Best Reed spacer positioning for low end power

  • Between Engine and Cage

  • Between Intake and Cage

  • No spacer


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Tanker_01

Member
Oct 17, 2018
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Southern Indiana
I am planning to set up my little '06 Blaster for trail riding. I have an oil block off kit, a non-tors carb with a longer throttle cable, and a reed spacer with Boysen fiber reeds.

I am planning to set up the quad for trail riding so low end power is my target. I have a skidplate already installed and I did wheel spacers in the front. I also have trail-oriented front tires and I used mx/trail rear tires. I will be keeping the stock rear axle and front arms.

When installing the reed spacer it is my understanding that if I put it between the cage and the engine I will optimize low end and if it is in between the intake and the cage It optimizes top end. So I will be installing it between the cage and the engine at the moment.

As far as intake modification is there really much power to be gained by drilling holes in the top of the airbox? I do not really want to drill it out if I dont have to since it will most likely be getting wet trail riding. Are there other options for getting more airflow without compromising water resistance?

Right now the engine is having some issues leading me to think I have broken/chipped reeds. I know that bad reed symptoms are the same as a blown top end so I have also ordered a new top end with piston if I need it.

I will keep this thread updated with my build and will post pictures when I get a chance.
 
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As far as intake modification is there really much power to be gained by drilling holes in the top of the airbox? I do not really want to drill it out if I dont have to since it will most likely be getting wet trail riding. Are there other options for getting more airflow without compromising water resistance?

so I have also ordered a new top end with piston if I need it.

I will keep this thread updated with my build and will post pictures when I get a chance.

As to that air box, more air = more power , bigger Jets. Unless you're taking it swimming, just remove the lid. If you you do a lot of water/sloppy mud, either get an outerwear lid, or just the material and make your own. A good pipe like fmf, or dmc will add more power than any reed spacer.

My son had them on his Banshee and I took them off because it made it nearly impossible to to get the carbs on.

As to the new top end, hopefully you're NOT looking at those cheap cylinder kits, they're JUNK !!
 
Boysen reeds installed. Waiting for the spacer coming tomorrow. I'm going to install the spacer since my faith in thermodynamics states that more volume and lower compression ratio will give me better low end torque.
 

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For the airbox I am going to try to either increase the size of the oem snorkel or add a second and/or third snorkel. I do not want to modify or delete the lid if i dont have to.

I do not think I am going to have to replace the cylinder and piston so for now I will keep the new one as a spare for when it eventually loses compression due to rings or cylinder gouging. I am putting on aftermarket master cylinder for the front and an aftermarket more adjustable clutch lever as well.

I am doing some research into running LED lights without a battery. I have looked into doing this for my XR600R as well and it requires a capacitor and a bridge rectifier to emulate DC power with AC. I have the equipment to do this but it is rather low on the list as of now.

The carb I got has a cable neck style cap to it and the throttle cable I ordered will not work with it so for now I will be still using the OEM carb. I will be taking that off and cleaning it in an ultrasonic cleaner.

My oil block-off system should be in today and I will be installing that as soon as I get the intake back together.
 
Boysen reeds installed. Waiting for the spacer coming tomorrow. I'm going to install the spacer since my faith in thermodynamics states that more volume and lower compression ratio will give me better low end torque.

Interested in how a lower compression ratio would increase low end torque? Is this a 2-stroke thing, because my understanding is that increasing compression bumps the power curve up everywhere.

Also does adding a reed spacer change compression at all since it does not change the cylinder vloune?
 
Gotcha, but that wouldn't affect the compression ratio, would it? And wouldn't lowering compression hurt power everywhere?


It would yes. The distance between the reeds and the cylinder head at tdc is the final compression value and the same distance at bdc is the initial value. increasing the tdc volume lowers compression ratio. lower compression ratio does cause lower overall power but increases low end torque and reliability. it is well known that lower compression prolongs the life of an engine, honda exploited that in thier older xr 4-strokes that had super low compression ratios, and that is why they were notorious for being bulletproof as long as you didnt skip time or drop a valve.
 
Upon further research, apparently the main reason to install reed spacers into the YFS engine is because the boost port is underneath the reed cage per oem spec, installing the spacer pulls the reeds back so the boost port is more in the airflow and can potentially cause better fuel atomization and therefore cleaner and more powerful burn. So with that along with lowering overall compression, bottom end should be more torquey but my top end will suffer a little, probably not enough to tell by the seat of the pants dyno.