It accelerates nicely down your long driveway- no sign of stumbling?? -and then backing off throttle it surges- about how fast are you going?
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prosnomonkey
Guest
It will surge at any speed, from 10 mph to 70mph only as long as I am trying to maintain a steady speed. If I accelerate, no stumble or surge. When I decelerate there is a slight popping sound to the exhaust, but I don't notice any engine performce issues. It feels like I'm on a bucking horse.
I wasn't able to get back to the bike last night, but hopefully I can get to it tonite, take the carbs off and make sure the butterfly valves are set where they are supposed to be. I will also recheck all the places where air might leak.
Thanks for the heads up on bikebandit, I just made a quick look there to get a ballpark and I didnt really do any shopping around
I wasn't able to get back to the bike last night, but hopefully I can get to it tonite, take the carbs off and make sure the butterfly valves are set where they are supposed to be. I will also recheck all the places where air might leak.
Thanks for the heads up on bikebandit, I just made a quick look there to get a ballpark and I didnt really do any shopping around
At 70mph, your idle circuit is doing nothing -it's all the main jet circuit. popping in exhaust upon decelerating ? -maybe unburned fuel /air leak ??
But the stumbling.....
Edit; It looks like this bike does not have rubber caps over idle (pilot) jets? yes? is setup similar to Keihin carb (see following post)
But the stumbling.....
Edit; It looks like this bike does not have rubber caps over idle (pilot) jets? yes? is setup similar to Keihin carb (see following post)
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so, fuel overflow is fixed, but one cylinder or just possibly both is firing intermittently at cruising speed....but spark is ok because bike accelerates fine up to 70. You saycarbs are super clean so it's not the main jet that this needle slides into blocked and dirty and air-leaks at manifolds are off the table-Is that where it's at?
just thinking....because I haven't had this issue myself unless A) I was running out of gas! B) carb was dirty,maladjusted.... so when you are accelerating, vacuum in manifold drops, slides rise and gas is delivered...but when you hold the throttle steady ,manifold pressure should equalise and slides settle at equal height (given the carbs are synched per the throttle plates)...unless one has a pin hole in diaphragm.,or is not placed correctly.. or one needle is maladjusted or ?
..if you test the slides for smooth operation and (needle height settings) and hold ing a vacuum (ignore purple circles) plug the oval hole you see here with your finger, slide should stay up)...or
if you happen to have even a single vacuum gauge you can attach and compare while running, this would help.
just thinking....because I haven't had this issue myself unless A) I was running out of gas! B) carb was dirty,maladjusted.... so when you are accelerating, vacuum in manifold drops, slides rise and gas is delivered...but when you hold the throttle steady ,manifold pressure should equalise and slides settle at equal height (given the carbs are synched per the throttle plates)...unless one has a pin hole in diaphragm.,or is not placed correctly.. or one needle is maladjusted or ?
..if you test the slides for smooth operation and (needle height settings) and hold ing a vacuum (ignore purple circles) plug the oval hole you see here with your finger, slide should stay up)...or
if you happen to have even a single vacuum gauge you can attach and compare while running, this would help.
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I think Gorminrider is on to something with vac problem. When you back off throttle and hold constant ,vacuum changes dramatically both on diaphragms and petcock vac line. I know you said you tried running on "PR" spot on petcock, but try again, this time also blocking off vac line in case it's leaking fuel and fouling a cylinder causing a misfire that causes surging effect.
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prosnomonkey
Guest
Thanks for all the input! I have had to take some time off from trying to figure this out due to work and family constraints. I am going to get back to it this week.
Gorminrider you are correct: The carb is clean and everything is put back together correctly as far as I can tell. I replaced the o-rings at the manifold but left the original intake boots there as they were still pretty soft and seemed in good shape. The troubles I am having indicate that the simplest and most likely problem/solution is air leaking in this area, so I went ahead and purchased new intake boots and they should be here in a few days. I'll replace those and when I have the carb off, I'll try the test that Gorminrider has suggested
Tom203- there is no rubber cap that I can find like you are suggesting, and it seems simliar to the carb picture you posted. I am not sure what you mean by blocking the vac line... you mean just disconnect it?
Gorminrider you are correct: The carb is clean and everything is put back together correctly as far as I can tell. I replaced the o-rings at the manifold but left the original intake boots there as they were still pretty soft and seemed in good shape. The troubles I am having indicate that the simplest and most likely problem/solution is air leaking in this area, so I went ahead and purchased new intake boots and they should be here in a few days. I'll replace those and when I have the carb off, I'll try the test that Gorminrider has suggested
Tom203- there is no rubber cap that I can find like you are suggesting, and it seems simliar to the carb picture you posted. I am not sure what you mean by blocking the vac line... you mean just disconnect it?
