Topic: "Help Juntjoo fix his CB650!" thread

[juntjoo]

how do you set the black idle knob without the engine running?  If I recall correctly somewhere close to having it turned all the way in it uncovers the hole, I believe it's the closest slow speed (jet?). What's the best way to ensure this is as close to not causing a problem?

also, how's my spark?

keep in mind I recently got it to fire on all four quite well albeit very high at idle. And I have the pilot screws turned out a couple times . I'm going to grab some new plugs only just to see but I won't open them if you guys convince me I should try something else at this point. So I'll keep the receipt. What do you think?

[Scott S]

 That's plenty of spark.

 I'm still not convinced that your carb base settings are correct.
 Maybe it's just a communication breakdown, but some of the ways you describe things make me think something's not quite right. The idle screw, bench sync, something. Can't put my finger on it, and maybe it's just trying to read stuff on the 'net.
 I kinda wish I could put my eyes and hands on them!

[Yamahawk]

Unscrew the Black knob while your bike is running, that will lower your idle speed. Don't screw it all the way in, as that will raise your idle speed to a very high rpm.
Charlie

[juntjoo]

That's plenty of spark.

 I'm still not convinced that your carb base settings are correct.
 Maybe it's just a communication breakdown, but some of the ways you describe things make me think something's not quite right. The idle screw, bench sync, something. Can't put my finger on it, and maybe it's just trying to read stuff on the 'net.
 I kinda wish I could put my eyes and hands on them!

well, I cleaned the two jets that really appear in same shape as my new ones, pilot screws turned out a couple turns, presumably fixing carb boots got all four going, after last overhaul, after all four ran for a bit, gas made it to vent tubes(forgot to plug it to air box=spill) initially only, now here we are.

Could the spark be off? if so is there a way to check that without running engine(ie check timing plate alignment with piston position? Anyone possess the magic question(s) that would lead to answer here? or what else possibly can I do at this point?

[juntjoo]

Okay, got it going. looks like it just needed a good battery charge and a good crankin' but now we're back two steps where I'd just got it running on all four but it idles at like 2krpms and turning the black idle knob out didn't lower it a bit (step 1, adjust knob to attain 1k rpm). BTW, how to get that knob back on? it turned out all the way off. having trouble screwing it back on. anyway, i'll start searching but just wanted to update. will report back if I find something. getting close!

oh, and pilot screws out 2&1/4. also tried them completely closed to no effect. so all idle controls set, or out of the way.  it's like it's just waking up and wants to run. that would be bad ass diagnosis from a mechanic. 'she just needs to be taken out and ridden til she's tamed'

and throttle is not being pulled on it's own, cable adjusted

and when it first starts(I'm guessing after a while) it revs high as mentioned but also climbs on it's own to about 5-6krpms I believe as I had to either kill it or open choke.

Okay, found leaks at the boots again at 3&4. so that should be it no? extra air flow basically like opening the throttle right? I think I'll try to temp repair them again somehow while waiting on an order of new ones and just replace them next time they fail.. am I on the right track? will report back...

mm... just pretty much stopped leaks by tightening boot clamps, if not completely then 98% and no difference. Can't keep choke closed without it screaming

[juntjoo]

[Scott S]

 ". Can't keep choke closed without it screaming"

 That, for example, confuses me. The choke is closed for warm up, open when running.

 The advancer mechanism,  the one with the timing marks on it, has a pin that locates it on the crank. As long as that pin is there, it only goes on one way.
 Then adjust the plates so that the mark lines up at the II marks for the F at ~2500 rpm.

 There are a few things that can make the engine run too fast:

- timing advanced too much. I don't think you can advance it enough to make it run at 6k rpm, though.
- lean condition. This can 've from incorrect jetting, vacuum leaks, fuel level, the air filter choice (which is really just mismatched jetting), etc. Are you doing these tests with the air box and filter off? Are you running pods?

-the high RPM could be the mechanical settings on the carbs.  I think you may have the butterflies set too far open from static. Are you sure you're not changing things when you install the cable? The fact that you can back the idle knob completely off and it still idles at 6K tells me the butterflies aren't right. It IS possible to assemble things so that when they are "at rest" they are incorrect and too far open.

 Man, I wish I could put my eyes and hands on those things.

 You're 100% correct to make sure the boots and clamps are good, too. BTW, the Honda clamps have built in "stops" of sorts. You can only tighten them so much.

[Scott S]

 You posted the video while I was typing. I see the air box.

 What is that sticking out of the #3 carb? Is it capped or open to the atmosphere?

 My CB650 engine didn't have that style choke; it had a knob you pulled up. Are you sure you're not operating the choke backwards?

[juntjoo]

You posted the video while I was typing. I see the air box.

 What is that sticking out of the #3 carb? Is it capped or open to the atmosphere?

 My CB650 engine didn't have that style choke; it had a knob you pulled up. Are you sure you're not operating the choke backwards?

