Shane661
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posted July 20, 2009 05:26 AM
 Edited By: Shane661 on 20 Jul 2009 13:28
MPH All over the Place
I've noticed that since I've been using some MR9, my mph is all over the place. I mean, 1-2 mph is not too bad of a variance...but I am sometimes seeing 4-5 mph on the big end. In fact, I've seen as high as 152 mph...but couldn't back it up...just 148's to follow. My 1/8th, on the same day, has varied 123-126, with essentially the same ET's.
Have you guys noticed this when running MR9, or is it something I am doing??
It just seems odd. I have a feeling it is the setup and shift points, but it is pretty strange to see it vary this much.
Shane
  
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Shane661
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posted July 20, 2009 05:45 AM
Edited By: Shane661 on 20 Jul 2009 13:45
Here is a good example of what I am talking about (#55):
Look at the 1/4 mile trap speeds.
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smokinZX14
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posted July 20, 2009 05:48 AM
Thinking back Shane back when i has running MR9 it hit 157 once or twice but most times 153 to 154 ... 1/8 mile 124 to as high as 128.99 .. On pump gas my MPH stayed pretty much the same ...I never gave it much thought because the ETs stayed the same ..
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Wheelie
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Old Man
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posted July 20, 2009 05:55 AM
mine does the same thing smokin, on pump gas, 146-150. 1/8th was 121-123
wee
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1badzx12r
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posted July 20, 2009 06:05 AM
maybe your tire is spinning .. i had that issue with my booza saturday lost 7 mph between a 1 hour span on pump gas .
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CrotchRocket
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Bracket Racing with Betsy
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posted July 20, 2009 06:17 AM
It could be because you have a little pump gas mixed in...
Also, the way this humid weather has been it could be more humid winds blowing in across the track at times???...I doubt there is any problem with your bike Shane!!!
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Wheelie
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Old Man
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posted July 20, 2009 06:19 AM
my et's are pretty much the same, I guess it could be spinning
wee
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Shane661
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posted July 20, 2009 06:36 AM
Edited By: Shane661 on 20 Jul 2009 14:51
quote:
I doubt there is any problem with your bike Shane!!!
I agree, Rick. I'm just not used to this much variance. There are a few things that might be contributing to the mph difference...but the ET's are pretty consistent, and that is what's most important.
I am going to do a few things:
1) Clean and re-seat tire on rim (I know it is spinning on the rim, on the launch, at minimum).
2) Run either 100% pump, or 100% MR9...no mixing at all. Draining the tank is a pain, but I'll get used to it.
3) Tighten up my shift points, run to run.
So, we'll see where that gets me.
Shane
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kawasakijockey
Pro
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posted July 20, 2009 06:55 AM
For how close the et's are the 5mph difference is a lot. It looks like the last 320 ft of the track. With the gearing you have the last shift might be right near the mph lights. I'm curious if you shifted in two different places. We have about identical gearing and it seems like 5th gear shifts 70ft from the finish. Hell, it could be 150ft but hard to tell at 146mph.
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Shane661
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posted July 20, 2009 06:57 AM
Edited By: Shane661 on 20 Jul 2009 14:57
quote:
For how close the et's are the 5mph difference is a lot. It looks like the last 320 ft of the track. With the gearing you have the last shift might be right near the mph lights. I'm curious if you shifted in two different places. We have about identical gearing and it seems like 5th gear shifts 70ft from the finish. Hell, it could be 150ft but hard to tell at 146mph.
I noticed on one pass where I wound 4th way out that my mph seemed to go down, as it put the shift too close to the lights. I need to check it a few more times to verify, but I think may be a part of it.
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dubious
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posted July 20, 2009 07:38 AM
maybe its due to tire spin on the rim...
I noticed you have them marked, but how are you counting the number of revolutions it spins on the rim....
just playin with ya buddy!
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billeason
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posted July 20, 2009 10:41 AM
Are you sure your not getting out of the throttle to soon? The measured mph is between the first and last beams and et is in the middle of the two. If you start the first mph beam, set the et light but let off the throttle just slightly it will really show on your speed. Shifting in the lights will sometimes raise your mph but hurt et,so maybe it is how your shift points are!...................Bill
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FlatoutBu
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posted July 20, 2009 11:43 AM
Mine bounces around too. It can be anything between 146 and 154. As long as your running the same numbers i wouldnt worry about it. You can't predict mph everytime. You could have had a strong headwind one minute and not the next. Maybe you tucked a little sooner one pass. Maybe you shifted 200 rpm later on one pass. Your MPH is just a good look at how much HP your making.
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icarus
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posted July 20, 2009 01:59 PM
Could it be that the beams at that track are not set correctly? One varies from the other?
I'm just going by the mph differences on both bikes.
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8.820 @ 161.05
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NINJA12
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posted July 20, 2009 02:21 PM
Could be because your shift point is between the lights.
If you have a gear change between the timing lights it will make your MPH look slower,
but your ET is the same because you were going to make it at sometime anyway.
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Shane661
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posted July 20, 2009 02:24 PM
My shift point is before the lights. I will change/monitor a few things and get it square. 
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davej
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posted July 20, 2009 05:59 PM
Have you ruled out clutch slip?
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14nooby
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posted July 22, 2009 05:02 PM
Shane,
I have noticed on runs where have a little tire spin cause your mph to increase.
Think if you spin the tire you should be going through the traps at a little different point in your gearing. Runs where you don't spin and you hit your shift points you will certainly be at different spot on your gearing. Let me know your thoughts.
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ninjaboy311
Zone Head
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posted July 22, 2009 06:46 PM
I was having the same issue, but I figured out my issue was due to my low profile tire/single rotor/polished wheel was playing games with the top end MPH beams. Now since I've powder coated my wheels black, my MPH's are the same now.
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dubious
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posted July 22, 2009 08:59 PM
Better get some flat black krylon for the BST's Shane!
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natural selection.....
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Some are not worthy of the effort.
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