Forum Posts

Michael Hathaway
Jan 25, 2022
In Yamaha
There are a few Yamaha service manuals available for sale in the digital sales area. Most of them are free. Just add them to your cart and check out as normal. 😀
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Michael Hathaway
Jan 25, 2022
In Yamaha
The Rmax sheave gets really really hot, enough to melt the outer edges of my weights. My weights can handle 500F but the belts tend to explode around 250F. 2" snorkels are not enough! Come on... If a 2" snorkel is not enough on a Viking, why would it remotely be large enough on a Rmax? Yes, you are going to explode belts with 2" snorkels. If someone is selling kits with 2" tubes, don't buy it. The way I recommend pluming it is with that thin walled 3-4" drain pipe you get from Home Depot and use silicone turbo elbows found on ebay. 80mm silicone tubing couplers and corners work great. A 4" tube is preferred here. Why 3" and not two - 2" tubes? The best way to look at airflow is by the surface area of a circular opening. The area of a circle is pi x radius squared. A =πr2 So a 2" tube has an area of about 3.14sq inches. A 3" tube has 7.07sq inches. A 4" tube has 12.57 sq inches. So that is more than double the air flow. The stock tubes on an Rmax inlet is about 4" and there are two of them. So you are really just barely meeting the minimum requirements for snorkels at three inches in diameter. (pi=3.14159265359, does not equal pie, but cherry is great)
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Michael Hathaway
Jan 25, 2022
In Yamaha
I wanted to revisit the basics of how the Yamaha CVT system operates because I am seeing so many questions from operators who are new to the system. For many of you, this will just be a repeat of your already known knowledge of the system. I hope this clears up how the CVT operates and minimizes the myths and/or incorrect information that I am seeing in the threads. Starting with engine idling, the wet clutch is retracted or in a neutral position. As engine rpm is increased, the clutch pucks swing outward and begin to engage the wetclutch bell. At this point, the primary and secondary clutches begin to turn in their lowest ratio. The CVT will continue to operate at this low gear position until the rpm and vehicle speed has reached the shift out phase. This is when the outward centrifugal force of the weights becomes stronger than the spring pressure on the secondary clutch. On the Rmax, I believe this is about 15mph in stock form. This means that all crawling and low speed driving is in the low ratio position, which has nothing to do with the size of weights installed or any shims or sheave modifications. Now just to clarify, an added shim or lower cut sheave will produce a lower starting gear ratio. This means you will have more torque to the wheels in the 0 to 15mph range of the clutch operation, however due to the lower gearing, you may now be in a 0 to 12mph range before the weights make contact and begin the shifting cycle. There is no difference in noise, it is just lower gearing for taking off with big tires, crawling, climbing, etc. There is also no difference in rpm for your first shift, it will just come sooner in vehicle speed due to the lower gearing. When the weights are spinning fast enough to overcome the secondary spring pressure, the weights will be forced against the camplate and slide the primary sheave inward. This forces the belt to ride in a higher position, increasing the gear ration to the secondary clutch. Because the belt remains the same length, the belt is lowered in the secondary as the belt raises in the primary. This gives you higher gearing automatically. It is during this process that the weight sizes effect the operation of the CVT. Heavier weights will apply more force at lower engine rpm. Lighter weights will require more engine rpm in order to obtain the same force required to push the primary sheave inward, over coming the rear spring. After the CVT is shifted to its highest position, in order to accelerate the vehicle forward at a faster speed will require higher engine rpm. This is where most of the engine and transmission noise becomes a problem. The engine rpm can be lowered by increasing the weight size and/or machining the sheave to operate at a higher gear ratio. Letting off the throttle reverses the process until the primary sheave slides back into a lower gear positions and the weights slide back to their starting point. There is a one-way bearing which engages to keep pressure on the clutch and limit its free spooling. A shim will give you a lower starting gear, but it will subtract a small amount from your highest gear ratio. However, a machined sheave will give you both a lower starting gear and a higher top gear.
Yamaha Continuously Variable Transmission Basics (CVT) content media
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Michael Hathaway
Jan 24, 2022
In General Lobby
RULES 1) English is our main language. 2) No recording of others without permission. 3) There is a fine line between being funny and being derisive. Don't be mean. 4) Religious/Political discussions are discouraged, merely because this never works out. We’re from all over the world, have some respect. We're here to talk about innovation in tech and more specifically 3D printing/CNC/CAD. We're not here to talk about power struggles unless these struggles directly intersect the main topic. 5) Whenever possible try to put truth finding ahead of your own ego. There is no shame in admitting that you are wrong, or simply dropping the argument. We are here to learn from each other, have fun, and make friends in the process. 6) Be respectful: everyone is here to learn, help and contribute. 7) No personal attacks: discuss an issue rather than attacking the person. 8) No spamming: this will get you banned immediately. (edited) Changes/Additions to Rules: This is a relatively new community, we may expand the rules as we grow. Breaking the rules: Generally we will warn you before banning you. Repeated offences will lead to banning. (edited)
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Michael Hathaway

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