".....I am not sure what you mean by blocking the vac line... you mean just disconnect it? "
Unplug vac line at petcock- and stick a plug in line and try running in "PR" spot again. It's possible that fuel is being sucked down vac line (during high vacuum- like closed throttle) and fouling out that cylinder causing misfire/stumbling.
Unplug vac line at petcock- and stick a plug in line and try running in "PR" spot again. It's possible that fuel is being sucked down vac line (during high vacuum- like closed throttle) and fouling out that cylinder causing misfire/stumbling.
per tom203's test, I know he meant to include that you will need to plug the place on manifold that the tube attaches too!...
New carb intake boots won't do any harm, that's for sure!
am I hearing that you can't hear this happening running the engine in neutral in the yard...?only on the road? and what bike is this? 4 cylinder? two cylinder?
if the issue being that the bike reacts well to an increase in "load" (ie: accelerating,) but misses on the steady throttle (less load) sure, I am hearing that this line of troubleshooting suggests that the extra gas from gastap's vacuum line tom203 is suggesting and/OR an air leak (per the intake rubber) is the only time the bike runs right...in other words, the 1 or 2 wrongs make a right when accelerating...and a wrong (rich mix) on that cylinder when at steady speed...but it seems like a plug would foul if too much gas was causing it to misfire..?
if the above are not the problem...I'm just trying to think to some easily-tested ideas with my sticking slides ? or slide diaphragm. a vacuum gauge on the suspect carb while running compared to other carbs is a good trouble-shooting tool and if not the slides, it will indicate other problems too. Used one on my Rambler all the time .....
New carb intake boots won't do any harm, that's for sure!
am I hearing that you can't hear this happening running the engine in neutral in the yard...?only on the road? and what bike is this? 4 cylinder? two cylinder?
if the issue being that the bike reacts well to an increase in "load" (ie: accelerating,) but misses on the steady throttle (less load) sure, I am hearing that this line of troubleshooting suggests that the extra gas from gastap's vacuum line tom203 is suggesting and/OR an air leak (per the intake rubber) is the only time the bike runs right...in other words, the 1 or 2 wrongs make a right when accelerating...and a wrong (rich mix) on that cylinder when at steady speed...but it seems like a plug would foul if too much gas was causing it to misfire..?
if the above are not the problem...I'm just trying to think to some easily-tested ideas with my sticking slides ? or slide diaphragm. a vacuum gauge on the suspect carb while running compared to other carbs is a good trouble-shooting tool and if not the slides, it will indicate other problems too. Used one on my Rambler all the time .....
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prosnomonkey
Guest
Sorry its been so long since I last posted. per a previous suggestion I ordered parts through Boulevard Suzuki and it took 2 and a half weeks to get them here (north Idaho). Not sure if this is normal, but Bike Bandit always gets me parts in about 3 days.
ANYWAY... I installed the new boots and orings, bench tuned the carbs and took it for a test ride. There is still the stumbling/accelereating when I am trying to remain at steady throttle but not nearly as bad as before. I stopped in a parking lot and put the kickstand down, and when I turned the handle bars, the idle picked up to about 3k... I looked and realized the throttle cable was being pulled and it was opening the throttle on the carbs!! When I righted the bike, the cable was still stuck and I had to reach down and pull the cable from the carb end to get the cable to return to idle. I realized that I had the cable way too tight, but I also realized that the cable is sticking inside the housing. Later, sitting in the garage I turned the throttle handle and watched the cable... it pulls and releases like its supposed to, but when I hold the throttle handle part-way and tap on the cable with my other hand I notice that the cable moves as if I'm turning the handgrip. I think that when I'm riding down the road, bumps and wind buffets are moving the throttle cable even though I am trying to keep a steady throttle hand.
What I know now:
1. there was air leaking in between the carbs and the engine even though I replaced those o-rings, I still needed new boots.... FIXED
2. the throttle cable is moves whenever the housing moves
I assume I can lubricate the throttle cable and this should fix the issue? Off to search for answers!
