Topic: 1975 CBB550 build- very first bike and first build

[CBertels]

Hello everyone! Chris from Orlando, FL! 

I recently acquired a '75 CB550 project another guy had started a cafe' build with but never finished.  Its in good shape overall but definitely needs some work to get it to level I expect.  Any suggestions on where to start, it would be appreciated.  Given all the prior owners mods, I'm still figuring out whats still CB550 and whats aftermarket, modified, donor parts, etc. 

After a new battery and some wiring corrections, I've got in running, albeit terribly.  It only runs with a wide-open throttle, idling at about 2k.  Let off the throttle and it dies immediately.

Per the prior owner, "The short block is original and in wonderful condition. The head i had ported and installed new in/ex valves and dual valve springs with new seals and retainers. I also installed larger jets due to the increased air flow. It is also running a new electronic dyna ignition with new wires and plugs."

I welcome anyone interested in coming by to swing wrenches or have a few beers anytime.  I start a proper build thread when tedious stuff is finished.  I've already gotten some great help in the new member section but wanted to start a "build thread" to document the progress.  The attached photos are the bike as I got it.

Wish me luck!

[SOHC4 Cafe Racer Fan]

Lots of work and money thrown into the bike (according to the owner and many visible mods).  The ported head and NEW valvetrain is something you cannot confirm without taking the motor apart, AND there's not need to do that UNLESS you have a leak or any strange noises emanating from the engine. 

The front is definitely NOT stock.  It looks like the prior owner (PO) added a second disc and reversed the forks and mounted the dual calipers aft of the forks.  This is a nice mod, and it looks familiar (like a fellow member's build posted her before).  The PO also added a fork brace.  I would not be surprised if the forks were rebuilt and the brakes.  The front master cylinder is aftermarket as well.

The PO removed the speedometer and tapped in some LEDs to serve as idiot lights on the bar clamp. 

The PO added aftermarket rearsets.

The PO adapted a disc rear hub, rear master cylinder, and re-laced the rear wheel with a wider rim.  These are all valuable mods assuming they were done correctly.

The only thing I don't like is the seat and the loose wiring under it.  The seat looks cheap.  Have a nice sheet metal steel or aluminum one made.

 

[goldarrow]

75 550 carbs come with 38 slow jets and 100 main jets in stock oem setting.  Since no oem air box in place, I say change the slow jets to 40 and see how bike idles.  For exhaust, I say try to see about 105 or even 110 main jets, but better yet try adding 4 into 1 collector and add muffler to the tail.  Rework the seat and bike would look many time better as it sits. 

[CBertels]

Thanks for the tips!  Pulled the carbs off today as well as the in-line fuel filters.  The filters have what looks like a ton of rust in them.  I pulled one of carbs apart and the gas that came out was VERY brown.  The seals and gaskets looked like a rebuild was done not long ago. 

I've drained the tank and gas didn't look great there either.  Looks like I'll either need to clean and seal it or look for a new one.  Given the prior owner doing the less than even knee dents in the tank, I'm not sure which route I want to take.  Any suggestions?

Given the rust, should I go ahead and do a full rebuild or would running some new gas through them be enough?

[knottedknickers]

Thanks for the tips!  Pulled the carbs off today as well as the in-line fuel filters.  The filters have what looks like a ton of rust in them.  I pulled one of carbs apart and the gas that came out was VERY brown.  The seals and gaskets looked like a rebuild was done not long ago. 

I've drained the tank and gas didn't look great there either.  Looks like I'll either need to clean and seal it or look for a new one.  Given the prior owner doing the less than even knee dents in the tank, I'm not sure which route I want to take.  Any suggestions?

Given the rust, should I go ahead and do a full rebuild or would running some new gas through them be enough?

If by 'rebuild' you mean remove the jets, etc., and meticulously clean out all the fuel / air passages, then yes, rebuild them. If that's not what you mean, do it anyway. ;-) Sounds like a good cleaning is in order. The fuel valve at the bottom of the tank should also get a good clean. Have fun! View it as an opportunity to learn (if you don't know your way around the inside of a carb). Oh, and grab a copy of your bike's manual before you start. Could come in handy...

