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

[skip]

Skip, the fuel will be regulated at the smallest passage or gap along the needle jet and tapered jet needle and main jet.
Generally, when the throttle is at 3/4, this is the point where the gap becomes larger at the needle jet and tapered jet needle and so the smallest passage, now through the main jet, regulates the fuel flow.
In the case of a correctly set up 78/79 1000 in good mechanical condition, you would not need to install larger mains in the 2/3 cylinders to help with 3/4 throttle and above. If you did, this would be compensation jetting. Compensating for something else wrong.
Yes, it can work, but it usually creates another problem.

ok keith Im catching on here , but i thought hoomies plug readings were at less then 3/4 throttle? he is jetting and adjusting for midrange or needle setting no? I agree with you that he may be compensating for somthing else, but if the other adjustments have not worked then maybe going up one jet size on the center two cylinders should be considered. When I jetted the stock 1150 carbs with k&n's I got a jet kit from FOURS AND MORE it was a performance shop out of california that the magazine Motorcyclist used all the time in the 80's That jet kit also came with different size main jets for the center two cylinders. the reasoning was two fold. one was that somtimes the outside cylinders have so much air passing over them that they create a vacume and make it hard for the air to get sucked into those clinders so they rin richer. The other reason was somtimes you ride with your legs ( on the 1150 anyhow) right up against the out side cylinders once again blocking air to those cylinders and making them run rich. Could be a bunch of crap, but the bike ran great with the two different jets installed and so did my ZRX. Hoomie will be riding about 400 miles a day(Mostly in the midrange on the needles)) for 5 days or so so as a last resort, he should do what ever he has to to get those clinders richer. You are A much better tech adviser than me and I marval at your knowledge. keep up the good work

[KEITH KRAUSE]

Mark, be real exact about the float levels at 2/3.
Check it first, just in case you could have done something wrong the first time. If they're at .94 or .95, then go to .92". If you did set them wrong (too lean or higher than .95), then set them to .94.
Do the same with the synch. Check the initial levels at 2/3. I'd like to know if they "moved" lower than 1 and 4. That would suggest sticky slides. Sometimes, quite often actually, you can clean up the inside of the carb cylinder with Semi-chrome, Blue Magic, or Mothers aluminum polish, to a mirror shine and that will help a sticky slide. Just don't go crazy with the stuff. About 50 "up and down pokes" with your finger around the whole surface should be fine. Just don't get any dried paste where you don't want it if you end up doing this.
Of course, this would mean more work removing the slides, re-synchs... :roll:
Check in with you later.

PS: I wasn't frustrated. I just thought you were changing your mind and it kind of threw me for a loop. Believe it or not, I've gotten some negative reactions from the wife about how much time I spend here. That factored into why I sounded unhappy about you maybe giving up on the re-jet. I didn't want all the time spent here to only result in her getting mad at me. I come home and check in with you if I can to see if you need help. She can't understand why I help "strangers". This isn't your fault mind you, I DO spend too much time here and it's just getting on her nerves a bit.
Enjoy the night out with the wife. I better do something for mine too!

[KEITH KRAUSE]

Skip, maybe I'm mixing you up.
Marks plug reads were at 1/3 throttle position or very close to.
At that point, you're on the jet needle with maybe a slight overlap effect from the pilot circuit. But you can say you're on the needle.
The main jet has no effect until the tapered jet needle rises at about 3/4 throttle.
At that point, the gap or passage between the jet needle and the needle jet becomes larger than the hole in the main jet. The main jet will now regulate the fuel flow because it is now the smallest passage along the entire circuit.
Installing larger mains in 2/3 carbs will do nothing unless you're at 3/4 throttle or more. Larger mains will have no effect at the throttle position Marks testing at.
I'm well aware of the need for the bike to run decent on the trip. Temporary fixes are not out of the question. But the larger mains won't help this situation. That's why I'm suggesting the latest adjustments. Nothing unusual, just a little attempt to richen 2/3. I'm hoping it helps enough.
Along with a few other thoughts, I'm hoping the intake valve clearances at 2/3 aren't too wide and not admitting fuel correctly. I suggested setting the clearances way back, but Mark assumed they were good, which they may be, but I have a procedure I do when re-jetting and a valve clearance check/adjustment is always done. I have go with what Mark wants to do at times. Correct clearances are very important to get an accurate carb synch/plug reads too. This gives you one less possible cause/problem if you end up trouble shooting instead of jetting.