ANYWAY... I installed the new boots and orings, bench tuned the carbs and took it for a test ride. There is still the stumbling/accelereating when I am trying to remain at steady throttle but not nearly as bad as before. I stopped in a parking lot and put the kickstand down, and when I turned the handle bars, the idle picked up to about 3k... I looked and realized the throttle cable was being pulled and it was opening the throttle on the carbs!! When I righted the bike, the cable was still stuck and I had to reach down and pull the cable from the carb end to get the cable to return to idle. I realized that I had the cable way too tight, but I also realized that the cable is sticking inside the housing. Later, sitting in the garage I turned the throttle handle and watched the cable... it pulls and releases like its supposed to, but when I hold the throttle handle part-way and tap on the cable with my other hand I notice that the cable moves as if I'm turning the handgrip. I think that when I'm riding down the road, bumps and wind buffets are moving the throttle cable even though I am trying to keep a steady throttle hand.
What I know now:
1. there was air leaking in between the carbs and the engine even though I replaced those o-rings, I still needed new boots.... FIXED
2. the throttle cable is moves whenever the housing moves
I assume I can lubricate the throttle cable and this should fix the issue? Off to search for answers!
Well, that's a possibly new one! Thanks for this report,prosnomonkey!
Yes, lubricate by all means but if the cable is connected to the surging issue that cable+housing is possibly really defective and in that case, you should replace it. It Could be a broken strand inside, catching the housing and that is dangerous....if a bunch of rust comes out when you are oiling it, turf it and replace.
a bit different issue, but Ive had this cable-routing issue myselfwhere turning the bars pulls on the throttle. I used pull-ties to hold it to the frame under the tank once I had it so moving the handlebars doesn't affect the throttle. It can be difficult to get it the routing just right and when I use the adjustment at the handlebars to (temporarily!) adjust the idle, the "turning acceleration" can show up again on one bike even now.... Oh, usually, it wouldn't cause surging unless it's in the parking lot making sharp slow turns but that's not so safe either...
I wonder if Possibly somebody has put taller handlebars on without lengthening the cable ...?
Yes, lubricate by all means but if the cable is connected to the surging issue that cable+housing is possibly really defective and in that case, you should replace it. It Could be a broken strand inside, catching the housing and that is dangerous....if a bunch of rust comes out when you are oiling it, turf it and replace.
a bit different issue, but Ive had this cable-routing issue myselfwhere turning the bars pulls on the throttle. I used pull-ties to hold it to the frame under the tank once I had it so moving the handlebars doesn't affect the throttle. It can be difficult to get it the routing just right and when I use the adjustment at the handlebars to (temporarily!) adjust the idle, the "turning acceleration" can show up again on one bike even now.... Oh, usually, it wouldn't cause surging unless it's in the parking lot making sharp slow turns but that's not so safe either...
I wonder if Possibly somebody has put taller handlebars on without lengthening the cable ...?
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prosnomonkey
Guest
Yes there are taller handlebars but there seems to be plenty of slack in the cable. I was able to loosen the cable so that there a little slack in it when it's completely at idle. I have to turn the throttle grip about 1/4 - 1/2 inch before the slack is taken up. At idle, the handlebars can move the whole range without moving the throttle cable. However, if I put some tension on it, say at 1/2 throttle, the cable gets tighter and opens the carbs up when I flick the housing with my finger. It doesn't seem to release though. I'm going to get some oil on it tonite and see what happens
yes, a bit of slack at idle at the twist is a good thing for most of us.
Maybe a squashed cable housing might be pinching the cable too...? Wiggling or pulling on the housing at half throttle will of course tweak your throttle if the ends are lifting out of their "cups" at the carb and twist grip. Therefore, the housing should be held to the frame so that these ends stay happy and relaxed in their cups.
Maybe a squashed cable housing might be pinching the cable too...? Wiggling or pulling on the housing at half throttle will of course tweak your throttle if the ends are lifting out of their "cups" at the carb and twist grip. Therefore, the housing should be held to the frame so that these ends stay happy and relaxed in their cups.
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prosnomonkey
Guest
You have got to be kidding me!!! I lubed up the throttle cable and by golly the surging has pretty much gone away! I took the bike for a test run that turned into an hour and a half ride and it only surged once or twice and very little at that. What an enjoyable ride it turned out to be. I did notice that as the gas tank got emptier, the surging came back a little more, but nowhere near as bad as before. I can't believe I rode long enough to go through most of a tank of gas!
