Topic: CB650 CV head ALTERNATE carbs!!(w/kawa GPZ600 isolators fits '79/80 heads too!)

[Soos]

I have found an alternative to the stocker carbs for CV cb650 head bikes!!!

If you didn't notice my post in "other bikes", I got a freebie Kawasaki (12/84) GPZ 600cc bike today.. 
Not quite what I want for a bike... DOHC and all you know 


But the carbs DROP RIGHT in using stock cb650 CV carb isolators!


The carbs almost look to be "flatside" carbs.
The CV slides have a very small round center area, with flat "wings" extending to the sides of the venturi.


Will have to look up those carbs to see how good they really are.
They are marked in bold letters at the top on the sides with "CVK".
Near the float bowls on the side they are also marked with "V153   WJ25"
They are Keihin carbs to boot.


ALSO.... Using the Kawasaki carb isolators they will fit the heads off a cb650('79/'80) that uses mechanical PD50 carbs!
Not a drop in... But the Kawasaki carb isolators have JUST enough of a jog in them to allow you to get them to fit.
 

Mind you, I put these on HEADS ONLY... the heads were NOT on motors, nor in frames, so i cannot guarantee any clearances or anything.
But they (by eye) look shorter, and thinner(head to airbox) than CV cb650 carbs.

So anyone out there looking for CV carbs to go on a '79/80 head... here is an option now!


I will post later after I get a chance to measure them and give comparison measurements of the CV and mechanical CB650 carbs.

l8r

[Soos]

Ok... got some time now that i've done cleaning those carbs out.....


OD of intake side 1.970/50mm
OD of motor side 1.495/38mm
ID motor side 1.280/32.5mm The bore of the carbs are that diameter, but bell out on the intake side to 47mm

front to back 3.705/94.1mm

spacing -
center to center middle 2 carbs 3.600/91.4mm
center to center outside 2 carbs 8.920/226.5mm
center to center left 2 /right 2 carbs 2.660/67.56mm
Height, tip of drain on floatbowl to top cap 5.42/ 137.66mm



Now here are some measurements of stock CV cb650 carbs....

OD of intake side 2.12/53.8mm
OD of motor side 1.570/39.8mm
ID motor side is 1.260/32mm, the bore of the carbs are that diameter, but bell out on the intake side to 1.97/50mm.

front to back 4.81/122.17mm

spacing -
center to center middle 2 carbs 3.650/92.71mm
center to center outside 2 carbs 8.87/225.29mm
center to center left 2 /right 2 carbs 2.61/66.29mm
Height, tip of drain on floatbowl to top cap 6.100/154.94mm



Also the GPZ600 carbs are about 2-3 lbs lighter than the stocker cb650 CV carbs are.
Will weigh them one day mabey...
l8r

[kayaker43]

Thanks for the info, I sprung for a set of CR29's but may run the Kawi carbs on another street bike.

[Soos]

I can never leave a new toy(or set of carbs) alone....
I put them on my '79cb650 about an hour ago....

WOW... i WILL post more in depth on my '79 build thread. But they work!!(REALLY WELL!!)
I'm getting ready to pull them again so i can put the breather box back on....
Not too sure whether the stock '79 intake rubbers will work, or if I will have to use the GPZ's...
Will let you all know tomorrow.

l8r

[Soos]

The only downside so far is starting in the cold.
I leave work at about 5am and it's a PITA to start now.
I choke it, and turn in the throttle idle screw 1 full turn, and then she likes to start OK.

Thats the only major benefit I have noticed for the '73 750 carbs I had been running.
At no point whatsoever could I NOT start that bike.

But overall, they are worth the effort for a cb650.
I would wager for even a un-modified motor they would be worth trying.


l8r

[paulages]

good find. i always figured there are plenty of four-rack carbs that would fit these bikes if one simply had the chance to experiment. I'd bet there are some much newer carbs out there that could be made to work also.

[DarkRider]

Now this makes me wonder...are the carbs spaced similar on the 500/550?

