Author Topic: Just got a cb650. A few questions. (Read 6942 times)

Nickdawg18 · « **on:** December 15, 2011, 08:18:07 PM »

I just bought an 82' cb650 with 10xxx on the ticker. it had old gas in it so I drained the tank and all 4 bowls. Now here's the thing. After I put in new gas and a new fuel filter I tried to fire it up. I got it to fire with ether but gas immediately started to pour out of all 4 carbs. Not out of the overflow but the bowl gaskets. So I took the bowl off of one of em and saw the p.o. Used silicone to make his own gasket on top of the oem gasket. So I went ahead and ordered a full rebuild kit. Now. My first question is, how hard is it to get the carb assembly out of the bike??? (I don't have a clymers yet). Second question. I've seen some people have done away with the airbox and put on individual filters. Should I go this route and get some bigger jets or keep the stock box and stock jetting? I like the look of the 4-1 exhaust, has anyone had any trouble or issues with em?

chewbacca5000 · « **Reply #1 on:** December 15, 2011, 08:27:55 PM »

I have had a couple 1981 CB650s and getting the rebuild is a good move. The float needle springs are very prone to getting too weak and wearing out. As for removal they are not that bad. Just undo the air box clamps and the clamps on the engine and twist down with your hands. Pulling straight out just causes you to strain. A good 90 degree twist down and they should comes off.

The CB650 is probably the most cold blooded of all the SOHC bikes out there and more so with PODS. That said it can be done, but I would be sure to get it running stock before making any changes. A common thing that seems to be neglected on the bikes is cleaning the mechanical advance. You really need to take it apart and make sure it's not rusted and snaps back and works properly. Will save you tons of trouble. You can probably get pods to work, but there will be flat spots at the lower RPMs.

Hush · « **Reply #2 on:** December 15, 2011, 08:33:30 PM »

When you get the cars off, check the condition of the accellerator pump diaphram, it should be soft and flexible. I have had them snap and turn to dust on the 650.

Nickdawg18 · « **Reply #3 on:** December 16, 2011, 04:29:57 AM »

Where is the mechanical advance??? On the left side???

chewbacca5000 · « **Reply #4 on:** December 16, 2011, 06:04:31 AM »

The mechanical advance is on the right side cover there is a couple screws holding it in. The advance is part of your ignition system and helps control spark. As your RPM increase the flyweight on the advance the spark as they RPM drop the springs on the advance decrease the rate of spark. The problem is that many CB650 owners give up on these bikes not knowing this. Since it's not points based they never think to clean and lube the advance.

You might not have a problem at all. I bought one with 5,600 miles rode it a summer only to sell it do to hard starts. The problem was the bike sat for 10 years and the advance had never been cleaned or greased. I rode it for a summer and it was ok, but I must have used up what ever good grease was left. Grease dries up over time and the advance itself will rust.

If you take it apart to clean it be sure to pay close attention to how it goes together the cam only works right one way. The other way the bike will just backfire. I learned about this from Volker_P over at hondacb650.com.

As for the carbs drop an outside float bowl and see what kind of stuff is in there. If it looks clean I would do nothing. Make sure you tank is rust free by pouring some gas into a clear mason jar and look for rust particles or dirt.

Rust / dirt can keep float needles from seating properly and cause overflow issues. In other words your carbs may not be the problem. Hope this helps!

Stev-o · « **Reply #5 on:** December 16, 2011, 06:21:51 AM »

First off, welcome! +1 on keeping stock airbox, could be very difficult to tune properly with pods on.
4 into 1 exhausts are great, you may need to rejet the carbs depending on what system you go with.

cb650 · « **Reply #6 on:** December 16, 2011, 06:32:27 AM »

The 81/82 cv carbs are very forgiving to jetting issues.

Nickdawg18 · « **Reply #7 on:** December 17, 2011, 07:19:58 AM »

ok, i figured out why the gas poured out. the 3ways that connect 1&2 and 3&4 are completely dry rotted. anyone have a lead on a set for cheap?? All I can find are some that are $34 a piece.

onepieceatatime · « **Reply #8 on:** December 17, 2011, 09:42:40 AM »

I have no personal experience with it, but here is a link to the same topic on the CB650 forum.
http://www.hondacb650.com/viewtopic.php?f=4&t=4960&start=0

Nickdawg18 · « **Reply #9 on:** December 17, 2011, 12:14:04 PM »

looks like i'm goin with the honda ones. damn thats not cheap. btw, why did honda powdercoat carbs? its a pain in the arse gettin that crap off.

cb650 · « **Reply #10 on:** December 17, 2011, 01:12:45 PM »

Honda didnt.