So it seems the throttle cable was a major part of the problem, and I will probably end up replacing it in the near future, though it seems to be ok for now. Although I wonder about the occasional surging that I experienced...? Could it still be the throttle cable or is there another ghost wandering about? There was no pattern to it except I noticed it more when the tank was maybe 1/4 full. At this point I was near home again and although I should have gassed up again and kept going, I didn't. Oh well, looks like I have to go for another ride tomorrow for more "testing"
I can't express enough my gratitude to all of you for your help! THANK YOU THANK YOU THANK YOU!!!
So it seems the throttle cable was a major part of the problem, and I will probably end up replacing it in the near future, though it seems to be ok for now. Although I wonder about the occasional surging that I experienced...? Could it still be the throttle cable or is there another ghost wandering about? There was no pattern to it except I noticed it more when the tank was maybe 1/4 full. At this point I was near home again and although I should have gassed up again and kept going, I didn't. Oh well, looks like I have to go for another ride tomorrow for more "testing"
I can't express enough my gratitude to all of you for your help! THANK YOU THANK YOU THANK YOU!!!
hi,prosnomonkey! more good news,eh! perhaps the surging is a bit of stickiness at the carb float needle too...less fuel in tank, less pressure on the needle- or maybe the strainer in the tank is a bit choked.
But keep on it -You don't want surging.
But keep on it -You don't want surging.
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prosnomonkey
Guest
The float needles didn't stick at all (I checked when I had them off) but I did notice one was not as responsive (springy??) as the other, so this maybe something to look at... as much as I do not want to take the carbs apart AGAIN. As for the strainer in the tank, I took the petcock off and there was just a hole in the bottom of the tank, didn't seem to be anything inside that would strain/filter anything. The screens on the petcock seemed ok but it might be worth taking it off and having another look. I did notice that when I put the petcock at PRIme and waited, that gas began leaking out of the swtich/lever area after 15 seconds or so, not sure if this is normal but makes sense as the carbs get filled, the gas has to go somewhere. Petcock seemed to flow well when I had the tank off and set it to PRIme and drained the tank, but did not flow at all when on REServe or ON
No, it shouldn't leak around the tap with PRI on.and it doesn't make sense. for a Motorcycle to drip gas at any time.s
......since the vacuum-activated Run and Res(reserve) is apparently functioning,is there any dripping while you are riding? ie:Imagine the headlines-"Motorcycle Explodes and Burns at Stoplight"
fingers crossed, but Occassionally, just turning the tap a few times stops the leaking on a tap that hasn't been moved much in its life.
......since the vacuum-activated Run and Res(reserve) is apparently functioning,is there any dripping while you are riding? ie:Imagine the headlines-"Motorcycle Explodes and Burns at Stoplight"
fingers crossed, but Occassionally, just turning the tap a few times stops the leaking on a tap that hasn't been moved much in its life.
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prosnomonkey
Guest
no it doesn't leak at any other time ... I wouldn't be riding it otherwise. Also it doesn't always leak on PRI. Yesterday I moved the tap to PRI to start the bike and no leak, so I'll keep an eye on that. Rode the bike to the gas station and filled her up, did some errands around town and there was no surging, did not use much of the tank of gas tho
Edit: I just checked prices on the float needle and bike bandit has it at $48 while Boulevard has it at $40. Buying two on a "maybe this is the problem" seems like a pretty steep price. Is there any way I might test this theory before sending another $100 down the fuel line? As stated in above post, neither one "sticks" as Gorminrider suggested and the springs inside seemed not very springy... are they supposed to be quite springy or a little soft?
Edit: I just checked prices on the float needle and bike bandit has it at $48 while Boulevard has it at $40. Buying two on a "maybe this is the problem" seems like a pretty steep price. Is there any way I might test this theory before sending another $100 down the fuel line? As stated in above post, neither one "sticks" as Gorminrider suggested and the springs inside seemed not very springy... are they supposed to be quite springy or a little soft?
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prosnomonkey
Guest
I took it for a short ride today, about 50 miles started with a full tank. It surged a little bit at the beginning, but did not seem to do so any other time in the ride. I haven't tuned the carbs except for a bench tune and making sure the adjustment needles at 2.5 turns out as well as setting the float height correctly. Going to attempt to sync the carbs as shown elsewhere on the forum tommorw and see if I notice a difference in performance.
Again thanks for all the help! Nessism, thanks for the heads up about Z1. They sell the float needles in a six pack for $25. I wonder if anybody needs 4 of them?
Again thanks for all the help! Nessism, thanks for the heads up about Z1. They sell the float needles in a six pack for $25. I wonder if anybody needs 4 of them?
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