Author Topic: 1980 CB650 Cafe Racer (Read 21278 times)

The_Crippler · « **Reply #25 on:** April 12, 2010, 07:33:47 PM »

Quote from: Kit on April 12, 2010, 07:14:52 PM

These bikes, with the stock carbs, are extremely lean on the idle circuit, and because of the press-in idle jets, this isn't really very adjustable. I usually leave my choke at least 1/4 to 1/2 out for the first half mile.

BTW - I finally remembered to dig out the owners manual: 45 seconds for choke, they say. Silly 1980 engineers.

manjisann · « **Reply #26 on:** April 12, 2010, 07:36:48 PM »

If the oil pump turns out to be contributing to your leak don't despair. Mine was dropping oil like the Exxon Valdez, when I pulled it off the o-rings were uber flat. I had bought an o-ring kit at Harbor Freight for like $10 a while ago and it finally came in handy, all the needed oring sizes were in there. Clean it up, put in new orings, a little gasket sealant because I really didn't want to ever have to take the dumb thing off again, some hex bolts because phillips are hard to torque properly (one note on the hex heads, the lower left bolt is a bit close to the pump body so it's not easy to put on with a socket, in retrospect I think I should have went with the allen head bolts) and the oil leak is gone. I've only been able to idle her so far, but I've revved her as far as 6k rpms (spike, I'm not holding it there without a load, just gives me the creeps) and no leaks so hopefully all is well.

Brandon

Kurlon · « **Reply #27 on:** April 12, 2010, 07:55:21 PM »

Press in slow jets... lovely. Any chance there is an easy carb rack swap with something more modern, I'm even willing to put up with CV carbs if I have to.

Does anyone make a full gasket kit for the first gen CB650? I'm looking at $55 in gaskets and seals for the bottom end, at that price I might as well get a full kit if one's available.

The_Crippler · « **Reply #28 on:** April 12, 2010, 07:57:20 PM »

Got a link for that lower-end gasket setup for $55?

Frankenkit · « **Reply #29 on:** April 12, 2010, 08:25:14 PM »

I think I got mine off Partsnmore.com for $86 but very quickly the valve cover rubber gaskets started just flaying away. Athena, I think it was.

The_Crippler · « **Reply #30 on:** April 12, 2010, 08:30:38 PM »

Yeah, you get what you pay for, I guess. I'll be taking off all the lower case panels, and I wasn't sure if I wanted to use liquid gasket like the PO did.

Frankenkit · « **Reply #31 on:** April 12, 2010, 08:47:49 PM »

oh! oh! ask Twotired if you should use liquid gasket on the lower case panels. I think I could hear the exasperated sigh from here if I tried.

The_Crippler · « **Reply #32 on:** April 12, 2010, 09:13:52 PM »

Don't worry - I wasn't actually planning to, which is why I'm trying to source some new gaskets. I generally try to avoid summoning forth the TT demon if I can help it.

Frankenkit · « **Reply #33 on:** April 12, 2010, 09:22:42 PM »

aww don't say that. He really, really knows his #$%*... enough to deserve the right to talk down to the whippersnappers a little and keep us in line.

Kurlon · « **Reply #34 on:** April 13, 2010, 04:49:12 AM »

If you're going to use liquid gasket maker, there is a Loctite product for the job. I can't recall the exact techinical term for what it is, but rather than an RTV style goop, it's similar to thread lock in that it can't dry if exposed to air. As a result if you use it on a motor, any excess that squeezes out inside the engine stays liquid, gets swept up by the oil and eventually gets flushed out, caught in the filter, or burned off. It doesn't block oil passages/etc like strings of RTV can. A bunch of dirtbikes and modern motorcycles now explicitly call for it rather than using gaskets in many places now.

Zaipai · « **Reply #35 on:** April 13, 2010, 05:22:14 AM »

Quote from: Kurlon on April 13, 2010, 04:49:12 AM

If you're going to use liquid gasket maker, there is a Loctite product for the job. I can't recall the exact techinical term for what it is, but rather than an RTV style goop, it's similar to thread lock in that it can't dry if exposed to air. As a result if you use it on a motor, any excess that squeezes out inside the engine stays liquid, gets swept up by the oil and eventually gets flushed out, caught in the filter, or burned off. It doesn't block oil passages/etc like strings of RTV can. A bunch of dirtbikes and modern motorcycles now explicitly call for it rather than using gaskets in many places now.

I have a friend that used that loctite stuff, 6k miles and still going with no sign that anything was plugged etc..

.: Scott :.

Kurlon · « **Reply #36 on:** April 13, 2010, 03:34:03 PM »

Much ado about nothing? Pulled the chain off, pulled the front sprocket off... the countershaft seal is NOT contributing to the mess underneath. That's good. Shift shaft seal is a leaker, the cap/bolt that goes into the chain side of the oil pump is a leaker, one or more of the oil pump to case o-rings are leakers, the oil filter cover retaining bolt is a leaker, and the clutch arm seal is leaking...

Oh, and I found I'm missing a motor mount bolt up front on the chain side... whoops!

Kurlon · « **Reply #37 on:** April 16, 2010, 12:05:33 PM »

Carbs get wrestled off tonight, I am NOT looking forward to fighting the boots to get them off... and really don't want to deal with them later when the carbs go back on. It has to be done though, bike will only run with choke despite loading the tank with rocket fuel and draining the bowls periodically. Only way to get those pilots cleaned is to do it the old fashioned way.

http://forums.sohc4.net/index.php?topic=38704.msg467517#msg467517

32mm CV cabs could work though... what size are the stock PD51s?

