Not getting full shiftout

[snowbeast]

I agree 100% with the free rolling chassis! I'm just getting to wear mine is really rolling nicely again. My slides are worn bad so waiting for the duponts to come in. So far mine has responded well to the extra wheels on the skid. I'm going to add atleast one more set. The suspension on these sleds is very stiff and people don't realize the drag that puts on a sled. Was testing today with a friend who has a base ltx with very similar clutching. He has duponts, I have 1 set of extra wheels with worn hyfax. He is setup on softest settings, I'm setup in middle settings on torsion blocks. Ran 10 times in 1000' and he could pull me by 2 sled lengths. He was running 94-95 mph I was running 90-91. We both weigh sighing 20 pounds so no big weight difference. I then switched my torsion springs to softest setting and that is it. I went from getting beat by 2 sled lengths to beating him by 2 sled lengths. Fastest speed I seen then was 97mph. Simply by loosening up the rear torsion blocks I gained 4 sled lengths and 6 mph in the same exact field doing back to back runs. Simple things make an amazing difference. All that to me goes to show that the stiff suspension on these sleds and not being able to roll freely affects them tremendously! Do what journeyman said and get the sled rolling freely and it will perform. I can say already that extra wheels or worth the money and the duponts I'm sure will be an improvement. No doubt with new slides I'll be hitting 100+ mph in the same distance with a totally stock sled with clutching and it is a rocket getting there. Address the chassis issues first, then worry about clutching if it's not suitable.

Barry,i agree about the rolling free,but you did say all this started with a pooched/glazed belt if I remember correctly,that was your major milestone back when you went from 96 mph to 84mph on that grass surface correct.

 

[Studroes144]

Belt certainly could have been an issue there. I soaked my belt in hot soapy water over night and scrubbed the edges of the belt. Realistically it did help because I did gain speed but my thoughts are that the belt began slipping because of the chassis not rolling freely. After extra wheels and softening up the rear suspension is when I seen the biggest gain. Yes the belt being glazed did not help matters at all and I could tell the sled gradually losing speed. It's one of those things like which came first the chicken or the egg. The belt certainly was slipping but I think that was a result of the skid dragging hard as it was gradually getting worse.

 

[BlueByYou2000]

I didn't read this whole thread so if this has been covered, sorry for the redundancy. Yamaha clutches in stock form will not fully shift out. Split collar modifications among with mild machining in the primary, along with helix mods are needed to achieve this. To properly check this, remove your primary, take the spring out and install the belt between the sheaves. Now close it and see how far the belt rides, it's will not go to the top. Most will run 3/16-1/4 inch below the top of the sheaves. Now do the same with your secondary, but open it and see how far the belt goes down. To attain full shift, both mods must be done because even if you do the primary, your secondary will be the limiting factor because the belt isn't capable of getting any lower in the secondary without machining the tips of the helix.

 

[Studroes144]

Here's another thing to keep in mind. It seems as tho most all the vipers in totally stock form are turning roughly the same rpm in the 8400rpm range. Here is the dyno sheet from my viper with 100 miles on it. Notice peak hp is right at 84-8600rpm yamaha obviously knows this so that is why the clutching is set up for that. As far as doing straight line testing to get the fastest setup.. I'm sure is not done at all by yamaha, that's something for the performance guys to check in to. Just because the clutch kits are setup to run at higher rpm doesn't mean that stock clutching at 8400 is wrong because in reality that is more than likely going to be a very good setup without other clutch work being done.

 

[cannondale27]

I always had 8950 rpm stock from day one. At 8400rpm and loose conditions mine becomes a very boring sled.

 

[NOS-PRO]

I always had 8950 rpm stock from day one. At 8400rpm and loose conditions mine becomes a very boring sled.

And I have to wait for you

 

[snowbeast]

I didn't read this whole thread so if this has been covered, sorry for the redundancy. Yamaha clutches in stock form will not fully shift out. Split collar modifications among with mild machining in the primary, along with helix mods are needed to achieve this. To properly check this, remove your primary, take the spring out and install the belt between the sheaves. Now close it and see how far the belt rides, it's will not go to the top. Most will run 3/16-1/4 inch below the top of the sheaves. Now do the same with your secondary, but open it and see how far the belt goes down. To attain full shift, both mods must be done because even if you do the primary, your secondary will be the limiting factor because the belt isn't capable of getting any lower in the secondary without machining the tips of the helix.

Now I never heard of cutting the helix tips,on all my apex secondaries once the primary was fixed,we just cut the helix center,bushing area,i think like .125-.160 3-4mm to allow more shift of the helix? Can you post a pic of the mod you speak of on helix tips. thanks pete

 

[NOS-PRO]

Pete, I believe that is what BBY2000 means....at least that is what I have always machined.

The primary I have never machined but I have changed split collars.

 

[BlueByYou2000]

Pete, you machine both the bushing area and about .020 off the tips of the 3 ramp sections of the helix. The bushing alone will not do it because the tips will make contact at full shift and not allow it to fully open.

 

[NOS-PRO]

Just an update.....

Ran at winterfest 2014 Radar runs in Manitowoc yesterday.

http://www.ty4stroke.com/viewtopic.php?t=125850

My clutches show my belt running about 3/16 (.190 roughly) from the top end of the sheave. But, I was also on the brakes hard to slow down. I do believe my reading could be off as my sled had more to go.

But, if you read the post under the race section, My son and I creamed a lot of competitors.

Also forgot to add my GPS (which the radar there was gospel) was reading 89-90 when I started backing off. This was only 490ft. of track.

 

[NOS-PRO]

https://www.youtube.com/watch?v=L2zzQj9744c

My viper run