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XL600 fuel delivery question

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Ok... those of you who have read my previous posts know that I am tinkering with a newly acquired 1983 XL600.

It also has "ok" acceleration, and a crummy top end... snarls and sputters is the best way to describe it when you try to get on the gas in an aggressive manner.

I might have found the culprit, or at least A culprit.

I took off all the body work, which was so simple, I couldn't help but smile at the basics of it all... anyway, I found what appears to be a fuel line running off of the right hand (top end/accelerator) carb... it comes off of the top right hand side. I blew into this thing, and gas eventually spit out of the left hand (low end) carb's fuel inlet pipe. The carbs don't appear to share a float bowl, though they are connected via a line between them. This line that I found wasn't connected to anything. Logic tells me that this line should be attached to SOMETHING. I couldn't find any references concerning this second line in the manual as of yet. No solid pictures of where it is supposed to go to either.

Did the XL600 have a dual outlet petcock, or a fuel line splitter? It would be very convenient if this was the problem with my bikes poor performance. I mean, you can't have a second carb kick on for higher RPM, or act like an accelerator pump, if it isn't supplying fuel along with the extra air. It would also explain the engine behavior when you try to whack the throttle open aggressively as well.

Any insight to this conundrum would be amazing.

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Well, that makes life more difficult.

So much for the easy answer. Valves, timing, and carbs it is then!

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Hmmm...

I noticed something when fiddling with the bike today.

The boot for the right hand carb (secondary carb) was poorly seated to the carb body, part of it might not have even been attached. So I loosed the airbox up, and got the boot on as far as I could (it has a non-stock hoseclamp on it... too wide I would say, probably part of the reason the boot had been pulled off), put the hose clamp as far forward as I could and tightened it back down. I put all the bodywork back on, and things seem to have improved. It still pops a bit, but there was more power, and better throttle response. Could an improperly installed carburetor boot cause enough of an air leak to lean it out to cause the crappy top end running? It would be ok at lower speeds with just the primary... duh, that's more or less what it is for. Perhaps I should get some new boots... or at least a new boot for the right hand carb. This I am sure is part of the problem. The carb air vent was confusing because I had never seen one set up that way.

Does anyone know if there are newer model parts that I can substitute for the boots? XR600 pieces? XR650L? Times like this I wish I had a crossover manual. My boots are pretty hard, and they should be more pliable.

Thoughts?

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You may be able to still get that intake manifold. I'd suggest you take the carbs off and give them a serious douching. I had that exact bike back in 83'. Man what fun it was...wheelying down the freeway...boulevard, side street...everywhere...its amazing Im not still in jail.

There is only one fuel line that feeds both carbs. It could easily run lean if the manifold is leaking and that would make it nose over on the top end (what little there was anyway)

Change the oil frequently. The trans and valve train grinds the oil up in very little time.

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Spray some carb cleaner around the manifold with the engine idling. If the engine rpm's change then you have a leak leaning out the mixture.

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Good news:

The right side airbox boot is still available. So I put in an order for that one. I was kind of hoping that both were still available, but since the right side is the most problematic of the two (the left seats, but a little old, still usable though), I figured that was a step in the right direction. So in about 10 business days, I will have a solid replacement boot. I guess I'll just source some thinner clamps from an auto store, or hardware store or whatever. Then I will make sure the left hand boot is fully inserted into the airbox (there's about 1" worth not placed properly). While I am waiting, I suppose I will check the vavles (on Thursday or Friday). If making sure the air inlet system is nice and tight, and the valves measure up correctly, then the carbs will come off for cleaning, and perhaps a step up in jetting.

Here's to troubleshooting!

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Well, what's the good option for the pilot jet? I have read that the pilot is more of a bear than the rest of the jetting woes... upping the pilot will give better off idle response, plus help eliminate the infamous cough and stall. One step up? Two?

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My 83 xl600R is jetted stock (per previous owner) and has big supertrapp on it with 10 discs. It starts right up and idles very well once warmed. It accelerates without coughing or stalling. My 1980 XL500 seemed to accelerate from low down better, though, probably due to it having an accelerator pump. I have purchased one size bigger main jets and intend to install them, as well as to raise the needle jeta little when I get around to opening up the airbox, per the 5-strokes.com XR500 article (cut open top where snorkle is) and remove backfire mesh inside air box. I personally don't see a need to change the idle jet. I think your problem is something else.

Did you remove the resistor from the spark plug cap and replace with steel/copper/brass? Put your screwdrive up there, unscrew and you'll know what I'm talking about.

Good Luck. I really like my bike. - It's the newest and best condition and best engineered bike I ever had. I just love the smooth shifting, excellent power and maneuverability. I ride mostly on street around town with 15:50 sprockets

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No, I haven't removed the resistor, or uncorked the airbox. I am actually thinking of taking out the airbox, since I need to replace one boot anyhow, and making sure they are solidly installed.

I am guessing that unscrewing the resistor, and replacing it with a conductive piece of brass or coper (or whatever other metal is good at conducting eloectricity...steel, silver, gold, platinum for that matter) would send more juice to the plug, and therefore get a "hotter" spark?

I have to nose through my manual to figure out the procedure for doing this... every time I have removed an airbox is what a royal pain in the dick though. Last time I just trashed the stock airbox, since I was going to do pod aircleaners anyhow. This is naturally, not the route I want to take, since I want to preserve the high location of the air intake for extra security if I ever have to cross water. Chances of that are low, but it is a good thought to bear in mind for exploring.

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Dont take the resistor out of the plug wire. It prevents the spark noise from interupting the CDI and stabilizes the coil.

I'm not 100% about the XL, but I know on the XR they only offered one size up on the pilot and you cant even get a pilot in that proper configuration beyond a 52 anymore. I know the one on the XR was a 55 stock with an option of a 58 from Honda. The newer carbs have 42's in the pilot. I know this because Ive got a set of 600 carbs on the bench with OEM jets, 42 pilot 130 mains in both carbs.

Just remember the adjusting screw is an air screw, so if you want it richer, turn it in, not out..

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"Dont take the resistor out of the plug wire. It prevents the spark noise from interupting the CDI and stabilizes the coil. "

This is interesting. What is the source for this information?

An article posted on 4strokes.com reprinted from cycle world 9/83 comments on the resistor as being a source of misfire.

http://www.4strokes.com/articles/honda/cwxr350_500/

Honestly, I don't know if it really changed anything about the bike's performance when I removed it. I thought it might possibly avoid problems. It seemed like its function would be similar to carbon plug leads used to suppress interference with auto sound systems.

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"Dont take the resistor out of the plug wire. It prevents the spark noise from interupting the CDI and stabilizes the coil. "

This is interesting. What is the source for this information?

An article posted on 4strokes.com reprinted from cycle world 9/83 comments on the resistor as being a source of misfire.

http://www.4strokes.com/articles/honda/cwxr350_500/

Honestly, I don't know if it really changed anything about the bike's performance when I removed it. I thought it might possibly avoid problems. It seemed like its function would be similar to carbon plug leads used to suppress interference with auto sound systems.

The resistor does exactly what carbon resistor wires do on cars for the exact same reason. You dont want the RFE (Radio Frequency Emissions) messing with the CDI. Not saying the resistor plug caps dont go bad every now and then but you really shouldnt delete it.

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