Author Topic: CB550 - CB650 interchangability (Read 19423 times)

bill440cars · « **Reply #25 on:** July 10, 2006, 06:57:59 AM »

Quote from: cb650 on July 10, 2006, 05:03:10 AM

Remember the heads/carbs break down into 2 groups. 79/80 and 81/82.
Terry

Terry,
Is one group more desirable than the other ? I'm thinking that previously either you or
someone else had said that the early models were but, I'm not sure on that. Could you clarify?

Later on, Bill

Ibsen · « **Reply #26 on:** July 10, 2006, 10:33:01 AM »

It depends on what type of carbs you wan't to fiddle with,and how easy it is to find parts for them. The 79/80 head can only take the 26mm PD carbs, and the 81/82 head can only take the larger CV carbs. The difference between the heads is the distance between the intake ports.

kayaker43 · « **Reply #27 on:** July 10, 2006, 03:40:49 PM »

I just bought a 79 650 head off ebay. Carb centers are the same as 500/550 like was mentioned, but the spigots are a larger diameter so you need 650 rubber couplers. Should mate up with 750 carbs well because they were too tight on the 550's.

Other obvious differences are more fin area, cast in spigots instead of separate manifolds and larger ports. Looks like a great head with perfect hemi combustion chambers and decent ports. There are some mismatches and casting boogers to clean up of course.

Intake runners look a but shorter so may be a bit more room for K&N filters too?

DammitDan · « **Reply #28 on:** July 10, 2006, 10:08:52 PM »

Quote from: kayaker43 on July 08, 2006, 08:40:04 PM

. Dennis Kirk has 650 valves on clearance for $1.99 each!

Where?! I can't find it!

Ibsen · « **Reply #29 on:** July 10, 2006, 10:57:54 PM »

The 650 head also have larger valves than the 550. And the 650 have got a HyVo camchain, so to be able to use the 650 cam, you will have to use the camchain sprocket from the 550. I don't know if this sprocket is a direct match though.

If I were you, I would try to find a 650 engine and drop it into the 550 frame. Less work, and then you already have more power to start with. The 650 engine isn't just a bored out 550. There are some other differences as well. I think one of the members on the old forum, LLoyd?, listed all the work you have to do on the 550 engine to fit the top end from a 650.

kayaker43 · « **Reply #30 on:** July 11, 2006, 08:26:00 AM »

Look in the dennis kirk ebay store for bargains http://motors.search.ebay.com/_W0QQfgtpZ1QQfrppZ50QQsassZdkQ2dtrader

The valves may be gone by now? There was also a private seller, with an auction for a full set of Dennis kirk valves for sale. Search cb650 valves, but it may be too late??

I agree, everything about the 650 motor makes it a better starting point for a hot-rod. I just can't seem to find a complete motor. Saw a couple on ebay but they wouldn't ship them. Others part them out on ebay but they want too much for all the pieces. I'll just wait till I find one locally.

jt · « **Reply #31 on:** July 11, 2006, 11:15:49 AM »

The valves may be gone by now? There was also a private seller, with an auction for a full set of Dennis kirk valves for sale. Search cb650 valves, but it may be too late??

To late, I bought em, ( DK ones) Cound'nt pass it up for $20.
JT

DammitDan · « **Reply #32 on:** July 11, 2006, 04:08:26 PM »

*sigh*

Back to scrubbing my own old ones, I guess...

kayaker43 · « **Reply #33 on:** July 11, 2006, 04:41:22 PM »

This article says the valves are the same size a Cb500!

http://sohc4.us/650/articles/79650rt

I kinda believe it because they are on the same centers and can't get any bigger. I'll bet the part number differences have to do with the change to unleaded fuels? Probably a good idea to use 650 valves in a 500?

Ibsen · « **Reply #34 on:** July 11, 2006, 11:12:43 PM »

Quote from: kayaker43 on July 11, 2006, 04:41:22 PM

This article says the valves are the same size a Cb500!

http://sohc4.us/650/articles/79650rt

I kinda believe it because they are on the same centers and can't get any bigger. I'll bet the part number differences have to do with the change to unleaded fuels? Probably a good idea to use 650 valves in a 500?

