Idle circuits closed

[motogtp]

'78 Super Sport with 6,000 miles. It has always run rich since I got it last fall (on my 4th set of plugs). Just for fun I screwed the idle circuits fully closed and I am running pods to try to lean it out. It started right up and I took it out for a couple of miles. It ran great. In the latest carb removal I noticed that the slides were not seated. PO had this thing totally screwed up. Is it possible that the throttle lifters are adjusted too high? Why would it run with the pilot screws all the way in? Thanks.

 

[dirtdigger]

The throttle slide position is something that should be taken into consideration when doing carb sync. Getting the carbs synced to the same level is only part of the process. You also need to note what the actual vacuum reading is. A low vacuum indicates throttle valve excessively open and the opposite if it is closed to far. Closed throttle high vacuum, high throttle is low vacuum. The slides wont be completely sealed tight ever...if it was tight it wouldn't run because no air would be drawn through the carbs. Your throttle valve position is in direct correlation with idle speed. If they are set too high then you would have a really high idle speed. If it still runs with the screws all the way in then you have some other issue going on with an internal air leak. Do you have the sealing o-rings on the idle circuit screws? Should be stacked up: o-ring, washer, spring, idle screw. If the oring is gone, or bad then it would suck air in by the threads.

 

[motogtp]

I checked the O-rings in the idle circuit earlier. One was cut and another was missing a chunk. They were replaced and stacked in the order you listed. Got a sync kit on the way. What should the base line vacuum be? I read somewhere around 8 in. water column. More tweaking but know I know the relationship. Thanks as always DD.

 

[dirtdigger]

Honda says normal is 20-22 cm of mercury. Yeah you will need to do some conversions depending on what your gauges read. This is a stock motor in good condition at probably sea level. It will change with altitude, engine condition, compression, camshaft, etc. I know what I look for with my gauges depending on all the factors, you just kind of have to watch what the gauges do with different adjustments to determine what is normal for you. Kind of hard to teach stuff that needs to be seen first hand.

 

[motogtp]

Thanks DD. I can do the conversion. Just nice to know where the starting point should be. I agree with your comments. I am slowly learning to temper my instincts with what I actually am seeing.

 

[motogtp]

Honda says normal is 20-22 cm of mercury. Yeah you will need to do some conversions depending on what your gauges read. This is a stock motor in good condition at probably sea level. It will change with altitude, engine condition, compression, camshaft, etc. I know what I look for with my gauges depending on all the factors, you just kind of have to watch what the gauges do with different adjustments to determine what is normal for you. Kind of hard to teach stuff that needs to be seen first hand.

So I got the carbs sync'd this weekend. 1 & 4 were a little off but what really bothered me is that the base reading from #2 was only 5" (12.5 cm). Stock motor. Clymer calls for a base of 8". Could this be the issue with it always running rich? Is there a way to adjust #2 (there is no adjustment under the carb top)?

 

[dirtdigger]

The keyhole carb rack has a "base" carb...number 2. All of your syncing adjustments are to be referenced off of #2 carb. So you would adjust #2 first then adjust the other 3 to what #2 is reading. You should be able to adjust #2 with the idle speed screw then adjust the others with the sync adjusters. This is all of course assuming cylinder 2 is mechanically sound which I am beginning to wonder about with all of the issues you are having. I dont recall...have you done compression and leakdown tests to make sure you dont have ring or more likely valve issues??

 

[motogtp]

The keyhole carb rack has a "base" carb...number 2. All of your syncing adjustments are to be referenced off of #2 carb. So you would adjust #2 first then adjust the other 3 to what #2 is reading. You should be able to adjust #2 with the idle speed screw then adjust the others with the sync adjusters. This is all of course assuming cylinder 2 is mechanically sound which I am beginning to wonder about with all of the issues you are having. I dont recall...have you done compression and leakdown tests to make sure you dont have ring or more likely valve issues??

Yeah, I think I am about at my limit. Done all the things you suggested and it still doesn't seem to make a difference. I am looking for a local mechanic to put another set of eyes on it. No compression test because it always runs strong with a new or cleaned up set of plugs so I never thought about it. Didn't think I would have to tear down a motor with such low miles but it may come to that. Thanks for all your help.

 

[motogtp]

So I removed the main jet and needle jet holder on carb #1. I was expecting the needle jet to drop out but it didn't appear that there was anything there. I shined a light down the shaft. The needle is there and there appears to be a brass guide for the needle at the top of the shaft. But certainly nothing that looks like it can be removed. The PO had the floats installed upside down, did he forget to put in the needle jets? Would that be the source of all 4 cylinders running rich?

Side question. After I put on the CycleX ignition I also installed the CycleX regulator/rectifier. Later I found out that the reg/rect was defective and my voltage was almost 17.5V at about 3,000. Could that have damaged my coil set? Is there a way to test it to be sure?

 

[dirtdigger]

The needle is attached to the slide in the carb and it doesn't drop out with the jet holder.

Cant really damage coils, if you have spark they are probably ok. I take that back you can damage coils but I dont believe the 17 volts is enough if you haven't run it that long. On older cars they used to run a lower voltage coil and on startup it would bypass a resistor and run direct battery voltage to make higher spark voltage for start up. It normally takes a fairly long time at a high voltage to hurt the coil and then it usually burns out inside and stops working all together.

 

[motogtp]

OK, but the Service Honda schematic shows a needle jet (not the needle) above the needle jet holder. The jet looks like a small, ribbed cylinder that fits between the jet holder and the carb body. I also measured the jet holder and shaft depth and there is a gap with nothing there. In any case I ordered a set a four from Service Honda. At this point I have nothing left to try and it seems to answer both the low vacuum and uber rich condition.

I maybe put 30 miles on the bike while it was overcharging before I realized what was going on. I am going to assume it's OK for now.

 

[motogtp]

Crap! You were right DD. The needle jet is in there so I did not find the source of the problem. Son of a bitch. So now the last thing I do before tearing into the engine is to sonic clean and rebuild the carbs. They are junk and gunk free so I never felt the need for a rebuild.