So, I removed my carbs, and cleaned out the whole fuel side. All the jets are stock, and are now unplugged.
Here's what I found:
Both of the jets that hold the main jet clip thing in were about 1/2 plugged.
Both pilot jets were mostly plugged.
The main jets were fine.
I didn't touch the air side at all.
Before I started, the bike would idle, although a bit high ~1500 - 1800 rpm. It ran lean before, backfiring and everything.
Now, It will idle, but only if I keep on the throttle a bit or keep the choke at about 1/3.
It also sends some smoke out of the right side carb (into the air box) when it dies. I don't know if that's normal, I've never ran without a filter before.
I think the carbs are working good, but I've never had a bike that didn't have an idle adjust knob hanging somewhere. Is there something I'm missing?
I don't have any fancy tools, like vacuum gauges or carb sync'ers. Just the basics.
P.S. It's a 99 750
Should be a Philips head screw On the under side of the carbs that adjusts your idle.
Not sure about the smoke.
Quote from: Cloner on November 16, 2011, 12:45:58 PM
All you need to sync the throttle bodies is a manometer (you can make your own) and a screwdriver. You will need an exhaust gas analyzer to correctly set the air bleeds, though.
Sync and tps can both cause the symptom you've described.
For a twin-cylinder engine you can use a loop of clear tube for a manometer. Use a tube five or six feet long. Fill about two feet of it with fluid. Hook each end of the tube to one of the nipples on the intake manifolds (one at each manifold, obviously) and hang the tube in a loop (high-low-high) so that the fluid is in a vertical position....the oil will fill the bottom foot of the loop, one foot at each leg. The exact amount of fluid is irrelevant. With the engine shut off the fluid in each leg will be at the same level. When you start the bike the cylinder with the greater throttle opening will run slightly faster and will have a higher vacuum signal. It will draw fluid into its leg and away from the other, showing an imbalance between the two legs. Adjust the balancing screw to make the fluid levels even (after you've bottomed the bleed screws).
You can fill it with virtually any liquid. I prefer a more viscous liquid, like transmission fluid or motor oil, as it tends to filter a bit more "noise" than a less viscous one, like water or antifreeze.
Quote from: Carbon 14 on January 10, 2012, 07:26:34 AM
Thanks, I'd heard of this, but this is probably the best "how to" i've read.
I guess I'll be stopping at home depot on the way home today. any idea what size tube?
I'll also check the idle adjusting screw.
I think that the manometer works best with a fairly small tube (something like 3/16" inner diameter works well for me), but you need a bit bigger than that to fit over the nipples (I think a little bigger than 1/4", maybe 5/16"?). Automatic transmission fluid works nicely in the manometer (really easy to read because it's red, and it wouldn't ruin your engine if everything went terribly wrong and fluid got sucked up into the intake manifold). You'll have to let the ATF settle for a few hours at least for the bubbles to go away. I took a few quick videos of mine before and after mostly for my own reference, but if you want to see what it looks like before/after, here you go:
Before:
Ducati m750 carb sync results - before (http://www.youtube.com/watch?v=WcZRSFAIY14%3Cbr%20/%3E#)
After:
Ducati m750 carb sync results after (http://www.youtube.com/watch?v=Fcahij8dwD8#)
Note that the bike was running fairly well before, so the difference in heights may be much more for yours. It's pretty much impossible to get the two lines perfectly aligned in my experience, but according to an article that I read (http://www.powerchutes.com/manometer.asp (http://www.powerchutes.com/manometer.asp)), a difference of roughly 3/4" with this setup translates to a difference in height on a mercury manometer of 1/20", which is practically indistinguishable. Another good how-to article is here: http://www.airheads.org/content/view/183/98/ (http://www.airheads.org/content/view/183/98/) .
Cool. I'll probably just try witht the bigger tubing, don't want to mess with adapters for something I'll probably only use once. It should tell me if they are way off, or if they are fairly well matched. I don't need perfection, just decent.
And I'll probably go with regular oil. I have some left over from my last oil change.
Thanks for all the help guys!! I'll post some results when I can.
Ok, so I built a sync tool. I used 1/4" ID tubing, 10' long. strapped it to a 2x2 and put some mobil1 v-twin oil in it. I would use slightly bigger tubing next time, maybe 5/16"ID. It was a tight fit getting it on those manifold nipples.
Worked great. My carbs were way out of sync.
Adjusted my idle to around 1k. My manual says it should be 1100-1200. What do you guys think?
Anyway, it is kinda acting like it did before I started all of this, which is: It starts fine, idles fine, but sometimes idles high and won't drop all the way into idle. Hovers around 1500, and maybe drops down after anywhere from a few seconds to a few minutes. Could my air/fuel mix be off? I know where to adjust it, but how do I know how much to adjust?
This is a symptom of a high idle though there are other possibilities. If you are using the tach on the bike as a guide even though it reads 1K RPM you might be idling faster. Factory tachs are not as accurate as the ones used when tuning.
Try turning your idle mixture screws out (anti clockwise) half a turn. A tiny flathead screwdriver is needed. A hanging idle is often a sign of lean idle mixture, or a vacuum leak from the inlet manifold. Go also for the recommended idle speed. That is a phillips head screw up between the carbs on stock carbs and easier to see than the synch screw.
Let us know how you go.
i'll try to rich it up a bit. my manual didn't way which way to turn to make it richer, so now I know. I would rather run rich than lean anyway. Thanks!
Well, some spring updates, and a new question or two.
The idle is fine now, must have just been cold before.
It has now developed a hesitation. Starts fine and idles great and smooth. When I go for a ride, it has a bit of a hesitation when I hit the throttle at around 5k-6k. It takes a split second, and then it goes fine. Maybe a fuel delivery problem? Pump? Float? I didn't mess with the floats at all when I had the carbs apart.
Suggestions? easy things to check or adjust?