Odd things...Carb related

[The Lorax]

I have a 79 F model..looks more like a special due to heavy mods made by a previous owner. When I bought it, there were no carbs, the gas tank leaked, it had trans issues and a bad clutch. thankfully, I got it for next to nothing, otherwise... . anyway, it runs strong, I love the pull however, from the time I put it together, I had the vacuum advance line tied to the intake boot and the port on the carb plugged. it has always had a bit of a low end lag,(once you get to about 3k hold on!). today, I moved the advance line to the carb body as I understand it should go. the throttle response seems a bit better but, now it tends to lag after you release the throttle. as I was slowing down, I pulled the clutch in and the revs stayed @ about 3 - 4 k for 10 seconds or so and then slowly crept down. I thought this to be rather odd so I experimented with it, not every time, but regularly, the engine RPM stays up after the throttle has been backed off. I need to synch the carbs as it has not been done in the 2 years I have owned them...(you think that's bad, I have an old Kaw I've owned for fifteen years and never synched), but tis seems almost like a vacuum leak somewhere, but where, I swapped a plug and a line. this is not an emergency as I can slow the engine speed adequately by leaving the clutch engaged and braking, but it is a trifle bothersome. perhaps one of the many people here who know more than I do about these beasties could shed some light for me. oh by the way, Jardine 4-1, pod filters, 136 mains, stock pilots (1980 Carbs) screws 4.5 turns out. plugs look pretty descent, I haven't checked float level as it doesn't seem to be off mixture wise, and really runs pretty good. I'm sure I forgot some detail or two, but from the looks of things I am bordering on war & peace for the length of this post. thanks in advance.

[79XS11F]

When the vac advance was hooked up directly to the boot did you not hear the auto advance unit bouncing fully back and forth. Perhaps it got damaged so check it to the manual. Also check the simple stuff like a sticky or poorly routed throttle cable.
Rob

[The Lorax]

Never heard the advance bouncing, as for the trottle cable, when I replaced it, I tied it to the old one and fishe it via the identical routing...although, I think there were some issues there as the cable does pull when the bars are tuned hard to the right...like all the way to the right. never notice anything odd with the cable when riding, only when I'm manuvering the bike into its spot between my dead volvo and the garage door. I will switch the lines back tomorrow and see if my throttle issue goes away. I would like to fix this so it works as it should, but it will likely take some time as I tend to travel in my work and am sometimes gone for weeks at a time.

[TopCatGr58]

What did you use to cap off the Intake Boot Port? A member posted about how his old caps had gotten hardened, and even though they were on the ports, they were leaking, causing an uneven lean condition in a couple of cylinders, hanging idle, etc.!?
You can get replacements from auto parts stores, or use some hose with a large bolt/screw in the end!

Just a thought!

[The Lorax]

The intake boots originally had caps on them, but only two I think, and they were dry rotted. I took some inch or two lengths of vacuum line and ran screws into them to seal them. I think Iwill check the boot and associated caps for leaks tomorrow....a leaky boot or cap might explain my issue, but why only after I moved the line and cap....could the cap be leaking? could my vac. port on the # 2 carb be blocked? I will delve into this deeper on the morrow, unfortunately, I have to hit the rack due to the unfortunate fact that I, like most must venture off into the world of gainful employment....curses!

[prometheus578]

won't solve you'r whole problem, but...
a throttle cable, even if routed properly, can still rev the engine when the handle bars are turned if there is not enough slack in it.
Nobody likes a sloppy hand throttle, but there still must be a little play in the grip.
turn the handlebars all the way right, and adjust the cable slack so that there's maybe an 1/8 inch of freeplay at the grip before the cable pulls the throttle.
Otherwise... yes, sounds like synch or vacuum leak.

[red bandit]

why only after I moved the line and cap....could the cap be leaking? could my vac. port on the # 2 carb be blocked?

what they said. vacuum line or cap could be cracked or leaky. Or other vacuum leak. spray with wd40 or carb cleaner when idleing, listen for engine to change rpm.

80 carbs with 136 mains (didn't know that size existed)....way too big.

[audijunky]

I had similiar issues with the idle staying high after pulling in the clutch and sluggish up to 3K rpms. If you let the clutch back out a little, until it just starts to grab and then pull it back in, your rpms should go down and stay down. If this happens (happened to me), it sound like a carb sync is in order and your carbs may be running rich. I did these and it fixed the idle isssue.

[The Lorax]

Alright, I swapped the lines and took it for a ride today. not real difference in the way it runs, except that it idle a little higher with the line on the boot. set back to the way it should be. I sprayed carb cleaner on the boots, no change in engine rpm so I am guessing that the boots are in ok shape. I will spooge rtv over them to be certain but , I believe I have eliminated that as a potential cause. I did not notice the rpm staying up with the vac. line on the carb boot. but, I believe all will be resolved when I get the carbs synched. I do have some other small adjustments to make in the mean time ( until I get a set of gauges or sticks). thank you all for the excellent suggestions and Ideas. I am most pleased with this site and its quite knowledgeable members. thanks again all

[The Lorax]

Updates:

I covered the boots with RTV, it helped with the hanging Idle. (apparently I'm a bad shot with carb cleaner or the stuff I was using to check it was non flammable...not) I also have dealt with the trottle cable pulling when the bars are turned to the right. (the idle adjustment was backed all the way out...oops ) by and large the bike is running well now. I also believe the carbs are the odd ball set that take the larger jets as I have been running jets that are considerably too large for 1980 carbs but my plugs are not all sooty and fouling the look to be pretty close, just a touch on the gray side. it is possible that the boots were leaning the mix out and affecting the size of jets I was using to get it right. I will try to get it out and ride a bit this weekend and will check the plugs again. it's supposed to rain here in ohio tomorrow so maybe no riding but I think monday is supposed to be good so I'll probably take it to work and back and check them on mon. eve. thanks again for all the really helpful suggestions fellas, soon I hope to have all issues resolved and actually get to put some real miles on her this year.

[The Lorax]

ok, rode the bike sunday, broke my talipiece I made for the bike, (the taillight & the liscense plate fell off...I guess I'm not a good welder) left the bike @ mom's went over today, put the stock parts back on, (turn signals, original tailpiece, rear fender) checked the plugs: #4 slightly Tan, the rest gray. turned the mix screws out 1/2 turn on 1,2,3 after I put everything back together, rode home...about 1/2 hour. checked the plugs...still a touch of gray. I guess its time to look into fatter mains and maybe a size up on the pilots. I'm sitting @ I think 4 turns out on 4 and 4.5 on 1,2,and 3. my mains have 136 stamped in them and the pilots are stock. finding happy mixture can be frustrating, but i guess I just love to tinker 'cause I'm not aggrivated yet..hmmn

[mro]

You might try droping the float level 1/2 to 1 mm (carbs inverted) to richen it up... before going to another jet size.


mro

[The Lorax]

Thank you, I went through and checked the float levels today, all of them different from the others. set them all to match #4 and then did the pre-synch with a little wire, #3, & #4 were good to one anther, #1 & #2 were good to one another but #2 was just a little off from #3. adjusted, put the carbs back on and took it for a ride, felt a good bit better, got home just as dark was setting in, checked the #1 plug, had a bit of a tan color on the one side so I think I'm getting real close. I'll check # 2 & # 3 plugs tomorrow. but so far, it's starting to come up roses. thanks again to all who had such useful input and suggestions, every little step makes it all a little better . have a nice day and ride safe.