surging, poor idle, fuel leaking from carb overflow tube

[prosnomonkey]

Since I posted last, I needed to take a break from removing, reinstalling the carbs. I've done this maybe 5 times so far, mainly becuase I read how to do things, then go to the garage and do them but leave out a critical step (moving butterfly valve back to almost closed ) Anyway, I am going to get back to it tonite after work hopefully.

I mentioned earlier that the petcock is fine -- it doesn't leak when left in ON or REServe, and seems to flow nicely in PRIme.
However, since the problems I have are when the bike is running and the fuel system is working with vacuum, I thought maybe the problem might be in the petcock. The Mega-Welcome page mentions that petcock replacement is a good idea, but at $120 at bikebandit.com I want to make sure that I really need to do this. While riding around I did run the bike with the petcock in PRIme but it didn't seem to make a difference. What do you guys think?

Thanks
Jeremy

[koolaid_kid]

1) I would not replace it until you prove it is faulty.
2) I would not give Bike BANDIT my business. Try Boulevard Suzuki, their prices are generally much lower.

[tom203]

So running in "PR" didn't improve things (you said seems to flow nicely in "PR" position ), which are .....accelerates fine, but surges at constant throttle setting. Does it start to "surge" quickly or only after you've been cruising for a while? If latter, try running with gas cap loose, in case a vacuum is being formed in tank.

[prosnomonkey]

by flowing smoothly in PR, I mean it drains out on the floor nicely when I had the tank off to clean it, thats how I emptied it... set the petcock to PR and set it over as gas can. Later, riding the bike down the road with it in PRI made no difference in performance.

It starts to surge as soon as I'm at speed after leaving the house

[Steve]

The Mega-Welcome page mentions that petcock replacement is a good idea, but at $120 at bikebandit.com I want to make sure that I really need to do this. ... What do you guys think?

I think you need to take koolaid_kid's advice and AVOID THE BANDIT.

Boulevard Suzuki's price for your petcock is $81.48. Retail price is only $108.63, which is why we feel that BANDIT earned their name.
By the way, I just checked at the BANDIT, they claim retail price is 119.49 and sell it for 92.34, but you still save about $11.

Similar savings on all other parts for your bike, so avoid the BANDIT, if you can.

.

[tom203]

It starts to surge as soon as I'm at speed after leaving the house

It accelerates nicely down your long driveway- no sign of stumbling?? -and then backing off throttle it surges- about how fast are you going?

[prosnomonkey]

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

[tom203]

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)

[tom203]

Keihin CV type carb

[Gorminrider]

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.

[tom203]

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.

[prosnomonkey]

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?

[tom203]

".....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.

[Gorminrider]

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 .....

[prosnomonkey]

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!