Topic: "Help Juntjoo fix his CB650!" thread

[Yamahawk]

How to get a large seized philips head scew out. https://imgur.com/a/pOOyY

Here is what you need... this, and a hammer!
https://www.ebay.com/itm/TEKTON-2905-7-pc-3-8-in-Drive-Impact-Screwdriver-Set/252647790242?epid=2254312164&hash=item3ad2fb56a2:g:Bk8AAOSw~HBaLpXa

Charlie

[juntjoo]

How to get a large seized philips head scew out. https://imgur.com/a/pOOyY

Here is what you need... this, and a hammer!
https://www.ebay.com/itm/TEKTON-2905-7-pc-3-8-in-Drive-Impact-Screwdriver-Set/252647790242?epid=2254312164&hash=item3ad2fb56a2:g:Bk8AAOSw~HBaLpXa

Charlie

interesting didnt know they existed

[juntjoo]

so timing didn't help. going to sleep...

[juntjoo]

here's a vid on the timing. Still inconclusive.

[juntjoo]

quick 1 min vid. vac gauges all fluttering

[Yamahawk]

quick 1 min vid. vac gauges all fluttering

did you instal the little valves in the rubber tubing? If so, throttle the valve closed until the fluttering minimizes. Each vacuum gauge should have its own valve inline with the tubing, thats how you get rid of the flutter. Close the valve, until it still gives a reading, but the flutter in almost gone.
As for your timing, I still think you are chasing the wrong area, ignition and timing are not going to change your fuel mixture being rich on those two cylinders.
Charlie

[juntjoo]

quick 1 min vid. vac gauges all fluttering

did you instal the little valves in the rubber tubing? If so, throttle the valve closed until the fluttering minimizes. Each vacuum gauge should have its own valve inline with the tubing, thats how you get rid of the flutter. Close the valve, until it still gives a reading, but the flutter in almost gone.
As for your timing, I still think you are chasing the wrong area, ignition and timing are not going to change your fuel mixture being rich on those two cylinders.
Charlie

Well I didn't think so either, I was just covering all bases as someone suggested. And thanks for the tip on the gauges. I wondered what those little things were. Now, I think I have good news, but I'm going to hold back going to the store right now to grab a little something that MacGyver would have on hand and see if I can work some magic.  ill upload video

[Yamahawk]

cut the tubing, and insert the valves.. easy peasy!
Charlie

[juntjoo]

cut the tubing, and insert the valves.. easy peasy!
Charlie

huh?

[Scott S]

 Your timing video seemed to be at idle. The T mark is used for the valve adjustment.  Ignore it when checking/setting the timing.
 The marks for the F won't be on the II marks at idle. Those are the advance marks. They should line up to the marks at around 2500 rpm .

[Scott S]

quick 1 min vid. vac gauges all fluttering

 Yeah, definitely need the dampers inline.

 Don't mess with the carbs too much until you've confirmed timing. Carbs come last.

[Yamahawk]

cut the tubing, and insert the valves.. easy peasy!
Charlie

huh?

Well, did your gauge set come with separate short pieces of rubber tube? (4 of them) If not, you can cut the tubing about 3" from the gauge, and insert the little valves in each side of the tubing you just cut. The valves will have a barbed nipple on each side of it, that you insert into the tube you cut, (making two ends) and then adjust the valve to minimize the flutter of the needles. Closing the valve smoothes the intake pulse. Do all 4 evenly, to make the needles look the same as to wagging back and forth, don't mind if they aren't on the same place on the gauge, that is what you are going to sync them for, as the needles may not be the same reading, and so you want to follow the sync procedure if they aren't.
Charlie

[juntjoo]

so I had discovered vac leaks at the carb boots, and spraying carb cleaner in them, 1&3, the cold ones, would cause the engine to rev and that would heat up their headers woo hoo, but that doesn't kean anything as 2&4 have leaks too and spraying on their boots stalls the engine. What does this tell you if anything new? I thought the normal response to spraying would be engjne revving not stalling, which if true, ironic how the good cylnders stall while bad ones run better. I can take anyones suggestions but it helps to male some sense and I'm pretty lost here. What do ya think?

