340 invader bog

[78invader2]

No problem with your language! Im 21 and just started getting into the old sleds. I will get the carbs balanced next weekend (going on a trip to texas for college). So after the screws are back to the same, how do I go about adjusting one carb or the other with the throttle cable? Is it just the nuts on top of it? I know of people who use nails to hold the throttle can up in each and adjust it that way. Is this a good way or is there an easier/better way?

[Gilson435]

No problem with your language! Im 21 and just started getting into the old sleds. I will get the carbs balanced next weekend (going on a trip to texas for college). So after the screws are back to the same, how do I go about adjusting one carb or the other with the throttle cable? Is it just the nuts on top of it? I know of people who use nails to hold the throttle can up in each and adjust it that way. Is this a good way or is there an easier/better way?

Well there are a few different ways... First off yes it is just the lock nut and cable adjuster on top on the carb slide that you adjust. It is not so important that both carbs are adjusted the same as it is to adjust each carb so both cylinders are equally drawing in the same amount of vacuum. Take into consideration one cyl may be stronger than the other. You want each cylinder to produce an equal amount of power at any given throttle position. This can only be achieved using carb sync gauges. I like to use the Edelbrock carb sync tool. I start with adjusting the throttle cable so both carbs are achieving wide open throttle(verify the slides are both all the way open). Start the sled and sync the carbs at idle using the idle screws(big ones). Cover the mouth of the carburetor with the sync tool and adjust the tool so the red float gauge is floating in the middle. Keep checking both carb and adjust screw until both carbs are measuring equal on the gauge while maintaining 3,000 rpm idle speed(NOTE: This speed may change depending on how cold or hot the engine is.) Next with the track suspended off the ground I insert a small screwdriver between the throttle lever and throttle block to hold it open off the idle screws. You can now adjust the cable adjusters to achieve equal measurement on the gauge. Tighten lock nuts. Double check your throttle lever free play and make sure it is still achieving wide open throttle on both carbs.(with engine off of course

[Checkmarks]

Elderbrock is way to high tech for me.  A six foot piece of hose the size that fits the barbed vacuum ports that is also the ports for the priming pump on the carburetors works for me.  Old school is my school.

Fill with about two feet of water.  The water then goes to the balance of the middle of the hose.    While the motor is at idle, crimp the line, so your water will not just get vacuumed into the motor when you hook up each end to the ports.  I step on it with my left foot and plug each end to a carburetor, while crimped. 

If you are close to balance the water will stay in the hose.  One side may be higher up the column of hose.  Adjust until the water marks in each column is equal. 

When you are way out to lunch, your 2ft of water will race into the cylinder that has way more vacuum.  Increase the other carburetor idle screw or turn down the water gulping carburetor.  Now get some more water. 

Worst case make sure the motor gets to operating temp after injesting h2o, THAT DAY.

[78invader2]

I got the carbs synced over the weekend. It wasnt too bad once I figured it out. It is however still boggy when its warm and seems to be running rich. I have 175 mains in it and 25 for the pilots. The needle is set on the 3rd mark. Is this the correct set up or do I need to re jet?

[Gilson435]

Everything you'll ever need to know right here

[rminier]

 Your 175 main and 25 pilot jets are the stock jets from the factory. The stock needle clip position is the 2nd (from the top). You might try that to see if it cleans up the rich condition.
 Also, make sure the enrichener plungers are fully seating down in the carb body with the choke handle "off". You might try a lttle extra free play on the cable adjusters for those plungers just to make sure they're not hanging up.

[78invader2]

So I went and adjusted the plungers and it did help quite a bit. It no longer seems to flood itself out. It still has the bog though. If I go from an idle to full throttle, it bogs for 3-5 seconds before it revs up, when it does, it really flies. There is no bog from starting mid throttle and going to full. Could this be something in the clutch?

[Checkmarks]

Your bog could just be the design scheme called piston port.  When reed cage design came in Polaris the bottom end of snowmobiling changed.  Rotax's rotary port is also a mechanism that whips butt on the bottom end.

