Setting a street 1125R up to drag race

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Stripping away the unwanted pieces!

 

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I used a cut-off wheel to remove the lugs that held the cush drive.

The material is hardened but not to the point where it could not be cut.

 

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Turning down the diameter which will serve as the outside retaining ring for the new pulley.

 

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Finished that and now on to cleaning up where I cut the lugs off.

 

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A few passes to insure that the surface was flat and square to the outside lip.

 

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The pulleys were cut to match the original width of the compensating sprocket.

As you can see there is a difference in diameter from the original center hub and the pulley center hole. There is also a height difference from the mounting flange on the pulley stock to the original cut up piece of compensating sprocket.

 

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Turning down a piece of stock to make the spacer needed to close up all of the differences.....

 

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The spacer dubbed the "retaining ring".

 

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No more gaps/space differences.

 

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The original center piece of the compensating sprocket.

Cut the flange off.

 

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Turned down to maintain the original thickness of the compensating sprocket as well as maintaining stock bolt length.

 

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The aluminum piece on top is the belt retaining ring. It will get drilled along with the flange which also gets tapped and drilled for 7/16" dowl pins. So I'll have 3 bolts holding the assembly together as well as 3 dowl pins to drive the pulley.

The new assembly with the 27 tooth sprocket weighed in at 2 pounds 6 ounces. That is 2 pounds 8 ounces lighter than stock. What affect do you think that will have on the motor spooling up? Rotating mass!

 

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The 25 tooth magnesium pulley weighed in at 2 pounds even. 2 pounds 14 ounces lighter than stock!

 

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I machined all three pulleys so I can maintain stock gearing as well as dropping two teeth in the front. I may consider machining one more pulley, a 28 tooth. This may help with some top end for the MPH runs.

27/70 = 2.59 to 1 Stock R gearing
26/70 = 2.69 to 1 (4% change) 1 down on trans sprocket
25/70 = 2.8 to 1 (8.3% change) 2 down on trans sprocket

After drilling and pinning the the hub next up is seeing how the belt and tensioner will take these changes. If there isn't enough movement on the tensioner to take up the two tooth change I may make a slightly larger idler pulley.

 

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My intentions are to replace the idler pulley with a tensioner pulley. I have some preliminary belt tension readings from the stock set up and now I'm trying to convert them over to what the tensioner industry uses.

As a quick test I bolted a manual XB chain adjuster to the bike (with the sprocket removed). That will definitely take the slack up. Now it is a matter of getting the tension correct with either an elastomer or spring type self adjuster. For my application a manual adjuster is just fine as my suspension is strutted for drag racing hence no swing arm travel. However I would like something that will adjust on its own for the various pulley sizes while maintaining sufficient tension.

 

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Here is the 27 tooth pulley pinned and bolted with the belt retainer in place.

 

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I ordered a 180 and received a 190.

This gave me the chance to weigh the two tires.

The 180 weighed in at 11 pounds 10 ounces.

The 190 weighed in at 13 pounds.

A 1 pound 6 ounce difference.

 

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I hit the track again last night. While it was still humid it was not nearly as hot as it has been.

I made 5 passes, 4 were 10.3's and 1 11.4 where I spun off of the line and the bike shifted into 2nd gear.

60' ET MPH
1.682 10.336 128.030
1.686 10.318 133.610
1.692 10.398 131.770
1.671 10.357 125.960
2.005 11.490 129.140

The bike felt good with the direct drive front sprocket. I had my tire pressure high as a starting point. I did expierence some tire spin so I will start dropping pressure to find what the tire/track likes. Something new, the bike was shifting into 5th at the line. This is a first as I would catch 4th before the traps and run through the lights with some RPM left. I'm considering lowering the front a little. I have to read up on this some however I noticed that the fast bikes were slammed.

 

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I hit the track again tonight. I'm getting better a little at a time. I did experience a little tire spin from time to time. As the night went on I did drop the tire pressure some.

On one particular run the bike launched, spun, hooked and than shifted into second. It shifted so hard that the air box came up and slammed me in the chest knocking a little wind out of me. I was laughing like a little kid when it happened, that was cool.

1.644 4.357 6.587 109.750 8.532 10.218 138.100
1.669 4.405 6.636 109.710 8.580 10.256 136.330
1.663 4.373 6.604 109.770 8.548 10.221 133.700
1.628 4.338 6.581 109.070 8.538 10.221 132.990
1.673 4.386 6.638 108.520 8.613 10.320 133.100
1.633 4.378 6.648 107.580 8.640 10.364 131.500
1.630 4.306 6.560 108.340 8.545 10.262 129.800
1.647 4.353 6.621 107.800 8.616 10.344 128.870
1.626 4.340 6.618 107.600 8.620 10.353 128.650
1.678 4.354 6.610 107.900 8.600 10.323 134.400
1.623 4.305 6.572 107.250 8.571 10.297 134.270

 

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I finished my tensioner project this week. The first one wasn't quite strong enough so I used the next one up which seems to be just fine. With 11 runs on the bike tonight everything is working as it is suppose to.