Viper Clutching Confusion

dcfjef

dcfjef

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ND
I am not a clutch tuner by any stretch. But am trying to maximize my top speed on my Viper with 144 track extension. I don't drag race at all, just a ditch banger and farm field rider. But I don't like to get beat if we have a long stretch where we can open them up.

My setup: SLP Pipes, HeelClicker weights, Red H/C primary spring, Dalton 46/36 Helix, Green Yamaha secondary spring.

We have had 45 F temps for a week so the snow melted and compacted a lot. Now it had been 5-9 F the last 2 days. So I made a couple trial runs.

4.8g shoulder weight, 0 center, 3.3g tip, H/C red primary spring, 51/43 Yamaha Helix wrapped at 60, pink secondary spring = 9000 RPM and GPS speed of 98.6 and the belt was fairly hot.

4.8g shoulder weight, 0 center, 3.3g tip, H/C red spring, 46/36 Dalton Helix wrapped at 70, green secondary spring = 9000 RPM and GPS speed of 95.9 and belt was just warm to the touch. Felt real good but not sure why I lost almost 3 MPH. Outside temp 9 deg. F.

Added 1g weight to each tip. 4.8g shoulder weight, 0 center, 4.3g tip, H/C red spring, 46/36 Dalton Helix at 70 wrap, green secondary spring = 9100 RPM and GPS speed of 92.5. I am running on the same 1/2 mile stretch of ditch and the snow is as hard as ice, so I believe the conditions are the same. Outside temp 4 deg. F.

What am I doing wrong to try and get more speed?
 

If it is stock, you have a 22 tooth on the top and a 38 on the bottom, which is a 1.73 ratio. The guys at SLP told me that because mine is stretched to 136" that I needed to go down a tooth on the top gear, which changes the ratio to 1.81. By doing this, it makes it easier for the engine to turn the longer track, but in theory would end up costing you top speed. However, making this change is supposed to increase the efficiency of the clutch system (by getting the load on the clutches back to where it is supposed to be), so maybe with a more efficient setup you will be able to get everything else dialed in easier and not see a loss on the top end. I am guessing that with the 144" you may need to be running a 20 tooth top gear. I haven't changed my gearing yet... hopefully I will do that this week and I will let you know what the outcome is.

Another thought is that you are not operating in the sweet spot for the pipes. The horsepower starts to drop after 8900 RPM, so keep adding weight until you get it down to 8800 - 8900. It seems weird to me that in your last run after you added a gram to the tips that you RPM went up. I was told that 1 gram is supposed to drop your RPM by 100.

I am by no means an expert at this... we are both in the same boat right now with trying to get the most out of the pipes, so please don't take anything I say too seriously. I am just passing on the info that has been given to me by others!
 
Last edited:
bigreis said:
If it is stock, you have a 22 tooth on the top and a 38 on the bottom, which is a 1.73 ratio. The guys at SLP told me that because mine is stretched to 136" that I needed to go down a tooth on the top gear, which changes the ratio to 1.81. By doing this, it makes it easier for the engine to turn the longer track, but in theory would end up costing you top speed. However, making this change is supposed to increase the efficiency of the clutch system (by getting the load on the clutches back to where it is supposed to be), so maybe with a more efficient setup you will be able to get everything else dialed in easier and not see a loss on the top end. I am guessing that with the 144" you may need to be running a 20 tooth top gear. I haven't changed my gearing yet... hopefully I will do that this week and I will let you know what the outcome is.

Another thought is that you are not operating in the sweet spot for the pipes. The horsepower starts to drop after 8900 RPM, so keep adding weight until you get it down to 8800 - 8900. It seems weird to me that in your last run after you added a gram to the tips that you RPM went up. I was told that 1 gram is supposed to drop your RPM by 100.

I am by no means an expert at this... we are both in the same boat right now with trying to get the most out of the pipes, so please don't take anything I say too seriously. I am just passing on the info that has been given to me by others!
Click to expand...

So I don't want to get up over 88 or 8900 RPM? I read in the HeelClicker instructions that they suggest RPM's of 8400 for the Viper and SRX. In another part of the instructions is says "moving" weight to the tip will help increase top end speed. I also have heard the adding 1g = 100 RPM drop. So 1g per weight would drop the RPM's by 300. So I need to take off my primary again and add more weight. But not sure if I need to add any to the center or keep adding to just the tip.
 
dcfjef said:
So I don't want to get up over 88 or 8900 RPM? I read in the HeelClicker instructions that they suggest RPM's of 8400 for the Viper and SRX. In another part of the instructions is says "moving" weight to the tip will help increase top end speed. I also have heard the adding 1g = 100 RPM drop. So 1g per weight would drop the RPM's by 300. So I need to take off my primary again and add more weight. But not sure if I need to add any to the center or keep adding to just the tip.
Click to expand...

