Author Topic: 80 pd's vs 81vb's carbs (Read 6590 times)

rb550four · « **on:** November 26, 2012, 05:57:22 PM »

So , I've been happy enough with the performance of my 80 cb 650 custom with bone stock pd carbs . Recently I've picked up an 81 650 custom (that will run but I haven't run it yet) that came with a spare rack of vb carbs and I was wondering if anyone knows if they are superior to the pd's, meaning , would I notice significant power increase if I change out the carbs on the 80 650 to the 81 set? I'm wondering if it is worth getting the rebuild kits for 2 racks and making the change on the 80 since I'll be rebuilding a rack of vb's anyways?

onepieceatatime · « **Reply #1 on:** November 26, 2012, 06:25:10 PM »

The '81 VB carbs wont work on your '80 unless you replace the head too. The head intake spacing is different for the CV carbs than it was for the PD carbs.

rb550four · « **Reply #2 on:** November 26, 2012, 06:52:47 PM »

Thank you,didn't know that. You just made up my mind and saved me a big pain in the a$$. Thank you.

onepieceatatime · « **Reply #3 on:** November 26, 2012, 08:15:55 PM »

Check the 2 racks of VBs you got, see if they are VB44A or VB44C. C has removable slow jets, A has press in. The As were on '82s and Cs were on '81s. If you have a set of Cs I would suggest that be the set you rebuild.

rb550four · « **Reply #4 on:** November 27, 2012, 05:45:02 PM »

Thank you, I have a rack or vb44a on the 650 now, those will be the ones. While removing said carbs, it seems that one of the PO's had removed this rack and was unable for some reason to get the carbs mounted properly on either side, they were just resting on the edge of a couple of the rubbers, no seal at all.
They are all out now and I'm hoping to get to them tomorrow ,the slides are stuck so I shot them all with pb blaster to see if that'll loosen them up. If not I plan to run a hairdryer on them until they loosen up then take them apart for a good cleaning.
I checked the tank for rust, it's like chrome in there so that won't be an issue. I thought this 650 was as nice as my 650 but the more I dig the more I find that needs attention. Haven't taken down a 650 yet, this should be fun.

trueblue · « **Reply #5 on:** November 28, 2012, 12:43:37 AM »

Quote from: onepieceatatime on November 26, 2012, 08:15:55 PM

Check the 2 racks of VBs you got, see if they are VB44A or VB44C. C has removable slow jets, A has press in. The As were on '82s and Cs were on '81s. If you have a set of Cs I would suggest that be the set you rebuild.

Close but not quite, the A's were from '81 and the C's were '82. To free up those stuck slides try a little acetone, works wonders

.

onepieceatatime · « **Reply #6 on:** November 28, 2012, 08:56:09 AM »

Quote from: trueblue on November 28, 2012, 12:43:37 AM

Quote from: onepieceatatime on November 26, 2012, 08:15:55 PM
Check the 2 racks of VBs you got, see if they are VB44A or VB44C. C has removable slow jets, A has press in. The As were on '82s and Cs were on '81s. If you have a set of Cs I would suggest that be the set you rebuild.
Close but not quite, the A's were from '81 and the C's were '82. To free up those stuck slides try a little acetone, works wonders .

Not sure how I typed that backwards. Sorry for the confusion and thank you for the correction, Trueblue.

rb550four · « **Reply #7 on:** November 28, 2012, 05:14:49 PM »

I looked over the other two racks, all A's , all filthy on the outside , so I figured that I would take a couple of those apart first just to see what I'll be in for. The set that I took off the machine to clean up were spotless inside. Not what I expected, there was even a green/blue Stabil like stuff in the bowls. How nice is that? And the outside of them weren't bad either.
Hit the slides with a hairdryer for a few seconds each , fingered them up and they returned. Did it a few more times with a couple of shots of carb cleaner. Slides up easily and snaps right back down. This never happens to me, a pleasant surprise.

rb550four · « **Reply #8 on:** November 28, 2012, 05:44:51 PM »

