78 GS1K Carb Rejet? Bad Fuel Economy - KEITH KRAUSE!

[Anonymous]

On our CV carbs, the mixture screws are really tough to set. Everyone says to adjust for the highest idle, but most of us have found that the screw settings are extremely subtle, almost undetectable unless you ride the bike. If you figure that the settings will be between 1/2 turn out to 6 turns out and every 1/4 turn in between and that all the carbs could be different, you have thousands of possible combinations of settings.

I found nothing less than 1/2 a turn was noticeable when I was jetting for pods. I never went for the highest idle method, I went on plug readings, start up/idle, and throttle response. At 2.25 turns the throttle response was very abrupt (a sure sign of a lean condition) and the plugs were reading a very light tan/dark grey color. At 2.5 turns everything improved a bit and at 3 turns throttle response is sharp but not at all abrupt and the plugs show a nice medium tan color. You should never turn out the mixture screws more than about 3.5 turns, at that point you are wide open on the adjuster and you really need to step up one size on the pilot jet and start over. At least setting the mixture screws is a 5 minute job. You can get a lot of testing done in an afternoon with a screwdriver bit and some time...

Mark

[Hoomgar]

I played with my colortune a bit and saw the same thing Jethro. What I noticed is that there is a base blue color to it all the time. What I think goes on is you have to read the color of it the instant it fires. I played with the air adjustment screw with it in and the blue color never changed. However the color around the rim and inside post everytime it fired was changing colors. Just like they show in the chart. I am sure that this is what your to be looking at. I haven't used it beyond that though yet.

The Carbtune II tool rocks though. I can't give it enough of a good word. It seems to be just as good as a mercury one would be but you never ever have to worry about sucking mercury into your engine and it will never fog up like the mercury ones do. I am not saying it is better than a mercury tool. I am simply saying that I think it is every bit as good.

I am going to get this, no worries

I actually spoke with Keith K. on the phone about this last night and I am glad I did. Getting to pick his brain a bit in a more time reative situation like a call was way faster and more informative than a hundred posts.

And I can tell you another thing, he is all business. Very serious about tunning these bikes. If you guys are ever asking him questions about something be sure to follow EVERY thing he says. There are little tid bits of info that he gives that if over looked can turn your entire project into a waist of yours and his time.

And that's all I have to say about that... <--- Forrest Gump


This bike will run right before the southern rally.

[Hoomgar]

Keith. We have made some major progress here tonight.
This is by far and hands down the best the bike has ever run.

It is still not perfect but it has a snap to it now that it never had.
It is running so smooth after tonights sync that the speed you
generate is deceptive. At one spot I looked down just to see where
I was as I was swapping along through the night air on a mildly windy
road and the speedo said 110! 8O 8O

I verified what gear I was in. It has a 0 to 60 right now that is smooth
and fast.

Anyway, that said, it was for sure that brass shrapnel I found in them last
night. I got all that blown out tonight.

Here is what I have done and where I'm at. Pics included:

I took the carbs off and pulled all needles and screws, floats, etc...

Blew it all out with 180 PSI and then verified with light and air that all
passages were clean open.

I checked the float levels, they were still spot on so I did them right the
first time.

Buttoned it all back up. Set both pilot and air screws at 1.5 turns out
each.

Did a really meticulous bench sync and popped the carbs back in.

Low and behold the air screws actually have an affect on the idle now
So I set them all for max idle. I should have written them down but I
didn't think to do it. None of them went over two turns out. They are all
somewhere between 1.5 and 2 turns on the air screws.

I have not touched the pilot screws, they are all still at the starting point
of 1.5 turns out.

After I got that all done I did my best sync yet. They really were not far
off. Maybe 3/4 from each other. Here is a pick of the sync for you
Keith. Note the RPM's



After all that I put the tank, seat and side covers on and went for gas.
That is when I got to see how good it is running.