I have read throug a few other articles, and compared to the 550 these articles claims that the intake valves are 31mm(4mm larger), the exhaust valves are 26mm (3mm larger), the bore increased with 1,3mm and stroke with 5,2mm. Intake ports are larger, carbs size is increased fom 22 to 26mm (1979-1980 PD carbs), and the camshaft profiles on the 650 are made to fit the the larger valves and carbs.

Here is one of those articles:

http://kz400.com/CB650/650%20Marathon.pdf

cb650 · « **Reply #35 on:** July 12, 2006, 04:42:18 AM »

Quote from: bill440cars on July 10, 2006, 06:57:59 AM

Quote from: cb650 on July 10, 2006, 05:03:10 AM
Remember the heads/carbs break down into 2 groups. 79/80 and 81/82.
Terry

Terry,
Is one group more desirable than the other ? I'm thinking that previously either you or
someone else had said that the early models were but, I'm not sure on that. Could you clarify?

Later on, Bill

AHH I havent been able to get here for a couple days.
I am most familiar with the 81/82 cvs. Had a couple 80s on the road but only a short while. Bike that is almost on the road is a 80 so I'll be learning them. Bottom end of the carbs no big diff just the slider operation. Bill Santa will be visiting you soon.

Terry

kayaker43 · « **Reply #36 on:** July 12, 2006, 07:30:35 AM »

I'm excited to hear about the larger valves. My fuzzy memories remember hearing about 75HP from Yoshimuras racebikes, and how the old CB500 head was the bottleneck. The next issue is cams, I have a Yosh TT100 "Daytona" cam I was going to use. Did anyone make a good cam for the 650? I suppose the aftermarket springs for the 550 will work.

Back in 78 I was running kz1000 carbs on my CB590 racer. They required straight manifolds insted of the stock offset ones due to wider carb spacing. The 81-82 650 heads have wider spacing and I wonder if they would fit KZ900/1000 carbs? (27-29mm)

I really need to get a complete motor for comparison. These little details are so important. Does anyone know the carb spacing on an 81/82 head. I can measure the earlier head if anyone cares?

jt · « **Reply #37 on:** July 12, 2006, 09:49:01 AM »

Quote from: kayaker43 on July 12, 2006, 07:30:35 AM

I'm excited to hear about the larger valves. My fuzzy memories remember hearing about 75HP from Yoshimuras racebikes, and how the old CB500 head was the bottleneck. The next issue is cams, I have a Yosh TT100 "Daytona" cam I was going to use. Did anyone make a good cam for the 650? I suppose the aftermarket springs for the 550 will work.

Back in 78 I was running kz1000 carbs on my CB590 racer. They required straight manifolds insted of the stock offset ones due to wider carb spacing. The 81-82 650 heads have wider spacing and I wonder if they would fit KZ900/1000 carbs? (27-29mm)

Hey kayaker,
What type of manifold did you use with the carbs?
I am in the process of building a motor also. I have a Action Fours 572cc piston kit. and their megaphone header along with a Kenny Harmon "D" grind cam and ported head I am using for now.

I also have a NEW Yoshimura "TT grind cam and Yosh alloy rods that I want to build into a 590 motor with a 550 lower end and 650 head.

thanks
JT

Pinhead · « **Reply #38 on:** July 12, 2006, 10:08:51 AM »

This brings up an interesting idea... What aftermarket 550 cams would help a 650? I've heard that the 650 and 550 cams are almost idendical, except for .001" of extra lift on the 650? If that's the case, than aftermarket cams for the 550 would surely help out on the 650 as well. Thoughts?

kayaker43 · « **Reply #39 on:** July 12, 2006, 10:16:11 AM »

JT... I just welded some short tubes to a flange and bolted them up to the head,.. don't have them anymore.

I've got lots of yosh parts too,.. TT100 cams, super rods, 5 and 6 speed close ratio trans kits. That TT100 cam is tuned for high rpm power. I thought it was great until I mated it with the yosh racing header with short primary tubes, then it REALLY came alive. You need a short tube header for the best match, otherwise use a milder cam? The power didn't hit till 8-9000, then it pulled like a two stroke. Not very good for the street, but with a close ratio trans it was perfect for the track.

I sure wish I had a 650 head back then...

Pinhead, I'm thinking the TT100 cam may be more civilized in a 650 than a 500, you might even advance it a bit so the intake closes earlier to lower the powerband for street use?