This 81 motor only has 8,800 miles on it, the frame is a little rusty in places and the shine is gone , so I was thinking to remove the engine , prep and shoot the frame a nice gloss black...... then , over in the corner, there are 3 frames, 1-500 and 2 -550's. I really like the size of the 550 frame but it doesn't have the snot that the 650 engine has, and I can't help but wonder if this 650 engine wouldn't feel at home in that 550 frame? Maybe if it was modified with the 650 swingarm, wheels and front forks. I'd like that, I think.
I haven't measured anything yet , but it looks like the swingarm is at least 2 inches longer. The forks look like maybe 4 inches longer, and the tires look allot meatier than the ones on the 550's....Oh Oh , drooling on the keyboard.... air forks , dual front discs.... is it getting hot in here....more horsepower! If this doesn't sound like a plan , someone please stop me.

rb550four · « **Reply #9 on:** November 29, 2012, 03:58:30 PM »

While in okay condition , the new 81 650 needs to be broken down for frame cleaning and painting

Then I saw this clean 550 frame in the corner and thought.... well ,you know.
Even though my 80 650 hasn't been washed in a while, it's still allot cleaner than the new one

So my last post was on for 24 hrs, there has been no "please stop" or "what the hell is wrong with you" posts so, I'm thinking that this is an acceptable idea, maybe even a good idea,and that it should start right away. Right?

cb650 · « **Reply #10 on:** November 30, 2012, 06:32:59 AM »

I believe there are a couple 550's with 650 engines in them floating around this site or the 650 site. The biggest problem is the electrical.

trueblue · « **Reply #11 on:** November 30, 2012, 11:52:59 AM »

It has been done a number of times, and there are numerous threads on it, do a search

. The 650 motor is pretty much a drop in fit, like cb650 said you just need to fiddle with the electrics a little.

cb650 · « **Reply #12 on:** November 30, 2012, 03:06:39 PM »

Wittom is parting out a 550 with a 650 in it now.
http://www.hondacb650.com/viewtopic.php?f=6&t=7590

rb550four · « **Reply #13 on:** November 30, 2012, 04:32:12 PM »

Yeah, I know the 650 in a 550 cradle has been done before, and especially on this site. I liked the idea that it is basically a drop in making the stock looking 500/550 a sleeper . And I am going to go through the threads on the subject only if I get stuck, that way it is all on me to make it work with no outside influences and it won't seem so easy or be an over simplified build just to go through the motions. The mind should be busier than the hands.
But what I really find exciting about it, it hasn't happened in my garage yet. I need something that isn't run of the mill 500/550, something that I can put what I've learned into it ,and learn what I didn't know out of it. Like the breakaway frame on the 650, I had that motor almost half ways out before realizing that this was an option. wish the 500/550's had that. I'm learning stuff and liking it.

rb550four · « **Reply #14 on:** December 01, 2012, 06:01:46 PM »

Ain't Saturday afternoons great! Last week I installed a hot air furnace in the garage. It's got to be heaven. No more freezin my butt off, I can actually get stuff done instead of just trying to warm up my hands.
Got into the shop around 2, cleaned up and painted that 650 engine, let it dry a bit and installed it in the 550 frame

Layed the frame over the motor this time,that was easy.
drilled out the swingarm bolt holes and installed the 650 swingarm,chain, shocks and rear wheel.

I'm pleased with it so far , maybe a shot from the other side

Yeah I'm liking it but need to spend some time with my wife, she's expressed concern about too much time spent on motorcycles. Is there such a thing?

rb550four · « **Reply #15 on:** December 03, 2012, 07:53:20 PM »

Sunday afternoon I had a couple hours out in the shop and got to put the 650 forks on the 550 frame.

I thought that it might stand too tall, but it seems just right.

Now the next thing I'm toying with is the tank. I like the 650 tank allot and would like to use it but I'm really torn. I have extra 550 tanks but, will the 550 totally loose it's identity if I didn't use the 550 tank?

rb550four · « **Reply #16 on:** December 08, 2012, 10:27:41 AM »

Trueblue you are right there is a little fiddling with the electrics, not bad though, I strung the 81 wiring harness back in it. The only place where it is a bit tight is on the electric side under the sidecover. Trimmed the backing plate, didn't like it, ended up removing it entirely and attaching everything to the 650 battery box, much better.
I used he 650 airbox, nice and tight. Could get a sidecover on that side but not the other, gonna have to bend up some sheet good to fit, that should be fun.
The battery box fits in the frame, able to bolt on with the front mount, had to fab a mount for the two back mounts, paints drying now,I'll mount it later and shoot some pics.
I mounted the 550 coils instead of welding mounts for 650 coils, anyone see a problem with that?

rb550four · « **Reply #17 on:** December 08, 2012, 01:34:33 PM »

So the battery boxlooked like it had proper clearance from the frame(it has to be isolated)but upon bolting it down I was thinking maybe it doesn't. but it does fit in the 550 frame opening so, just to be sure that the box would remain isolated, I cut a length of fuel line, slit it down the middle , and overlayed it on a weld bead .

then added a piece of flat stock,cut to fit including isolation gromets and washers and bolted that in.

