What's wrong with my carbs?

[drumstyx646]

I'll let the video do most explaining, but the background is that I cleaned and rebuilt the carbs on my 1999 Katana 750 earlier this year, set the pilot screws to 2.5 or 3 turns (forget which, but I recall going between 2 and 3 didn't really make a difference). I rode the bike for a bit; between it and my Vulcan 900 I much preferred the Kat when commuting, for the maneuverability and acceleration.

Anyway, I couldn't get it running for a couple months, then found somehow someone set the idle way high which of course would lean it out on startup. Fixed that a bit. On starting, it revs high, then settles to idle, 'choke' isn't very consistent, making things go wild, but it's either 3000-5000RPM or nearly dying. While warming up, it dies on any throttle, even with choke it seems.

So...pilot circuit still dirty? I don't know how it can be...I sprayed carb cleaner through all the passages (seeing it spray out the other ends) and blew them all out with air after. Is it possible for the passage to be partially blocked, but still allow a seemingly full-pressure spray of carb cleaner through?

Without further ado, here's the vid: https://www.youtube.com/watch?v=d41Ae_gE4_o

[92xjunker]

Yes, it is very possible to have a partial blockage in a passage. Were the carb bodies dipped in carb dip or did you just use canned carb cleaner (doesn't work)? Did you sync the carbs with a sync tool, not visually. Visual only gets you running for a proper sync.

[drumstyx646]

Yes, it is very possible to have a partial blockage in a passage. Were the carb bodies dipped in carb dip or did you just use canned carb cleaner (doesn't work)? Did you sync the carbs with a sync tool, not visually. Visual only gets you running for a proper sync.

I've got a proper sync tool, gauges, not motion pro or anything, but they do the job.

It was only canned cleaner, since I haven't been able to find a dip in Canada.

Come to think of it though, having a peek in there, I recall one of the 2 air jets can come out? I don't think I pulled it because I didn't have a screwdriver with a shaft narrow enough to get in there.

[92xjunker]

Air jets? On the outter lip of the intake bore? Or in the bowl? Either way, yes they do come out and need to be in place for proper carb function.

[drumstyx646]

Air jets? On the outter lip of the intake bore? Or in the bowl? Either way, yes they do come out and need to be in place for proper carb function.

Yep, air on the outer lip. Looks like the pilot jet comes out, and it seems I don't have any tools capable of doing it right now, so im at the hardware store looking for something to work. It's a bit of a long shot given how the circuit looks according to the manual, but worth a look to see if there's gunk in there

[drumstyx646]

Little update. I pulled those pilot air jets, cleaned up the pilot fuel jets again even though they seemed fine, then went from 2.5 turns on the pilots to 3 turns out instead.

WOW. It seems to respond predictably to enricher position, something which was erratic before. Throttle is responsive (except where expected, like coming off the choke too fast).

Once warmed up, I found I couldn't really adjust the idle speed much without it significantly affecting how fast the RPM falls after blipping. This actually makes sense to me, and it seems to just want to idle right around 1050-1100, and no faster.

Aside from wondering if the above unchangeable idle speed is normal, how rock-steady must a carb'd bike's idle be? It's like this https://www.youtube.com/watch?v=gZvDim6iP5s but only jumps and wiggles maybe 50RPM either way, with sometimes a dip to 1000 or a jump to 1200. All approximate, of course.

[92xjunker]

Idle not changeable above 1100 is an issue. Your carbs are still dirty.
Since your in Canada I recommend you use the Yamaha carb dip. A Yamaha dealer should have it or can order it for you. Good cleaner.

[arsenic]

If your carbs don't run well with the A/F screws at 2.5 turns out, they aren't clean. That's not my opinion, that's a fact. The fact that it gets better when you back the screws out to 3 turns is a tell tale sign the pilot circuit is dirty. I'm sure you did a good job cleaning the jets, but that's only part of the circuit. Just because the jets are clean doesn't mean that passage in the carburetor body itself are clear.

[drumstyx646]

Alright, I've found a source for berrymans chem dip in Canada. Cost a pretty penny at $55 shipped for the small pail, but I finally have the heralded juice coming to my doorstep.

Question though: do the throttle plates stay on, or do those come off for a dip too? My cb750 had felt 'seals' for the throttle shafts...is there anything to damage? Carbs 102 seems to indicate dipping with the throttle plates still on...

[arsenic]

Removing them is a PITA, they can stay on. It won't hurt anything.

[drumstyx646]

Removing them is a PITA, they can stay on. It won't hurt anything.

Kind of what I figured. Are there no seals for the throttle shafts? Just a tight fit I assume then?

[arsenic]

No, there are seals, it just doesn't hurt anything to soak them. It it helps you sleep easier at night, go ahead and remove them. I'm telling you, it's not easy and you'll probably end up doing more harm than good.

[drumstyx646]

No, there are seals, it just doesn't hurt anything to soak them. It it helps you sleep easier at night, go ahead and remove them. I'm telling you, it's not easy and you'll probably end up doing more harm than good.

I'm incredibly surprised, but after actually reading materials on the chem-dip, apparently it's officially safe for most rubber and plastics. That blows my mind... I always thought 'the good stuff' had to be hard on anything not metal.

How long should I dip them for? I've read everything from 1 hour to 3 days. I've also heard about it eating metal if left for too long...

[arsenic]

On average, 24 hours is good. No, it doesn't "eat metal" if left in too long. That's 24 hours for each carburetor body. So 4 days. I can't say with 100% certainty is won't eat metal. I've never put something in the dip and taken a trip to the Congo. As long as you're not a complete idiot, you should be good.

[92xjunker]

I have dipped carbs for a week before, no issues.