Need help, Invader runs but wont build high RPM like it should

[The Great Jashu]

I just had new crank seals put in my green invader. Installed new primer. Put it all back together. It starts and idles well. Seems everything was going great, set the idle and thought everything should be great. Running some premix gas since its all been in a box for a year. Took it out across the yard and it just wont make power. Its dropping the mag side cylinder. Carbs were all very clean when it went back together. When its idleing seemed like it wasnt always on two. Pulled the plug wire on the mag side and it continues to run, pull the pto side and it fumbles and quits. Compression is good both sides. When I pulled the plugs its shows that light smoke from the mag side cylinder , (tells me its rich). Replaced the spark plug boot on that side and still have the problem. Pulled the air box off and there is raw fuel in the airbox. Pulled the carb back off the mag side and it has fuel in the barrel. I am sure this is a rich condition. When I got the sled it did not have an airbox. Could someone have changed the jets? I cant find anything written on them to tell me the size, so I cant give you that information. The only jets I am aware of are the two in the bottom of the carb. One is the small opening, I believe to be the pilot jet, the other feeds the power jet. The large one the needle goes through I can see through. I believe the needle clip is set in the center.

Sorry for the long post, just giving you all the info I have. My knowledge has come a long way thanks to all of you and I have been able to keep the other two running very well. This one is one problem after another, I have conquered all of these problems so far and will conquer this one. "Its a machine and I will win"!

What do I need to do to try and correct this problem?

[The Great Jashu]

I have changed plugs too. Its just not making Invader horsepower, RPMs are not coming up. When it was apart I replaced piston and rings on the mag side. Though I am running some premix fuel, it has the oil injectors hoooked up too.

If I move the C-clip will that make a difference?

[kawhead]

pulled the pto side and it still runs the same tells me its the pto side......if its not idling well i litely pull up on the choke cable at the carb one at a time to see if its rich or lean.

[The Great Jashu]

Kawhead- It dies if you pull the enricher.

I wrote that the wrong way on pulling the plug wire, I will change it. The PTO side runs well.

What do you suggest I do to fix this? I think its rich both sides.

[The Great Jashu]

Cleaned the mag side carb again. Moved the C-clip to the top on both sides. Idles better and seems more responsive to the throttle now. Will put the secondary back on tomorrow and see how she acts under a load.

If that is not it. Could it be the one of the clutches isnt operating properly? I another primary and secondary to try.
Would the secondary be the one causing it to not power up by opening too early?

[Checkmarks]

Jashu,

It is best to completely disassemble the carburetors when the machine is new to you.  You can have no idea what 'hardware' somebody put in before you.  When you say you cannot read the numbers on the jets, get new jets period. 

New main, power and pilot jets and new rubber o-ring.  The main and the power jet are obvious in the bottom of the float bowl.  The pilot jet you have to look into the 'top half' of the carburetor there is a tube like hole maybe 10 mm deep.  It takes a thin screwdriver to reach down there to unscrew the pilot jet. On the emulsion tube you look for the Mikuni symbol and right beside it is the #.  Pull the brass bolt fitting that holds the rubber o-ring and then slide out the needle jet.  It is a brass tube that slides out into the venturi then out through the throttle valve (slide) to remove.   Watch to remove that brass washer.  Make sure it matches what you have in your running sleds should be P-6.  Check the Throttle valve (slide) number (2.5) it is stamped on the bottom and the needle (6DH7)

Since you have other carburetors that are running good on another sled, slap them on.   This should eliminate if the problem is fuel or ignition problems.

[Checkmarks]

Had a old belt that was worn out before.  The sled would start fine and when it took off it was boggy until 6k then it would scream up to 8k.  When you would let off the throttle and hammer it again it would be boggy, back down to 5k and struggle back up to 6k.  After a few moments when it got back up to 6k the motor sang back up to 8k.  Changed the belt and the problem was fixed.

[The Great Jashu]

Thank you Mark! I knew you would have good insight into the jetting. This was the first Invader I got many years ago and have been all through the carbs. New O rings were put in two years ago. I was not aware of the pilot jet way up in that little tube. I will work on this issue a little further and if I cant get it, I will move a good set of carbs over.

It does seem to run better and revved right up after the second carb cleaning and moving that C-clips up to the top. But, I dont have the secondary on and havent taken it back out yet.

Does moving that C-clip up or down have that much influence? Can I lean it out to much if its all the way up?

Thanks again, I will keep after it.

[Checkmarks]

Jashu,

Glad you can hear what I have to say.

Think of the carburetors as having four unique systems AND it does not matter what rpm the motor is spinning.  The idle circuit has nothing to do with the 1/4 throttle position(TP) 3/4 TP and last wide open throttle (WOT).

