Carb/Starting Issue

Thought I posted this here already but couldn't find it on a search.

Starting procedure when engine is cold. Turn on petcock, pull the choke knob out, turn ignition on and wait for fuel to stop clicking, hit starter button. Should fire up instantly and go to high idle like my previous RSV's but doesn't.

Will only start if I crack the throttle slightly. Then it takes a little while to go to high idle. One would think it is running rich, but I don't think so seeing that the the caps are still on the idle mixture screws and factory settings are usually lean.

Other than that, it runs great. Starts instantly once warmed up. Pulls hard, crisp acceleration, averaging anywhere from 42 to 48 mpg mostly 2 up riding. It has a new fuel filter and carbs are synced and there are no vacuum leaks.

Pulled the carbs today. Much easier than a 1st Gen for sure. Plugged all the openings and gave them a good exterior cleaning for disassembly. I decided to check the choke mechanism and noticed that the slides that contact the choke plungers were out of alignment. When pulling out the choke knob slowly, the slide on the right side came in contact with the plunger tips and the left side was still approx a strong 1/16" to almost 1/8" away from contacting the plunger tips. Thus the plungers were not in sync on the right and left side. A quick tweak of the linkage, they are back in sync. I don't know if that was the problem, but I am not going to put the carbs back on to see if that fixed the problem, only to have to take them back off if it didn't fix it.

Opened one of the float bowls and everything is sparkling clean in there. Pulled the main and pilot jets and they look like new, float height is right on. Blasted some carb cleaner and compressed air thru the choke venturi hole, then pulled the idle mixture screw after counting turns in. Blasted that and the pilot jet hole and put put it all back together.

So as I thought, the problem has nothing to do with anything in the float bowls except for maybe something along the lines of the pilot circuit and choke venturi. Maybe. It has to be somewhere in the choke circuit. I noticed 2 jets on the intake side of the carb. What are these for? Haven't pulled them yet to inspect. I ask because when I pulled the carbs, there seemed what appeared to be a very slight amount of extremely fine dirt along the outer edge of the intake. Almost film like. I mean a very slight amount. Not on the outside of the carb , actually on the inside of the outer edge of the intake. I don't know what those jets do and if they have anything to do with air flow at choke or pilot circuit. I am thinking that they may be clogged from this film.

1 other thing, I noticed some random very fine, very small white fibers, for lack of a better term, in the air box that attaches to the carbs, so I pulled the air filters and I could see some of these same fine fibers in the tubes the filters attach to. They look to be the same material as air filters? Wondering if that stuff is maybe clogging something.

The jets you see on the intake side are air jets. Been awhile since I've been in 2nd gen carbs but I believe there should be 3 total. One or more may be under the diaphragm. They typically aren't a problem but it wouldn't be a bad idea to spray some carb cleaner and compressed air through them while you're at it.

The film you see is probably some oil with a little carbon in it. Shouldn't be an issue.

I think you're probably a tad lean. As you pointed out they come from the factory so lean they barely run. Then over time some of the rubber bits age and start to leak just a bit of air pushing it over the edge. Since the caps are still on the idle screws it's likely they've never been opened up from the factory setting. I'd add 1/2 turn out from where they were set while the carbs are out. 2nd gen mixture screws are tough to get to with the rack on the bike.

Also, make sure you squirt some carb cleaner through the idle jets. Ethanol fuel can make little clear globs that pass light just fine but will stop up a small jet.

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Boy...I don't know. Guess it won't hurt to continue on the carbs... but I think you found the problem with the choke/enrichment circuit not being in sync. If she pulls hard and gets great mpg's....the rest of the carbs should be in great shape![/color]

Quick question, when was the last time you changed your plugs??They may be OK enough for running, but maybe for starting the spark is not quite up to snuff. The reason I ask this is that it is a known fact that our bikes eat plugs and ideally should be changed at 10,000-mile intervals or less! Using Iridium plugs helps to make the interval longer. NGK's work best in the Venture. Also, you may want to measure the resistance of the plug wire caps, corrosion can and will get into the spring and disc causing a higher resistance.

So, if carb work does not fix the issue, I would explore spark next...

I haven't gone any further since my first post as I only had about an hour to kill when I started tearing the bike down. Tomorrow or Friday I will hopefully be able to clean all the jets, passageways etc. Wish I knew what model mikuni carbs they are and some kind of documentation on them so I know which direction the jets and passages flow through the carb. I prefer not to blow them out in the direction they flow so as not to force any possible foreign material further into the passageways. I'll take my time and figure something out.

