track dyno results for oem yamaha weights

mrviper700

mrviper700

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As you can see on the dyno graph there are certain weights which outperform other weights, even against the opinion of others who claim the opposite. A 8bu-10 weight is only marginally better then the stock 8dn20, and the 8dn 20 actually will out accelaerate it on the way up to peak then the 8bu-10 only puts 1.3hp more to the track then does the stock srx weight, simply because it weighs more. The 89a10 and 8bu00 are way better weights for both drag and even put more power to the track on topend by far. This dyno test was performed on a stock 20001 srx all on the same day. Each clutch weight was given its optimum helix and spring set up to produce the best, highest result, this is the make up of all the test on one graph. Also this is very good hp to the track on a 140hp snowmobile, above 50% output which means each of the clutch set ups was above the norm!!!:2strokes:

red=8dn20
black=8bu10
blue=8bu00
green=89a10
 

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This post is important. Can someone pin it? Another thing, can you try a set of heelclickers with your suggested setup? I even have my own suggested set up which I wish there was a graph for.
 
Nice post. Its crazy how they only get a little over half hp to the ground. Makes a lot more sense why the clutching can change so much. Also why its important to have every bearing as smooth as possible.
 
Very interesting! An Srx dynos at 74 to 77hp at the track? That's crazy inefficient!

I added 3g per weight on my 700 Venture cause it was over reving to almost 9000rpms . I now Rev to 8500 rpms and ended up gaining 10-13 km/h top speed depending on conditions. I probably gained 15% more power to the track. Maybe I should add more weight to get it down to 8300 rpms!
 
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Vincent said:
Very interesting! An Srx dynos at 74 to 77hp at the track? That's crazy inefficient!

I added 3g per weight on my 700 Venture cause it was over reving to almost 9000rpms . I now Rev to 8500 rpms and ended up gaining 10-13 km/h top speed depending on conditions. I probably gained 15% more power to the track. Maybe I should add more weight to get it down to 8300 rpms!
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A friend of mine is having the same problem with his sxr, it's getting up to 9000rpms and he would like to bring that down, what did you use for rivets?
 
After careful review of that dyno chart...... i dont see much difference in those weights. Just a few extra horse either direction. The best weight compared to worst is is less that 1 percent change. What am i missing??? Tony don't be offended. You and Mr Viper both contribute alot of info.
---mac---
 
Quick stupid question. Is a track dyno physical attached to the track drive cross shaft in some manner or is the track sitting on rollers like a car wheel would. If one roller it must an asphalt track I would imagine.

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BornYamaha said:
Quick stupid question. Is a track dyno physical attached to the track drive cross shaft in some manner or is the track sitting on rollers like a car wheel would. If one roller it must an asphalt track I would imagine.

Sent from my SM-G920V using Tapatalk
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the track dyno attaches to the sled via its own skidframe that's bolted into the sled and has its own set of rear cogs which drive off the track. track still driven by the sleds driveshaft up front. not a stupid question at all.
 
norwegian said:
This post is important. Can someone pin it? Another thing, can you try a set of heelclickers with your suggested setup? I even have my own suggested set up which I wish there was a graph for.
Click to expand...

Norwegian, dyno runs were made with aftermarket weights which outperformed these Yamaha weights by as much as 8hp to the track. I will tell you upfront tho the gain was changed tho by the addition of blueprinted cylinders and heads so it might not be as much as 8hp with a stocker but none the less it was significantly more then oem weights. When you lose as much power as you do in a sled a gain of track hp is significant.
This was just meant to show what the oem weights can do and the difference between them and some of the claims made here that certain weights were so much better then others when in reality they are not. Track dyno chart of the weights, this was the BEST runs the weight profile would offer, so they can be, and likely are lower then whats here in field testing. The typical guy clutching in the field would likely not be this high without the use of a track dyno to tell you what direction to go to transmit more power. Always funny how a dyno is used to either defend a claim or try to discredit it, and when they are on the losing side of the argument, tend to discredit real testing information.. whatever benefits the othersides argument I guess....lol, just shake my head.

information is power..... you either use it or lose it!
 
shaggyzr2 said:
A friend of mine is having the same problem with his sxr, it's getting up to 9000rpms and he would like to bring that down, what did you use for rivets?
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I added the heaviest yamaha rivets i could find (4.5g) and two 6mm washers on each weight tip. I don't remember the part numbers for the rivets off hand but they were cheap. You need to do some trimimg on the washers for clearance issues. I believe the total gain to each weight after trimming was 2.8g.