1 gram to each weight will drop rpms by approx 100, not 300.
 
How tall is the lug on the 144?

A 121 sled with a 1.25 rip saw installed shaves off 5 MPH top end, and thats just a 121 with a 1.25 track

I dont think your going to get big top end from that track.
 
tomseal6 said:
How tall is the lug on the 144?

A 121 sled with a 1.25 rip saw installed shaves off 5 MPH top end, and thats just a 121 with a 1.25 track

I dont think your going to get big top end from that track.
Click to expand...

The 144 has 2 inch lugs.
 
I forgot to add that you probably have 8 tooth drivers with the 2 inch lug,

In order to correct the ratio for the smaller diameter drivers, (If I am correct on you having 8 tooth drivers) I would go to a 24/38 ratio since top end is what you looking for.

You will have to play with the clutches again to get the RPM's right for doing the gear change.
 
tomseal6 said:
Holy CRAP!!!

and your getting over 92 MPH on GPS with SLP's with stock gearing???

Your motor is pushing a windmill
Click to expand...

So a 1.25" lug would be a better track?

Do you know if gearing has anything to do with what the speedometer reading (i.e. the yamaha dream-o-meter)? When I am at 92 GPS speed my digital readout shows 122 MPH.

I need to pull the chaincase cover and see what I have under there. Never pulled a chaincase cover before so it's a little intimidating to me.
 
dcfjef said:
So a 1.25" lug would be a better track?

Do you know if gearing has anything to do with what the speedometer reading (i.e. the yamaha dream-o-meter)? When I am at 92 GPS speed my digital readout shows 122 MPH.

I need to pull the chaincase cover and see what I have under there. Never pulled a chaincase cover before so it's a little intimidating to me.
Click to expand...


That is fast for a 144x2 track. I hit 94.9mph Gps 173Km(107mph) on speedo with my 144x1.25 and was extremely happy I have 22/39 gears. tach was on 8500
 
Gearing won't change what the speedo tells you, but different size track lugs and drivers will. To run that 2" track, you must have 8 tooth drivers (which I think would actually cause your speedo to read lower, not higher). But once you take into account the extra circumfrence of the 2" track, that may more than make up for the smaller drivers, and that could explain why the speedo indicates so high. That problem can be fixed by grinding teeth off of the speedo pickup gear.

As far as the chaincase goes, it really isn't a big deal at all. Drain the chaincase oil first (the plug is on the inside of the tunnel). Remove the exhaust, and then remove the 12 mm bolts holding the cover on.

If all you are looking for is top speed, then you will want to go to a bigger top gear as others suggested. But be aware that you are going to lose some of your low end acceleration... there is always a trade off!
 
bigreis said:
Gearing won't change what the speedo tells you, but different size track lugs and drivers will. To run that 2" track, you must have 8 tooth drivers (which I think would actually cause your speedo to read lower, not higher). But once you take into account the extra circumfrence of the 2" track, that may more than make up for the smaller drivers, and that could explain why the speedo indicates so high. That problem can be fixed by grinding teeth off of the speedo pickup gear.

As far as the chaincase goes, it really isn't a big deal at all. Drain the chaincase oil first (the plug is on the inside of the tunnel). Remove the exhaust, and then remove the 12 mm bolts holding the cover on.

If all you are looking for is top speed, then you will want to go to a bigger top gear as others suggested. But be aware that you are going to lose some of your low end acceleration... there is always a trade off!
Click to expand...

That is a tough balance. I don't want to lose my low end or mid-range power or speed.

Can I take my 2" lugs and cut them off to make it into a 1.25"? Will that ruin the tracks performance or balance any?
 
Cutting the lugs down sounds like a lot of work and would probably royally screw up your traction. If you are going to have the chaincase open already to look at the gears, I would spend the extra time to put in a Cobra or Ripsaw track (and it you have lots of miles on it then replace the drive shaft bearings. I would think your 2" track would bring in some decent money to help offset the cost of a different track.
 
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