Float bowl question

[egleaves]

Doug, you know about the 4-5k stumble that I've been chasing lately; journey after journey into the carbs did little or nothing for it. Last night I checked out the wires going to the coils and found one bad spot and another iffy spot. I replaced two connections and cleaned some others, now I hardly have a stumble at all.

I guess the point is you're right, it's easy to get tunnel vision and assume the problem lies in the carbs when it turns out that a simple electrical connection, that actually didn't look all that bad, was holding everything back. I'm done screwing with the carbs for awhile and turning my efforts toward the electrical components.

[dbeardslee]

Eric - glad you located the culpret. After fixing the wires you might put the multitester on it again like we did here and verify that the resistance is back within spec. Should be 720 ohms plus or minus 20%.

I'm getting ready to go pull the carbs (again), and I'm going to set the floats back to 25mm. I'm also going to pull the ignition switch out and clean the connections. That's about the only one I have left that I haven't messed with. I'm getting 12.6v at the battery, but only showind 11.6v at the TCI. It was 12.3 at the battery and 11.3 at the TCI with the old battery. It's making me crazy trying to figure out where that other volt is going. I charged the new battery for 4 hours yesterday, and put it in late last night. The lights definitely look brighter with the ignition on, but I haven't actually started it yet. Man I'll be glad to put this issue to bed!

[81xsproject]

Have you re-checked for an intake leak? What condition are your intake port sync caps? Have you checked at the dreaded butterfly seals? It sounds like you have 79 carbs, so I am glad to here you are going back to the stock 25mm. You never did say where you got those pilot jets from. After that, you might be headed in the right direction by looking elsewhere for problems. Like I always say, the carbs should be the last troubleshooting point.

[bikerphil]

DB, an electrical problem that gave me grief once was the double connector at the + side of the coils (red/wht). I had a stumble at launch and half the strands on that wire were broken where it was crimped. Fixed that and the problem went away. Might be worth a look.

[dbeardslee]

The pilot jets that are currently installed are the same ones I've been running for close to 2 years - they came from Jets-R-Us. The 47.5's and the 147.5 mains (currently installed) came from Mikes XS. I've been through almost every red/wht connection I could find. I completely remade the leads that come from the coils to the red/wht, grey, and orange wires. I have not done anything but clean the double red/wht connector, and the orange and greys. Might be worth replacing the connectors.

Here's what I've done today - I set the carb floats back to 25mm, synched and colortuned. I completely dissassembled and cleaned the ignition switch (got me another tenth of a volt back at the TCI). The connector for the ignition switch looked a little crispy but still serviceable. I'm going to order some new connectors from Z1 and get rid of that completely. Colortuned and synched, and it sounds better, but it's raining so I won't really know 'till it stops. Since you can only get the iridium plugs in the resistor variety I installed non-resistor caps and brand new plug wires a couple weeks ago. I checked the resistance in the plug and found it to be 5k ohm - just like the caps. When I test the resistance from cap to cap I get 15k ohm, and 3.3 ohm on the other side at the TCI connector, so it appears that the non-resistor caps were the right choice with the resistor plugs. I also replaced the plug wires when I put the new caps on, and I used 7mm copper core automotive high tension wires ($12 got me enough wire to do it twice). I ran a resistance check on the wires just to make sure they weren't resistor wires, and they have no resistance.

The other thing I'm considering is getting a more modern rectifier/regulator from Oregon Motorcycle Parts. It throws more amperage and provides full charging at 1200 rpms. Since installing the 750 FD I've been doing a fair amount of low rpm putting, so maybe I'm dragging the charge on the battery down. The lights were definitely brighter with the new battery installed. The more I delve into this the more I'm thinking it's electrical.