When the motor will not idle the only item in the carburetor that does anything is that pilot jet and the air mixture screw.  Not exclusively perfect because the pilot jet influences the transition from idle to 1/4 throttle.  Assumed you do not use the enrichener (choke).

1/4 throttle thru 3/4 TP has four elements that regulate the fuel metering.  One, throttle valve (TV)(slide),  Two the needle jet (the thing the needle slides up and down in), three the jet needle (looks like the big sewing needle) and last item four (exclusive to the power jet carburetors) on Invaders the main jet.    Lots of elements that make significant changes to the air/fuel (A/F) mixture.

The TV has its most influence in the 1/4 throttle range.  The needle jet and jet needle (I know that is confusing but that is how they are differentiated).  These NJ and JN play the major role in the 1/2 to 3/4 throttle range.  Last in PJ carburetors the main jet plays it role in the  3/4 throttle range.

Lock this information into your head.  I tell you about this stuff so you you can best understand how moving an e-clip affects the system.  So inside; lets call them our carburetors (invader PJ's) we have a P-6 needle jet.  We could move the clip up or down assuming you have the clip in the third position.  Lower is leaner so clip position 2 or 1 is respectively leaner (think dropping the needle) and vice-verse richer.  When you need lean by two clip positions say you have moved the needle to that #1 position another alternative that is nearly exactly the same is to change the needle jet from a P-6 to a P-4 AND leave the clip in the third position.  The big trick is to understand why leaner and there are two ways to quantify (measure).  The first use exhaust temperature gauges (EGT) and second an oxygen sensor gauge.  Worry if your EGT's are reading >1400 (more like panic); your piston is getting ready to flow out your exhaust pipe.  Moving that clip can put you into the danger zone.

All those who live at 1000ft elevation are lucky all the work has already been done for you including safety margins with very respectable power results.

Directly answering your question "Can I lean it out too much if its all the way up"; probably not.  Then if it is a cold day in the -20F category and you hold your throttle position constant across a mile long lake cruise, cross your fingers.  The EGT will save your pistons and allow you to make better judgement.

You only need to look where the clips are positioned on the other carburetors and your problem is solved.  Correct A/F mixtures is all you can ask, Mikuni's are designed to match hardware and have exact replication of fuel delivery.  This is say compared to Tilliston where you turn screws to manipulate A/F ratios.

When you hold your throttle WOT the only influence of the A/F ratio is the main jet plus the power jet.  You could take out the NJ an JN, plug the pilot jet and for that matter take out the throttle valve and the sled would run no different than holding WOT.  Heck take the carburetor top off and plug the hole start the motor and hang on, it will run exactly like holding WOT except you wont slow down to make the corner.

[gixxer6]

These graphs from the manual always help me visualize it. 

[The Great Jashu]

HOLY COW!!!!
I am printing this off and putting it in my toolbox.
Thank you very much for the education.

[The Great Jashu]

Thanks to you guys I am getting this dialed in a little better. It will now make serious 8grand HP on the high end, but is missing its low end. Gonna get a set of jets and play with it till it screams.
I think we are making progress.

[Checkmarks]

Low end power?  The jets have next to nothing to do with low throttle lever position power.  TV, NJ, JN, these manipulate the A/F ratio at <3/4 throttle position.

Once you have the right jets and hardware in the carburetors there is no or very little extra power to be had via changing jets. 

Run the motor for a good duration and look at the piston wash through the spark plug hole.  By good duration, a 40 minute trail ride fits that criteria.  I take a LED light and put it down the hole and then a person can see the piston head beautifully.  When you have perfect wash that is the best it will get with respect to power out of a 440 motor.  Another faster more expensive way to check for the correct jetting is to use a new spark plug for a four second run with the sled up on a jackstand.  Once the plug marks the electrode the party is over and you have a spare plug for when you foul a plug.

Other power bumps.  Put in a LTD CDI, the timing curve is different.  This CDI will get you out of the hole best (low end power).  There is no power gain >6k the CDI's finish their curves at the same destination. 

[Lloyd (ljm)]

Mark

 Just a question

 Using the LTD, CDI, I know it has a different curve. Do you change the timing on the stator? or do you get the bottom end boost from just the CDI?

 Thanks
 Lloyd

[Checkmarks]

Lloyd,

You do NOT change the stator.  The difference of retarding takes place within the CDI its self.  The Ltd CDI starts with 31° BTDC and runs out to 12BTDC(retarding advance), or something like that (I am not looking at my graphs).  The regular invader CDI starts with 8° BTDC and runs out at 12°BTDC (progressive advance).  In the end they both go to the same place, thus no peak horsepower gain difference.  Note the word peak, there is change in the horsepower curve and the Ltd makes a broader curve.

Bolt on upgrade that does not give you any more horsepower. 

Working to make a 440 have more power, priceless or pointless.  Forced induction, on the other hand, you could keep up with 800's.