Bogging down

[smokeeater]

I'm a first time poster and XS owner, (1980 1100 SG) and I am not real familiar with carbs and the like but decided that it was about time to learn so when I thought the bike was running a little rough I tore apart the carbs, cleaned them and reset the floats, which had an inconsistant setting and were set at a measurement greater than the clymers manual said they should be. Also found out that the main jets were 110's all the way across which is incorrect for this model but left them as they were for the time being. Put it all back together, took it for a test ride, and the bike ran terrible at the start or low end of the rpm scale. Then would seem to catch and just about leave me standing on the street! Did I set the floats too rich and need to reset them? I didn't record their measurement when I reset them but I did reset them to 23 mm and I am geussing that they were at least 26 or so. It has always run a little richer than I thought it should and I am sure at least two of the jets should be bigger. Am I correct in my geuss?

[beechfront]

first time i took stuff apart i forgot to re-connect the vacuum advance.

maybe something as simple as that?


these bikes do have a helluva power curve though - that really kicks in about 3500-4000 rpm.

[smokeeater]

I did double check all my hose fittings and connections,because I had just replaced all the carb boots while I had the carb off and also had to replace the vacuum line to the diaphragm which had a tear in it. Near as I can tell I didn't miss anything.

[Ken Talbot]

Cleaning the carbs and resetting the floats is a good place to start. Now you need to get the pilot air screws set and the carbs synchronized. That will take away a lot of that 'all of a sudden' feeling. When in proper tune, these bikes will pull strongly all the way from idle to redline. Although there is a range where they pull hardest, it really shouldn't feel like flicking a switch when they wake up.

[sidecarKev]

Well if you have your floats set at 23mm they are a little on the rich side. You should get them closer to 25mm. But then again you were having the same problem with your floats at 26mm. Also make sure you are measureing from the gasket surface with no gasket in place.

Check to see if you are running on all cylinders at low rpm's. Start with a cold engine and start it up. Check all the pipes for warmth. Be careful with how you do it though. Might be best to use a spray bottle and shoot them with a little water to see if boils away right away. I usually just touch em real fast but you have to watch out for burned fingers.

I had a similar problem. No power at low RPM's. First I reset my floats and it was a little better. Then I realized I was still only running on 3 cyl at low rpm. What you need to do is clean those carbs again and pay special attention to the air pilots, these are what contols the fuel at low rpm. On my 79 they are under a screw next to the main but on a 80 I think that there is no screw. These jets are kind of hidden. Make sure you find them. I cleaned them out and it made all the difference in the world. No more problems at lower rpm's. Now I can take off from start with no throttle and pulling a sidecar. Okay so maybe my idle is a little over spec, somewhere around 1500, but it made a big difference. Also make sure you get the air screws adjusted and make sure one or more doesn't have the end broke off. Have you checked this page out?

Carb FAQ

Another good one from another forum member I think.
Carb Diagram

[smokeeater]

I appreciate your input. I don't mean to imply that it is running fine and then really fine. It seems to idle fine, and then when I give it throttle bogs something terrible and then will seem to switch on and go. Even, for instance, turning a corner, as I come out I start to throttle up and it bogs, and wants to just quit. Have to play with the throttle some untill it decides to go and then it really wants to go.

Just love this site.

[beechfront]

just curious...

does it do this all of the time?

i have been having trouble with my bike at times - if i slow down for whatever reason and get in the 2-3krpm range - i will lose pretty much all power. i can pull the clutch in and no matter how much gas i give it - will take several seconds (really) to reach 5-6k. i let off the throttle and let it go back to idle for just an instant - then wham - full power once again. this only happens for me occasionally.

[TopCatGr58]

Hey there SmokeEater,

The 80-81 carbs are similar. The pilot fuel jet in next to the main jet down in a little tube, smaller diameter, delicate, care not to break off the brass slotted edge. Then there is the Pilot Adjusting screws on top of the carb, in front where they attach to the intakes! They were capped off at the factory with brass plugs. If they are still there, you'll need to drill a small hole in them, careful not to go too deep, the screws are a few mm below them. Then screw a sheet metal screw into the cap, and then use a locking plier to hold onto the screw and tap up against the plier to pull them out and THROW THEM AWAY!

Now you can remove the adjusting screws, along with the pilot jets and really clean the idle circuit which is a considerable amount of involvement in just off idle throttle response. Also, like they said, try setting the floats to ~25mm. Don't worry about the 110 across, even though the book says they should be 110-120-120-110, for cooling purposes, my 81 came stock with 110's across also, ran terrific!!!

Did you separate the carbs from the rack when you tore into them? And before you reinstall them after your 2nd cleaning(only 1 more to go "triple clean") use the breadstick tie to eyeball synch them to get them close.

For your pilot screws, be careful when removing them, delicate tips, and several little metal and rubber washers on the ends, sometimes get stuck in the well!!! Then when putting them back in GENTLY seat them, then back them out about 1&1/2 turns to start. Also, what type of airfilter....stock box or Individuals, exhaust, stock 4-2 or 4-1?? These can affect how it breaths and the jetting it needs! HTH.
T.C.

[TopCatGr58]

Hey Beech,

That sure sounds more like your pickup coils, due to the rotation from the vacuum, and you find that certain flex point and loss of power, let off the throttle and vacuum changes, timing plate rotates, wires connect, and wham, instant rev!?!?!
T.C.

[randy]

Beechfront,

Have you checked the pickup coil wires for breaks?

Randy

[beechfront]

sorry smokeeter for getting away from your problem...

randy, topcat - this is getting into an area i am not too familiar with -

but if it is the pickup coil wires as you suggest - i would think that i would not be losing as much power as i am now.

would this not give me the same power loss as when i forgot to hook up the vacuum advance? because it is much, much worse than that.


might take a look tonight since i have the cover off already. i did look over the wiring in there last year and everything looked good.

[smokeeater]

Thanks everyone for the ideas. Maybe I need to do more than I thought. It did run fine before I tore into it, just thought it sounded a little rougher than ususal and kind of liked the idea of tearing into it. I didn't completely take them off the rack but I did remove the diaphragm and needle jet, floats and float needles, float needle seats, main jet, and air jet. I didn't remove the idle jets because I was a little afraid to mess with something that looked like it was supposed to be permanent. I did find crud in the float bowls. I did use the bread tie pre-synch method to synch the carbs before I put them back in. It also seemed to sound better to me while it was idling. It is firing on all cylinders, and I run a stock 4 into 2 exhaust. It really only seems to have a problem when I initially put a load on it. Got a sprinkler system to fix and a couple of honey do's to take care of so I won't get to it untill tomorrow but I'll let you know how it turns out.

Thanks again everyone. Need to get some inline filters.

[beechfront]

i examined the wires and could not see any damage whatsoever.

internal break? should i go ahead and replace the wires anyway?


i need this fixed. i can only see the problem getting worse.

[randy]

The wires are prone to breaking insdie the insulation. Give them a gentle tug while it's running and see if you can duplicate the symptom.

HTH

Randy

[beechfront]

alright.

i am headed to radioshack tonight to get some of that voltmeter wire.