Topic: 82cb650 boggs down around 4500 rpm.

[harleyguywithahonda]

One more dumb question and I will stop wasting your time.
I am assuming the 4500 RPM  bogg is in 5th gear.  What is the highest RPM you can get to in 3rd gear?  And what speed is that

It boggs down in every gear I can get it to around 8 now in first, 6300 in second and from there it just goes down third is 6000 fourth is 5800 etc

[harleyguywithahonda]

One more dumb question and I will stop wasting your time.
I am assuming the 4500 RPM  bogg is in 5th gear.  What is the highest RPM you can get to in 3rd gear?  And what speed is that

3rd gear is around 6000 and about 35-40 mph

[2wheels]

One more dumb question and I will stop wasting your time.
I am assuming the 4500 RPM  bogg is in 5th gear.  What is the highest RPM you can get to in 3rd gear?  And what speed is that

It boggs down in every gear I can get it to around 8 now in first, 6300 in second and from there it just goes down third is 6000 fourth is 5800 etc

I think you are on the right track check the ignition stuff.  Seems like you are loosing (or partially loosing) one side the the pickup - CDI module - coil    set.
Is there a gaping measurement on the pickups.   (dam -- i asked another question and promised i would not)

[harleyguywithahonda]

One more dumb question and I will stop wasting your time.
I am assuming the 4500 RPM  bogg is in 5th gear.  What is the highest RPM you can get to in 3rd gear?  And what speed is that

It boggs down in every gear I can get it to around 8 now in first, 6300 in second and from there it just goes down third is 6000 fourth is 5800 etc

I think you are on the right track check the ignition stuff.  Seems like you are loosing (or partially loosing) one side the the pickup - CDI module - coil    set.
Is there a gaping measurement on the pickups.   (dam -- i asked another question and promised i would not)

What I found did not mention anything about gaping the pick ups

[harleyguywithahonda]

I found a post on  another forum that says the pick up gaps should be around .4mm I stuck a feeler blade between the pick up and the cam and got .838mm I am going to try adjusting it.

[2wheels]

pick up gaping --  this guy did valves and pickup.  i have no idea if this is right
https://www.motopsyco.com/tag/pulse-generator/

[harleyguywithahonda]

pick up gaping --  this guy did valves and pickup.  i have no idea if this is right
https://www.motopsyco.com/tag/pulse-generator/

Well I adjusted it to 0.4mm it didn't seem to make a difference. It definitely doesn't feel like a miss just like a surges when it hits the higher rpms. I'm really starting to think that I need to Jett it up again.

[2wheels]

It has the CV carbs, they can be finicky.  Try running with different amount of choke on and see the effect.

[harleyguywithahonda]

It has the CV carbs, they can be finicky.  Try running with different amount of choke on and see the effect.

It's the metal slide style cv carbs half choke makes it worse

[scunny]

go the opposite way then, if the airbox has a removable lid take that off, if not remove the air filter and try it.

[BomberMann650]

Did i read there was an accelerator pump in those carbs?

[harleyguywithahonda]

go the opposite way then, if the airbox has a removable lid take that off, if not remove the air filter and try it.

There's only the piece that holds the airfilter in, I have ran it with and without the air filter and it did not change it, buy I will try again.

[harleyguywithahonda]

Did i read there was an accelerator pump in those carbs?

There is an accelerator and it is functioning through all 4 carbs. The carbs number I'd is 44CATJ there's also a VB stamped on the side above the I'd number

[fizzlebottom]

The troubleshooting guide in the FSM says that it may be the spark units, pulse generator, or spark advancer. If none of those are problematic, might even be weak/worn valve springs.

[scottly]

So I found a 78 cb650 manual online says I should have 530 plus or minus 50 ohms, my meter is reading 641 and 620 ohms for the coil resistance  on the pulse generator side of the harness and 159 ohms on the other side of the pulser coil plug oh and thats 641 for the yellow wires and 620 for the blue wires

If your meter is correct, than both coils are way out of spec. Is the bike running on a four cylinders? Do a "spit sizzle" test on the exhaust pipes. Also, have you looked at the spark plugs?

[BomberMann650]

Has OP looked at the spark plugs?

If I'm interpreting your description accurately.  The machine bogs in the midrange, but surges in the upper rpms.  (That is assuming it does race to the redline)

Gives rise to wondering if the accelerator pump is over doing it.  There should be a proper setting described in the manual.  Could be contributing to a rich run condition.  Over rich until the pump is done and the motor gets back to its happy a/f mix.

Other possibility might be the slide rising too soon.  If someone tried to hot rod the cv carbs with a "spring mod" - that could also render moot the taper of the needle jet. 
Further exacerbated by any back n forth working of the throttle causing the accelerator pump - to pump more.

