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Old 04-28-2012, 02:30 PM   #1
sigpe57 OP
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'83 R80ST occasionally high idle at 3.4K rpm

After a 10 minutes 70mph freeway run, the rpm stuck at 3.4K for few seconds and back to normal. The right carburetor is leaking fuel. What seems to be the cause?

Thank you for the reply,

SIG
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Old 04-28-2012, 02:43 PM   #2
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Tight intake valves

Thats what it was on my ST. I mean TIGHT! Like no clearance at all. Set them and all will be well. Drippy carb means float isnt floating. Needs a new one.
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Old 04-28-2012, 03:09 PM   #3
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Usually its from the idle being set a bit too high and/or the mixture screw being set a bit lean.

Fix you leaking carb and re-adjust your carb settings when the engine is completely hot like after riding it for 30 miles at 80mph on the highway. It can be a bowl gasket or just some dirt in the valve or a bad valve or a bad valve seat or both or just a maladjusted float or maybe even a bad float.

Usually all kinds of people pipe in and say to check your ignition timing for a sticking advance but it is rarely that and that is rarely so heat sensitive like the carb adjustments but you have got bigger problems to fix first anyway being the leak.
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Old 04-28-2012, 07:53 PM   #4
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If nothing else, it's time for a bit of a tune-up. How long since the last one?

It's difficult for us to give any real spot-on advice with missing relevent data like that. Give us some history - how long has this been happening? Is the bike new to you? What's it's recent past history? Mileage?

The more data provided, the better we can picture what's going on and possible causes.
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Old 04-29-2012, 07:54 AM   #5
mark1305
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Re the carb drip: Don't just run out and buy new floats. The drip can be as simple as a piece of debris blocking the needle from seating, or the float level needs to be adjusted.

There is a reason Bing float bowls are held on with a bail instead of screws. Actually two of them in the paragraph above. Turn off the petcocks, drop the bowl, turn on the gas with one hand while gently flicking the float up and down to seat and open the needle and wash any grit out. Turn off petcock. Reinstall bowl and check for drips again.

If that doen't fix it, then check and adjust float levels.

If you find the floats are visibly eaten up or sogged with gas, then it is time to run out and buy new floats.

Edit: Oh yeah, the high hangin idle. Mine has done it on different occasions for probably all the reasons listed above at different times. More times than not, it has been idle set ever so slightly too high. Idle circuits in the carbs starting to get dirty and gummy is probably second most often cause on mine.
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Old 05-29-2012, 02:28 PM   #6
sigpe57 OP
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I found out the right Bing carburetor will leak gas after 20 minutes of freeway runs. Freeway speed average 4.5K rpm at 75mph+. Where might be the problem that's causing fuel leak?

Thanks,

TT
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Old 05-29-2012, 02:36 PM   #7
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Check and clean the float needle. Look for a worn in ridge in the needle's tip. If there is something noticeable then you should replace, good or bad, you should recheck the float height. a worn needle will raise the float height and cause the overflow.
As stated earlier: Time for a tune up. No point in fine tuning carbs if other stuff is whacked out.
SS is probably right too, your idle issue is probably related to improper carb settings.
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Old 05-29-2012, 02:45 PM   #8
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Quote:
Originally Posted by sigpe57 View Post
I found out the right Bing carburetor will leak gas after 20 minutes of freeway runs. Freeway speed average 4.5K rpm at 75mph+. Where might be the problem that's causing fuel leak?

