912UL Issues

[68niou1]

Weenie. Sounds like a excuse to me.

[Av8r3400]

Today's peak temperature… (-35º tonight)

C'mon over and put it together for me. I'll buy you lunch.

[Av8r3400]

Just another note: Further conversations with LEAF, Lockwood and CPS techs have lead me to believe that this is not a completely unheard of issue with the 1-4 Kitfox models with the oil tank in the rear. (Needing the reversed intakes) Sometimes the engine mount modification (SB 54A) fixes the issue. Sometimes it's the gearbox rebuild. And sometimes it requires the addition of the clutch.

The guys at LEAF had this issue with a IV and finally resolved it by adding the over-run clutch. I'm hoping I don't need to go that far…

[HighWing]

Larry,
Interesting because I have not heard of it talked about over the years. One thing you might check. I was reading some historical stuff on one of the other forums and a guy with a rough running engine traced it to backward facing slides in the carburetors. they look the very similar front to back, but are not the same. If they are installed with the front facing back, it will result in roughness due to poor fuel mixture. Have you rebuilt your carburetors lately?

[Av8r3400]

I've had the carbs apart three (3) times through this ordeal. I have gotten very intimately familiar with them and their nuances. I agree, it would be very easy to get the slides turned around.

If you look closely at the slides and the diaphragms, there are clocking marks that denote the direction of the slide to the diaphragm and then the diaphragm to the body of the carb.

Just to put it down, these are the steps I've taken so far…

1. Synced Carbs
2. Disassembled, cleaned, adjusted and re-synced carbs
3. Disassembled, cleaned, installed rebuild kits, adjusted and re-synced carbs
4. Serviced engine mounts per #SB 54A
5. Removed, replaced spring discs, cleaned and re-assembled gearbox
6. Removed, cleaned, re-shimmed, lubricated and re-assembled gearbox

[Danzer1]

If I remember right, you also rebalanced your prop. After you do the gearbox parts change, it may pay to re-balance the prop again.

Although, I would consider doing it with a Dynavibe GX2 for a $100 or 2 more than the standard. It uses 2 sensors and can balance quicker and with much better accuracy. Also with 2 sensors, it can pinpoint engine related vibration location issues. Like a mis-alligned alternator, etc.

I've been researching them somewhat lately and they are getting great reviews for balance and finding other problems. Link here: http://www.rpxtech.com/DynaVibeGX2.html

Might be worth a shot!

Greg

[Slyfox]

I would like to put some understanding into the mix.

first one is the balancing of the carbs. how are you doing it. where are you pulling the vacuum for the balancer outfit, either vacuum gauges or a device for showing balance.

with this thought remember that you are balancing two engines in one. you have a left and a right side, hence the balance pipe in the middle. if you pull your vacuum for testing off the big ports that the balance pipe runs off of, you have a problem doing so, trust me. reason. there is too much opening. so, Yes you can do this, but you need to remember that you now have a problem. that problem being to much of a good thing. if you use a vacuum gauge you will see right off what I'm talking about, the gauge will bounce all over the place. the fix for this is to install a ball valve and close it off, if you do this you will almost shut it off before it stabilizes. than you can use the gauge and continue with your test.

my answer is to block the tube between sides. how I do this is to remove the tube that the factory has and replace it with rubber hose, as a perminate install. now I have a means of taking a clamping fixture or pliers in the form of locking pliers with a round surface and clamping off the hose.

than I take my balancing device and hook it to the carburetors. there is a fitting with a screw in it right in front of the carb. using this connection, use of a restrictor is not needed and can connect direct. the results is a nice smooth vacuum source. now the reading is trustworthy.

Now if you want to know if the carbs are truly balanced try this and it has proven true for first start and to find if my adjustments slipped on my carbs. you open the throttle all the way and look at the relationship of each carb at the throttle lever to the full open stop. if you really can't tell than pull the throttle back to idle very slightly to give you about a .030 clearance on one side between the arm and the stop at full throttle. now you can compare each side to see if they are basically the same. if not . than your balance is off. you can even just start from scratch and put both arms to the same position when at full throttle, or just off full, for comparison reasons. once you have both carbs opening at the same spot, now you start it and I can almost guarantee it will run good. now go from there.

[68niou1]

So got my parts this week, pulled my gearbox apart and did some comparisons. The dog gear is completely different. It looks like the gears are slightly different as well.

[68niou1]

Here is a side view of the new gear-

[68niou1]

Comparison of the old dog gear vs. new one-