Now What..

[Scud]

1980 GS750E

Well..I still have black and sooty plugs after cleaning the carbs and adjusting the floats to 24mm (wihtout the gasket and upside down). I synched the carbs and checked for cracked or leaky induction boots and they check out fine. I checked resistance at both the primay and secondary sides of the coils and they were all within ranges specified. My air screws are 3 turns out. Air filter is clean and secure with no leaks. I replaced the plugs and took her for a ride and when I looked tonight they were all black and sooty...all four of them . Spark appears to blue and sharp, plugs are NGK D8EA.

I still have the problem of the rpms staying up high when revved, if I just rev to 2,500 they return to 1,200 fairly quickly, if I reb to 4,00 they stay at 3,500 then retreat slowly to 1,200. What does this tell you guys? :?

HELP!!!

Scud

 

[Scud]

It's late for me...that would be rev to 4,000 and she stays at 3,500 before returning to 1,200 after about 5 seconds.

Scud

 

[earlfor]

Re: Now What..

It makes me ask two things.

1. what vacuum are your carbs pulling at 1200 rpm? It should be 8-10 in.hg.

2. Have you checked your throttle linkage/cable for rough spots? have you disconnected the throttle cable from the carb, rev'd the engine by twisting the linkage on the carb by hand with the cable disconnected and watched it to see if it does actually return to the throttle stop?

Earl

1980 GS750E

Well..I still have black and sooty plugs after cleaning the carbs and adjusting the floats to 24mm (wihtout the gasket and upside down). I synched the carbs and checked for cracked or leaky induction boots and they check out fine. I checked resistance at both the primay and secondary sides of the coils and they were all within ranges specified. My air screws are 3 turns out. Air filter is clean and secure with no leaks. I replaced the plugs and took her for a ride and when I looked tonight they were all black and sooty...all four of them . Spark appears to blue and sharp, plugs are NGK D8EA.

I still have the problem of the rpms staying up high when revved, if I just rev to 2,500 they return to 1,200 fairly quickly, if I reb to 4,00 they stay at 3,500 then retreat slowly to 1,200. What does this tell you guys? :?

HELP!!!

Scud

 

[Scud]

Hi Earl,

Yes, they all read 10 in. at 1,200 RPM, when I first hooked up the synchronizer they were all off and were adjusted equally, what if it was higher or lower?, if it were higher or lower what would that tell you? With regards to the throttle cable, there is slack in the cable where it attaches to carb #3 and about 1/8 inch of free play while twisting the throttle so I am pretty sure it is resetting fully to the stops.

Scud

 

[KEITH KRAUSE]

Going on your previous posts, the bike had problems AFTER you serviced the carbs? You could have more than one problem.
Besides the things you've already checked, are you sure the air jets are clear? Did you re-set your mixture screws to the same settings? Did you disturb the jet needles? Are your rubber diaphragms correctly seated?
If this bike is stock, are you sure the jets are stock?
I know you say you checked for intake leaks, but did you actually replace the manifold o-rings?

 

[Scud]

Hello,

I guess that there could be some sort of blockage in the passages but I was very careful when I cleaned them. The carbs have been off and on the bike three times and the same symptoms occur. I have CV carbs and they do not have manifold o-rings. All jets are seated fully except the air screw which was at 2.5 turns out when I removed them originally. Am I correct when I say that turning the screw in richens and backing out leans? I replaced the stock main jets with one from a kit that were the same size, 112.5.

Scud

 

[earlfor]

When the linkage on the carb stack reaches its sticking point, the cable would go slack even though the linkage may not be fully returned. The cable has nothing to do with where the linkage stops moving (unless of course the cable were to be adjusted so tightly that the linkage could not close). The linkage could still be sticking. That it returns to idle normally from 2500 rpm which is a range beyond the idle jets and then does not return to idle normally from 4000 rpm tell me it is not your idle jets that are the cause. At 4000 rpm, you are in midrange, not idle. A slow return to idle is always a lean condition in the range the problem occurs in. If it will not come down immediately from 4-5000 rpm, you are lean in that range. I do not believe your carbs have adjustable slide needles, so the most probable cause in an induction leak. Do you have a filter in the airbox and is the airbox sealed. Filter fitted tightly? Clamps on the induction hoses tightly? What color is the center ceramic on your spark plugs?

Also, turn your petcock to prime for about 20 seconds, then turn it to the off or run position (bike not running) Get 4 small cups or whatever you have and remove the drain plug from each float bowl, draining it into a cup. Check to see that there is the same amount of fuel in each float bowl. You may have a couple of carbs running lean due to too low a fuel level.

Earl

Hi Earl,

Yes, they all read 10 in. at 1,200 RPM, when I first hooked up the synchronizer they were all off and were adjusted equally, what if it was higher or lower?, if it were higher or lower what would that tell you? With regards to the throttle cable, there is slack in the cable where it attaches to carb #3 and about 1/8 inch of free play while twisting the throttle so I am pretty sure it is resetting fully to the stops.

