Yamaha Starbike Forum banner

1 - 9 of 9 Posts

·
Registered
Joined
·
98 Posts
Discussion Starter #1
I have an '04 650 that's been parked for two years, now it's having idling problems. Here's the rundown; I drained the gas, pulled the carbs and thoroughly cleaned them, cleaned pilot jets (numerous times through this process), scrubbed every piece, looked through every manual and website I can find. Still don't think I've fixed it properly.

Before I parked it, I installed a Baron's Big Air Kit. Followed instructions, installed 130 main jets, 22.5 pilot jets, new needles with clip in 4th slot, mixture screws 3.5 turns out. Everything precisely per instructions. But, I never rode it to get it set properly. Now after sitting, I went to start it, and couldn't get it to idle without choke. Yesterday, I pulled the needles and moved the clip to the 6th space, then messed with mixture screws until it idled good, and until popping disappeared, as per Mikuni website. Now the screws are 7.5 (front) and 8 turns (rear) out. Since I see everyone else is fine at 3.5 turns, I can't help but think that something else is screwed up, and the mixture screws are simply compensating for it. But at least now it runs without the choke. After a short test ride, I hit the brakes, and it stalls out. (since it's not registered anymore, all I can do is end of street and back, but up to 30 mph) When I went to park it, lean it over on the kickstand, and it stalls. I believe that shows a float level problem, but I'm 100% positive I didn't alter the floats or the little tab that connects to the needle in any way.

What the heck is goin on!?!?!?!?!

One other point, I noticed a vacuum hose that ran from the carbs to near the rear of the air cleaner. For some reason I can't find this hose adressed anywhere, but I plugged it, and made it run better, so I left it plugged. AIS has been removed.
 

·
Registered
Joined
·
98 Posts
Discussion Starter #2
Update, figured out the hose I plugged is the carb vent hose, so I unplugged it. Doesn't want to start at all this morning. Wants to fire when you crank it, but if I give even a little throttle, kills any sound of firing, just cranks.
 

·
Registered
Joined
·
1,324 Posts
Update, figured out the hose I plugged is the carb vent hose, so I unplugged it. Doesn't want to start at all this morning. Wants to fire when you crank it, but if I give even a little throttle, kills any sound of firing, just cranks.
check the bowl levels with a piece of clear tubing then go from there. doing that will at least tell you the pump is working and carbs are full.
 

·
Registered
Joined
·
98 Posts
Discussion Starter #4 (Edited)
Thanks Paul.

Just another update; on a whim I went out and started it again last night. Fired up instantly (with the choke on). Then I took a piece of duct tape and with the air filter off, I covered about 3/4 of the air filter joint. Ran like a champ. I noticed before what I believed was some superficial surface cracking on the joints between carbs and cylinders. Pretty sure they're much more than superficial now. So, I'm gonna start by replacing those joints, clamps and o-rings, as well as the upper joints to the air box. I'll check back later and update that. I will also double check the float levels, though I believe what was happening was I was just dumping so much fuel into the heads that the carbs, even set properly simply couldn't keep up.


Also, anyone have a line on some better vaccuum caps for the joints? these have only been on there for a couple months and one is already cracked. And, the bike wasn't even running.


PS, don't ever walk in the house pissed and forget to turn off the key. Word is that will kill the rest of the night for ya. Or so I've heard.
 

·
Registered
Joined
·
1,324 Posts
when all the ducts and intake boots are tight with no leaks anywhere in the system the air box is pretty noisy especially at low speed in 5th at least mine is. so i'm insulating the silencer box inside and out with 1/8 rubber soundproofing material, i'll let everyone know how it worked in the spring. as far as a vacuum cap go's a short piece of hose with a nice short stainless carriage bolt threaded in always worked for me.
 

·
Registered
Joined
·
98 Posts
Discussion Starter #6
Well I got it figured out. Along with the vacuum leaks, the throttle position sensor also tested bad. So after replacing that, and the joints, returning the needles to the 4th slot, and the PMS screws to 3 1/2 turns, she runs great. A wee bit of tuning and sync'd the carbs, she settled at 3 1/8 turns front, 3 1/4 rear.

So, lessons learned, vacuum leaks will cause all kinds of fits, and a 90 degree screw driver is essential for adjusting the mixture screws, unless you want to spend $50 on the after-market finger adjustable screws. You DO NOT want to strip the head of one, and have to use a screw extractor to get it out. Incidentally, the thread chaser size is M6 x .5, (extra fine) and a real mutha to find. :surprise:
 

·
Registered
Joined
·
1,324 Posts
Well I got it figured out. Along with the vacuum leaks, the throttle position sensor also tested bad. So after replacing that, and the joints, returning the needles to the 4th slot, and the PMS screws to 3 1/2 turns, she runs great. A wee bit of tuning and sync'd the carbs, she settled at 3 1/8 turns front, 3 1/4 rear.

So, lessons learned, vacuum leaks will cause all kinds of fits, and a 90 degree screw driver is essential for adjusting the mixture screws, unless you want to spend $50 on the after-market finger adjustable screws. You DO NOT want to strip the head of one, and have to use a screw extractor to get it out. Incidentally, the thread chaser size is M6 x .5, (extra fine) and a real mutha to find. :surprise:
i'v sprayed plasti dip on the outside of carb joints to seal micro cracks and it works and holds up very well.
 

·
Registered
Joined
·
98 Posts
Discussion Starter #8
Never thought about that. They're just rubber anyway. But, since I'm sellin this one, I wanted to do it right. Hate having someone else inheriting my problems.
 
1 - 9 of 9 Posts
Top