T-500 carbs-will not idle correctly

bucky

Just got my 1974 T- 500 up and running but the idle is too low and it dies at idle. I have it at a shop but he hasn't been able to figure it out yet. Thought I might ask here on the forum. The service manual says turn idle screw out to increase idle -he disagrees. The bike runs strong and clean with no bog or hesitation.The gas is fresh and the carbs are clean and rebuilt-just will not idle up fast enough to stay running at idle. It idles at 750 and according to manual should idle at 1500.I would settle for 1250. Dying out in the middle of traffic[should I rephase that!!] is a bit nerveracking-to say the least. Your input will be appreciated -Thanks -Mike

Russell · Posted: Wed Mar 10, 2010 5:13 pm Post subject:

Going entirely on memory here.Others will soon correct me if I'm wrong. Doesn't the idle screw on the Suzuki 2 stroker twins simply lift or lower the carb slide? If my memory is correct that would mean that turning screw IN will lift the revs by lifting the slide.

Qingdao · Posted: Wed Mar 10, 2010 6:30 pm Post subject:

There is an idle screw on each of my carbs on the 71 model; are you twisting both?

I have mic carbs... I don't know if they are stock.

dorT500 · Posted: Thu Mar 11, 2010 1:56 am Post subject:

Hey Mike,
First simple thing I would do is see if it will idle with the gas cap open. (clogged cap vent?) Fully charged and known good battery? I would then recheck timing. Then I would check the air filter (foam)... clean and oil the filter as described in the manual. Fuel filters added after cleaning carbs? Did your guy make the cable adjustments at the top of the carbs as per the manual, did he do the throttle sync described in the manual. You could just use a mirror with the air box off to see if the the throttle valves (sliders) are opening and closing at the same exact time in addition to just listening for a single bottoming out sound. Throttle cable adjustments correct? As your manual should say the standard pilot air screw setting for Stock Mikuni's on your bike is 1 1/2 turns out from the bottom....might be 1 1/4 on your model...but go with 1 1/2 for right now. Just turn it in or out within a 1/4 turn until the engine runs smooth. Then just adjust slider stop screws(Idle screws) until the engine idles about 1250-1350 when warm. As Russell said, turning stop screw (idle screw) in would make the engine run faster. I might check the throttle valves again and see if there is any hint of damage anywhere on them especially at the point where the stop screw catches it. Forget about the 1500 RPM you referred to....that is too high. All this is pretty basic stuff covered in even a Clymer Manual....might be something else going on if your mechanic is having a little trouble. Let us know how it comes along. Anyway Mike...How the Hell are you? Smile

...long time no pm. Good Luck

Steve Searles · Posted: Thu Mar 11, 2010 10:43 am Post subject: 2 +2 Idle

dorT500 already hit the ball nicely. The throttle slide idle screw should indeed turn in to raise the throttle slide and increase RPM. Must do it equally to both carbs and both slides should be coming up "balanced" together. The is where the threaded locknut ferrule on the top of the carbs comes in, during "syncronizing of the carbs or (making sure both slides are moving at the same openings). Heck set the idle high first and work your way down.

Bikegeezer

dorT500 · Posted: Fri Mar 12, 2010 10:03 am Post subject:

Here is a nice shot of exactly what the original carbs on my 1975 T500 look like and the height position of the throttle valves(sliders) happen to look right. Of course adjust yours as needed.

http://cgi.ebay.com/ebaymotors/SUZUKI-T500-GT500-CARBURETORS-CARBS_W0QQcmdZViewItemQQhashZitem2559527e99QQitemZ160412368537QQptZMotorcyclesQ5fPartsQ5fAccessories

Bikegeezer · Posted: Sat Mar 13, 2010 7:49 am Post subject:

Right. The '74 carbs were the same. BTW, remember that mod I introduced to synch these carbs with a manometer or gauge set? Easy to tell if the adjuster is doing anything - vacuum should drop when the slide is raised. If not, the speed screw isn't doing anything. And Bucky, just to make sure we're all on the same page, the hand wheel you see in the pic with the yellow paint dot on it is the idle speed screw. The smaller brass screw to its left is the idle mixture screw. Turn that one in till it seats lightly, then back it out 1 1/2 turns.

Stu

dorT500 · Posted: Sat Mar 13, 2010 11:57 am Post subject:

MNellis · Posted: Sat Mar 13, 2010 9:32 pm Post subject:

Bikegeezer · Posted: Sun Mar 14, 2010 7:03 am Post subject:

MNellis · Posted: Sun Mar 14, 2010 7:44 pm Post subject:

Thanks for posting that. Sometimes the simple stuff just hits you in the face. I didn't even think to use the existing port and just drilling the carb. I would have gone ahead and drilled the manifolds but, obviously, I like your solution better.

I also have a '68 CL350 that I've partially restored and I'll be drilling the manifolds as well.

Here is the mod I did on my restored '70 CB450

Thanks again. I'll have to look closer at your T500 Blog. After I finish sorting out the problem on my '76 GL1000 carbs I'm going to start on my T500. The Suzuki actually runs pretty good so it'll be mostly cosmetic but the bike is slow to return to idle so I think there are some sync issues that, based on what you've shown me, should be easy to fix. Did you drill the port on the right carb while it was on the bike and just use a vacuum or did you remove the carb to perform the task.

Bikegeezer · Posted: Sun Mar 14, 2010 8:54 pm Post subject:

MNellis · Posted: Sun Mar 14, 2010 9:39 pm Post subject:

Bikegeezer · Posted: Mon Mar 15, 2010 8:12 pm Post subject:

Ultrasonic cleaning may be your only hope.

Stu