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Old 08-22-2010, 06:03 PM
clcorbin clcorbin is offline
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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!
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Last edited by clcorbin; 08-22-2010 at 06:07 PM. Reason: spelling
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Old 08-22-2010, 06:15 PM
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bikerphil bikerphil is offline
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Quote:
Originally Posted by clcorbin View Post
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
If you blew the vent lines out with compressed air with the bowls on, the brass floats will collapse and be damaged, probably not "floating anymore". JAT
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Old 08-22-2010, 06:25 PM
clcorbin clcorbin is offline
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The bowl drain screws where off, so it couldn't pressurize the carb body. And it is going to take a lot of pressure to cause them to collapse.

But, it is one more thing to check and I am pretty much at the point of pulling the carbs one more time to reset the float level anyway...
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Old 08-22-2010, 07:13 PM
clcorbin clcorbin is offline
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You where right Phil. 7 of the 8 "tanks" had the outside end pushed in. I'm going to see if I can use hot air to pop them back out. If now, I'll drill a small hole in the edge and use compressed air to push them back out then solder them closed again.

I'm surprised it could build up enough pressure to collapse those tank with the bowl drain screws out. Live and learn!
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Old 08-22-2010, 07:36 PM
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I think a member here, Dbeardslee has fixed those dented floats before by putting them in the vacuum chamber of a Mityvac, I guess the vacuum will pop 'em back out. Be careful if you plan to solder them. If you get them hot enough to melt the already existing solder, that'll be the end of them.
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79F - owned since '89 - FJ fork mod, solo seat mod, Dyna 3Ω's, 14MM M/C (168K miles)
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Old 08-22-2010, 08:04 PM
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DGXSER DGXSER is offline
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Mihgt be a good time to consider the black plastic floats and the XV920 float needle valves. Not cheap, but easier to find than the brass ones in good condition.
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Old 08-22-2010, 10:38 PM
Larrym Larrym is offline
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Less is more than Adequate?

Now again: my version of compressed air for any and all carbs.




Yes. I do have a "real" air compressor too. Used it last week to fill the tires on my XS.

I know that you were so very close to having the bike running the way you wanted it. Sorry to hear that it'll be delayed for just a little while longer.
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Old 08-23-2010, 09:14 AM
BigRed BigRed is offline
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After you get your floats fixed, make sure you do a wet-check on your fuel level in case they changed shape when you popped them back out, or in case you added weight by soldering. All you have to do is hook up a clear 3/16 or 1/4 vinyl line to each carb drain (you can do one at a time), and loop the open end up higher than the carb. Open the drain, and check what the fuel level is against the side of the carb. Make sure you don't have any air bubbles because they'll throw off the measurement.

Good luck!
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Old 08-23-2010, 03:40 PM
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If you do get to the point of resoldering the floats put the whole float in a jar of water and just have the area around the hole to be soldered up and out of the water. This helps the float to not overheat and it also keeps all the other solder joints from coming loose when you heat it up.

AND make sure you do not get any water in the float before you solder it. I would suggest drilling and reinflating and soldering one side before you go and drill a hole in the other side.

If you want to get real anal about it (but its actually not a bad thing to do anyways) get a small scale and weigh the floats before you do anything to them. Then after your done weigh them again. If the floats are heavier or lighter then you will need to adjust your float height to compensate for the different weight of the float. It might not be much though so it may not have much of an effect.

Good luck. I had to solder a bunch of holes in 3 of my floats. It sucks and its time consuming.
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Old 08-23-2010, 05:36 PM
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Ken Talbot Ken Talbot is offline
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Quote:
Originally Posted by clcorbin View Post

.... I am confident that each carbs float height was set consistently (my target was 25.7mm using a nice digital caliper back in January).....