In other news, the CB is registered, so once it's where I'm happy with it, I can take it for a test spin. : )

Kurlon · « **Reply #38 on:** April 16, 2010, 03:34:09 PM »

Carb rack removed, and I found one boot on the airbox side is ripped. Looks like Honda doesn't sell it as a separate part, but they will soak me for an entire air box assembly. Pod filters may be in this bike's future.

Is there a trick to squeezing the carb rack in/out without dropping the motor first? I can't see that you can get the air box out of the way before you remove the carbs?

cb650 · « **Reply #39 on:** April 16, 2010, 05:20:46 PM »

did you pull it back with bungee cords or a ratchet strap ?

Frankenkit · « **Reply #40 on:** April 16, 2010, 05:21:23 PM »

yeah use either ratchet straps or bungees to pull the airbox back toward the frame, then wrestle the carbs out to the left, making very, very sure not to break the little plastic throttle linkage, because it's made of unobtanium and you will be in a world of crap if you break it.

Most people can't run the PD50 carbs properly with pods, so I'd nix the pod idea unless you replace the carbs. See if you can find a used airbox w/ rubbers on feebay.

Kurlon · « **Reply #41 on:** April 18, 2010, 06:10:53 AM »

I was working by myself, and didn't think to force the issue with ratchet straps. Finally got the GD thing back together, and it runs and idles! Fuel bleeds are 4 turns out and it really wants more fuel, but at least it idles off choke now. If I go WOT right off idle it still dies, but if I roll it to about 4k first is screams. The accelerator pump is a new thing to tune around also, blip the throttle, it would die and then rev for a moment after the throttle snapped shut, which was confusing the crap out of me.

I highly suspect new carbs are in it's future if I'm going to race it, but at the moment I'm just going to focus on making it sound. There is a good chance I'll be selling it to a friend to use as their first bike seeing as we've taken what he bought for himself away as inappropriate - an 84 GPZ 1100 setup as a drag bike. EFI removed and a rack of Mikuni flat slides swapped in, with a 1/8th turn throttle. Not the hot setup for a learner. : )

Kurlon · « **Reply #42 on:** April 18, 2010, 09:31:58 AM »

Took it for a quick jaunt down the road...

Dies if given full throttle, even wound up. Resumes pulling as you roll off. Couldn't see how it really runs on top as a result. Bike as 90 mains in it right now, too big, too small? (Stock airbox/filter, stock'ish 4 into 2 system, headers are OEM, mufflers are from a Kawasaki.)

Shocks are junk, no damping at all.

One fork seal is completely toast.

Front brake has good feel at the lever, but no bite. Not sure if it's prior fork oil contamination or a dirty caliper? Brake doesn't drag though.

nitroeagle · « **Reply #43 on:** April 18, 2010, 07:32:07 PM »

Check the hose too. I had to clear both ends, small holes where the rubber meets metal, with a piece of wire. They were clogged with rust. Worked great after tough.

Kurlon · « **Reply #44 on:** April 19, 2010, 04:42:13 AM »

Which hose are you referring to?

Kurlon · « **Reply #45 on:** April 19, 2010, 07:20:10 AM »

I'm going to check my float heights tonight with some clear tubing. You'd think a 'stock' setup even if poorly chosen by the factory would be able to at least pull at WOT even if it's not happy. Based on the pilots needing to be 4 out to even idle, and how badly it reacts to WOT I'm way lean across the board, low float levels would account for that, yes?

When tube testing floats, do these carbs like to have the level right at the bowl gasket, or somewhere else?

Frankenkit · « **Reply #46 on:** April 19, 2010, 08:12:26 AM »

yeah, you'll want to raise those float levels... Hondaman suggested having them somewhat high and having very new very good gaskets, so yeah, pretty close to those gaskets... basically if you flip the carbs over, the tops of the floats should be and parallel to the gasket mating surface and even across the top... so all four look like this ----, no nosing down or nosing up. make sure your float needle springs aren't sticky either. they should spring back up with vigor when you tap down on the floats.

Ideally you should only be two or three out on the pilots- it's not an air screw but a mixture screw- so you just get more or less of the pre-arranged mixture, which kind of sucks.

When this bike is properly tuned, you use choke for about a half mile (or at least less than 3 miles) and should be able to go WOT right off the bat, but with choke.

being that the bike likes its choke so much and sometimes it can be hard to tell if it's warm enough to idle right without choke, I run iridium plugs- much harder to foul so I can run choke a little longer than necessary without screwing up my plugs.

Kurlon · « **Reply #47 on:** April 19, 2010, 03:19:51 PM »

Checked the float levels, right at the gasket on all 4, so I don't think that's the problem. Pulled a plug, and I can see some brown on the insulator for a change, a big improvement from the first time I looked at them (all black). I just noticed though, it doesn't look like the plugs 'seat' in the head? The threads are rusted starting halfway from the electrode end to the crush washer, and there's no sign that crush washer has ever hit anything. They thread in ok, and are hitting some kind of stop, doesn't feel cross threaded?

I'm going to grab 4 new plugs tomorrow just for giggles.

Kurlon · « **Reply #48 on:** April 20, 2010, 05:08:30 PM »

New plugs, bike's behavior has changed a bit...

It'll idle with the mix screws at 3 turns out. Still has a bit of a habit of racing for a bit then dying down till you hit the throttle.

Going down the road, it'll take WOT at 5k and above now. Sometimes it'll accept it all the way down to 4k, and it doesn't die completely, it just stumbles and doesn't pull when angry.

I've got a tapping from the left side of the motor, hoping it's just a noisy/loose valve that I need to investigate.

Zaipai · « **Reply #49 on:** April 21, 2010, 05:43:59 AM »

Keep going at it, it seems to be making progress.. Little by little you will get her running perfectly.. Any chance the noise is a timing issue?

.: Scott :.

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Author Topic: 1980 CB650 Cafe Racer (Read 21278 times)

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