How does it run from 4k and up?  Do you have a new belt in there and the deflection C-C set and square? 

[gixxer6]

I agree with Checkmarx.  Your description sounds alot like how these piston port motors act.  There are a few things you can do to minimize it:

1.  Like Checkmarx said, check your belt condition and clutch alignment

2.  Run an original airbox, this will help reduce the bog, and will greatly reduce the boggy sound

3.  Make sure carbs are clean and synced. 

4.  Check the ignition timing. 

5.  Make sure the track tension is set correctly.  Being too tight slows things down. 

Once you have it all tuned to run as good as it can, if you are still not happy then look at the clutching.  Raising the engagement RPM will help with the boggishness, but makes it less trail friendly.  You'll run higher rpm just cruising down the trail and will lose fuel economy.  I played with this on my 440 and ended up back at stock.  I preferred the sluggishness over the higher revs. 

[rminier]

 As usual, Checkmarks and gixxer6's comments are dead on the money, IMHO.
 I must re-tell a story about my frustrations with the dreaded bog I experienced 35 years ago when I first owned my Invader.
 I thought I had everything dialed in perfectly, but could not get rid of an initial bog from a standing start. I went back thru the carbs several times....convinced I was missing something.
 It wasn't until I received one of the snowmobile magazines in the mail, with an article on clutching, that the problem was revealed to me.
 Kawasaki's shop manual specifies a 12" center to center distance for the clutches....I had them set to precisely that distance. I was using a nearly new Dayco Max 1078 drive belt...which was the correct belt.
 After reading the clutch article, which also discussed belt deflection, I was amazed when I pushed down on the mid-way point of the drive belt and could push it down to where it almost made contact with the bottom of the belt.
 I went thru the process of moving the jackshaft back until I had about 1 1/4" deflection with about 8 lbs of downward force on the belt mid-way between the clutches.
  If you don't have a scale, I use the analogy of using the same amount of force as holding a gallon jug of milk.
 This made all the difference in the world....my Invader would now launch from a standing start with some authority.
 I no longer care, or pay attention to anything relating to center to center distance.....drive belts vary slightly in length when new. Moving the jackshaft even 1/8" inch backwards is like shortening the belt 1/4"
 The Kawasaki K-line chassis are different than most. You can't loosen the engine mount bolts and scoot the engine fore or aft. You have to loosen the chaincase mounting bolts slightly, and the bearing carrier bolts behind the secondary clutch, and move the jackshaft equally backwards to get the belt deflection dialed in.
 As you move the jackshaft fore and aft, its distance from the tunnel changes....which may require you to change the shims under the bearing carrier on the clutch end of the jackshaft.
 IF...this is part of the problem causing your bog, I would get the jackshaft moved back and run the sled with the limited time we have left this winter.
 True enough...you would want to get that bearing carrier shimmed properly so that the jackshaft sits dead centered between the bearings at each end, ..but you can run it with a slight misalignment for awhile...
 Go push down at the center of your drive belt and see how it acts...

[Interceptor398]

All very well said, but would be easier to try a few belts until one fits?

[78invader2]

The stock air box is on. I will check the clutch alignment and ect when im back home from college. I do know the belt on there now is from an arctic cat. I remember the PO saying he put it on there for racing cause it grabbed better or something.

[gixxer6]

I would start by checking to make sure the belt is the correct size, and replacing it if it's not. 

[78invader2]

Sounds good ill give it a shot! Only problem is all the snow is gone up here

[jskal]

Hope you've gotten your 340 running well.  I had similar issues and found a mis-match of carb components had been installed.  This is what it took to make mine right with standard mikunis (I don't think any 340's ran econojets).

2014 winter setup
Replaced 30 idle jets with 35
175 main
   Stock:175
6DH7 needle 3rd clip
Needle jet P8
   Stock:P8
Slide 3.5

Mixture 1- 1/2

RN2C plugs

Also - I added UFO's and it really woke up the mid-range.  Changed the pilots to 17.5 (and did not require any carb mods that I had read about)

Best of luck!