counter or clockwise to desired idle RMP. Counter clockwise should make the RPM rise and clockwise should adjust the RMP down.
9. Unfortunately, the scoot is not equipped with a RPM gauge, so you will have to do this by listening to the engine rev noise. The ideal engine noise should be a medium hum noise. After you have adjusted the fuel and air, roll the throttle to get the rpm up, then release, and see if engine rev come back down. If it did not come back down, you have given it too much fuel. Turn the fuel screw counter clockwise to lower RMP. Repeat these steps until your engine running smoothly with no puttering. Remember that the fuel flow is the one that get adjust the most and the air is to fine-tune the idle.

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