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Old 08-22-2010, 07:03 PM
clcorbin clcorbin is offline
XStremely XSive
Join Date: Jan 2010
Location: Albuquerque, NM
Posts: 495
Am I chasing my tail???

Ok. This is a long summary of what has been going on with this bike to get everyone that wants to help up to speed:

1) Back in December, I got the bike back from brother. It took quite a bit of work to get things running mostly smoothly: new battery (surprise!), new jets (to make sure I had stock jets of the correct size), through carb disassembly and cleaning (not quite the "triple cleaning", but close), new fuel filters, electrolysis of the gas tank, new fuel and vent lines, new NGK spark plugs, new tires, oil/filter change all around, cleaned and regreased the final drive splines, carb sync, etc.

At this point, the bike ran fairly well, but the jetting was not quite right. Ride-able, but not right. The only real problem was a slight oil leak at the head gasket which I would need to take care of eventually. Also, the bike was getting more and more oil past the valve stem seals (a goodly amount of smoke on cold startup and it was worse the longer the bike sat between rides) Which lead to 2):

2) In May, the carbs came off once more and went through another round of cleaning (might as well once they are off, right?) and where regetted and the carbs where once again synced. The bike was running pretty well at this point. It was still slightly lean on the bottom, but only slightly. Definitely running better than it was during the spring...

3) During the summer, the bike started running richer and richer over the course of two and a half months or so. I first noticed it on cold start in the morning. Initially, it stayed on full choke for about 1 minute (usually enough time for me to get my equipment on and get the bike to the street), then on half choke for about a mile or so, then it ran a touch lean for another couple of miles before settling down into it's "hot" state, which was pretty good! At the end of this summer, it almost didn't want full choke even for a cold start. Half choke was only on for about 1/4 mile. Unfortunately, once it was fully hot, it had the symptoms of running too rich from idle to about 3500 rpm: hesitation and sputtering. After 3500 rpm, it cleaned up and ran strong, but I did notice that my fuel economy dropped from about 32 mpg down to around 28 mpg during this summer time period.

This brings us to the current work.

I started this project with four priorities: 1) Replace the head gasket, 2) Replace each of the valve stem seals with NEW seals (and not 15 year old dried up seals like I did back in January!), 3) Install new intake boots, and 4) Find out what is going on inside the carbs.

I can say I did fix 1), PROBABLY fixed 2) (Time will tell), 3) is MUCH better with the new boots but 4) is kicking my butt up one side of the street and down the other! Here is what I have done with the carbs, and where I am at (yes, I KNOW I am sitting at my computer... I meant where I am at with the BIKE!):

1) Pulled the carbs
2) Dumped the gas out of each carb into a narrow, clear cylinder to see how much fuel each one has. I marked the amount of gas from cylinder 1 with a line from a sharpie. The gas in the other three carbs went up almost to the exact center of the line, so I am confident that each carbs float height was set consistently (my target was 25.7mm using a nice digital caliper back in January).
3) Gave each carb a quick blowing down of each of the air/fuel jets and passages with mineral spirts to help flush out any gunk that was either trying to build up or was coming loose from use. Everything appeared to be in order with each carb.
4) Reassembled the carbs, installed everything and fired it up. One THREE cylinders. Number 3 was either not firing, or was firing poorly as it's header was SIGNIFICANTLY colder than the other three cylinders.
5) Pulled the carbs to double check things. Found one of the float posts in #3 was broken. Bloody heck! I tried to be gentle with those things when I was playing with them, but obviously I wasn't gently enough. It was a clean break and some epoxy got the post reattached. For how long, I do not know...
6) Took each metal float in and dunked them in near boiling water to see if any of the where leaking. They were all good. Kind of surprising, actually...
7) After doing some reading and thinking about how the bike was behaving, I started thinking I might actually be a bit too lean on the pilot jet and am then over compensating with the idle mixture screw. From my thought process, this COULD lead to the too rich way down low, but some of the lean popping on decelerating I have heard around 4k rpm. Either way, I raised the float level to 24.7mm to see if I could lean out the idle mixture screws.
8) Reassembled and resynced. It took a bit to get the carbs fully synced and the mixture screws set. At this point, the bike was idling VERY well and it would spool up VERY quickly when I blipped the throttle. All appeared to be right with the world...
9) Went for a test drive and was very surprised to find that one cylinder would run out of fuel under even a light load. Much cursing, later, I decided to go ahead and pick up another set of fuel filters, just in case...
10) Original filters appeared to be ok (I could blow through them with no problems), but I went ahead and installed the new filters. I also used compressed air to blow through the vents and fuel lines of each carb as well as the air box nipples. I would removed the bowl plug on one carb at a time so I could verify that everything was flowing like I thought it should.
11) Tested each carb to make sure it was getting fuel when the petcock was open by removing the bowl plug for one carb at a time and turning the appropriate petcock on the prime position. Each carb appeared to flow about the same amount of fuel out of the bowl, so I assumed everything was ok and buttened it all up.
12) When I fired it up, it was definitely running VERY rich. Even after it was up and running and the choke was fully closed (quickly found that not only did the bike not NEED choke at this point, it REALLY didn't want it!), it was still running very rich and would barely idle. I can confirm it is a rich condition from the exhaust smell. DEFINITELY a rich mixture! More cussing ensued...

So, at this point, I have decided to call it a halt for a bit and ask for advice. It almost seems like I am chasing my tail here. I DID raise the float level, but after I initially did it, it appeared to be running right. It was only when it was under a load that things seamed to be running out of fuel. After the new filters where installed AND the vent and fuel lines where blown out, that is when it started running so rich. I can't see how blowing things out could have caused a rich condition, unless it blew out some junk that had previously caused a lean condition...

So, for the few that made it to the bottom of this tail of woe, any ideas? At this point, I am leaning towards pulling the carbs (once again!) and resetting the float level back to 25.7mm and seeing if that gets thing back in the ball park.

Fuel injection is looking better and better to me!
-- Clint
1979 XS1100F - bought for $500 in 1989

Last edited by clcorbin; 08-22-2010 at 07:07 PM. Reason: spelling
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