The jets you see on the intake side are air jets. Been awhile since I've been in 2nd gen carbs but I believe there should be 3 total. One or more may be under the diaphragm. They typically aren't a problem but it wouldn't be a bad idea to spray some carb cleaner and compressed air through them while you're at it.

 

The film you see is probably some oil with a little carbon in it. Shouldn't be an issue.

 

I think you're probably a tad lean. As you pointed out they come from the factory so lean they barely run. Then over time some of the rubber bits age and start to leak just a bit of air pushing it over the edge. Since the caps are still on the idle screws it's likely they've never been opened up from the factory setting. I'd add 1/2 turn out from where they were set while the carbs are out. 2nd gen mixture screws are tough to get to with the rack on the bike.

 

Also, make sure you squirt some carb cleaner through the idle jets. Ethanol fuel can make little clear globs that pass light just fine but will stop up a small jet.

Thanks for the info. I was almost certain that they were jets. There's only 2, none under the diaphragm.

Quick question, when was the last time you changed your plugs??They may be OK enough for running, but maybe for starting the spark is not quite up to snuff. The reason I ask this is that it is a known fact that our bikes eat plugs and ideally should be changed at 10,000-mile intervals or less! Using Iridium plugs helps to make the interval longer. NGK's work best in the Venture. Also, you may want to measure the resistance of the plug wire caps, corrosion can and will get into the spring and disc causing a higher resistance.

 

So, if carb work does not fix the issue, I would explore spark next...

I put new Iridiums in early spring 2017 while snow still on the ground along with new tires, fuel filter, oil change, radiator flush, brake fluid flush, brake pads etc. I bought it in November 2016, winterized it and put it to sleep for the winter. Bike only had just over 4300 miles on it. Now just under 12,000 miles on it. It's getting new plugs this winter along with other maintenance items like new air filters since I noticed those tiny white fibers that look they are coming from the filters and also a few upgrades as well. It had the starting problem since day one that I got it.

Wish I knew what model mikuni carbs they are and some kind of documentation on them so I know which direction the jets and passages flow through the carb.

The passages are a lot larger than the opening in the jet. Anything that gets through the jet will blow on through.

I clean a lot of carburetors every year. I always pull the fuel jets, blow carb cleaner through them and then compressed air through them. I rarely pull the air jets, just spray carb cleaner through and then blow them out. You should do all that with the slides, mixture screw assembly, choke cylinders and coasting enrichners (air cut off valves) removed. Carb cleaner is hard on rubber parts so don't let the bodies soak - blow out with compressed air shortly after spraying them.

The passages are a lot larger than the opening in the jet. Anything that gets through the jet will blow on through.

 

I clean a lot of carburetors every year. I always pull the fuel jets, blow carb cleaner through them and then compressed air through them. I rarely pull the air jets, just spray carb cleaner through and then blow them out. You should do all that with the slides, mixture screw assembly, choke cylinders and coasting enrichners (air cut off valves) removed. Carb cleaner is hard on rubber parts so don't let the bodies soak - blow out with compressed air shortly after spraying them.

How about using Spray Seafoam and let it sit for a little while before using compressed air? I am trying to avoid breaking up the 4 carb assembly. The only reason I would have to break them up is to disassemble the coasting enrichers. I can get everything else with rubber removed without breaking up the assembly.

Basically, I am trying to not to disturb the TPS.

Carb cleaner is a lot more powerful for cleaning when the carbs are being worked on.

If it's too much trouble to get at the coasting enrichners then I'd only use compressed air on the carb body.

Pull the fuel jets (especially the slow jet) and clean them with carb cleaner. Blow out the body with compressed air.

NOTE: Don't push any kind of wire through the jets, it doesn't take much to damage them.

Yesterday, I wound up taking every carb apart but left the TPS on the side bracket. Soaked everything, blasted all the jets with carb cleaner and compressed air then reassembled everything. Had some time this morning to put everything back on the bike. Started instantly with the choke on although not at high idle, but still a pretty good idle. First time this bike has started for me without cracking the throttle a little so things are looking up. It did smell rich so needs a little tuning.

Once warmed up it revved good but a slight popping when closing the throttle on one of the right cylinders. Again a little tuning and a sync. Will use my Colortune then sync.

3 of the carbs fuel adjustment screws from the factory were fairly close, but the #4 cylinder was quite a bit different that I thought was kind of odd. Would suspect that's the cylinder that's popping when I close the throttle.

(Rear left = #1 Idle screw 1 3/4 turns, Front left = #2 Idle screw 1 7/8 turns, Rear right = #3 Idle screw 2 1/8 turns) (Front right = #4 Idle screw 1 turn)\

I will probably dial everything in tomorrow morning.

Oh, wait a minute. No I won't.

Merry Christmas everyone!