[paulages]

Now this makes me wonder...are the carbs spaced similar on the 500/550?

they're spaced almost exactly the same as the slide carbs 650 heads. whether or not they'd work depends on which way they were slightly off for the 650.

[DarkRider]

Hmmmm me thinks im gonna have to go searching for some Ninja carbs then.

[Soos]

Well another note to add I guess......


Today I put a new stock air filter on, with the stock('79cb650) air cover.
Ran like a dog.
Got up to 45mph without any real difference.(right when i shifted into 4th gear)
Past that, it had a hard time accelerating.

Took off the air filter cover, a little better, bogged at about 60mph(after shifting into 5th gear)...

Took the air filter back out...Ran like a banshee.
I pulled a ton in a heartbeat, with plenty of power left it felt like..


I either need a bigger/less restrictive airfilter, or just run with the one I gutted the paper media out of.


Oh well.... Live and learn.



l8r

[Ecosse]

A bit of a bump here but if it's not a bunch of trouble Soos could you post a image of what the carbs look like mounted?

I know, you keep giving and we just want more.

[Soos]

A bit of a bump here but if it's not a bunch of trouble Soos could you post a image of what the carbs look like mounted?

I know, you keep giving and we just want more.

And I love sharing my "finds"!

Yeah, when I get off work, i'll pull the beast into the garage and take a few detailed pics of them on my '79 for you.
I know i've posted at least 1 pic of them... but not sure in what thread.

l8r

[Soos]

Well here you go, a few pics of my new kawasaki CV ninja carbs on my '79cb650(with a origional '79 head mind you)....

 
Can't wait until riding season is over and next one starts... i'm putting my ported head on this winter!!! These 32.5mm carbs should LOVE the extra breathing ability.....
And my clutch should hate it even more than they hate it now.
I have been getting clutch slip in 4th and 5th when going WOT above 7500 or 8000 rpm lately.
The taller than stock gearing I'm using probably doesn't help either.
Wonder why...  
If i ride sensibly, or at least under 3/4 throttle, no clutch slippage at all though.
(hahahaha.... could you with these on your bike??!)


But anyways...You can really see the jog these carb isolators have to them.
It is somewhat exaggerated due to the mis-alignment, but 90% of it is from the offset already in the kawasaki carb isolators.

The last pic is my stopgap fix until I get ahold of some actual caps for the vacuum ports.
It's cheesy, but they seal. They are made of some clear (aquarium?) tubing and the caps from the ends of ball point pens.

next post should make some people jealous.... clip changes on the bike easily in 10 minutes.


l8r

Oh, and I have only changed jet needle clip position, the main and idle jets are the ones that were in them when I got them.
So far the spark plugs look like they are running about perfect. Will find out here soon enough.

[Soos]

And heres the teaser.....
The clip changing pics.
No I didn't change them at this time, just demonstrating how easy it is on the bike.
No special tools, or procedures. Ok, a stubby phillips is pretty much mandatory for this, or a 90 degree offset phillips.


l8r

[Ecosse]

Wow, to an untrained eye they look like they were born there! Thanks for the detail shots; and my next question was going to be about plug condition but you addressed that so it seems the 650 likes the retrofit. As long as the isolators aren't really stressed or pinched I don't see any problems either.

Thanks for the tech tip Soos!

[MRieck]

The only downside so far is starting in the cold.
I leave work at about 5am and it's a PITA to start now.
I choke it, and turn in the throttle idle screw 1 full turn, and then she likes to start OK.

Thats the only major benefit I have noticed for the '73 750 carbs I had been running.
At no point whatsoever could I NOT start that bike.

But overall, they are worth the effort for a cb650.
I would wager for even a un-modified motor they would be worth trying.


l8r

Remove the idle mixture screw plugs and turn the screws out(if the plugs haven't been removed already). That needle looks like a Dynojet piece.

[Soos]

Oh, the other thing I have changed besides needle clip position...
The idle screw.

Not sure where it should be on the kawasaki, but best engine throttle response is around 2 1/2 to 2 3/4 turns out.
Possibly too small a idle jet?