I did my best 1/3 throttle chop test. It ain't perfect as it was hard to see
my marks in the dark but it is still very close to a good 1/3 throttle chop
test Keith. Here it is:

[img]http://groups.msn.com/_Secure/0SwD9AuAVSS*JRdMUQy38vZ2H5Lg8F7DNNBujvo6irIj6mO8yh i5rrD4RVW2JU0l1*9LTKfWxezG8qqDFY2JCuD0WPVliYYudZAD Xay0i3!OIatKJkO3lTw/DCP_7406.jpg[/img]

One thing I found that maybe I was doing wrong before too. The vacuum
hose for the petcock has always been open when trying to tweak it
before. This time I plugged it shut while using my tune tank and the
results were way better. Maybe this was the most of my issue?

What do I do from here to get rid of the lean on that 2 and 3 cylinders?

[KEITH KRAUSE]

I never went for the highest idle method, I went on plug readings, start up/idle, and throttle response.

If the plug reads at all 3 circuits are their best, your start up and idle is good, and the throttle response is it's best, then your bike is running its most efficient. When the bike is running its most efficient, it's also running at the highest rpm. They're one and the same.
You may not have made a deliberate attempt to adjust for highest rpm, but if the above is true, you'll find the mixture screws (CV) or air screws/pilot fuel screws (VM) are at a point that just happens to be the highest rpm achievable on that bike.
When your bike was new, it came set this way too.

[KEITH KRAUSE]

Mark, I just read your last post and I'm glad you're getting there.
It's way late and I'm getting the evil eye from the wardon. I'll think about those plug reads and do my best to reply after work tomorrow.
As before, I can't see them like you can, but 2 and 3 are lean as you said. Exactly how lean? Is the insulator whitish/gray, or bone white? Are 1 and 4 pretty good?
One quick thought, are you POSITIVE the timing for 2/3 is the same as 1/4? Talk to you soon.

[Hoomgar]

Mark, I just read your last post and I'm glad you're getting there.
It's way late and I'm getting the evil eye from the wardon. I'll think about those plug reads and do my best to reply after work tomorrow.
As before, I can't see them like you can, but 2 and 3 are lean as you said. Exactly how lean? Is the insulator whitish/gray, or bone white? Are 1 and 4 pretty good?
One quick thought, are you POSITIVE the timing for 2/3 is the same as 1/4? Talk to you soon.

Yeah being up posting after midnight can generate those looks

I am 100% positive that the timing is smack on in both the 1 and 4 and 2 and 3 sets. They both idle right on the f mark and when you crack it to 3k they both sit right on the higher mark. The gaps are also perfect. They are spot on.

Yeah the photos are always deceptive. Makes things look lighter than it is. Here is what I would say about the plugs by comparing them to the color chart.

Plug 1 is just a little on the rich side. It is too dark and is carbing up a bit.
Plug 2 is just a tad lean. It could stand to be a bit darker.
Plug 3 is lean with both the tab and the insulator being pretty whitish/tan
Plug 4 is almost perfect. Maybe just the slightest hair on the lean side.

I rode it to work this morning and boy is it running strong. You crack the throttle and you?re gone! When down in the idle circuit and the early part on the needle circuit it runs a tad rough and sporadic until you give it a little more gas. Then it runs near perfect.

WOT is exhilarating!

What is next? Pilot screw adjustments?

[Jethro]

One thing I found that maybe I was doing wrong before too. The vacuum
hose for the petcock has always been open when trying to tweak it
before. This time I plugged it shut while using my tune tank and the
results were way better. Maybe this was the most of my issue?

Sorry to laugh Mark, I do it WITH you, not at you becasue I have made that mistake more than once! I finally came up with a solution for me- I made a little plug for the vaccum nipple and now velcro it to the end of the hoses on my synch gauge! Now I have to take it off and put it somewhere when I attach the hoses. It does make a difference- a huge difference!

[Hoomgar]

Yeah it supposed to be plugged huh? That little bit of info was missing. It isn't in my manuals that I saw and no one mentioned it. There is a 500 to 700 RPM difference in the idle with it plugged or unplugged! 8O


:? :? :? :?

