8dn-20/8dn-00

EricMichael

EricMichael

New member
Joined
Dec 25, 2005
Messages
543
Location
Presque Isle, ME
what is the diffrence between the two??i'm looking for a set-up to run on the lake. I was at a radar run today and I was using 8ca's, the sled only ran 92 mph in 1000ft with stock gearing and 192 chisel tooth so traction wasn't an issue...was getting beat by the same sleds that i beat on the grass..my old 01 sxr ran 92 single pipe in 1000ft...dont know what the issue is here..Sled has triple pipes also..if anyone could help me out here that would be nice..thanks

Eric
 
Try the 8DN-20's with 15.6mm rollers.Should help you a lot. Got them on my SXR600 and they work awesome.Super pull to the top at 8500 rpm.Experiment with the weights to get your desired launch and WOT rpm's.Never felt a pull like my sled does now,and it is quick,mind you I also geared down 1 tooth upper.
 
The 8dn 00's have a heavier tip thean the 20's.I have tested them speed running in a 1000ft the 00's mph higher than the 20"s
 
Is your belt slipping...,bushings worn in clutches and you said you had good traction yet,you should have been faster then.What were you getting for speed at season's end last year.What have you done differently to your sled prior to this season. Something changed.
 
the belts not slipping, I even tried the stock weights and that wasn't a good idea. I put new rings in the other day, but that shouldn't have hurt it, my buddies firecat that i beat on grass has new rings adn cylinders on it prior to the race..i'm currently running 8ca's with 2.7 tip, 51/45 helix green secondary tried 60/70 wrap, hauck orange primary couple shims...also has v-force reeds..the sled just didn't seem to pull like others...was neck and neck with an srx and ahead of the f7's and mach's but then then half way down the lake they just pulled right past and kept pulling...i'm thinkin i need a diffrent setup in the primary just not sure where to start...i mean 92 mph jsut doesn't cut it lol
 
check your center to center measurment on your clutches and check to see if an engine mount is broke or bolt missing. I dropped a bolt out of my front engine mount clutch side last year,didn't even know till this summer ,my engine must of been flexing a bit when I pinned it,throwing things off .Check every detail.If your rpm's are on target,something is wrong somewhere.Is the belt the right size?Are your brakes locked on or seized up and binding.Put with a black marker lines running up to the top of your sheaves ,then take it out for a boot and see how far your belt is travelling on the clutches.Don't know what else to say.
 
First off your using a weight designed for short distances, remember all the ring a round the rosie we went thru when you wanted to drag race? You wanted to know why the 8ca would work better then the stock weights, because its designed to, its more aggressive in a short run, thats why you needed them, now we are doing the opposite type of racing so we need a differnt profile weight to fit the racing type!! You cant drag race, trail ride and speed run all with the same set ups and expect to do good at all of them.

I think the best thing for you to do is get a copy of the yamaha weight profile charts and study the weight force charts and look and see how they compare, like for instance your 8ca weight.... its got a heavy heel and very aggressive mid section, but its a razor point at the tip right doesnt carry any tip weight? We know that more weight equals more force squeezing the belt, and this propels the snowmobile faster.

Now looking at the opposite profile of a 8dn-00 wieight, its weight is all out at the tip mostly and isnt near as aggressive on take off, but provides way,way more force to the belt on topend, which makes the sled go faster top speed.

I like to help people go fast and understand why something does what it does. So they can correct thier own problems and become better tuners, but you have to test, learn and retest to get results!!!. Get a copy of the weight charts and check em out you will see which weights do things better then others and then be able to choose the correct weight for the type of riding or racing your doing. You can also get a set of aftermarket weights, these are more adjustable but here again they too would need to have differnt weight placements and helix,spring set ups to differnt types of terrain.
 
I'm running 8ca's in mine, and the top speed is awsome. The 8 ca's have very little weight in the tip, but the profile is very agressive, even out at the end. The force is actually more than a 8dn-20 @ full shift out. The yami charts show this. Similar to the 8bu-00 profile. With all of that force you need to use a helix angle thats very low on the finnish, and weight at the tip is very hard to get properly tuned. One gram can really mess up the whole deal bigtime.

Like bluemonster said, make sure that everthing is is proper allignment first, then do some tunning. a finnish angle down around 38 or 36, i'm running a 34 with a roller.
 
Weight force 8dn-20 @ 30mm =280kgf no rivets
Weight force 8ca @ 30mm =350kgf no rivets

You probably need more finnish angle to slow down the shift out.
 
mr.viper, i'm just learning all of this tuning...have always been into sleds but not as in-depth as I want to be now. So the more tip weight means more grab on the belt at higher speeds because why?This means the belt will be higher on the primary correct?So with the 8ca's the weight is mostly in the heal meaning it grabs the belt harder and sends it to the top of the primary quicker, resulting in quick acceleration but falls deaper into the sheaves the more the clutch gets closer to the tip right?

I'm trying to study the charts but dont really understand them..the force and stroke are confusing. It shows some such as the 8bu falling off near the end of the stroke, but great at the beginning..What do they mean by stroke, clutch or motor?