Nickdawg18 · « **Reply #11 on:** December 17, 2011, 04:55:38 PM »

My bad. Thought I read somewhere that Honda did a run of powder coated motors so I figured they done the carbs as well.

cb650 · « **Reply #12 on:** December 17, 2011, 08:58:04 PM »

The 82 nitehawk was black but dont think it was powdercoated. Some or the 750 are too.
Also as it came up about being cold blooded.
None of mine really are. my current ride I start it for about 1 minute to get the blood going then finish getting ready go restart and leave with a little choke and after a mile or so its off unless its really cold out. i have had (have) many and all act mostly the same. Only exception is the drag bike it liked to be hot. but it liked to be jetted lean.

Hush · « **Reply #13 on:** December 18, 2011, 12:04:19 AM »

If you are going to pull the auto advnce unit (and it ain't a hard thing) just remember to mark the adjuster plate where the pick-ups are and also mark the casing so you can line them up when you have finished without having to retime the engine.
My 650 had dry as rusty advance mechanism, once cleaned and lightly lubed it would pull a wheel stand.

Nickdawg18 · « **Reply #14 on:** December 21, 2011, 10:21:26 AM »

Ok. A few more questions. Does anyone know the sizes of all the orings that connect the carbs?? Can the be found at lowes or anything like that? What's the size of the screws that hold the choke butterfly onto the shaft? I noticed that they were peened from the factory so how do you fix this once you take them out? And is there a sync video out there anywhere and what tools do I need to perform the sync? Thanks guys.

70CB750 · « **Reply #15 on:** December 21, 2011, 10:40:54 AM »

I use Lowes o rings for my Ts. They are for water and the gas make them expand and seal even better. Not sure what size. I took the T with me and matchedthe ring to it.

Hush · « **Reply #16 on:** December 21, 2011, 11:26:29 AM »

Not sure about the size of screws holding choke butterflies on as I have never removed any.
As for syncing the carbs there are plenty of how to's on here even advice on building cheao synch machines but I got mine done by a pro so I knew they were right for the first time anyway, synch lasted at least 3 years so pretty cheap in long run.

onepieceatatime · « **Reply #17 on:** December 21, 2011, 11:49:03 AM »

Quote from: Nickdawg18 on December 17, 2011, 07:19:58 AM

ok, i figured out why the gas poured out. the 3ways that connect 1&2 and 3&4 are completely dry rotted. anyone have a lead on a set for cheap?? All I can find are some that are $34 a piece.

Someone posted this link on the 650 forum and said they work great.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=330560815984&fromMakeTrack=true&ssPageName=VIP:watchlink:top:en

Nickdawg18 · « **Reply #18 on:** December 21, 2011, 04:03:26 PM »

I don't see how those would work. The look too wide and those are male fittings. I need female.

scunny · « **Reply #19 on:** December 21, 2011, 09:20:34 PM »

the screws holding the butterflies are 3mm from memory. to remove the old ones use a dremel and cut off the staked part, otherwise you will bugger the threads. I replaced with new ones and loctite. no probs after 3 years this way. can't help on the o-rings sorry.

Gentlemanjim · « **Reply #20 on:** December 22, 2011, 10:56:45 AM »

Not to crash the party, but how do you remove the pressed in pilot jets?

cb650 · « **Reply #21 on:** December 22, 2011, 12:42:06 PM »

What year? 79/80 you use vice grips and slowly work them out while twisting.
81 your screwed mostly. Never heard of anyone successively getting them out.
82 screw out.

Nickdawg18 · « **Reply #22 on:** December 25, 2011, 09:16:04 PM »

Update. So I've searched everywhere online for some cheap "T" hoses to no avail. Before I spend $70 on 2 pieces of rubber I'm gonna try something. I got some really thick high temp rubber from work and I whittled (if you will) the two "T"'s that I need. Work great. Easy fix and I'm not out anything. I know they don't leak but the carbs are not on the bike yet so she's still not runnin atm.

Nickdawg18 · « **Reply #23 on:** December 26, 2011, 07:22:15 PM »

Another question. Is there supposed to be some sort of liquid in my floats??? All 8 float chambers have a liquid in them that I can't imagine how it got in there.

ThomasD883 · « **Reply #24 on:** December 27, 2011, 05:59:54 PM »

Those float's should be dry, intrusion makes em drop and your carbs over flow. They may actually fill up and drop, then release the fluid during removal and only seem partway full. If they are brass you may be able to repair them with some serious soldering skills, plastic leaves you kinda f'ed. Best of luck to you, those 650's are rockets

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Author Topic: Just got a cb650. A few questions. (Read 6942 times)