Shift point

Yes it is a back half conversion, i built it strong enough to handle more power
Rear slick is a 5" wide 16" rim ( harley rim laced to a KZ hub) M&H is the only one that make a tire for it.

Not sure what im going to do this up coming season. Just want to get the bike more consistent. Seems the more questions I ask, the more opinions I get, the more I'm not sure what I should do...LOL

So is it possible to get this little motor to be more consistent as the weather gets more hot and humid through the day? My launch is getting more consistent but my ET just gets longer every pass, I cant even begin to come up with a dial in. The other bikes all seem to be able to hold less than a tenth and im going up 2-3 tenths every pass through the day 

Southpaw wrote:

So is it possible to get this little motor to be more consistent as the weather gets more hot and humid through the day? My launch is getting more consistent but my ET just gets longer every pass, I cant even begin to come up with a dial in. The other bikes all seem to be able to hold less than a tenth and im going up 2-3 tenths every pass through the day 
 

I was always told that Lectron carbs were one key to having consistent running as they self adjust for temp/humidity/altitude.

Southpaw wrote:

So is it possible to get this little motor to be more consistent as the weather gets more hot and humid through the day? My launch is getting more consistent but my ET just gets longer every pass, I cant even begin to come up with a dial in. The other bikes all seem to be able to hold less than a tenth and im going up 2-3 tenths every pass through the day 

I've reread this entire thread and have a few questions -
-  are you running a shift light?
- how many passes on your rear slick?
- how consistent are your 60ft times?
- you mention that your ET's are going up 2-3 tenths - what about MPH?  Is it falling off with the increase in ET?  
- as the day progresses, what variation do you typically see with your 1/8 mi time and speed?  
- how much hotter and humid does the air typically get?  And, are you computing "density altitude" or just looking at a thermometer?

Also, keep in mind that a lot of the top dogs in bracket racing will carry a few tenths in their backpocket (sandbaggers) when posting their dial-in.   So, while they might appear to be not slowing down while going rounds in eliminations, they actually might be to some degree.  You'll never know it, however, because they'll always have enough in reserve to "run the number", if need be.  

Sorry for all of the questions, Southpaw.  Getting a bike to go downtrack consistently is a somewhat complicated process.  All that we can do is minimize variables to gain control of the process.  Look forward to your feedback and hopefully we can help get you sorted out.

Mike



 

Dragbike Mike is asking a lot of good questions there that may point to the slick. 

I believe he has air shifter/shift light delay box/auto shift so as consistent as possible. This only leaves the clutch/chain/tire as the possible drive train culprits.

Are you checking the clutch pack between races? The chain only needs adjusting so that just leaves the rear slick.

Not sure how many seasons you can get with that brand/size of slick. A fresh slick will be more consistent than a worn one.

The other thing guys often overlook is consistent tire pressure (easy to do)

Personally I try to count how long my burnout is (one one thousand method) and try to do the same every time.

I have seen guys writing those numbers in a log book comparing track temp to tire temp after a burnout. Only way to do that is with some help.

I've reread this entire thread and have a few questions -
-  are you running a shift light?  No shift light Schnitz Racing Air Shift Module using auto shift
- how many passes on your rear slick?  New slick this past season 25-30
- how consistent are your 60ft times?  60 ft times vary 1.56-1.60
- you mention that your ET's are going up 2-3 tenths - what about MPH?  Is it falling off with the increase in ET?  Yes it does
- as the day progresses, what variation do you typically see with your 1/8 mi time and speed?  I generally dont pay attention to the 1/8. Should I be?
- how much hotter and humid does the air typically get?  And, are you computing "density altitude" or just looking at a thermometer? Thermometer and how much im sweating

Injected,
I used to check the clutch  every pass but it never seems to wear it always looks brand new, I put new fibers in at the beginning of each season. I made a gauge to check the air gap of the lock up I check that every couple weeks and pull the pack about once a month and inspect it
I realize its a process and work to get a bike to run consistent just need some guidance

Just wondering what fuel you are using. Also on really hot days at the strip I would keep my fuel can in an ice chest, (not kidding), and refresh the fuel amount in the tank before each pass.... Just my 1/2 cents.

Southpaw wrote:

I've reread this entire thread and have a few questions -
-  are you running a shift light?  No shift light Schnitz Racing Air Shift Module using auto shift
- how many passes on your rear slick?  New slick this past season 25-30
- how consistent are your 60ft times?  60 ft times vary 1.56-1.60
- you mention that your ET's are going up 2-3 tenths - what about MPH?  Is it falling off with the increase in ET?  Yes it does
- as the day progresses, what variation do you typically see with your 1/8 mi time and speed?  I generally dont pay attention to the 1/8. Should I be?
- how much hotter and humid does the air typically get?  And, are you computing "density altitude" or just looking at a thermometer? Thermometer and how much im sweating

 

Okay, thanks Southpaw for your reply.  Without having a whole lot of data to work with, it's only possible to generalize as to what might be going on.  So, just a few additonal thoughts.
- if your 60 ft times only vary between 1.56-1.60 sec, I'd say that's good enough for now.  That's only a difference of .04 sec, which is not unreasonable for your combination.
- I asked about your 1/8 mi times and speed.  If those are relatively consistent like your 60 ft times, then something's happening on the top end.  Maybe the motor is nosing over slightly, to varying degrees, as you approach the traps?  
- Taking your atmospheric conditions and then computing air density will give you a single number to track throughout the day.  And, over time you'll see what affect, if any, this has on performance.  Motors tuned to a razor's edge (think Pro Stock) will be most affected by changing conditions.  A bracket type combination - not nearly as much.  

And another random thought - maybe an ignition issue?  Not sure what you're using but I'm guessing a more modern electronic setup (Dyna maybe?).  What has me thinking is that, back in the day, everybody (including your's truly) was running an MSD box.  They worked great, until they didn't; at which point your ET's would be all over the place.  Had a lot of people scratching their heads.  The fix was to send the unit back to MSD for inspection.  You'd get it back with a note saying that nothing was wrong (yeah, right), but they did do an "update" of some sort.  You'd plug it back in and you'd be good for a while, at least.    Again, just a thought.  

Mike

- 

Just a thought... are you monitoring battery voltage and charging between runs? (something easy to overlook) assuming your on a total loss system 

This is one of the reasons I eventually ended up running a magneto.

Injected wrote:

Just a thought... are you monitoring battery voltage and charging between runs? (something easy to overlook) assuming your on a total loss system 

 

Agreed!  Injected may be on to something here.  The voltage is certainly easy enough to check.  And, ideally you'd want to put a load on the battery when doing the test.

Using VP C12 fuel. Dyna 2000 Ignition, Total loss system I do charge between runs.

Let me throw this out there. It seems to me last season the bike was not as inconsistent as it was this year. So i started thinking about what i had done to it. Beginning of last season I changed the cams from running 2 stock intake cams to Webb Cam #118. 50 thousands more lift over the stock cams, My thinking at that time was bigger cams i need more fuel so bumped the mainjets up from 125 to 130. Could that be a contributing factor? I did do a plug chop first time out this past season and it didnt appear to running rich

What did the plugs look like after they got some laps on them? What is your total timing set at? 

Being a bit rich on a hot day will slow you down, but its a safe bet. Most guys want to run right at the lean edge for max power, but you really need closely monitor the plugs.

That main jet seems to be in the correct range, nothing out of the ordinary. Maybe try to up the timing or lean out the main gradually and see what that does.