[KEITH KRAUSE]

I'm gonna start mentioning to cap the vacuum nipple if you're using a seperate fuel reservoir. You're the second person I've tried to help this year that's done that. I finally mentioned it to the other guy. I didn't before because I didn't want him to think I thought he was stupid. It just seemed so obvious to me. This info is supposed to be included with your synch tool instructions. I know it is with the Motion Pro tool.
With a vacuum leak that big dragging down the motor, each cylinder air screw will have little effect on the rpm's. I do suggest to use the tank for a fuel source during synching, by using longer fuel/vacuum lines. Pingel owners don't have this "problem".
As usual, I gotta get to work. As for the leaner 2 and 3, If everything else has been done the same regarding jetting, cleaning, timing, etc, then make some pilot fuel screw adjustments. Be sure to keep a record. Be sure you turn them the right direction. Some people don't because they're upside down. Also, be sure you didn't go past the sweet spot on those two carbs when you adjusted the side air screws. A combination of smaller mistakes can cause a larger problem.
Try an ADDITIONAL 1/4 turn out on #2. Try an additional 3/8 turn out on #3. Try 1/8 turn IN on #1. Test again.

[Hoomgar]

I'm gonna start mentioning to cap the vacuum nipple if you're using a seperate fuel reservoir. You're the second person I've tried to help this year that's done that. I finally mentioned it to the other guy. I didn't before because I didn't want him to think I thought he was stupid. It just seemed so obvious to me. This info is supposed to be included with your synch tool instructions. I know it is with the Motion Pro tool.

Never under estimate the impact that the ignorance of your pupil can have on your advice Keith! 8O

With a vacuum leak that big dragging down the motor, each cylinder air screw will have little effect on the rpm's.

Ding! Ding! Ding! Ding! We have a winner!
Now we know why my air screws were not affecting the idle.
I told you I wasn't going crazy. I knew I had to be missing something!

I do suggest to use the tank for a fuel source during synching, by using longer fuel/vacuum lines. Pingel owners don't have this "problem".

But plugging that hose and using the tune tank should be fine too right?

As usual, I gotta get to work. As for the leaner 2 and 3, If everything else has been done the same regarding jetting, cleaning, timing, etc, then make some pilot fuel screw adjustments. Be sure to keep a record. Be sure you turn them the right direction. Some people don't because they're upside down. Also, be sure you didn't go past the sweet spot on those two carbs when you adjusted the side air screws. A combination of smaller mistakes can cause a larger problem.
Try an ADDITIONAL 1/4 turn out on #2. Try an additional 3/8 turn out on #3. Try 1/8 turn IN on #1. Test again.

Exactly what I was thinking believe it or not. But I wanted to hear it from you first. I'll recheck the air adjustments first just to be sure.

[KEITH KRAUSE]