Who cares.. it runs like a raped ape. 


If anyone does try these out, on the '79 head...
Align the carb isolators so they best match the spacing of these carbs.
Upon insertion of the carbs it may seem easier to start with carb 1 or 4 and work the rest in...
don't try it.
it turns into a fight.

angle the intake side down so they are touching the motor, and get the lower edge of the motor side of the carbs to cradle in the bottom of the kawasaki isolators.
With one pull put all 4 in by pulling, and rotating the carbs into place in the same movement.
I gotta say these were actually easier to install than the 750 carbs were. And I was using NEW cb650 carb isolators with those.


It makes it even easier with some type of lube.

Personally I have the off chance of having a tube of Dow Corning "55 O-ring Lubricant".

On the tube it also refers to this stuff as "MOLYKOTE 55 M Grease", "Designed to meet MILG 4343", "contains silicone", "swells rubber for better sealing", and a temp range of "-85 F to 350 F".
Also "not recommended for use as a lubricant on silicone O rings and seals"



In the past with my '73 750 carbs, I have used di-electric grease as a insertion aid.

I know the Dow Corning stuff is made for rubber, and the di-electric grease is supposed to be non-damaging to rubber... but given a choice, i'd go with the Dow Corning stuff any day.


As a side note for cb650c and cb650sc riders(CV head cb650's)...
I have tried insertion using non-CV isolators stock for a '79cb650.
They dropped right in as the stocker CV carbs do.
I have tried putting them on a CV head with the (old) CV carb isolators, and it worked too... just that they were harder to install, since the isolators were stiffer due to age.

I have read that the longer the intake the better the lower rpm torque... not sure if this is true, but the '79 carb isolators are longer, so it may give even more benifit to a CV 650 with them than stockers in low rpm torque.
But thats just from reading, no personal proof there.


l8r

[Soos]

Remove the idle mixture screw plugs and turn the screws out(if the plugs haven't been removed already). That needle looks like a Dynojet piece.

You mean there are supposed to be plugs under the idle mixture screws?
This set of carbs didn't have any when I got them.

Someone may have been into these carbs... not sure.
The mainjet was... 108 if i remember right. No idea what the idle jet size was.
And that jet has 6 notches for adjustment if that gives anyone an idea as to whether it is a stock jet needle or not.
I put it on the 3rd from the top, or 4th from the bottom, depending on your view of the world.
It was originally lower on the needle.... 2nd or 3rd from the bottom.

Anyone know what jets are stock for a '85 kawasaki GPZ600?
I've looked online, but not found anything conclusive yet.


l8r

[Ecosse]

OK Soos you opened up a can of worms! Now I think what's called for is a thread discussing the differences between 650's from year and model for those of us thinking about conversions.

It's your fault.

[MRieck]

Remove the idle mixture screw plugs and turn the screws out(if the plugs haven't been removed already). That needle looks like a Dynojet piece.

You mean there are supposed to be plugs under the idle mixture screws?
This set of carbs didn't have any when I got them.

Someone may have been into these carbs... not sure.
The mainjet was... 108 if i remember right. No idea what the idle jet size was.
And that jet has 6 notches for adjustment if that gives anyone an idea as to whether it is a stock jet needle or not.
I put it on the 3rd from the top, or 4th from the bottom, depending on your view of the world.
It was originally lower on the needle.... 2nd or 3rd from the bottom.

Anyone know what jets are stock for a '85 kawasaki GPZ600?
I've looked online, but not found anything conclusive yet.


l8r

The plugs were pressed in at the factory after the mixture screws were set. Dynojet kits contained a pan head screw that you screw into the plug after drilling a hole. I've seen many screwed up screws secondary to ham fisted drilling. If those brass (or aluminum) plugs are gone I have to guess somebody installed a Dynojet Stage 1 kit (if the carbs had K&N individual filters attached I'd say it was a Stage 3. In general the only difference between the 1 & 3 were larger main jets and a different clip setting.

[Soos]

Remove the idle mixture screw plugs and turn the screws out(if the plugs haven't been removed already). That needle looks like a Dynojet piece.