Apparently you could just switch your primary spring for a weaker one and do the same thing. HTH
 
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Mrviper700, can you shed some light on the "optimum" helix and spring for each weight was? Not necessarily looking for the exact angle of spring and preload, more of a general "this weight liked more start angle, less finish angle, more spring preload, less.. etc. In other words, say someone had a "great setup" with 89a-10's and then switched to 8BU-00's, what direction would you want to go with helix and sec. spring?

Also, what did each weight have for rivets?

Thanks,
Scott
 
I'd like to try those weights, right now I use 8bu10's loaded but would like to test others on 1000ft ice. Works well but we always want that extra mph!
 
scott riley said:
Mrviper700, can you shed some light on the "optimum" helix and spring for each weight was? Not necessarily looking for the exact angle of spring and preload, more of a general "this weight liked more start angle, less finish angle, more spring preload, less.. etc. In other words, say someone had a "great setup" with 89a-10's and then switched to 8BU-00's, what direction would you want to go with helix and sec. spring?

Also, what did each weight have for rivets?

Thanks,
Scott
Click to expand...

Hi Scott, well each weight has its own profile and its strong suit or weak. For example if you look at the force generated( Yamaha force graphs found in manuals show this) by a 8bu-00 in the first bit of clutch travel vs say a 8dn-20 weight , its clear the 8bu would be more aggressive and harder/faster upshifting then the 8dn 20 is, therefore it would be just a general rule of thumb the start angle of the helix would be smaller then that of the 8dn 20 if you were trying to get the same result. The 8dn20 being more docile on the upshift from a less abrubt curve in the weight would take to a larger first angle helix to help the secondary upshift at a faster rate to compensate or maybe I should say even out the rates of upshift between the 2 clutchs. After all, its all about upshifting quickly at a linear rate to make the sled go faster putting it in a higher gear ratio in the cvt. you asked about the finish as well, with some of the weights they don't have a lot of tip weight, so many times you can still get good belt grab by shallowing out the finish angle of the helix to keep pulling up top. By shallowing out the angle you automaticly apply more pressure to the belt, smaller angles apply more pressure. Along with more pressure you can back off on sec. spring tension, another thing that will give you more mph. since the helix is shallower you require less spring tension to keep ahold of the belt.
Each weight has different pro's and cons. The hard upshifting weights like the 8bu00 and the 89a10 don't backshift really well because of that first trait, where as the 8dn20 and 8bu10 type profiles will to a much better degree. Today we have the technology of multi angle helixs and roller secondarys and you can tune quite a bit of backshift even into a 8bu00 or 89a10 and possibly be pleased with the performance, it comes down to your personal choice and what your doing with sled to render your own decision as to how to set it up. I just merely put up a dyno run to show some weights simply outperform others and we are talking hp to the track.With sleds at a 50% loss every hp you gain back is a lot of sled lengths. no way would I leave 7hp to the track off the table if all I had to use was stock oem Yamaha weights.

the aftermarket weights literally stomped these weights in their best configuration, gaining as much as 12hp to the track, that's a ton of power to leave sitting at home on raceday!
 
Can you give me a good start to what a great setup for 660ft would be. I have no experience with clutch and am learning a lot about it from this site. From what I can tell looks like the 89a10 weights are what I need.
 
I was fresh out of beer and popcorn. I come back from the store and...... everyone is gone?
---mac---
 
mrviper700, Thank you. This is very helpful. For me, our sleds are dedicated asphalt sleds so backshifting is not a concern. Not much trail riding down here in South Carolina! LOL!

What are good aftermarket weights worth trying?
 
Thanks for great post Mr viper now can you post the 3 best aftermarket weight you like to use
 
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