[dbeardslee]

I managed to get a test ride in, and the condition was a bit better, but still not right. I replaced the connector that goes to the handlebar switch, and gained another 2/10's of a volt at the TCI. Once again it was raining, so no test on that repair, but it sounded a bit better at idle. Tomorrow I'm going to see if I can find a three prong automotive electrical connector to replace the ignition switch connector in the headlight bucket. It had obviously gotten hot, so there had to have been some resistance in that connector. IIRC there's a red/wht wire in that connector, so maybe that's the gremlin. I'll find out tomorrow.

One nice thing that happened when I took the ignition switch apart - I found out I do have a handlebar lock. Prior to cleaning the key wouldn't turn all the way to the left. Now it will and I have a lock, so that was cool.

[red bandit]

Make sure you don't go past the first handlebar lock, to the second lock position and turn on the tail light. It will drain the battery.

[boyat68]

Just in case you have not addressed this issue:

Some of the carbs for the 80s (my carbs), came with the hole drilled in between the pilot and main towers. This also necessitated putting a rubber plug in the pilot pickup to force the fuel in the main through the drilled hole up through the pilots. Without this rubber plug, the carbs deliver too much fuel at lower rpms.

[dbeardslee]

Red - I did notice that - I wonder what the purpose of that feature is? I didn't think it had a lock on it before I took it appart. Either it wasn't assembled correctly (doubtful), or the crud that was down in the bottom of the switch wouldn't let the pin go through the hole.

Boyat - The 78/'79 carbs are different than the 80/81's. The 79's have a bolt and washer on the top of the pilot tower.

After I saw the voltage gain I got from replacing a connector (that actually didn't look too bad), I ordered a bunch of 3, 4, and 6 pin connectors from Z1. With a little luck I'll have them Saturday and I can get rid of these old connectors in ernest. In the mean time I think I'm going to try a temporary fix with single spade connectors on the ignition switch connector just to see what happens. On the connectors I've replaced so far I dielectric greased them from the back of the connectors, and gave them another little shot right in the slots. Hopefully those connections won't oxidize again for a long time.

[dbeardslee]

Eureka moment

So I started removing the electrical tape from the ignition switch connection and found the blue wire completely broken off on the back side of the connector. I attached the wires with some fairly stout spade connectors - that got me another .17 volts at the TCI - up to 11.87v - and the problem is vastly improved. Still a very slight stutter on the launch, but I think that can be remedied by dropping the floats another mm. I'm also going to continue replacing electrical connectors in my search for the missing .13v. I can't tell from the wiring diagram what the blue wire does. Looks like it might be a ground wire. Whatever it is, repairing it really helped.

[randy]

Chasing fractions of volts is like chasing your tail only you don't have one! Hazards of DMM's realized!

[dbeardslee]

Randy - You da man. It was your suggestion a couple weeks ago - and Phil's a couple days ago, to track down the red/wht that got me started on this electrical odyssey to begin with - along with your help in diagnosing the TCI. But now you have me stumped. DMM? Digital Molecular Matter?

[bikerphil]

DB, the blue wire off the ign switch is for the running lights. DMM = Digital multi meter.

[dbeardslee]

Phil - it must have been making partial contact 'cause the lights were working. They're definintely a lot brighter now, but that coincided with the new battery.

I rewired my fuse block today and got rid of some old splices left over from the PO. That got me to 12.2v at the TCI. Still had a little stumble at launch and I wound up pulling the carbs two more times today. I finally set the floats at 25.7 and put the old 145 mains back in. The rpm range for the stumble shrunk but the d@@@ things still there. When I pulled the plugs I noticed that 3 & 4 were noticeably darker than 1 & 2. I guess it's time to take a look at the petcocks and make sure they're working right. Luckily that's easy to do with this setup - they just unscrew from the bottom so I don't even have to disturb the gasket. I'm not optimistic about finding the problem there, but who am I to argue with plug color.

[randy]

The petcocks have nothing to do with plugs being dark, they MIGHT affect plug color by being clogged = lean = WHITE. Float height, plug type, jet selection, needle settings and pilot screw settings will affect plug 'darkness'.