Idle Wierdness &/or Trottle Sticking???

[gmoore]

ok, so i finally got around to starting the project bike up and it started a little hard at first but once she got going she sounded fine.

here is the problem, when i give it gas the RPM's stay up when i disengage the throttle. sometimes after 20-30 sec the idle will drop back down around 1500-1000.

other times it seems like the idle screw is too far in and i'll adjust it to idle round 1400 and then when i give it gas it won't come back down.

now, it seems as though the throttle is "sticking" but the throttle spring is fine and the push cable seems to be fine & the throttle seems to be coming all the way back down so...

is there something in the carb that is sticking? should i just do a carb clean and start from there and see if the problem persists? any ideas would be greatly appreciated.

the posative of it is that she seems to be running and taking gas pretty damned good actually and once i get this in order i should be able to tune her right up nice!

 

[Steve]

Cleaning the carbs will be a good start, but your hanging idle is likely to be caused by bad o-rings in the intake tubes.

You can get new o-rings for your intake tubes AND your carbs at cycleorings.com.

While you are at it, it's also a wonderful time to adjust your valves.
(See my sig for a little bit of help.)

.

 

[gmoore]

just curious but, what leads you to believe i would need a valve adjustment?

are the intake tubes o-rings easy to replace? i imagine i will only have to take off the carbs?

thank you for your response.

 

[Nessism]

Until you do all the over due maintenance on the bike you are grasping at straws as to what is wrong. Oh, other than the symptoms indicate air leak as Steve says. Please check the links in my signature and get educated.

 

[cowboyup3371]

All of these bikes need that valve adjustment done periodically or you will burn them up. He is just trying to add in the recommendation since you'll have to replace the intake orings, possibly boots, after removing the carbs. Then it would be best to resynch the carbs so to do that, get your valve adjustment done first.

Yes, all you have to do is remove the carbs, remove the boots, and the orings are inside each one. If you still have the JIS screws on those boots be prepared to use an impact driver, dremel, and a flat blade screwdriver and then replace with hex or allen screws.

 

[gmoore]

hey, thanks guys!

 

[gmoore]

All of these bikes need that valve adjustment done periodically or you will burn them up. He is just trying to add in the recommendation since you'll have to replace the intake orings, possibly boots, after removing the carbs. Then it would be best to resynch the carbs so to do that, get your valve adjustment done first.

Yes, all you have to do is remove the carbs, remove the boots, and the orings are inside each one. If you still have the JIS screws on those boots be prepared to use an impact driver, dremel, and a flat blade screwdriver and then replace with hex or allen screws.

What do you mean by "boots"? are you talking about the intake manifold boots themselves? those are EXPENSIVE! damn!

or are you talking about Carb/airbox boots?

or am i an idiot and these are the same thing?

 

[Stahlgrau333]

Your problem doesn't sound like it's carb boots at all. Seems like if the wheel falls off of a GS, the first thing someone is going to do is blame your carb boot o-rings...

Disconnect the throttle cable from the carb, and hold / pull gently on that end of the cable as you roll the throttle on and then release. Chances are, it'll be hanging up at some point in the travel. If it does, spray some PB Blaster or equivalent down into the cable, let it sit for a bit, and and then work the cable until it pulls back from the full throttle position smoothly.

If the cable doesn't seem to be hanging up, check the motion of the carbs. Open them manually with the cable disconnected, and release. They should 'snap' shut very quickly. If they don't, the springs are probably binding. Spraying some penetrating lube on them may loosen them up. If not, may as well go ahead and dip them.

 

[gmoore]

anyone have a link to a VM carb rebuild guide and or tutorial? never mind i found it! sorry.

where is a good place to order the carb gaskets?

i also need to re-jet since i'm running pods(they came on the bike and don't have stock airbox) where is a good place to order those?

thanks again

 

[Steve]

anyone have a link to a VM carb rebuild guide and or tutorial?

I see you already found your answer, but I'll give it to you and anyone else that happens to see this, anyway.

As with most things relevant to this site, BassCliff has gathered it all on his site.

If you haven't done so already, bookmark it for FREQUENT reference.

The VM rebuild tutorial is the third item down in the right column, just to the right of his bike picture.

.

 

[Nessism]

Your problem doesn't sound like it's carb boots at all. Seems like if the wheel falls off of a GS, the first thing someone is going to do is blame your carb boot o-rings...

