Can I used a 150cc head with a 155cc cylinder?

santacruz · 01-11-2017, 04:03 PM

I needed an exhaust gasket and ended up buying a 58.5mm big bore kit that doesn't include the cylinder head, along with a 7" 'racing exhaust', an A9 cam, and a main jet set.

Can I use my stock 57.5mm head with this kit? Is an A9 cam ideal for a quick 3 mile run to campus? I'd like to be able to accelerate with cars at leaving the stoplight, and I don't think I'll ever got over 55 mph. What should I rejet to? From what I've seen online, I was thinking 125.

Finally, is there anything I should do to the CVT with these upgrades?

DisillusionedPrepper · 01-11-2017, 04:36 PM

Hi,
Tire pressure makes a bigger difference in performance than the A9 cams do. Don't get me wrong but the difference is nominal at best but there is a small increase in top end breathing so you may get another mile or two in top MPH.
I put the A9's in every scooter I install cylinders on so there is a market for them.

Your head will work just fine with both the BBK, and the cam so no worries there. There is another new thread here (forgot which one but it's new/recent) where the fella is having an issue with the valves interfering w/ the piston on an A9 set-up.
You'll see in that thread that I suggested a possible cure, and reasons so DOUBLE check your adjustments before firing up the first time, and retorque everything after a short test run (a mile or so).

Jetting... No one can say. Go with the fattest jet to begin with, and jet down until you get what you need.
When you first fire the bike up do not expect idle to happen. Use the throttle to keep it at a mid-high idle, and adjust your mixture screw to allow a slightly richer mix. That means if you have an air screw (closer to the intake manifold) turn it in (clockwise) a quarter turn at a time until you get a good idle.
If you have a fuel screw (closer to the air box side of the carb) turn it out a quarter turn at a time to get a good idle.

The rest is all A,B,C's.
Lighter rollers?sliders, stiffer control spring, and stiffer fly springs in the CVT.
These are where the best bang for the buck come from.
For around 30 bucks you can gain a lot of take off torque, and a few MPH in top end.

Hope this makes sense, and helps.

santacruz · 01-11-2017, 05:09 PM

Quote:

Originally Posted by DisillusionedPrepper

Hi,
Tire pressure makes a bigger difference in performance than the A9 cams do. Don't get me wrong but the difference is nominal at best but there is a small increase in top end breathing so you may get another mile or two in top MPH.

...

Would you recommend staying with the stock cam? And would 9g sliding rollers be a good place to start lightening my rollers

DisillusionedPrepper · 01-11-2017, 06:28 PM

I'd say 9-11 gram work best with a red/2000 control spring, and blue (1000 rpm) thru red (2000 rpm) fly springs in the clutch.

Again, this all varies on what the springs are REALLY, and if you use rollers or sliders.
I'd suggest sliders above anything else. That said, with sliders I find that one gram heavier than the rollers I used are best. Say a set of 9 gram rollers work best for you... Then 10 gram sliders will work better.

I hate to say this but that is the ONLY golden rule I have found in YEARS of working on,scoots, and posting/reading forums.

Springs are subjective. What the manufacturer paints them with or calls them means dirt to me until you get into the top two... Malossi or Polini.
Same for rollers or sliders. There are THREE brands to use (so you can trust them to last) Malossi, Dr. Pulley, or Ninja.

There is an old youtube video from Josh or Rich (I forget) that took stock springs from several brands of scoots, and then "Racing springs" from several vendors... In 75% of the tests the "Racing springs were weaker than the OEM springs, and the only real boost in performance came from the brands I mentioned.
In fact Malossi yellow control springs that are sold as an upgrade to OEM were actually weaker than OEM.

Point is, nothing but trial, and error (and a box FULL of spare parts) will tell what will work best for you. If you really want to tune your scoot to be its best for how you ride, I promise you will have several attempts at combinations of rollers, springs, jets, and air filters to go thru.

In the end it all pays off tho. This crap is cheap, and the spares are useful in helping the next guy get tuned. If there is no "next guy" in your neighborhood they make good spares for in-between orders, and deliveries.

Forgot... The cam.
Go with the A9! It will improve top end. Just make sure to double check everything before starting the bike.

01-11-2017, 04:36 PM	#2
DisillusionedPrepper Join Date: Dec 2016 Posts: 109	Hi, Tire pressure makes a bigger difference in performance than the A9 cams do. Don't get me wrong but the difference is nominal at best but there is a small increase in top end breathing so you may get another mile or two in top MPH. I put the A9's in every scooter I install cylinders on so there is a market for them. Your head will work just fine with both the BBK, and the cam so no worries there. There is another new thread here (forgot which one but it's new/recent) where the fella is having an issue with the valves interfering w/ the piston on an A9 set-up. You'll see in that thread that I suggested a possible cure, and reasons so DOUBLE check your adjustments before firing up the first time, and retorque everything after a short test run (a mile or so). Jetting... No one can say. Go with the fattest jet to begin with, and jet down until you get what you need. When you first fire the bike up do not expect idle to happen. Use the throttle to keep it at a mid-high idle, and adjust your mixture screw to allow a slightly richer mix. That means if you have an air screw (closer to the intake manifold) turn it in (clockwise) a quarter turn at a time until you get a good idle. If you have a fuel screw (closer to the air box side of the carb) turn it out a quarter turn at a time to get a good idle. The rest is all A,B,C's. Lighter rollers?sliders, stiffer control spring, and stiffer fly springs in the CVT. These are where the best bang for the buck come from. For around 30 bucks you can gain a lot of take off torque, and a few MPH in top end. Hope this makes sense, and helps.
	0

01-11-2017, 06:28 PM	#4
DisillusionedPrepper Join Date: Dec 2016 Posts: 109	I'd say 9-11 gram work best with a red/2000 control spring, and blue (1000 rpm) thru red (2000 rpm) fly springs in the clutch. Again, this all varies on what the springs are REALLY, and if you use rollers or sliders. I'd suggest sliders above anything else. That said, with sliders I find that one gram heavier than the rollers I used are best. Say a set of 9 gram rollers work best for you... Then 10 gram sliders will work better. I hate to say this but that is the ONLY golden rule I have found in YEARS of working on,scoots, and posting/reading forums. Springs are subjective. What the manufacturer paints them with or calls them means dirt to me until you get into the top two... Malossi or Polini. Same for rollers or sliders. There are THREE brands to use (so you can trust them to last) Malossi, Dr. Pulley, or Ninja. There is an old youtube video from Josh or Rich (I forget) that took stock springs from several brands of scoots, and then "Racing springs" from several vendors... In 75% of the tests the "Racing springs were weaker than the OEM springs, and the only real boost in performance came from the brands I mentioned. In fact Malossi yellow control springs that are sold as an upgrade to OEM were actually weaker than OEM. Point is, nothing but trial, and error (and a box FULL of spare parts) will tell what will work best for you. If you really want to tune your scoot to be its best for how you ride, I promise you will have several attempts at combinations of rollers, springs, jets, and air filters to go thru. In the end it all pays off tho. This crap is cheap, and the spares are useful in helping the next guy get tuned. If there is no "next guy" in your neighborhood they make good spares for in-between orders, and deliveries. Forgot... The cam. Go with the A9! It will improve top end. Just make sure to double check everything before starting the bike.
	0