Scud

 

[Scud]

I will check the linkage and airbox tonight. The center ceramic on all plugs are the same color and that would be black as night with fluffy dry sooty carbon on each. The induction boot clamps are as snug as they will go, they are tight, I always thought a black sooty plug meant rich, but never thought about it being in the midrange... I reset all floats to a height of 24mm, they were all set at 20mm before. I took the bike out and it had plenty of get up and go at that level. One other note is that as soon as I touch the starter the bike starts, I have never had to choke the bike to start it, the only exception was when I had the carbs off and then had to fill the float bowls, even then it started up immediately with very little choke. Sometimes it revs immediately to 3,500 then retreats to 1,200 after she has not been started - say overnight.

Should I take her on say a 80 - 90 mile trip and then check the plugs? I have only been taking her on 15 mile round trips since the last assessment. Also should I try a hotter plug? I replaced the plugs that the original owner had installed and did not check to see what type they were (he died sometime ago so finding out is impossible..), I replaced them all with NGK D8EA plugs, should I try a NGK D7EA or a NGK D9EA?

I will check the float bowl levels for consistency sometime today also.

I am leaving for Idaho Falls from Driggs in about two hours and would like to know if I should get different plugs while I am there.

Thanks

Scud

 

[earlfor]

Your plugs are the correct range. I would get some new ones because it is very difficult to tell what effect the changes are by reading a black plug.
Just get the same thing. soak the old plugs in vinegar overnight to clean the soot off of them.

Earl

I will check the linkage and airbox tonight. The center ceramic on all plugs are the same color and that would be black as night with fluffy dry sooty carbon on each. The induction boot clamps are as snug as they will go, they are tight, I always thought a black sooty plug meant rich, but never thought about it being in the midrange... I reset all floats to a height of 24mm, they were all set at 20mm before. I took the bike out and it had plenty of get up and go at that level. One other note is that as soon as I touch the starter the bike starts, I have never had to choke the bike to start it, the only exception was when I had the carbs off and then had to fill the float bowls, even then it started up immediately with very little choke. Sometimes it revs immediately to 3,500 then retreats to 1,200 after she has not been started - say overnight.

Should I take her on say a 80 - 90 mile trip and then check the plugs? I have only been taking her on 15 mile round trips since the last assessment. Also should I try a hotter plug? I replaced the plugs that the original owner had installed and did not check to see what type they were (he died sometime ago so finding out is impossible..), I replaced them all with NGK D8EA plugs, should I try a NGK D7EA or a NGK D9EA?

I will check the float bowl levels for consistency sometime today also.

I am leaving for Idaho Falls from Driggs in about two hours and would like to know if I should get different plugs while I am there.

Thanks

Scud

 

[Scud]

Will do, thanks

Scud

 

[KEITH KRAUSE]

Did you take apart the needle assemblies and possibly install any spacers in the wrong order? Are the rubber diaphragms in good condition and seated correctly? The screws I was talking about are the mixture screws. Turning them in leans the mixture, out richens.
Funny, you have black plugs but a hanging idle which is a lean sign.
Check the linkage as Earl says. Is the choke closing completely too?

 

[Scud]

I am confused as to the 'spacers'...I do not remember seeing any when I cleaned and re-assembled the carbs :?: , Where is the mixture screw on a CV carb?? I was talking about what I thought was the air screw or the screw that is under a factory aluminum cap that had to be drilled out and removed before dunking. I removed them and installed a new screw with spring, one washer and the o-ring. Where is the mixture screw and how does one adjust it in a CV carb? Rubber diaphragms? I am very confused, please give me more info with regards to these such as where they are?

The choke is completely disconnected, I thought too that maybe the choke was slightly engaged so I just disconnected it.

Scud

 

[Scud]

Hi All,

I have af riend coming over today at 1300, he is a very experienced and great mechanic, I will let you know what we find out and post it later on today.

Scud

 

[KEITH KRAUSE]

I am confused as to the 'spacers'...I do not remember seeing any when I cleaned and re-assembled the carbs :?: , Where is the mixture screw on a CV carb?? I was talking about what I thought was the air screw or the screw that is under a factory aluminum cap that had to be drilled out and removed before dunking. I removed them and installed a new screw with spring, one washer and the o-ring. Where is the mixture screw and how does one adjust it in a CV carb? Rubber diaphragms? I am very confused, please give me more info with regards to these such as where they are?

The choke is completely disconnected, I thought too that maybe the choke was slightly engaged so I just disconnected it.

Scud

The screws you removed the caps from are the ones I was talking about.
Hopefully you counted the # of turns out they were and after re-building them you returned them to the same settings.(?) Turning them out, richens the mixture and turning them in, leans the mixture.
As for spacers on the jet needle assembly, there can be differences from carb to carb. You may or may not have stock parts. If you did'nt take apart the needle assy', I would'nt worry about it. If you did, then you have to be sure to replace any spacers in the same order. Example: some carbs have two plastic spacers of different thickness. If you reverse these in re-assembly, the fuel mixture will be WAY off. These spacers can be under and/or above the needle clip. You would remember if you pulled out the clips from the needles I assume?
The rubber diaphragms are in the top part of your CV carbs under the top cover. They must be supple and in good condition to work right. If they've been removed, they need to be re-installed correctly. The diaphragms/piston valves/needle/spacers are all assembled "together".