To answer your last question, yes, you always plug the vacuum nipple and you can use a fuel reservoir as long as it's venting well (just like your gas tank would).
And as for the air screws and thinking you were crazy, I told you over the phone that something had to be blocking the air. I wouldn't think that someone had introduced a huge intake leak . I did mention to be careful when installing the tools adapter tubes. Oh well, live and learn.
At least you now know the benefit of adjusting these screws for the highest rpm. The screws being adjusted is the only thing that's different from your first "successful" synch and road test, and the synch/test you just did.
After your first road test, you were excited about the performance. After this road test, you sound twice as excited. Before the last adjustments, I told you on the phone that your bike can run better, but you said you know what a good running 1000 feels like and this bike was awfully close to that feeling after the first synch. Your latest comments tell me I was right.
I have to believe your gas mileage and the heavy exhaust is going to improve significantly. With the air screws adjusted for highest rpm, the fuel is being atomized as it should at all 3 circuits. Before, the stream of mixture entering the carb throat was too solid. Unburned fuel just blew through the combustion chambers. Hydro-carbon heaven!
Now back to the jetting set up you have.
Because I can't see the plugs and ride the bike myself, I have to go by what you post. You're doing a good job, but nothing replaces being there. There's a chance that pilot screw adjustments will richen those lean plugs enough and help with that little low speed problem you mentioned. The pilot circuit does overlap the needle circuit. I hope we're at that point of the re-jet. At this point, if you've found the sweet spot on the air screws, do not touch them anymore. Only adjust the pilot fuel screws. The only time you should ever need to make a minor adjustment to the air screws is at higher elevations, if the bike is starting hard. An additional 1/4 to 1/2 turn out usually helps.
After pilot fuel screw adjustments, if the performance is still a bit off and/or the plugs are still lean at 2/3 during 1/3 throttle tests, then we'll have to go to the next step. This would be the opposite of trying to richen 2/3 with simple screw adjustments. This would mean raising the jet needles and then leaning out any rich reads at 1/4 with pilot fuel screw adjustments. We'll see. I'm just waiting to hear if the heavy exhaust/fuel smell has improved.
As I've said before, I'm still surprised the bike is running as good as you say while on the jet needles. The 4th position on the stock needles is lean from my past experience. As always, there must be a reason, but we'll worry about it if it comes up.
I always get several reads by the way. A lean running needle circuit is very deceptive. The leaner mixture will provide a lot of power, but the surging/hesitation that should accompany it may not be noticable to some riders. Always error on the rich side. After you're positive about the needle circuit, test for the main. From about 60 mph in 5th gear, the bike should roll on under full throttle without any noticable bogging. If it runs strong, you can go up to the next larger main if you want. The best main is the one that provides the highest top speed, WITHOUT causing any roll on bogging. Everday riding/passing performance is worth losing a couple of top end mph.
And be sure you remove those blasted float bowl tubes if you still haven't. The bowls will breath better and the jets will draw fuel correctly.

[Hoomgar]

Yeah all good on all of that Keith except I don't understand what you mean by this?

And be sure you remove those blasted float bowl tubes if you still haven't. The bowls will breath better and the jets will draw fuel correctly.

Also, with the 1/3 throttle chop test/read, what circuit are we testing there?

[KEITH KRAUSE]

I meant the two float bowl VENT tubes. One is on carb #2, the other on carb #4. This is a requirement with pods and mentioned in jet kits. I've tested for it. It's important. Just be careful if you use a hose on the bike. The nipples must stay open. I've mentioned this before. You are listening?
At 1/3 throttle position, you're on the jet needle, though there is still some overlap effect from the pilot circuit. That's why I'm hoping screw adjustments will fix you up. Might as well try. Screw adjustments are easy. I'm also assuming your tests are at 1/3, not 1/4 or...This must be fairly exact.
If you don't like the results, we'll have to try raising the needles, unless there's a possibility something else is wrong.

[Hoomgar]

I meant the two float bowl VENT tubes. One is on carb #2, the other on carb #4. This is a requirement with pods and mentioned in jet kits. I've tested for it. It's important. Just be careful if you use a hose on the bike. The nipples must stay open. I've mentioned this before. You are listening?

Keith, we went over that back on pages 4 and 5

Yes I removed them dad, I am listening

Your comment about water getting in though is good point. Maybe I need to make up a smaller vent tube to slip on them with a screen on it so no bug can crawl in and long enough to hang down to avoid water? This has me concerned. I did take them off when you told me though and they have stayed off.

[KEITH KRAUSE]

Me!? Your Dad!? 8O Not with your mug....uh...I mean face.
I suggest leaving the vent nipples alone. Even a short tube causes fuel starvation. I don't know of anyone who has had a problem with a bug or dirt getting in there. Any little home made screen or downward facing tube is bound to cause problems. Hose water won't get in there if you use common sense.
It's your fault I'm worrying about every little detail now.
Mr."No one toooold me to cap the vacuum port". :P