[2wheels]

One more dumb question and I will stop wasting your time.
I am assuming the 4500 RPM  bogg is in 5th gear.  What is the highest RPM you can get to in 3rd gear?  And what speed is that

It boggs down in every gear I can get it to around 8000 rpm now in first gear, 6300 in second and from there it just goes down third is 6000 fourth is 5800 etc

Something makes me think this is important info in understanding what is happening.
Whether it is fuel or spark or valve spring or ?? , could one cylinder weak or failing do what is described above

[BomberMann650]

One more dumb question and I will stop wasting your time.
I am assuming the 4500 RPM  bogg is in 5th gear.  What is the highest RPM you can get to in 3rd gear?  And what speed is that

It boggs down in every gear I can get it to around 8000 rpm now in first gear, 6300 in second and from there it just goes down third is 6000 fourth is 5800 etc

Something makes me think this is important info in understanding what is happening.
Whether it is fuel or spark or valve spring or ?? , could one cylinder weak or failing do what is described above

Gear-dependent mapping isn't a thing on old bikes.
So its just that its not making power under load.

Doing a leak down test would be smart.

[harleyguywithahonda]

The troubleshooting guide in the FSM says that it may be the spark units, pulse generator, or spark advancer. If none of those are problematic, might even be weak/worn valve springs.

I'm checking the valves adjustment again today, I checked cam chain timing and it's right on. Is worn or weak valve springs a common issue on these?

[harleyguywithahonda]

So I found a 78 cb650 manual online says I should have 530 plus or minus 50 ohms, my meter is reading 641 and 620 ohms for the coil resistance  on the pulse generator side of the harness and 159 ohms on the other side of the pulser coil plug oh and thats 641 for the yellow wires and 620 for the blue wires

If your meter is correct, than both coils are way out of spec. Is the bike running on a four cylinders? Do a "spit sizzle" test on the exhaust pipes. Also, have you looked at the spark plugs?

I did try that and it is running on four cylinders, at this point I am also suspicious of the coils. I belive I read the meter wrong because it did say kohms, but it was also warm at the time i will check again today.

[harleyguywithahonda]

Has OP looked at the spark plugs?

If I'm interpreting your description accurately.  The machine bogs in the midrange, but surges in the upper rpms.  (That is assuming it does race to the redline)

Gives rise to wondering if the accelerator pump is over doing it.  There should be a proper setting described in the manual.  Could be contributing to a rich run condition.  Over rich until the pump is done and the motor gets back to its happy a/f mix.

Other possibility might be the slide rising too soon.  If someone tried to hot rod the cv carbs with a "spring mod" - that could also render moot the taper of the needle jet. 
Further exacerbated by any back n forth working of the throttle causing the accelerator pump - to pump more.

I have and they are generally pretty good looking but I will clean them and run them again to see, basically what happens is I will get to around 6000 then it just won't accelerate any more and feels like it just stumbles. It only red lines with no load I can get the rear wheel off the ground and run the bike through every gear and it will red line then just not when tire meets the road

[harleyguywithahonda]

One more dumb question and I will stop wasting your time.
I am assuming the 4500 RPM  bogg is in 5th gear.  What is the highest RPM you can get to in 3rd gear?  And what speed is that

It boggs down in every gear I can get it to around 8000 rpm now in first gear, 6300 in second and from there it just goes down third is 6000 fourth is 5800 etc

Something makes me think this is important info in understanding what is happening.
Whether it is fuel or spark or valve spring or ?? , could one cylinder weak or failing do what is described above

Gear-dependent mapping isn't a thing on old bikes.
So its just that its not making power under load.

Doing a leak down test would be smart.

Alright I will do a leak down as well

[harleyguywithahonda]

One more dumb question and I will stop wasting your time.
I am assuming the 4500 RPM  bogg is in 5th gear.  What is the highest RPM you can get to in 3rd gear?  And what speed is that

It boggs down in every gear I can get it to around 8000 rpm now in first gear, 6300 in second and from there it just goes down third is 6000 fourth is 5800 etc

Something makes me think this is important info in understanding what is happening.
Whether it is fuel or spark or valve spring or ?? , could one cylinder weak or failing do what is described above

I am pretty sure it's getting fuel but something just isn't right and I can't figure it out yet, but like my name says, I'm trained in the old 2 cylinder harleys.

[BomberMann650]

Thanks for a better description of whats going on.

I suspect the the slides could be lifting too soon.  At least, thats what was happening with the 750 triple i built.  The cv slides would jump to wfo in the midrange rpms.  Throwing off the fuel mix and turning the bike into a blubbery gutless pig.

You'd have to get an inspection camera into the venturi to see if thats the case with your 650.  Or take the airbox off.

[2wheels]

I was wondering if you could get one of those little cameras and stick it into the carb and watch the diaphragm pull the slide up.  Pretty much need someone sitting on the back doing the watching.

How else can you tell if the carb slide are acting properly?  Would a set of carb sync gauges tell us anything?