[Yamahawk]

so I had discovered vac leaks at the carb boots, and spraying carb cleaner in them, 1&3, the cold ones, would cause the engine to rev and that would heat up their headers woo hoo, but that doesn't kean anything as 2&4 have leaks too and spraying on their boots stalls the engine. What does this tell you if anything new? I thought the normal response to spraying would be engjne revving not stalling, which if true, ironic how the good cylnders stall while bad ones run better. I can take anyones suggestions but it helps to male some sense and I'm pretty lost here. What do ya think?

1 and 3 cylinders are getting no fuel at idle... fix the leaks, clean the idle mixture passages and pilot jets, on 1 and 3. Repeat as necessary... You have just confirmed spark, and ignition is now not the issue. Clean your pilot fuel passages, for your idle mixture, set all your idle mixture screws at 1 turn out, adjust from there.
Charlie

[juntjoo]

so I had discovered vac leaks at the carb boots, and spraying carb cleaner in them, 1&3, the cold ones, would cause the engine to rev and that would heat up their headers woo hoo, but that doesn't kean anything as 2&4 have leaks too and spraying on their boots stalls the engine. What does this tell you if anything new? I thought the normal response to spraying would be engjne revving not stalling, which if true, ironic how the good cylnders stall while bad ones run better. I can take anyones suggestions but it helps to male some sense and I'm pretty lost here. What do ya think?

1 and 3 cylinders are getting no fuel at idle... fix the leaks, clean the idle mixture passages and pilot jets, on 1 and 3. Repeat as necessary... You have just confirmed spark, and ignition is now not the issue. Clean your pilot fuel passages, for your idle mixture, set all your idle mixture screws at 1 turn out, adjust from there.
Charlie

thanks. at all ranges tho. only way to get them to fire is carb spray.

i thought idle mixture and pilot jets were the same. oh, the ones you adjust the black knob over? that single one in each throat?

okay, so pilot allows air passage where idle mixture allows fuel?

but this won't matter if they won't fire under acceleration

either way, I can get at the idle mixture from under the bowls with an E wire? pilots too. I  forget exactly what I did when they were out. Just sprayed carb cleaner through each hole and pushed the wire through

[Yamahawk]

Well, if it ain't getting ANY fuel, there is a problem with your gas feed into the two carbs that are dry. Open the float bowl drains for 1 and 3, and see if there is ANY fuel there at all. If not, see why not. If so, your float levels are off, or your float needles are not opening. Hard to say without looking at it. Hmmm... when you say your pipes are cold, are you saying you can touch them and not get burnt, even when you rev up the engine?
Charlie

[Scott S]

 Aren't the floats for the CB650 plastic and non-adjustable?
 And do your mixture screws have the little ears on them that stop adjustment (the old EPA thing)? I had a set of CB650 carbs once and I ground off the little ears so I could extend the range of adjustment on the mixture screws.

 The pilot jets and the mixture screws are NOT the same thing. They share a circuit, of sorts, and are both important for low speed operation, though. Are the mixture screws on the air box side of the carbs or the engine side of the carbs?

[juntjoo]

Well, if it ain't getting ANY fuel, there is a problem with your gas feed into the two carbs that are dry. Open the float bowl drains for 1 and 3, and see if there is ANY fuel there at all. If not, see why not. If so, your float levels are off, or your float needles are not opening. Hard to say without looking at it. Hmmm... when you say your pipes are cold, are you saying you can touch them and not get burnt, even when you rev up the engine?
Charlie

correct on touching the headers. cold. warm just because their next to the hot ones. all are getting fuel. 1&3 plus are wet.

[juntjoo]

Aren't the floats for the CB650 plastic and non-adjustable?
 And do your mixture screws have the little ears on them that stop adjustment (the old EPA thing)? I had a set of CB650 carbs once and I ground off the little ears so I could extend the range of adjustment on the mixture screws.

