Jetting for fall grass drags 440 Invader

[JDmatt]

There are some grass drags coming up that I would like to try running.  Does anyone have a jetting recommendation for fall weather, or a general guideline to follow for jetting for 50-60 degree days (increase 3 sizes, etc)?

[Checkmarks]

Dont hold me accountable for jetting guesses.  About one jet step per 20 degrees. 

Now put in the presumed correct jet and buy one new spark plug.  Put the sled on a jack stand with the motor warm (operating temp).  Put the new plug in and start the motor.  Hold wide open throttle (WOT) and count to four with the motor screaming.  Keeping the throttle WOT use the kill switch.  Pull the new plug and inspect the grounding strap.

Where is the line between the shiny new finish and the dull "burned" line.  It should be exactly in the center of the bend.

Cost you one plug if you start rich you can use that "just used plug" again for a leaner test.

evaluation:  past the bend and on the way to the threads of the plug you are too lean

on the way to the bend and you are too rich

[JDmatt]

Thank you for the tips.  The temperature ended up being in the 30s yesterday for the race so there was no issue with jetting.  The burn line was right in the center of the bend like you described with the needle clip in the middle slot. 

However, the sled would only bog coming off the line.  Played with idle, air screw, etc, could not get rid of the bog.  50 ft. down the track it would open up and haul ass the rest of the way. 

[kawhead]

what engagement rpm?stock clutches? belt deflection is pretty critical on invaders, i.e.  too loose, equals bog.....

[Tory944]

  ....   most Kawis I've had/seen excessive belt deflection...   here is one check you need to do.  When your belt is too loose you are starting off in "second gear"  (off the line bog).  Check your belt width...   too narrow will cause excessive belt deflection.  Clutch alignment checks and belt tension solve many of the problems with "off the line bog".  Also, check your primary sheave faces.  I've seen Kawi primaries that have heavy wear on the sheaves.  The belt will have to "overcome" the "step" created by the belt wear which will also cause poor off the line response.  This usually happens when the sled has spent too much time at a certain speed (mph) and the belt runs in the same spot on the primary.

[Tory944]

Have you checked/replaced your secondary cam (helix) wear buttons recently?  Another culprit for poor off the line response.  I spend much more time on my Interceptor clutching (with excellent off the line results) than carb calibrating...   when one, two or three clutch components are worn, doesn't matter how you've jetted.  Dead in the water.  Holeshot isn't everything, but you can lose a lot of races without it!

[JDmatt]

Clutching is the one thing on this sled I have not done anything with yet, so thank you all for the tips.  Stock clutching, stock engagement (3800, seems really low?)  New belt.

[Tory944]

That's not low for a stock Invader...   but it is low if you are looking for a good holeshot on the strip.  IMO

[kawhead]

i've had fair results changing to a lighter bolt on the weight arm. a blue or black spring if you can find one also

[gixxer6]

I played with all different combinations of weights and springs with different arms (F's, J's, E's, etc.).  I had the best results by modifying a set of E's to Aaen's spec, it makes for a great drag setup.  I didn't use their weight and spring combo though. 

[Checkmarks]

Burn line revisit. 

How not to burn down a piston getting maximum Hp at 1/2 WOT.  When you have the 'perfect' solution for WOT, then you go to work setting the mid throttle.  Same procedure.  RPM (not exclusively all true) of the motor has nothing to do with calibration of the carburetor.

The burn line at 1/2 WOT tells you where to put the needle clip or change the needle jet. 

Record all data and share.  After you have perfect calibration you can use a spreadsheet type of solutions for all altitude/ temp changes. Technically the jetting changes has to do with air density not altitude/temp.

When the light turns green, how do you apply the throttle when racing?  In the end when the spark plug burns correctly, the problem is somewhere else.  Do you see why adjusting the air screw or idle rpm screw has no effect correcting your bog 50ft down the track?

[JDmatt]

Burn line revisit. 

How not to burn down a piston getting maximum Hp at 1/2 WOT.  When you have the 'perfect' solution for WOT, then you go to work setting the mid throttle.  Same procedure.  RPM (not exclusively all true) of the motor has nothing to do with calibration of the carburetor.

The burn line at 1/2 WOT tells you where to put the needle clip or change the needle jet. 

Record all data and share.  After you have perfect calibration you can use a spreadsheet type of solutions for all altitude/ temp changes. Technically the jetting changes has to do with air density not altitude/temp.

When the light turns green, how do you apply the throttle when racing?  In the end when the spark plug burns correctly, the problem is somewhere else.  Do you see why adjusting the air screw or idle rpm screw has no effect correcting your bog 50ft down the track?

My line of thinking was that the idle settings effect how the engine RPMs come up from idle.  Does one have nothing to do with the other?  Plus I've been told that running idle high at 3K RPMs helps to get past the bog, however that's clearly not the issue here. 

[JDmatt]

On the clutch, I'm going to assume that Kawasaki clutch parts are hard to find, so I may try swapping to a Comet 102C with the Liquifire setup to start.  Does that make sense?

[Lloyd (ljm)]

 Hey Matt

 Yes putting a 102 setup for a Liquifire makes a lot of sense too me.

 I have some Kawasaki clutch parts if you want to use the Kawasaki clutch.

 Lloyd

[Tory944]

Don't want to stir up a can of worms here... but weight and spring selection for the Kawi's (Deere's) are poor at best. The problem comes with the "full shift rpm's".  Ya, you can get your engagement up with a yellow or purple primary spring, but take a look at your tach at full shift.  You will be waaay over your ideal shift curve.  Those Invaders and Liquifires should shift out at around 7800 rpms.  All of the advice through comet will be b 1 arms purple or yellow spring.    Your power will fall off with the comet setup.  If you are hell bent on going with the comet, you will need to try a lot of different spring/weight set ups.  Watch your tach.  IMO stick with the original Kawi clutch and if you feel that yours needs "too much work" get on ebay and find one that looks good.  Swap over your weights, springs, etc...           I have good intentions here....   save yourself a lot of headaches and $$ and stick with the Kawi clutch.  The comet clutches work great for "some sleds"  but it's the setup that matters...   I don't have the Comet spec sheet in front of me, but notice that their setups don't give any "ballpark" shift speeds.  Only aprox. engagement Rpm's.  The 102 works o.k. if you are running ported cyl's and pipes, but not stock.