RX-1 Tuning Info
To the Point:
Tuning tip number #1 ......... install the primary sheaves off of a VK 540 (Viking)..... they are 12.5 degree vs 14 degree stock..... we are finding that it is grabbing the belt much better.... also will produce more top end hopefully by allowing the belt to have more travel (sheaves close closer!!!!!)...... try it out... the sheaves are not very expensive... we ran the stock RX-1 primary and another stock RX-1 primary other than the sheaves and gained 3 mph in 500ft of grass... enjoy.... :-)
Stock
Primary Spring: Yellow-Silver-Yellow
Weights: 8FA-17605-00 69.43 grams
Rivets: 4.5 gram inner, 3.6 gram outer
Rollers: 15.0mm
Helix: 51-43 degree
Secondary Spring: Pink
Gears: 24-38, 70 link chain
Engagement: 34-3800 rpm
Shift: 10-10500 rpm
Proposed
Primary Spring: Orange-Pink-Orange
Weights: 89L-17605-00 43 grams
Rivets: 4.5 gram
Rollers: 15.0mm
Helix: 51-43 degree
Secondary Spring: Green
Gears: 24-40, 70 link chain
Engagement: 43-4400 rpm
Shift: 10,500 rpm
Quoted From Snow Fever
Tech Info:
As I have said before I don't type very fast or spell very well so I will post this in a few topics and number them. First off I want to explain a few things about the stock clutching to help make it easier to understand what I was shooting for. The stock weights are very flat in profile which even though they are heavy in mass they do not create a great deal of force do to their profile and where the weight is distributed. My first recommendation is to take those weights with you when you go fishing and use them to drag your lure to the bottom of the lake when you are jigging for bottom feeders. If you use a weight with a more aggressive profile you can use less mass to do the same or better job. And as a side benefit you have less rotating mass which means faster spool up or what translates to WAY better throttle response. Hear is what I have done, the stock weights on my little scale read 68 grams (officially 69.43 Grams) that’s with no pins (my scale is just one of those little diet ones so its not overly accurate but is good for apples to apples comparisons) The weights I am running now are 48 grams that’s 20 grams less and I know that sounds like bullshit because that would be 60 grams total for the three.
Now that I have lowered the over all mass by what even I wouldn't have guessed would add up and I spend what my wife says would be grounds for divorce in a court of law. The weights I'm using now are 89L's part # 17605-00-00 @ 43.0 grams with a steel pin part # 90261-06033 4.5 grams for an official total of 47.5 grams (my scale says 4Now you have a very aggressive weight but it seems to light right? So now we work on the primary spring.
Now that I've explained what I did for weights I'll explain the spring The spring does several things first engagement then the rate in which it shifts ( which is where it holds the RPM while its engaged ) then its ability to hold the RPM in its peak power band. The stock weights and spring work O.K. for this but by using the 89L's and matching a spring it is greatly improved upon. After doing lots of testing and experimenting the spring I came up with is a Part # 90501-601L8-00 an Orange-Pink-Orange with the stock Rollers In the Mountain version 16.5 diameter it makes the engagement 4900-5000 rpm tach indicated but it does tend to over rev on the top end so I put one grade 8-1/4" washer on either side of the pin in the weights (the washers weighed 1.75 grams each) so this lowered the engagement to 47-4800rpm with a shift out of 10,200rpm which is what Yamaha states is the Max H.P. RPM. I wanted my engagement lower because I mostly boon dock so I removed the 2 washers from each weight then I removed the 16.5 mil. rollers and installed 15 mil. rollers Part #8CR-17624-10 Which as a side note come stock in the short track versions, YOU LUCKY BUGGERS. This brings down the engagement because the weights swing out more before contacting the roller and they create more force all the way through the shift curve. Now my engine RPM engagement is 43-4400 rpm the up shift is slightly stronger and it holds 10,500rpm at full shift out. (When you first peg the throttle it hits 10,700rpm but quickly drops to 10,500rpm) This is what good clutching is suppose to do!!!!!!! Oh yea as far as my sled running 10,500rpm now Yamaha says Max H.P. is 10,250rpm plus or minus 250rpm so our altitude here is 2200' and we ride to about 6500' so if it drops 2-400rpm in the mountains its still right on.
Now that the front clutch is hitting hard out of the hole, pulling hard in the mid and maintaining Max rpm on top its time to fix the secondary clutch. First off the rear spring in this thing is robbing valuable H.P. because it is way to torsional (twisting force) and way to much side load force. (another item to put in your tackle box for fishing) By having a spring that is too stiff in these 2 dimensions it clamps the belt so hard that it takes H.P. to over come these forces. You only need enough side to clamp the belt and enough torsional to back shift well. They have use this over kill spring to over come the fly wheel effect of those BIG CHUNKS OF STEEL they put in the primary. (which act as a big flywheel) So now that I greatly reduced the rotating mass of the primary I was able to install a new spring part # 90508-556A7-00 Silver which lets the secondary still clamp the belt good makes for better up shift and still back shifts excellent. If you were not mountain riding I would run a part #90508-556A2 Green spring. This will sacrifice some back shift but will upshift even better. Now on to the helix.
The Helix in the short tracks is a 51-43 degree which I don't have but assume would work with this set up excellently. Here's what I found though. The mountain version come with a straight 45 degree and I've tried as high as a 48 and as low as as 37 degree and there is very little difference in how they act on the grass. This friggin motor doesn't really care much about the helix angle it just upshifts and back shifts like nothing I've ever worked on before!!!!!! So for trail or lakers I would run the steeper angles its going to help a bit but for the Boon Dockers or Mountains I feel that a 45-37 progressive will be DAMN close to perfection. Excellent up shift because this motor doesn’t care, Great belt clamp because a shallower angle holds the belt better and the back shift is to die for with the shallower angles once your moving. I'm sorry I don't have a part number for this Helix but it's a Hauck made helix but any one close to this made by anyone I'm sure will work GREAT!
So this is NOT JUST THEORY I have now run my sled lots on the grass making small changes each time till I got to this point. I have also went out with my dealer several times and they brought two Mountain RX-1's to compare to and after testing mine against their's the proof is in the pudding. They are now going to set their's and customers up the same way. And at this point I would just like to say thanks to my dealer PG Yamaha for all there help. This is what it is like to ride. Bring the RPM up to 4000 slam the volume control on the right handlebar and it violently launches and pulls hard till whatever speed you let off at 50mph the rpm is about 75-7700 and when you wack the throttle it again pulls as though you were taking off from a dead start. UNF#@%ing REAL!!!!!!!!!!!! Add any rpm or mile per hour you do this it is just the most RAPID UPSHIFT and BACKSHIFT I have ever rode in a stock machine. You know when your Rat racing with the good old boys down the trail this thing is going to have FUN FACTOR coming out of your YING YANG I know this is only on the grass but I have no doubt this will hold true no matter where you ride.
I have done several other things with my sled as far as set up goes but my dealer is running all this stuff in one of their sleds now and it works awesome. It pulls harder out of the hole, mid range and top end than the stock set up which was in the other sled with also much better throttle response and back shifting. It no longer seems tame as the stock on does. I hope this will help some of you guys and if any of you come up with something please share it with the rest of us. I know this is only testing on grass but have no doubt that it is going to work on snow in most conditions with very little changes even if you gear up or down from stock gearing. FOUR STROKES DO RULE
Snow Fever
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