[KEITH KRAUSE]

That said, back to business. Tonight, carbs come off.

Floats in 2 & 3 are getting set to .92 or at least just a tad higher.
I am going to test these levels with a clear tube as recommended in other threads.

Once that is right I am going out ? turn on the pilot screws for 2 & 3.

Recheck WOT setting screw. Back in the bike.

Recheck sync first!

Recheck air screws for max idle.

Plug test run.

Mark, I don't know if this will reach you in time, but I just want to clarify something about the float adjustment.
Above, you say "floats in 2 and 3 are getting set to .92 or at least just a tad higher".
In the inverted position, a higher float height measurement= lower fuel level and leaner mixture. A lower float height measurement=higher fuel level and richer mixture. Just want to be sure you have it straight. Measure first. If you did make a mistake earlier and they're higher than .94/.95, then set them to .94. If they are at .94, then set them to .92 and no higher.

[KEITH KRAUSE]

Hey Mark. Good morning.
I'm not sure what plans you have today. I have yard work to do and it will take me at least all day.
I'll take a break now and then to see if you need any help.
Sure hope the bike runs good.

[KEITH KRAUSE]

Just stopping by Mark. You got me a little concerned with your absence.
You were gonna go out with the wife and then try some adjustments.
Sure hope you're out enjoying life "away from carbs" or something.
If you got hurt doing high speed testing, I'd feel like crap.

[Hoomgar]

Just stopping by Mark. You got me a little concerned with your absence.
You were gonna go out with the wife and then try some adjustments.
Sure hope you're out enjoying life "away from carbs" or something.
If you got hurt doing high speed testing, I'd feel like crap.

You are a true friend indeed Keith. Thx for keeping up with me. Sorry for not checking in sooner. This is the first I have had a chance since Friday afternoon.

I haven't touched the floats. I simply don't have any more time now.

I did some tweaking of the pilots as you suggested. I took the pilot on 2 & 3 out 1/2 turn more and then readjusted all four carbs for max idle to make sure they are right. I rechecked the sync and it surprized me. I had it all even when I did it but now it was exactly where I would have moved them to if they were still even. 1 & 4 were right level with each other with 2 being about 1/4 to 1/2 higher. 3 was a good 3/4 higher and about 1/4 higher that 2. I left it at that and took it for a chop test.

The results? Much better I am leaving it like this for the ride.
The plug read was the best yet. None of them are alarming lean anymore. 2 & 3 are still lean compared to 1 & 4 but 1 & 4 seem perfect.

It is running really good now too. I am going to scoot with it this way and when I get back from the rally I will look more into it then. I want to open the top and check the valves and cams then too. I think the cams are walking from side to side a bit. I am used to that on my old bike and it would need new shims to fix it.

See you when I get back. Thx for all the help.

[Hoomgar]

Keith, yesterday I opened the valve cover and the intake cam valve gaps on 2 & 3 both needed adjustment. They were both too tight. 3 more so than 2. You could not slide a 1.5mm feeler under them.

After readjusting them all so that they are between 1.5 and 3.0 I buttoned it back up. The cam timing was good.

It ran so bad on the way home I thought I was going to foul out and break down. I had to keep hammering it to keep it running.

I got a set of DJ 122 mains from Joe and as time permits I am going back at this now.
I am thinking about trying them with the stock needles as money is tight. Do you think it will work?

The thing still smokes bad and is passing a lot of fuel as many who followed me can attest.

Just thought I would post this to wake this back up now.

[KEITH KRAUSE]

Hi Mark. Welcome back. I was hoping for better news.
First of all, you say you found 2/3 intakes too tight. HOWEVER, you say you adjusted them to between 1.5 and 3.0 mm. 8O The correct range of adjustment is no less than .03mm and no more than .08mm. Reset them ASAP.
As for the heavy exhaust, I wish I knew what was going on. When you left on the trip, you had two plugs reading tan and two plugs reading a bit leaner. How you can be passing fuel is strange. Now if it's ONLY during roll ons or wide open, then we can blame the main jets, we haven't really messed with the mains yet. But if it's passing fuel at normal cruising speeds/throttle positions and your MPG was still bad, it just doesn't figure.
What was your trip MPG? How was it ridden?