Thanks,

TT

Sounds like you might have a dirty tank or fuel lines. When you're flowing the most fuel you're more likely to suck debris out of the tank which gets stuck in the float valve and prevents it from sealing off correctly when the bowl fills. Try blasting out your fuel lines with something you know is clean and installing little inline fuel filters. The paper element ones work much better than the sintered metal ones. Next time you get a chance, pull the petcocks off your tank and give it a serious rinse out with some acetone or something and see if any crud comes out. Rust flakes are bad news, both for your tank and for your float valves.
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Old 06-05-2012, 01:50 PM   #9
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Bean can:)
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Old 06-06-2012, 10:39 AM   #10
sigpe57 OP
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Bean can:)
What's the reason? How to troubleshoot?
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Old 06-06-2012, 02:59 PM   #11
hardwaregrrl
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Quote:
Originally Posted by sigpe57 View Post
What's the reason? How to troubleshoot?
I had this problem, the weights were sticking and would hold the idle high. I don't know enough to explain the "why", but this is what I was told.
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Old 06-06-2012, 03:57 PM   #12
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They stick if they are sticking from lacking lube. There is an inspection window that you can squirt some lube into. I have fixed a lot of high idles. Some of them get gunked up from the front cover foam dry rotting and gunking up the mechanism. I might have seen a sticking advance in a bean can once but I did too many things at once to know for sure if that was the cause or not. So far for me, 48 out of 50 times it is something else. I have seen the advances on points stick a couple of times. I have seen those just worn out a couple of times too. It's usually the carbs needing to be adjusted. Or a combo of that and base timing and a air leak. In my experience, the carb spigots at the head are the biggest source of air leaks. I would guess 9 out of 10 times it's the carbs in my experience. I have known about that sticking weights in bean cans bulletin since it first came out and have been on the look out for it every since. That was over 25 years ago I believe? I just don't see it much at all.
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Old 06-06-2012, 05:16 PM   #13
sigpe57 OP
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"the carb spigots at the head are the biggest source of air leaks."

Which exact area is this? Any pictures?
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Old 06-06-2012, 07:40 PM   #14
mark1305
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Supershaft: They stick if they are sticking from lacking lube. There is an inspection window that you can squirt some lube into. I have fixed a lot of high idles. Some of them get gunked up from the front cover foam dry rotting and gunking up the mechanism.

I discussed this very topic with Hardwaregrrl at the O/S Spring Fling last month, after seeing her pics of the disassembly of her bean can.

I plan to do a preemptive clean & lube because in my case the bean can had no cover when I bought the bike, and not knowing it was supposed to, I put quite a few thousand miles on it before replacing the missing cover. No telling how many thousands of miles before that the cover went missing. Not bad, but some minor road grime has migrated into the front part of the can.



I might have seen a sticking advance in a bean can once but I did too many things at once to know for sure if that was the cause or not. So far for me, 48 out of 50 times it is something else. I have seen the advances on points stick a couple of times. I have seen those just worn out a couple of times too.

I once had a '66 Mustang I inherited and drove from GA back to FL - with the centrifugal advance stuck at the minimum end of the curve due to oxidation in the pivot.

That has led me to consider that effect as well as the high idle effect. In fact, on the ST I have noticed during the last episodes of high idle, I have also experienced periodic drop in power/torque when accelerating. My butt-dyno is pretty sensitive and notices both diminished and improved throttle response at all times.

So, I suggest that if you suspect hanging advance weights, pay attention for hanging at either end of the curve and the resultant swings between high hanging idles and unusually sluggish acceleration at different times.

My quick & dirty plan is to pull the can, open the inspection plug, point the can opening downward and spray elctrical cleaner up inside to flush out any grime. Follow that with a decent lube (maybe Remoil) applied liberally and allowed to drain back out. And see what happens.

It's usually the carbs needing to be adjusted. Or a combo of that and base timing and a air leak. In my experience, the carb spigots at the head are the biggest source of air leaks. I would guess 9 out of 10 times it's the carbs in my experience. I have known about that sticking weights in bean cans bulletin since it first came out and have been on the look out for it every since. That was over 25 years ago I believe? I just don't see it much at all.[/QUOTE]

I agree the majority of times it will be carb related, but my comments above I think are valid as another gremlin to eliminate.

Oh yeah, the spigots are the parts sticking out that the carb rubbers clamp onto. Spigots on the heads; spigots on the carbs. Short rubber hose connecting them. Its a generic term for things that stick out like that to have things connected onto them.
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mark1305 screwed with this post 06-06-2012 at 07:45 PM
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Old 06-06-2012, 07:42 PM   #15
mark1305
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Wow! Something in my editing screwed up the "Quote" part, but it makes sense with the two-color font.

Never mind... I fixed it a little bit.
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