Another carb problem....(long)

[jakeman]

Hi all,

I would appreciate some help from y'all on my carb problem. A little history first. I bought this bike new, a 1981 xs11lh, and only rode it a little the first few years. It sat around in the garage a little too long and things got plugged up, so I let it sit some more, like 2 or 3 years, and finally got it going again with a trip to Casey Cycle City for a cleaning and new kits. You could still get OEM stuff then. It never ran right when I got it back and I was doing other stuff so I let it sit this time for 10 or 12 years.

A few months ago I got the bug again and a friend of mine offered to clean her up for me. He's a biker and airplane mechanic and knows what he's doing. He got it running pretty good except at idle. It would start good, but #1 wouldn't fire right away. At full choke the rpm would gradually increase to about 4k and then #1 would heat up. After that it ran ok but rough at idle. At the higher rpm's the bike would scream. Also, when you let off the gas it would backfire a little on the left side.

Yesterday I decided to give the carbs a try myself to see if I could improve on what my friend had done. I had already bought a set of K&L kits. (all I could find) After reading all the tech tips and gleaning all the info I could find on this board, I tore into the carbs. I found 2 obvious problems. The starter jet in the bottom of the carb bowl on #1 was plugged solid, which explains why #1 didn't fire right away on a cold start. Also, the tip of the air valve on #3 was bent enough to notice. I replaced all main jets, air valves and needles and seats with the K&L stuff. I used the original pilot jets on the advice of several of you on this board. I got the starter jet cleared up with carb cleaner and the smallest wire in a torch cleaning kit. When I replaced the air valves I noticed that 2 of the tips protruded slightly further into the bore than the others. I set the screws at 1.5 turns out and put everything back together.

The main reason I started this overhaul was because I could smell gas in the crankcase. Also, there was a small amount of gas in the airbox when I removed it. I knew the petcocks in the tank leaked, so while the tank was off I did the bending of the washer trick and while it didn't stop it completely, it slowed it down to an occassional drip.

This is almost over. On startup, at full choke, the rpms rapidly climb way too high. On half choke it runs about 3k, with all cylinders firing. It seems like it takes longer to warm up to the point where it will take throttle w/out the choke. After warmup it idles about the same as before but with a lot of popping on the left side. I fiddled with the air valves a bit but ended putting them back where they were, at 1.5 out. I took it for a ride and it ran perfectly when you get into it. It doesn't pop or backfire at a steady rpm, only when you back off the gas. I brought it back inside and tried to adjust the air on #! and #2 because it seems to be way too rich on one of those, but I couldn't seem to make much change.

One other change I made while rebuilding the carbs was to adjust the float on #1 because it was lower than the other three.

Any ideas about why the excessively high rpm at full choke, the rough idle and apparent richness on the left side, and the backfiring when you let off the gas? The intake boots look like hell, full of cracks, but perfect on the inside. I spread rtv in all the cracks. I can't find any exhaust leaks.

I'm sorry this is so long, but I wanted you to have all the details.

Thanks,

Jake

[DiverRay]

Jake;
My first thought is did you syncronize the carbs? You NEED to have the carbs synced within a small amount to stop any backfires, etc. You should also check the valve adjustment and timing BEFORE you try the sync. They all work together, and if one is off a little too much, it will cause problems.
The next thing I would check is the pickup coil wires. The one that almost alway's broke first is for #1&4. The wires for this coil are usually pinched too tightly in a clamp on the advance unit. the coil is the front coil, and I think the wires are the light blue ones. There is a thread in the tech tips on checking and repair. You can also check for the "clear tube" setting for carb floats. You may be able to do this without too much problems, and it will verify that the floats and needles are shutting the fuel at the proper level.
Check back after these quick tests if it's still not running properly, and we can look at the next step. Just remember, as you do things with carbs, you want to make only ONE change at a time. That way, if something works, or not, you know what it was.
Ray

[skids]

He said he has an 81 model. Pickup wires are not a likely culpret for 81's.

Originally posted by DiverRay
(snip)The next thing I would check is the pickup coil wires. Ray

[jakeman]

Thanks, fella's, I have ordered a carb stick and when I get it I will do the sync. But, what could be causing the high rpm at full choke? My first thought is take them apart again and get rid of all the K&L stuff and put back original. Am I on the right track?

[John]

One possibility of the high revs could be the fact that at one time someone tried to clean the enrichener jets with a drill bit, and opened them up too big, and now there is too much fuel supplied when the enrichener is opened.

[jakeman]

John, I don;'t think so because as I stated, the jet was clogged when I disassembled the carbs. The smallest wire in a tip cleaning kit is the only one that would fit through the jet, the next bigger size wouldn't go. I've never seen a drill bit that small. What you say makes sense because I didn't have the high rev problem before I cleaned the starter jet, but I don't believe the jet has been buggered out.

Right now I'm inclined to believe I need to do another cleaning and put the oem parts back in, check float levels again and do the carb sync.

I'm still open to any ideas you guys can come up with. This board is great and I love my xs!

Thanks,

Hey, I got promoted to Xsive!! Now I got to buy a bigger hat!

[John]

There are drill bits that are sized by wire gauge. They're called number bits. I just had to buy a #60 (very small) bit, and a pin vice to drill out a broken pilot screw, by hand, in the carbs on a friends SF that I have taken on as side work. These carbs were so bad that I have 9 hours in them, just cleaning, repairing a float with a hole in it, drilling out the pilot screw tip, and replacing the fuel lines. I am charging him $30 an hour, and he is tickled pink with the labor rate. I still have to rebuild the brakes, replace the rusty front forks and seals, replace both tires, change all fluids, and get it running right. That will probably cost him over $500 for my labor, but that is less than half of what the stealerships around here charge for labor. The bike has been sitting for about four years, with fule in the tank and carbs. Man does that s#it stink!

[jakeman]

I think I may have cured my problem. To start with I checked the plugs, finding #1 and #3 to be just a little black. and all the gaps were different ranging from .028 to .036, so I set them all to .030. Thinking the K&L air valves were not exactly the right size, I started dicking around with them some. Backing off one screw at a time the idle speed would increase significantly. I readjusted the main idle screw and continued on to the next carb. In the end I had backed off each valve 2 to 4 turns. The rough idle went away. I took it for a test ride and ran the crap out of it. It seems perfect, no backfiring when I let off the gas.

When I parked her she was purring like a kitten, but I guess the real test will come when I try to get it started after it cools down. It's gonna be 70 tomorrow and my bride and I are gonna head on down the highway!

Jake

[John]

Y'all enjoy the ride. I'll bet it's pretty country out there, with some nice roads.