Now, when adding more total weight to the primary, what does this mean you have to do to the secondary?I dont understand if you use weights with more weight in the heal or tip how this effects the angles on a muli-angle helix or even a straight angle helix. I'm guessing that the first number lets say in a 53/43 wouldn't effect the top end as much as the first number and vise versa.

So rivets are just for fine tuning correct? How about primary springs, I know they effect the engagment, but must also have an effect on shift, and I dont fully understand shift either. Is must have to do with your secondary...I do see the diffrence when using an 8ca compared to lets say an 8dn-00 because the weight is totally opposite. Thanks for your help, and dave the radar runs were in caribou maine, not sure when the next one is. Top speed in 1000ft for the day I believe was 126, soft ice conditions.
 
vipertipplexxx, i'm using a 51-45 helix, some people say that finish angle is too steep...i'm trying to learn the diffrences here, and the full shift out procedure also. I know that turk says you can tune a clutch to the helix but isn't the best way for clutch tuning.
 
Thanks Eric I just live across from Fort Fairfield hopfully will make the next one you say 126 top speed thats not to bad
 
By looking at those charts you see the clutch shift line???, say the 8bu-00 for example, it falls off on topend, you see it noseing over? it doesnt supply the needed force to clamp the belt on topend, and if we look at the profile of the weight we can see the weight has no tip weight, so without adding multi angle helix into the mix to confuse you, it would have less topend speed then a weight with a straight line on the chart such as a 8dn-20. These are the basics.

Before someone argu's that the force is differnt, you have to always remember that the weight thats heavier applies more force, even though it may not provide the force in the right area of the shift curve. What this means is a 48 gram weight will show you more force then a 38 gram weight will but the 38 gram weight CAN OUTPERFORM the heavier weight in a given section of the shift curve and vice versa.

When you add in multi angled helixs you can change only some of the characteristics of the good/bad things about a weight, like some want to say that you can get good topend from a 8bu-00 or 8ca/8ab style weight and you can.......... but only to a point, a 5 gram point! You cant win the radar top speed contest with a weight with no tip profile, you can add weight out there but only to a point...... and using a shallow finish helix angle will get you even CLOSER to a better top speed, BUT, No matter what you add, you still cant make up for the correct weight profile to begin with. Basicly a multi helix allow you further fine tuning of a weight profile for the desired result.

The first number on the helix is the upshift speed , so a larger number on the beginning of a helix means it upshifts faster. Now heres where you can get easily confused, the helix upshifts faster but also provides less clamping power to the belt because of the bigger angle, this in turn requires a stronger spring to provide the extra clamping power to hang onto the belt. Stiffer springs eat up power, they are providing resistance to NOT upshift the clutch's! springs are a completely differnt post and discussion, I am trying to keep this very basic to give you a idea, and let you run with your own ideas.

The helix spread between the first and second numbers is a matter of personal preferance. I like big spreads ,others dont. The thing to remember in clutching is theres more then 1 way to skin a cat, and you can have 3 differnt set ups, that will accomplish the same speed or elapsed time in a given distance, but 1 will do something better then the others somewhere in the shift curve! Its testing the set ups and good notes that guide you to getting the best result for your paticular need!

correct clutching is the recipe of correct profile weights for the type of terrain going to be run in, the correct matching springs,helix angles and then the mixture of it all to get a good clean straight shift curve from beginning to end.
 
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mr.viper, bare with me because this is all very confusing to me. Now the 8bu-00 still shows more force (350) when it noses over at the end than say a 8dn-20 which only shows 275 or so at the end. I understand the tip weight and how its shown and understand why it would help top-end but going by the force on the chart (reading the chat) is what confuses me.

Also, you said the 8dn-20 has a flat line but the 8ca looks to show an even flatter line?Now why does the showllower finish angle help top end speed on a muli-angle helix, what does this do to the secondary clutch?When a secondary clutch up-shifts what is it doing?

Now, an 8dn-20 shows more force and a straighter line than an 8dn-00 but has less overall force. I'm trying to get a set-up that will give me good top-end on the lakes and good top end on the trails, because we have alot of long straight trails here, so there wouldn't be much diffrence between lake racing and trail riding. I see the 8dn-00 has alot more tip weight than a 8dn-20, so it should have more top end speed by alot, but both forces equal out to the same. You say you like helix's with big spreads betweens the numbers, so a 51-45 helix isn't a very big spread correct? Seems to me a 51 starting number would upshift quicker, and i'm waiting to learn from you what upshift means. What is your preference for a top end weight? I appreiciate you helping me understand all this, it seems theres alot to be learned still.
 
look at the 2nd paragraph on my last post, a heavier weight will show more force, even though its gonna provide less speed from the area the mass is located in the weight, so thats why a 8dn-20 will be less then a 8bu-00 , 8bu is heavier to start with. Dont focus too much on the forces listed as to the shift curves, they are of more value to you learning what each profile does and acts like.

I will post later tonight on helixs and how they work
 
dave, i'll let you know when the next radar run is, it probably will be soon.but usually every weeked we have about 7-8 sleds on arnold brooke lake here in Presque Isle, my number is 207-227-4284, give me a ring if you want and we can meet up some weekend.I have a couple buddies that own irish inc. they run an srx700,xcr800,and firecat 700, I beat them all on grass and they beat me to death on the lake :( but i'll get em back whe nI learn the clutching specs haha..
 
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