Pinhead · « **Reply #40 on:** July 12, 2006, 10:50:46 AM »

Quote from: kayaker43 on July 12, 2006, 10:16:11 AM

Pinhead, I'm thinking the TT100 cam may be more civilized in a 650 than a 500, you might even advance it a bit so the intake closes earlier to lower the powerband for street use?

I have always heard that you can advance the cam to "lower the power band" RPM-wise. I asked in another post about advancing the cam timing to lower the power band (when using the stock cam) and either Hondaman or TwoTired said it wouldn't help. I'll try to find it.

bill440cars · « **Reply #41 on:** July 12, 2006, 12:27:06 PM »

[/quote from cb650]

AHH I havent been able to get here for a couple days.
I am most familiar with the 81/82 cvs. Had a couple 80s on the road but only a short while. Bike that is almost on the road is a 80 so I'll be learning them. Bottom end of the carbs no big diff just the slider operation. Bill Santa will be visiting you soon.

Terry

Quote

Hey Terry, I was beginning to wonder about you. I figured you would have something to say about the carbs. And I'll be on the lookout for "Santa". Take care and I'll catch you later on, Bill

Ibsen · « **Reply #42 on:** July 12, 2006, 02:51:27 PM »

I belive Terry once said that Webcams can modify the 650 cam for more performance, but they will need a donor cam.

And regarding the difference between the 79/80 650 cylinder head for the PD carbs, and the later head for the CV carbs:

Compared to the intake ports on the PD carb cylinder head, the cyl.head intake ports for the CV carb cylinder head are shifted 4 mm (0.16 in.) inwards for both of the outer cylinders (cyl. #1 and #4) and 6 mm (0.24 in.) outwards for both of the inner cylinders (cyl. #2 and #3)

Pinhead · « **Reply #43 on:** July 12, 2006, 04:09:10 PM »

Quote from: Ibsen on July 12, 2006, 02:51:27 PM

I belive Terry once said that Webcams can modify the 650 cam for more performance, but they will need a donor cam.

Webcams, huh... Link?

Ibsen · « **Reply #44 on:** July 12, 2006, 04:12:25 PM »

Their correct name is Webcam. Sorry about that.

Link:

http://www.webcamshafts.com/

http://www.webcamshafts.com/what_motorcycle.html

cb650 · « **Reply #45 on:** July 12, 2006, 07:59:36 PM »

Webcams and mega was who I looked at. One had a mild 550 cam that was the same lift as a 650.
The other had a hot 550 cam that was .029 inch more. Dont know about the duration of a stock cam so dont know what that would gain. Compared a stock 550 and stock 650 and other than a little less lift (also.029 inch) on the 550 the where identical. There seems to be a tack reading issue though. Was going to run a few races and then just try the 550 hot cam but havent even made it to one yet this year.

Terry

kayaker43 · « **Reply #46 on:** July 12, 2006, 08:55:14 PM »

That's what I suspected,.. a hot cam in a 550 would seem less radical in the 650. The good news is that a stock 650 cam should make a decent upgrade in a stock 550 provided the pistons clear the valves?? can anyone confirm the 650 cam will work with stock 550 pistons?

Does anyone know the biggest bore practical in the stock 650 sleeves? I think were into 750 aftermarket pistons sizes here??

Pinhead · « **Reply #47 on:** July 12, 2006, 09:10:53 PM »

The bore and stroke of a stock CB650 is 59.8 x 55.8mm (2.35 x 2.20 in).

A CB750's bore and stroke is 61 x 63mm (2.401 x 2.408 in).

Edit:

According to my Haynes manual, the intake valve opens 5 deg BTDC, closes at 53 deg ABDC.
Exhaust opens 40 deg BBDC and closes at 5 deg ATDC.

Overall lobe height:

Intake........35.627 -- 35.787 mm
Exhaust......35.314 -- 35.474 mm

Cylinder barrels:

Bore diameter .................... 59.800 -- 59.810 mm
Service limit ....................... 59.90 mm

cb650 · « **Reply #48 on:** July 13, 2006, 05:12:57 AM »

Someone is running a 650 cam in a 550. It was in one of the older threads on this. Thats how the tack issue came up.

Terry

Ibsen · « **Reply #49 on:** July 13, 2006, 07:29:46 AM »

I have been wondering if you got the time to try out the 550 cam Terry.

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Author Topic: CB550 - CB650 interchangability (Read 19423 times)

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