 

[Scud]

Keith,

I remember counting the turns out then each one got stuck :evil: ...so consequently after taking the whole carb bank to the friend who is coming over right now, I forgot how many turns exactly. We eventually got them all out but it was challenge including drilling and using an easy (somewhat easy) out. I then replaced them all and started them at 2.5 turns out. The whole procedure from start to finish trying to remove the screws was two days, I have a hard time remembering what I had for dinner the night before let alone two days.

I know that there were not any spacers except for a washer under the main jet. The needle jet had a small screen over it and that was removed and re-installed after the carb dip. I did remove the clip that holds the needle in..is that the one you are referring to..sorry if it was, yes I did remove it to take out the jet and needle for the dip.

As far as the diaphragms go, I did have to take them out for the dip and replaced them all exactly like I found them, they were still supple and intact.

I realize that you had to go the extra mile ot explain where all the parts are form and I do appreciate it, I will get the lingo down as time goes by...

Scud

 

[Anonymous]

Any time I read about an engine that performs differently under different external conditions -- temp, atmospheric pressure, humidity, etc -- I wonder about an intake leak. Especially when the idle isn't stable.

You say that you have CV's so there aren't any intake boot O-rings. I don't see any connection between the two. Most GS's with CV carbs use the same intake boot style -- with O-rings.

You also mention much earlier that you have tightened the 'induction boot clamps' adequately. That means you HAVE induction / intake boots to worry about.

Read this:

http://www.cycleorings.com/intake.html

This is my standard sermon. Humor me. If your 'induction boots' (good enough term as any) are shaped like this where they meet the cylinder head, then there are O-rings between them and the head, and they're almost guaranteed to leak & cause grief.

I don't sell these, and I'm not trying to be argumentative, but it would be a shame to exert this much effort (and $$$) while overlooking a really fundamental possible cause.

 

[KEITH KRAUSE]

Just to help you with the names of parts. The "needle jet" with a screen and clip as you describe, is actually called the float needle valve.
The plastic spacer(s) I mentioned go on the jet needle, a long tapered needle that goes up and down in the needle jet.

 

[Scud]

Hello Robert,

The intake manifold is a solid piece that sticks out from the engine, there is no seam it was molded righ tinto the engine so I know that there are no o-rings in that area, I lloked at your link and my engine does not have a part that bolts on that could be hiding the o-rings. The rubber boots simply attach the carbs to the engine and the airbox to the carbs. I wish I had those it would be the very thing I would replace!

Keith,

Thanks for the the vocabulary lesson, I did not mess with the spacers in the jet needle, in fact I did not even remove the needle from the housing at all, just pulled out the whole assembly before the dip.

My mechanic friend stopped by yesterday and spent at least three hours with the bike, his conclusion was that the idle circuit is not working properly or possibly at all. He thinks that the only thing keeping it running at all is the main jet and he ruled out the choke system, he was scratching his head (he is a car mechanic and small engine repair guy, he is used to working with single carb engines, but knows about multiple carb units). He wanted me to ask if the timing was to advanced would it be possible to get the carbs to run correctly?

We had the sychronizer attached and would start the engine, he would adjust the air screw and the engine would speed up and he would back it off so that it would maintain a 1,200 RPM idle, then move to number two carb and do the same thing. As soon as he got done with the number two carb the engine would race to 3,500 and then he had to back off on the idle adjuster so it would be back at 1,200, but then he had to recheck number one and number two carbs. Does this information help to possibly point to a potential problem?

It still will return to 1,200 RPM when revved to 3,000 but it will stay high when revved to 4,500-5,000, returning to 1,200, it stays at 4,500-5,000 for eight seconds then drops fast to 1,200.

Hmmmm..............

:-({|=

Scud

 

[KEITH KRAUSE]

You should always set the ignition timing correctly before carb tuning.
I'm not familiar with your ignition except I know it's electronic. Set the timing as your manual tells you to and check everything for correct operation.
This brings back an experience I once had with an old "Martek" ignition. I'm not saying yours is doing this, it's just an idea. The collar (with the magnet) that fits over the end of the crankshaft, had a set screw that came loose and my motor acted similar to yours. At times, it was spinning freely, seperate from the crankshaft. Obvious delay in the rpm's returning to normal after revving it. So as I said, check everything and set the timing if it's off.

 

[KEITH KRAUSE]

Oh, and about your carb screw question. You're talking about the mixture screw on each carb, correct? I hope the CV carb experts will correct me if I'm wrong, but I think they should be set for the highest idle you can achieve and then re-set the idle using the idle screwknob.
If so, with the motor warmed up, adjust 2 screws at a time (if this makes it easier to hear the rpm's), adjust all 4 for the highest idle possible and then set the idle with the idle screwknob.
You did do a good carb sinc', correct?