I'm post another vid soon to answer your questions best I can and hopefully help you 'get your hands' on it better, but basically I couldn't detect any issues you suggested. I like the idea of the throttle being held open so I'll keep looking into it but I 6 think you'll see in the upcoming vid it closes completely when it should.  thanks...

[Yamahawk]

After watching and listening to your video, it seems to idle ok. The choke is functioning properly, as its adds fuel to the enriching circuit. I seem to hear valve noise though, a whole lot of clicking. Either that or it is bearing noise... but sounds like valves to me. No leaks at the intake boots, that's good, I assume you are using either starting fluid or carb cleaner in that can. Your idle should be around 1200rpm, so that's ok also. I would take it for a ride with the choke off after warming it up. Use some Seafoam in your gas tank, and follow the directions for 1 oz per gallon of gas. See if it doesn't clear thing up. Seriously, I think it isn't running badly, and you need to listen to those valves again or have another fellow listen to them They send like too loose on at least one cylinder, which is better than too tight...
Charlie

[Scott S]

 That barb sticking out of the #3 carb....is it capped off or open to the atmoosphere?

[juntjoo]

That barb sticking out of the #3 carb....is it capped off or open to the atmoosphere?

capped off

[Yamahawk]

Ok... vent tubes leaking gas... are these the overflow tube off the bottom of the bowls? If so, your float needles are not sealing, and allowing gas to flow when it shouldn't. Does gas leak out of these when the bike is off? If so, you need new float needles, preferably with neoprene tips.
Charlie

[juntjoo]

Ok... vent tubes leaking gas... are these the overflow tube off the bottom of the bowls? If so, your float needles are not sealing, and allowing gas to flow when it shouldn't. Does gas leak out of these when the bike is off? If so, you need new float needles, preferably with neoprene tips.
Charlie

Well that happened only once right after i last put up the carbs so it looks to have been something, some temporary blockage or fuel rushing through initially. idk but it doesn't appear to be a problem anymore. I'll keep my eye on it next time. thanks

[Yamahawk]

As you have a vacuum petcock, turn it to the PRIME indicator, and see if they leak gas with the engine off. If they do, your float needles are leaking by. If the floats are too high in the bowls, it will leak through the overflow tubes, also. As you have 4 float needles, you can pinpoint the one leaking by the tube the pees gas. The same with the float being too high...
Charlie

[Scott S]

 The 650 has plastic, non adjustable floats. If replacing the needle valves doesn't fix that....and it probably will...you have to replace the floats. You can't adjust the height on them.

[Yamahawk]

Ok, got it, thanks Scott! Then if it leaks, the needles and possibly seats need r&r
Charlie

[juntjoo]

I took out my vacuum petcock. And unfortunately I don't have overflow tubes. They just didn't make them for mine tho there is spot for where they'd be as I've seen in my carbs for other bikes, like the 750 I think.

Anyway, so one bowl at a time, I'll take the cover off and hold the float up with a finger while adding gas then test to find the point, if any that the float needle stops the flow of gas. Good idea? I'll assume so and report back. I'll also do the handlebar test

[juntjoo]

testing floats

[Scott S]

 That's a pretty ingenious little tool you made there.

[juntjoo]

That's a pretty ingenious little tool you made there.

thanks, can you make that it's own little thread? nah, it wasn't even worth it, but it was a fun exercise. your finger can handle it just fine, as a matter of fact if you have a catch tray long enough and you only use so much fuel you can do two at a time.

anyway, I think I got it. 92.65% sure I do. But feel free to guess before I reveal.  Gotta fix it first tho...

[scunny]

You shouldn't have to undo the drain screw that much. how come gas isn't coming out the overflow ?

[juntjoo]

okay, i dont want to kill anyone with suspense so here it is: 

it's the fast speed idle linkage, the one bendable arm, if adjusted too close to the throttle it will open it too much. I adjusted mine to the book, stupid book. it was probably fine as it was.... and in reality the PO wasn't as much of a POS as I gave him credit for and this bike in the end(just about there) it didn't need new charging or ignition system components or messing with the head. Just a carb tune up, I only needed a couple o-rings from the whole kit, replace rubber from MC to calipers, pads still new from the 80's, and replace a few bolts.

[juntjoo]

You shouldn't have to undo the drain screw that much. how come gas isn't coming out the overflow ?

mine are the ones that don't come with that tube. which I guess is a good thing I'm using clear tubes for my vent line.

[juntjoo]

I'm pretty sure i just need to readjust it AGAIN. at the end of the vid you can see a side by side of the different amount of throttle movement a good fast idle and one that goes out of control. only thing is with me trying to simulate the choke effect on throttle it's without the actual choke closed so idk if that's a good comparison. anyway, I'm getting pretty good at taking these carbs on and off lol

actually, what confuses me is the gradual climb. Is that normal choke function? If not then maybe I'm chasing the wrong guy?