 The pilot jets and the mixture screws are NOT the same thing. They share a circuit, of sorts, and are both important for low speed operation, though. Are the mixture screws on the air box side of the carbs or the engine side of the carbs?

the engine side. only #4 made any noticeable difference, and it's also the most powerful one. 2 fires too but like I said with my hand at the exhaust, the sound, little more heat, seems like #4 is the healthiest. 2 not far behind.

[Yamahawk]

But you state with starting fluid, you get a hot pipe on all 4 cylinders, correct? That is a fuel problem for sure... when you add a combustible fluid, it runs.
Charlie

[Scott S]

 If the mixture screws are on the engine side they meter fuel. In is lean, out is rich.

 A few posts back I commented on the timing. Did you set it at idle or at advance, with the engine at ~2500 rpm?

[juntjoo]

If the mixture screws are on the engine side they meter fuel. In is lean, out is rich.

 A few posts back I commented on the timing. Did you set it at idle or at advance, with the engine at ~2500 rpm?

at idle thanks. And Yes I have the ears but I actually cut off the stops on the bowl covers

[Scott S]

 Set the timing at advance. Run it up to ~2500 rpm and set the plate so that the II marks for the F line up to the notch on the case.
 It's off if you lined up those marks at idle.
 

[Scott S]

 This is a 500/550 advancer but the concept is the same. Rev the engine up and adjust the plate so the notch on the case lines up between the blue and green marks in the picture. Forget where it falls at idle.

[juntjoo]

But you state with starting fluid, you get a hot pipe on all 4 cylinders, correct? That is a fuel problem for sure... when you add a combustible fluid, it runs.
Charlie

Okay, so 2&4 bog the engine with carb spray, meaning they got enough fuel already, so that's normal, whereas 1&3 not getting enough BUT the plugs are wet...

Also, compression is slightly higher on them I noticed on my single compression test,

compression 1,2,3 & 4 https://imgur.com/a/MXrkx

if that MIGHT mean something.  So the black on the plugs shouldn't be oil, especially if they have better compression than 2&4

Thanks Scott for the explanation on the pilot jets. I was thinking air and was confused on how the book was repeating what you said about lean vs rich. And I was going by my own assumption it was air. So if 1&3 are blocked, that would affect overall operation but not be necessary under full throttle, where as Ive noticed no change. But maybe I really need to test that out again, like disturb my neighbors? I usually work on it at night so I'll try to get at it today and do it again, see if I can get the headers hot.

again I confirmed that whatever is going with 1&3 didn't change when using wire+plugs from 2&4, and all have little blue'ish spark. But on videos I've seen brighter spark. Possible weak spark?(even tho 2&4 esoecially 4 fire well)

Couple strange things I never mentioned cuz they only happened once or twice:

1)Header 1 once got really hot quick after I checked and greased coil-wire-plug connections, but never again.

2)a couple of times while bike has struggled to start, either by lack of battery juice or I believe at one point I had to gap and clean the plugs, right before the rotor stopped turning after a failed crank I heard a loud bang in the engine. I figured since I only heard that twice under those conditions and never while it was running that that was normal(?). But sure didn't sound good.

3) Ive seen smoke come up a couple times, struggling to start, once from around the starter, and I believe that the ugly makeshift fuse I replaced may have been blown while I was trying tobstart the bike at some point as Ive smelled the smoke before(not knowing from where/why).

Didn't wanna make it more confusing with things at least not related to my main issue but figured just in case I should put them out there. Thanks guys for checking back here once in a while. Very generous. This would be a whole lot harder

carbs out. Gonna smear boots with window weld or equivalent(read many threads on reinforcing/extending life) then install them the correct way, see if that eliminates the leaks, make sure pilot jets are clear(just spray from scew side up through? should come right up?), and slow speed(idle jets?(little group of holes under throttle plates?) jets too.