And the 2 1/2 to 2 3/4 turns out I have them at now basically gives the best throttle response.

At 1 1/2 out, it idles lower, starts harder and gives a slower 1000-3000 rpm increase.

at 4 turns out it starts just like it does at 2 1/2 turns out, idle is the same as 2 1/2 turns out, and gives no difference in 1000-3000 rpm climbing speed.

Mabey I should give it 3 1/2 and see what starting characteristics it gives the bike at 5 or 6 in the morning when it's as cold as the engine gets this time of year.

thnx for jarring that idea there....
I had only been doing starting tests in the garage to see the different idle screw settings.
Tuning for the real world is different than tuning to do well in the garage I guess....
Gotta remember that more often....


l8r

[Soos]

The stock airbox was hooked up when I got the ninja, so if anything the stage 1 would be it, if anything.
And I did wonder how the $&*@ someone broke off the shroud around cyl #3's idle mixture screw.

You mentioned it had to be drilled to adjust the IMS made me think thats how it got broken to begin with.
Thnx for the info.
You wouldn't know shat stock jetting is would you?


l8r

[Soos]

OK Soos you opened up a can of worms! Now I think what's called for is a thread discussing the differences between 650's from year and model for those of us thinking about conversions.

It's your fault.

hahaha......
And IMO, the '79 frame, is the best.
But after seeing a few different heads.
Hands down IMO CV heads are better.
One reason being that the intake tracts have less of a jog to them than the '79/80 mechanical carb heads do, the other... these kawa carbs drop right on with stocker isolators.
Other than that minor internal difference I think there are no other internal differences.
Now external, there are like 3 or 4 telltale items that you can use to spot a Later CV head VS a Earlier mechanical carb head.... mainly having to do with fin arrangements.
But thats more of a skill for people scouring E-bay for specific parts.


*************But someone like Mreick might know better than I on the internal differences *****************
(nudge, nudge, wink wink, nod, nod...)
Sorry... been watching too much monty python lately...

And now for something completely different...


I've only seen the innards of a small handfull of cb650 heads. 2 '79cb650 heads(mechanical), a '81 cb650c(CV) and a '80cb650c(CV).

Ported 1 '79 head, and lapped valves in 1 '81 head though.
Same valve diameters, spring lengths, keepers and retainers the same as well..... or at least the 2 heads i've been into were.


I tend to make either mental or written notes concerning cb650 year and engine differences. You should see the box of scraps of paper, notebooks, box tops, receipts etc with little notes on them concerning cb650 differences I have noticed.
Need to compile them one day and share all the tidbits...
But thats a task I have no time for at the moment.

 
l8r

[MRieck]

Remove the idle mixture screw plugs and turn the screws out(if the plugs haven't been removed already). That needle looks like a Dynojet piece.

And the 2 1/2 to 2 3/4 turns out I have them at now basically gives the best throttle response.

At 1 1/2 out, it idles lower, starts harder and gives a slower 1000-3000 rpm increase.

at 4 turns out it starts just like it does at 2 1/2 turns out, idle is the same as 2 1/2 turns out, and gives no difference in 1000-3000 rpm climbing speed.

Mabey I should give it 3 1/2 and see what starting characteristics it gives the bike at 5 or 6 in the morning when it's as cold as the engine gets this time of year.

thnx for jarring that idea there....
I had only been doing starting tests in the garage to see the different idle screw settings.
Tuning for the real world is different than tuning to do well in the garage I guess....
Gotta remember that more often....


l8r

4 turns out is the end of the idle screws effective range Soos. Sure....try 3.5 turns out. I've found most ofthe CV carbs work best 3 to 3.5 turns out. Also....if your jet needle is set to low (taper starts later) it will take a long time for the engine to warm up.

[StrongPerf]

Those carbs are similar to the CV's on my ZRX1200 and the EX500. Both seems to work best with about 2 3/4 -3 out on the idle screws. Also you can use a .020" (.5mm) washer as a shim under the needle clilp to go up 1/2 needle clip position when needed.