[CBertels]

Thanks for the tips.  I pulled one completely apart and it had rust and crude in every imaginable crevice.  I am going to tear them all the way down for a rebuild.  I will likely powder coat the bodies and zinc/polish the hardware and other parts.  Should look awesome.

I've never torn these carbs down but I have a lot of experience with Webers and Dellortos that I should be fine.  I take lots of pics along the way and keep organized so I should be in good shape.

While the carbs are soaking and I'm awaiting parts, I'll be going through the tank, lines, etc. and determine if the tank is too far gone or attempt to clean and seal it. 

Any suggestions on tank sealing products/

[calj737]

I'm a big fan of Caswell, and I prefer the clear not colored product.

[CBertels]

I'll check out Caswell.

I got the tank off and drained. Gas looked pretty good. Tough looking into the tank but from what I see it looks really good. Gonna give it a good cleaning and selling anyway.

I do have a question about the petcock. It's got two outlets, and they ran to carbs 1-2 and 3-4 respectively. When draining the gas, has only came out of one. The other isn't clogged and will pass fluid if the other is plugged with a finger. Is this the piper routing or is one like a vent?  I've seen this issue pop up with other members doing tank swaps.

[calj737]

You need the screen for that petcock. It's normal for the fuel to come from one or the other when disconnected from the carbs.

If you do line the tank, prep is essential. Grab a bottle of Prep'nEtch and be sure to clean the tank fully (I like a pint/quart of Acetone). Then PnE. Then split the liner into 2 applications. Pour half in through the petcock to coat the underside of the top. Drain thru petcock. Wait overnight, second half of batch pour thru filler cap focusing on tunnel, sides and floor. Drain thru petcock. This should insure you get 100% coverage of the entire interior.

[Adam77]

I have recently taken apart the carb on my 550. It was my first time even being inside a carburetor. This video was a ton of help. Really, it isn't complicated at all, especially if you already have some experience. 

[CBertels]

Thanks Adam!  I've gotten mine all apart and soaked in a mild cleaner.  I've dropped the bodies off to get powder coated and will have the hardware zinc plated.  I'm currently awaiting on a jet kit.  I noticed that the carbs had different sized jets between them, which I thought was weird.

While thats going on, I'm tackling the rear  brake.  The where has been swapped with a wider HD wheel and disc.  What I hadn't noticed is the rear caliper bracket doesn't fit AT ALL all and is just resting on old mount. 

Any ideas on whether I can snag a factory mount (CB750, HD) or if I'll have to fab something?

[CBertels]

Here are photos of that bracket.   In the last photo, you can see where a stock bracket would likely bolt from the caliper to the swing arm.  Without the bracket secured, it just rotates on the axle.

Thanks for all the help!

[calj737]

Got news for you: the 550 didn't come with a rear disc so your swing arm isn't configured to secure that caliper. Only 750 SuperSports had a wire wheel and discs. So either ditch your setup and replace with a 750 hub and swing arm and associated parts, or, fab a caliper bracket to secure what you have, or restore a drum rear brake. Only options.

Sounds your carbs were wonky. Good to restore them to stock jetting with only original Keihin brass (jets and needles). Don't use aftermarket brass!

[CBertels]

I'm beginning to think that finishing/fixing someone else's project is more difficult than starting from a junk stocker. After getting the wheel off I see the mount was welded on by a blind man.

Someone mentioned previously that the rear swing arm may be a 750 or something else non-550 so I thought there may be some options there. Im determined to make what I've already got work, as long as it's safe and performs well. This is the last major weird thing I need to sort I think so we'll see.

[calj737]

That's not a weld; someone with no knowledge or skill threw up their lunch of Flux on that seam. Cut it off, grind it down, and have it welded properly by a competent welder.

[CBertels]

There's quite a bit of that handiwork on here. The electronic's is tray and rear bump have the same handiwork along with the rear control mounts. I knew of those and planned to correct that already but didn't notice the brake situation.

