(Note: LANDRACING.COM donations are not tax deductible)


This is a public forum. The opinions expressed here don't
necessarily reflect the feelings of The Folks That Run The Site (that's us)
unless we explicitly say so, ok?


Author Topic: Spring Event motorcycle records observation and question  (Read 5865 times)

0 Members and 1 Guest are viewing this topic.

Offline Bullfrog

  • New folks
  • Posts: 25
  • Age: 61
  • Location: Newburgh, Maine
Spring Event motorcycle records observation and question
« on: June 04, 2015, 07:10:07 PM »
Looking thru the new motorcycle records I noticed that nearly all the new records had a faster time for the mile then the mile and a half. This was the case for me as I set a record in an open class. I know that the headwind was a factor but was it stronger past the mile marker? I think my gearing was too tall with the head wind but even one run that I held it in 4th without shifting to 5th it still lost speed. I thought it was just me but I see others had the same issue. I didn't see that the autos were having this problem. I went 7 MPH faster at the harvest event and the bike had a slipping clutch and also had jetting issues. The bike ran great at the spring event and felt really strong but I lost speed after the mile marker on every single run over the two days. Any ideas or comments on this? I think I'm going to try dropping down a tooth on the front sprocket for the harvest event.   

Offline blackslax

  • Sr. Member
  • ****
  • Posts: 329
  • Age: 51
  • Location: The Semi-Frozen South of Maine
    • Loring Timing Association
Re: Spring Event motorcycle records observation and question
« Reply #1 on: June 04, 2015, 08:18:00 PM »
Hi Steve,
Just read your post to the wife because she's kind of a smart girl.  She said that the reason your time is less at the mile and a half is because your bike is slowing down.
:-D :-D :-D

Tim
Tim Kelly
Race Director - LTA
www.loringtiming.com
People dont see the world the way things are, They see the world the way they are.

Offline blackslax

  • Sr. Member
  • ****
  • Posts: 329
  • Age: 51
  • Location: The Semi-Frozen South of Maine
    • Loring Timing Association
Re: Spring Event motorcycle records observation and question
« Reply #2 on: June 04, 2015, 08:23:55 PM »
Hi Steve,
All kidding aside, that is a matter that we have debated at the timing table for quite some time. I talked to Kevin Cameron about it last year in fact.  What we came up with is that air cooled bikes heat up as the run hard and the intake charge expands more due to the increased temperature of the head and barrel.  This causes the expanding intake charge to push back out of the intake or be drawn in less efficiently due to its lowered density.  Small intake charge then equals less power.  Then my wife's answer takes over.
Tim Kelly
Race Director - LTA
www.loringtiming.com
People dont see the world the way things are, They see the world the way they are.

Offline tallguy

  • Full Member
  • ***
  • Posts: 181
  • Location: Northern California
Re: Spring Event motorcycle records observation and question
« Reply #3 on: June 05, 2015, 01:53:38 AM »
About changing to a smaller countershaft sprocket . . .

Chains don't like to change direction suddenly.  Small sprockets put more
friction, wear, and tear into the situation.  I suggest that instead of a smaller
countershaft sprocket, you consider using a larger rear sprocket.  This will
not only help on rear wheel horsepower (compared to a smaller front sprocket),
but provide you the opportunity to take advantage of smaller increments of
ratio change (per tooth difference), thereby allowing more precise "tuning" .

Jessechop

  • Guest
Re: Spring Event motorcycle records observation and question
« Reply #4 on: June 07, 2015, 09:42:02 AM »
I think some has to do with the simple fact of thats just how fast a bike/car will go. My thoughts would be that if terminal velocity (peak speed) for a motorcycle is 125 mph and it reaches that at say the .9 mile mark and then traps at 125.444 now you the rider must maintain that speed for a half mile. The motor is "strung out" so to speak and you the rider are trying to tuck even more, elbow out and now you clicked the clocks at 124.943 (all examples of course)

When I raced small displacement bikes I have always trapped faster (or the same) at the 1 than the 1.5, bigger displacement the oppisite. Again I think that has to do with the simple fact of thats how fast whatever I was on would go.

Have you ran your gearing through gearing commander or similar? You might find peak hp @ a given rpm is right where you are at. If thats the case you will actually want to gear up a bit. Remember too that red line and max hp rpm are typically two different numbers. If your red line is 10k and you are trapping at 9600 you might think you are under geared, however look at a dyno chart for that particular motor. You might find that the hp falls off a cliff at 9600. Other might still be climbing at red line too, its just a research game to play.


Offline Bullfrog

  • New folks
  • Posts: 25
  • Age: 61
  • Location: Newburgh, Maine
Re: Spring Event motorcycle records observation and question
« Reply #5 on: June 09, 2015, 06:35:42 PM »
   Thanks for the help guys! Gearing Commander! What a great tool for setting up a bikes gear ratios! www.gearingcommander.com I knew my bike was geared higher then stock it was +3 teeth on the front sprocket and +1 on the rear. It was this way when I purchased the bike last spring. Using the calculator in Gearing Commander I would hit my red line in 5th gear at 142 MPH with my current set up. This is definitely too high for my naked GS 750 into the headwind that we had at the spring event. Dropping back one tooth on the front sprocket would put me at a 134 MPH red line in 5th, which should be a good starting point for the Harvest Event in the fall.