.... Either way, I raised the float level to 24.7mm to see if I could lean out the idle mixture screws.
As a point of reference, changing the float levels from 25.7mm to 24.7mm will richen everything overall. As you are having a problem with it being too rich, try resetting the floats again, but this time to 27.7mm Use that as a starting point, being aware that it may actually make things too lean. Start with that, adjust the pilot screws using the "colortune by ear" method, and see where you're at.

Be very careful with that expoy-repaired float post!
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Old 08-23-2010, 10:15 PM
clcorbin clcorbin is offline
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My first repair method was a bust due to lack of thinking things through... Namely, that at any temperature hot enough to build enough pressure inside the float to pop it back out would also be getting WAY too close to the melting point of the solder!

Yup! The test float came a part like popcorn! It ended up in five pieces: link bar, "ring" and one "side" still attached and a separate "side".

Thankfully, I AM good at soldering (and have the right tools), so it wasn't any trouble to clean up the brass, flux things up, mount them in a jig and use hot air and silver solder to reattach everything correctly.

For the other three floats, I used the small hole + compressed air method to pup everything back out. I still need to solder up the hole, but before I do, I want to get a measurement or two from folks here.

Mainly, I need the width of each float body. When you look at them in detail, the outer side of each float is a smooth, curved piece that pretty much only has one possible smooth shape. The inside, on the other hand, is a whole different matter. It appears that it was made so they could adjust the volume of the float before a tiny hole in the center was soldered up to hold it in that position. That piece does appear to be pushed out further than it should be on all the floats.

My plan, is to find out what the "normal" thickness of the float is and then set mine to this thickness before I solder up my holes.

And as was pointed out, I'll have to "calibrate" my float levels to see if I need to put in a height adjustment into my manual. Hopefully, I can get all the floats the same volume so I have the same adjustment for all the floats.

Or does anyone want to play Archimedes and measure the volume of an unmolested brass float assembly??? That would make it MUCH easier to retune these things!
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Old 08-24-2010, 05:03 PM
clcorbin clcorbin is offline
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So nobody has an old brass float sitting around that can be measured? It would really help me out a LOT to get an idea on the correct volume/thickness for one of these beasties..
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Old 08-24-2010, 05:54 PM
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I've got an old brass float, but have been puzzling over how to get a decent measure of its displacement. I think I've come up with something.

I found a small plastic jar that the float will just snugly fit into so it doesn't float. I put the float into the jar and filled it to just level, as near as I could make it out.



Next I carefully picked the float out of the jar with a fine dental pick.



then used a syringe to refill the jar

.

By my measure, it took 18.0 cc to refill the jar.

Looking at the whole thing, it seems to me that there is enough variability in trying to determine when a jar this size is "just full" to the same amount twice in a row, that this measurement might be a bit suspect. The syringe gives a good reading on the amount of water replaced, but the fill level concerns me a bit.

HTH...
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Old 08-24-2010, 07:14 PM
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That's good thinking there, Ken!

To get repeatable measurements:

Fill the jar until a miniscus forms above the lip and the jar can't hold any more water.

Drain the water with the syringe to measure exactly how much water is in the jar.

Put the water back in the jar and carefully add the floats.

Measure the water that remained in the jar and however much is missing will be very close to the actual float displacement.

Do it several times and average the results to get a closer approximation.
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Old 08-24-2010, 11:19 PM
clcorbin clcorbin is offline
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That is definitely creative Ken! I was originally thinking about half filling a graduated cylinder and then using a piece of wire to JUST fully submerge the float in it and then read the new volume off the cylinder. Of course, I don't HAVE a graduated cylinder big enough for this, but it should work.

The other method I could use would involve measuring the weight of the displaced water instead. Basically, I could fill up a small jar until it was complete full via the miniscus forms, then weight the jar on my 1/10 gram scale (yes, I would have to be very careful!). Then, carefully submerge the float so it displaces the water out of the jar and then reweigh the jar to get the weight of the water displaced (well, with a little math).

For a ball park measurement, could I get you to measure the width of each float? I caliper would be perfect, but I bet you could get close with just a good ruler.

Thanks for the help!
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