[Hoomgar]

Hi Mark. Welcome back. I was hoping for better news.
First of all, you say you found 2/3 intakes too tight. HOWEVER, you say you adjusted them to between 1.5 and 3.0 mm. 8O The correct range of adjustment is no less than .03mm and no more than .08mm. Reset them ASAP.
As for the heavy exhaust, I wish I knew what was going on. When you left on the trip, you had two plugs reading tan and two plugs reading a bit leaner. How you can be passing fuel is strange. Now if it's ONLY during roll ons or wide open, then we can blame the main jets, we haven't really messed with the mains yet. But if it's passing fuel at normal cruising speeds/throttle positions and your MPG was still bad, it just doesn't figure.
What was your trip MPG? How was it ridden?

Keith, I have no idea what I am talking about
The feelers I used were the ones Joe gave me and I am sure they
are right. They had a .0??? on the one and the other was the .08 you mention. It was 15 or 1.5 to 3 something. Terrible I know :roll:

They are right now. The best MPG stayed the same. 30 HW and 24 City.

It rode strong. I was able to keep up OK. It could be a lot better I know. But it ran strong for as bad as the setup is. But it smoked like a truck brake for the whole trip. The high altitude areas really brought it on.

[Anonymous]

78 GS1K Carb Rejet ? Bad Fuel Economy

Does your bike bog ? Does it seem to have more power when you first start out ? If you have not done any work on your carbs for a long time they may need to be cleaned and new O-rings . I had one hell of a time with my intake boots . Had to change all the intake boots . The O-rings were so flat and dry they fell off the old boots. Hope this can help you

[Hoomgar]

Keith. I am not sure what it may be but there must be something else wrong with this engine?

I now have the DJ 122 mains in and it runs good. Needles are at the fifth position (highest setting). Carbs are in sync. Pilots are 1 turn out on 1 & 4 and 1&1/4 on 2 and 1&1/2 on 3. Air screws adjusted for max idle.

Before I did that I recleaned all the openings in the carbs with carb cleaner then put all the needles back in. I then balanced the float levels with clear plastic tubes in the bowl drain holes so that all four are at the same level. They were actually good except the fuel level in carb 1 was low. Now they are good. I put brand new o-rings in the carb intake boots and helped seal them with hi-temp grease. The valves are all adjusted. That measurment I was looking for was .0015 to .003 inches that was confusing me earlier. It's from the manual. It is right. They all fall right between the two.

It doesn't seem to have quite as much top end/WOT power now but runs pretty good. Midrange is near perfect now and low end is a lot smoother while using a little throttle but still eratic when just cruising.

The kicker is, it still smokes and gets 24 MPG. No matter what we have tried it always gets 24 MPG and smokes.

What else do you think I should check at this point?

[Hoomgar]

OK I have dropped the main jet clear down to a 120 and I think I may be getting there. It seems I may have been going about this all wrong. I was talking with a local vintage UJM carb guru and he said to start with the main circuit first and get your main jet right. Then do your needle and then any idle adjustments that may still need done.

So my question is this. What is the prefered method for doing a WOT main jet plug read test? Just find a nice long open cop free road or what?

Any replies are welcome and wanted.

[Anonymous]

It seems I may have been going about this all wrong. I was talking with a local vintage UJM carb guru and he said to start with the main circuit first and get your main jet right. Then do your needle and then any idle adjustments that may still need done.

I might as well reply, since Keith K hasn't yet...

It is better to start at the bottom and work your way up (ie. pilots, then needles, then mains) than starting with your mains. The biggest reason is that what you do to your pilot and needle circuits affects running on the mains, but the mains do not affect running on the lower circuits. You could REMOVE your main jets and still toodle around town (and at legal highway speeds, for that matter) with no problems at all. Especially on a litre bike you will spend almost no time at WOT and most of your time barely off the pilot circuit. So sort those first and then worry about your mains after it runs well at small throttle settings. Actually, once you get the pilot and needle circuits set, it is a piece of cake to size the mains. I do feel your pain on getting the lower circuits set, they can be a bear to sort really well, as you have been showing here.


Mark

[Hoomgar]

Thx Mark. I believe that is the path Keith had me on. I just wanted to see what others thought as well since Keith isn't around right now and I was being told this.

I am getting closer I know. Time to get back to this now. It is running better now on the needle and WOT seems OK too but I get some coughing at idle at times.

Is there a place where I can see how to do all three plug read tests that are recommended?