And this is how it looks today

trueblue · « **Reply #18 on:** December 09, 2012, 08:42:15 AM »

The 650 coils IIRC are 2.6 Ohm the 550 ones IIRC are 5 Ohm. It should work but the 650 ones are better for the application.

rb550four · « **Reply #19 on:** December 09, 2012, 09:04:40 AM »

Point made, will change the coils out next, no sense in screwing up the recipe now. I'm still waiting for my Clymer manual to get here so I can find the particulars that I'll need to know. Tried the download, doesn't cover the 81, so I've only been wrenching on stuff that is familiar, can't tell the if electricals are interchangeable or better for the application just by looking at them. Thanks again Trueblue.

trueblue · « **Reply #20 on:** December 09, 2012, 09:24:25 AM »

No worries mate

. If I were to do this conversion myself, I would consider trying to adapt the 650 harness onto the 550 frame, rather than the 550 harness to the 650 engine. I would imagine it would be easier to adapt the lights and such in to the 650 harness than the ignitors bits into the 550 harness. I have never done it though so I could be wrong. Also, you may have mentioned this earlier, but make sure you use the reg/rec unit from the 650, it is a far better unit than the 550 one.

rb550four · « **Reply #21 on:** December 11, 2012, 12:22:13 PM »

The coils mount differently than the 550 which is a top mount to the mounting bracket that is then bolted to the frame, the 650 coil is a side mount to welded brackets on the frame. No biggie, I went to the hardware store and found weldable 1/2" wide steel cut it to 5 #/8" and rounded the ends. 2 lengths of 6mm rod about 4 inches long, 4-6mm rod connectors 4 nuts and 4-6mm lock nuts.
Place the 1/2" flat stock on the frame and mark the mounting bolt holes about 5 3/16" center to center. Drill the marks through both plates, from the back mount hole drill another hole at 4 5/16"c to c, that will be the mount for the front of the 650 coil. Slip threaded rod with rod connector through the rear hole center the rod thread on the connector for the other side and add a 6mm bolt to each end to lock them and provide space between the coils and frame. Bolt the front hole with a short 6mm and a locking nut, the hole in between gets the same treatment as the rear hole, slip on coils,hook up the ground wire with a washer and use those 4 locking 6mm nuts to tighten it all down. It should look like

on the right side and this

on the left side. Viola the no weld coil mount.

trueblue · « **Reply #22 on:** December 11, 2012, 12:35:48 PM »

Looks good

rb550four · « **Reply #23 on:** December 11, 2012, 12:45:39 PM »

Turns out the spark plug wires fit but they were tight, went to 3 auto parts stores , 2 stores had those young faced" Can I help you" kids behind the counter. Yeah I need 5 feet of accel wire with copper. The first kid had no clue, then another one shows up to help the first one and comes out with battery cable wire, I brought my spark plug wire with me so take a good look at it and maybe you can find something that resembles that. We have spark plug wire in sets they say, I said its gonna have to be a set for an old vehicle, the newer ones are all carbon and I need copper. Yeah ,Yeah, we'll find it . after six pair of carbon filled I thanked them and went to the next store, which was allot like the experience at the first store. With the exception of " they musta had that like 20 years ago". I'm in rural upstate,N.Y., there is no speed shops here so I stopped to NAPA,. The guy behind the counter was old, so maybe I'd have a chance, he came back and said "nope don't stock accel or the generic with copper anymore but here's a set from a tractor that has steel wire in it, should work. So I can't buy or sh1t a set of wires with copper in them so I bought them, does anyone think that there will be issues with a steel center spark plug wires?

trueblue · « **Reply #24 on:** December 11, 2012, 07:22:44 PM »

They should be ok as long as they are actually steel wire, they won't last as long as the copper though. There are some out there that are steel wrapped around a carbon core, these wouldn't work. Copper core plug leads are becoming nigh on impossible to find.

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Author Topic: 80 pd's vs 81vb's carbs (Read 6590 times)