Topic: New member question for the masses

[Mafia]

first of all I'd like to start by saying hello everybody and thank you for what you do. my name is Matt I currently own a 1977 CB 750 F2 that I purchased for 500 bucks in non running condition. Bike in s in great shape for sitting for 20 years.even has a full tool kit. So my two questions I'm starting off with are these...
1. The carb slides seem to be seized.turning the throttle does nothing and can't move them with my finger. What is the best way to get these puppys functioning as intended without a full rebuild.
2. There appears to be gunk/buildup in the front master cylinder. What can I put thru there to clean that crap out.
My plans for the bike are simple.get it running to confirm it can do so then go from there. Probably a cafe.ty all for your time

[flybox1]

welcome to the forum, Matt.
your carbs should come off for a chem dip and then a thorough, and i mean thorough, cleaning with carb cleaner/simple green.
the MC can be cleaned with brake cleaner.  lines flushed, and refilled with new brake fluid. 
But dont clean just the MC.  you'll need to service the caliper, too, by removing the piston, and at a minimum, replacing the piston seal.  if there's gunk in your MC, there's gunk in the caliper, which is not a good thing, especially if you want to, you know...STOP 

[wvshooter]

Ditto what Flybox1 said.

If the carb slides are stuck then you know the entire carb system is full of gunk. I know that's not what you wanted to hear but when they sit for years with fuel in them that's what you get.

You should also pull the rear brake hub to be sure the rear brake is working like it was designed to work. Front and rear bearings checked. Wheel spokes and control cables need checked as well.

Also, pull the battery cables and the large battery grounding cable where it attaches to the frame. Sand these connections to be sure they are able to easily transfer electrons.

[TwoTired]

I wouldn't pull of the carbs until I dropped a bowl to see what deposits are inside them.  If there are chunks of anything in there bigger than 0.016".  It is more than likely the pilot jets are plugged.  As those are pressed in, yanking them out is far easier with the carb bank on the bench.  It will also allow you to service the accelerator pump circuits and clear them as well.

The slides can usually be freed using a heat gun on the slide barrel portion of the carb.  It is also acceptable to remove the top caps of the carbs to squirt some penetrant oil at the slide to barrel interface.  I've seen these stick even with the rest of the carb clean.  Seems to occur regularly when the bowls are drained for storage.

Check the FAQ for  caliper rebuild walk through.  The master can be rag washed with Brake Kleen, the tiny bleed hole can be cleared and new fluid will reveal if the lever moves freely and it doesn't weep.  Otherwise, that will need to be refurbished, as well.


Pity about the cafe plans.

[Mafia]

Great advice ty. What's with the crazy verification everytime I wanna reply.sheesh.
So when removing the air box bolts one just turns doesn't wanna catch and unscrew. Any tips for this?

[Bankerdanny]

If you opt for a carb dip, and I used it on my 550 carbs with no issues, just don't overdo it. A couple hours at best. There are some felt washers in the carb bodies that are very hard to replace and will be destroyed by excessive time in the carb dip.

[flybox1]

Great advice ty. What's with the crazy verification everytime I wanna reply.sheesh.
So when removing the air box bolts one just turns doesn't wanna catch and unscrew. Any tips for this?

drill/dremel the head off.

[martin99]

If you pull the breather pipe off the top of the airbox, remove the bolts that attach it to the frame and undo the bands that hold the rubbers to the carbs it'll wiggle out as a complete unit. I find it easier if you bring it out on the right (kickstart) side.

[Stev-o]

What's with the crazy verification everytime I wanna reply.

Welcome.  Should go away after a few more posts.

BTW - we love pics and we can help better when seeing the issue.

[harisuluv]

Also be careful with the simple green, there is a type that is safe for aluminum but if you use the normal stuff limit it to 30 minutes as it will discolor aluminum. 

[TwoTired]

So when removing the air box bolts one just turns doesn't wanna catch and unscrew. Any tips for this?

There is a nut embedded in the plastic box bottom. These nuts round out the plastic and no longer stay in place.  A bent needle nose can grab that nut, allowing the bolt to loosen.

[Powderman]

IMHO there is no scenario that would not include a full rebuild of the carbs if they are in the condition you mention.

[Don R]

A thin socket can be heated, melted into the air box just enough to grip the hex. After it is unstuck and antisieze is on the threads the nut can be epoxied back into place.

The carbs should be looked into. It's possible they were drained but will still need attention.

[Mafia]

A thin socket can be heated, melted into the air box just enough to grip the hex. After it is unstuck and antisieze is on the threads the nut can be epoxied back into place.

The carbs should be looked into. It's possible they were drained but will still need attention.

Great idea!!!

[BobbyR]

TT is correct, drop the bowls and see what is in there. When fuel evaporates it the vapors can condense on the slides and the walls and act like glue. Solvents can wash that stuff away. If you find the bowls full of crap, do the job completely and it will save you time.

Denatured alcohol can totally dissolve dried brake fluid in the MC and the lines, but not a quick fix for the caliper. Most of your braking is in the front and trust me, you will need that brake.

Chances are you will need to tear down the carbs. If you do, take your time, the PD carbs have an accel pump which needs attention since there is so little gas in it, it oxidizes very fast.

Feel free to ask questions, that is what we all should be here for.

Good Luck!