I know my way around a welder and should have it sorted shortly. I'm going to fab a new bracket and rear mounts and try to reuse this rear wheel. I like the disc and big tire so if I can salvage it I will.  I'l also need to make some spacers to center the wheel cleanly.

I took this on to learn as much as fab/build so all the input and suggestions are really appreciated. Hopefully I'll have more interesting photos and build updates to post soon!

[calj737]

Then get off the computer, and fire up the grinder! 

[CBertels]

HAHA, once I get that thing going, there no stopping it.     Researched the 750 disc a little and stock, it looks awful.  The drums I've seen look indescribably better.  Given how little the rear brakes really do, I'm surprised many try to swap the drum out.  I guess it "matches" if you upgrade the front but I'd keep the drum if I was working from a stocker. 

I'll be getting that grinder out tomorrow and machining or modifying the existing bracket.  Wheel spacers will be needed too.  Photos to follow.

[madmtnmotors]

Subscribed.

I'm in Saint Cloud. Don't have any experience with the smaller CB's, but I'll contribute ideas if I can.

Some of the issues you are experiencing are why I consider "custom" or "café" or "steampunk" etc., to be of very little value to me. I'm all for improvements in function and performance, but the N.O. (next owner) should be able to maintain and repair it with readily available service manuals and parts lists. Total custom builds often require systems to be "reverse engineered" just to determine whether or not they are within acceptable limits as far as functionality and especially safety. Too many pie-in-the-sky dreamers with a grand vision and no practical understanding of basic physics, such as:

>Gravity
>Acceleration
>Deceleration (i.e. brakes)
>Steering geometry
>Suspension design requirements

Just to name a few.

    Good luck with the build, I ride all over (rode to Ohio and back last summer) and work in Orlando so we should be able to cross paths and compare notes at some point. Lots of knowledgeable members here should be able to help you get it on the road. 

[CBertels]

While waiting on carb parts, I started to strip the tank and get it cleaned up.  I've cleaned the inside real well but didn't get much out so I'm taking that as a good sign.  I'll likely seal it once I finish the metal work on the outside.  The knee dents definitely need some attention to get a bit smoother before filler, primer, paint etc.

[CBertels]

Got all my carb stuff back from plating/powder coating and the look AMAZING!  I got them assembled and bench-synced according to all the great tips on this site.  It fired up pretty quickly but I thought it was running rough.  Fuel is misting out the intake side as well.  Cylinder 1 and 3 are not firing.  The exhaust was significantly cooler as well.  I pulled the plugs and they were a bit damp and no soot.  Cylinders 2-4 are running VERY rich and soot build up on the plugs after only a few minutes of running.

I pulled the float bowl drains and fuel came out in equal amounts from all carbs so fuel is getting to them.  The plugs are all getting spark when turning the engine over with the kick, so I don't believe it to be a spark issue.  Really only leaves a carb issue but I can't seem to track it down. 

Any thoughts??

[calj737]

Those do look nice! After powder coating them, I would not be surprised to encounter some blocked passages. I would soak them really well, use carb cleaner, comroessed air, and blow them out at least twice. Double check your emulsion tubes and fuel levels via clear tube method.

If you had bench synched them, they should run well if they are getting fuel 

[CBertels]

The carbs were spotless when re-assembled. The was no powder where it shouldn't have been. I went through them carefully.

I did the bench sync thing using the 1/8 drill bit method, etc. Given the spaghetti mess of wires I'm suspecting it may be an electrical issue. Diagnosis has been incredibly frustrating. 

[SOHC4 Cafe Racer Fan]

The carbs were spotless when re-assembled. The was no powder where it shouldn't have been. I went through them carefully.

I did the bench sync thing using the 1/8 drill bit method, etc. Given the spaghetti mess of wires I'm suspecting it may be an electrical issue. Diagnosis has been incredibly frustrating. 

Fixed that for you. 

[CBertels]

Who said this forum isn't helpful...