Disconnect the throttle cable from the carb, and hold / pull gently on that end of the cable as you roll the throttle on and then release. Chances are, it'll be hanging up at some point in the travel. If it does, spray some PB Blaster or equivalent down into the cable, let it sit for a bit, and and then work the cable until it pulls back from the full throttle position smoothly.

If the cable doesn't seem to be hanging up, check the motion of the carbs. Open them manually with the cable disconnected, and release. They should 'snap' shut very quickly. If they don't, the springs are probably binding. Spraying some penetrating lube on them may loosen them up. If not, may as well go ahead and dip them.

Ha ha Mr. 205 posts. Hang out here a while longer, and after reading hundreds of times about a "creeping/hanging idle", you will be telling people to change those boot O-rings yourself.

 

[Stahlgrau333]

Lol, my post count is no reflection of my mechanical ability or experience. And I do believe that, in almost every case, that the o-rings need to be (or at least SHOULD be) replaced.

However, what he described is almost exactly the issue I just resolved on my 1100, and was a quicker, easiser fix than ordering o-rings, waiting on the mail, pulling the carbs, etc.

I never said it WASN'T the o-rings...just giving an idea of something easier to check first. If it doesn't fix it, no harm, no foul.

 

[gmoore]

what should i get for carb jets? i have pods and i need to re-jet.

why is there 6 main jets that are all different sizes shown in this parts list? also only 2 pilot jets? http://www.bikebandit.com/1979-suzuki-gs750en/o/m6104#sch279422

sorry if this a total noob question(i know there are pod/carb questions on here a plenty) but that is what i am! the positive is that i am very intent on learning and every bit of info and insight you guys provide to me is greatly appreciated and indispensable!

 

[MisterCinders]

what should i get for carb jets? i have pods and i need to re-jet.

why is there 6 main jets that are all different sizes shown in this parts list? also only 2 pilot jets? http://www.bikebandit.com/1979-suzuki-gs750en/o/m6104#sch279422

sorry if this a total noob question(i know there are pod/carb questions on here a plenty) but that is what i am! the positive is that i am very intent on learning and every bit of info and insight you guys provide to me is greatly appreciated and indispensable!

What kind of exhaust do you have on the bike?

This chart shows you what the stock jets are for your bike.

Stock mains are 100. Stock pilot are 15. These are Mikuni sizes, if you use other brands, their sizing will be different. Depending on your exhaust, you will need to move the clip position on your needle down one or two slots, increase the size of your main jet, and go up a size on the pilot jet, all to account for the increased air flow from pods and pipes.

On my bike, with 4-1 pipe and pods, I moved the needle down 2 slots, went to a 17.5 pilot, and 122.5 main. I may need to increase the main jet further, but I am still working out idle problems.

You can buy Mikuni jets from Z1 Enterprises. They are pretty cheap, so get 4 each in a couple of sizes to test it out.

Others here may be able to make better recommendations on jet sizing. BTW, you have VM carbs so the chorus of "Just get a Dyna Stage 3" won't help you. There is no stage 3 for your bike.

HTH

 

[gmoore]

awesome, i'll start looking around for some jets.

the exhaust is 2- 2 into 1's. they are definitely after market. not sure of the make.

thanks

 

[MisterCinders]

Sounds like stock exhaust to me. That is the stock configuration.

 

[gmoore]

Is the fuel line 1/4" on the 750? it looks larger but the local shop swears it's 1/4".

i'm asking because i'm about to buy some braided fuel line and an inline filter and just want to triple check.

thanks!

 

[gmoore]

anyone know of a good place to get the intake boots? i'm making a wishlist over on Bike bandit and they want almost $40 for 1.

thanks

 

[cowboyup3371]

Go back to Basscliff's welcome and look at the different vendors he listed in that.

 

[Stahlgrau333]

Is the fuel line 1/4" on the 750? it looks larger but the local shop swears it's 1/4".

i'm asking because i'm about to buy some braided fuel line and an inline filter and just want to triple check.

thanks!

If I remember correctly, the 1/4" IS too big. It will 'work', but it won't be 'right'. The correct size is metric, but I can't recall what it is off the top of my head. Perhaps someone with more than 200 posts will chime in with the correct size. (I tried to search for it, but for some reason search function isn't working for me at the moment)