Place your bets

I've a circa 1984 CB750 (I think it's an FD) that's been in the garage
since about 2000. I dug it out to have look at the week end:
+ New battery
+ New plugs
+ Started to change the oil but the new filter is the wrong size.
+ Both forks leak - how did the seals fail in storage?
+ The CDI units have *melted* (Google tells me this is not a unique
occurrence.)
+ Fuel tank was full of petrol - now in the lawn mower and the R30
(cue post about walking to the petrol station for fresh fuel later
on...)

How do you rate my chances of getting it running? Plan is to test the
ignition and hope the CDI units still work or it's £130 + VAT. Fill it
up with fresh fuel and give it a go. Is there anything else I should
do first?

My main worry is that the carbs will be full of shit.

If it goes I'll need an exhaust - MOT testers are a bit less lenient
these days...

Cheers,

Nick

 

They will be. Guaranteed. And it's a *bastard* job to get them
properly clean.

 

I'm guessing it'll be a *bastard* job just to get them off and back on
- never mind clean them. The rubbers will have turned to bakelite...
I've got my fingers crossed that I drained them before I put it away.

A new exhaust will cost me as much as the bike is worth so if I have
to GAMI to do the carbs I'll be fairly peeved.

Cheers

Nick

 

They're a few miles up the road: seem okay. Such dealings as I've had with
them have been unproblematic.

 

Had another look at the CB 750 last night...

Got the right oil filter this time, so that's sorted.
Cleaned out the fuel tank. Tap only worked on reserve. Messed with and
cleaned the tap / strainer arrangement. The strainer is split so I've
fitted an inline filter - sorted.
It fired up and ran for a few seconds on "Easy Start" but won't
sustain it. (Hmm, dentist's don't smell of ether anymore - why not?)
I let the fuel run through the carbs and out the drains 'till it
smelled of petrol, rather than old paint.
Still wouldn't run for more than a second or so. (Still on Easy
Start.)

TOG was on the money:
Took the carbs off and took float bowl off one of them - looks pretty
clean inside. Bottom of the float bowl is blackened, a few flakes of
"varnish" floating about in the petrol. The jets are quite blackened
and seem to be blocked - I can't see through them. Sprayed them with
contact cleaner and poked them with a nylon bristle from a tooth
brush. Managed to clean one of them out - still can't see through it
but I can spray contact cleaner through. The others remain blocked.
What now?
Is there a solvent for this?
Should I get an ultrasonic cleaner from ebay?
How do I know when it's cleaned out properly?

Cheers,

Nick

 

Use proper carb cleaner and not contact cleaner. Admittedly that's
fairly nasty stuff but a decent motor factors should have a can or two;
They're definitely worth the money.

I think most of them aren't quite up to taking in one carb, let alone
four. It may be worth it if you can get the proper cleaning fluid as
well - TBH I don't know if you'd use water or a different fluid on carbs
but I'd say this is something that needs looking into before you splash
out on the cleaner.

You'll have a running bike?

 

There's a dick on rmt who's forever banging on about some gunk in the
US. You can buy carb cleaner here: stuff you tip into the tank.

No - it's better to send the bank of carbs to a specialist who knows how
to use ultrasonic cleaners. The small cleaners won't take an entire bank
of carbs anyway.

When it runs properly.

 

Ok. I'll get some while I'm out.

Sure. I was just going to get a small one to put the jets and other
detachable bits in. I'll see how I get on with carb cleaner.

Sadly, I'll have to put it all together to find out...


Cheers,

Nick

 

Yeah. I think he must have a keyboard macro to paste that blurb
in.
I don't really see how "in the tank" stuff would work on a non-runner,
anyway.

I didn't know there were such specialists. Probably doesn't make
economic sense. I'm nearly at the point where I could have bought a
running CB750...

True. But if I put it back together and it doesn't run am I going to:
+ take the carbs off again?
+ look for another fault?
+ kick it over and shout??

Cheers,

Nick

 

That's *not* the stuff I was talking about - the one I'm talking about
comes in an aerosol.

And surprisingly enough, the stuff that Albrecht's been going on about
supposedly is rather good compare to the piddly stuff we can get over
here at Halfrauds.

 

Use Gunwash (cellouse thinners) about £7 for 5L from an autopaints shop.
Cheaper and as effective.

 

Not if you're sure they've been cleaned properly.

Yes

 

I'm sure. It's just that he regards it as the cure for everything.

 

I think he missed this bit on the label:

"Not to be taken internally"

B12 carb cleaner is excellent stuff, despite Albrecht's curious
obsession with it. Also Yamaha makes some very potent liquid carb
cleaner, you dilute it with petrol and fill the bowls directly,
bypassing the tank.

Personally, when removing carbs for cleaning I use the cheap aerosol
stuff from Wal-Mart, $1.82/big can, dissolves every sort of muck I've
seen so far.

 

A little more progress. I got a couple of cans of carb cleaner - it
certainly works. I have cleaned the three jets in one of the carbs. I
took the err.... top bit apart too and cleaned it. Didn't seem to be
much scope for things getting blocked in there. Am I done? Are there
some passages in the "body" of the carb? I have done three jets and
the slow running "passage".

I realy don't want to become as practiced at getting the carbs on and
off as I was at shimming my Ducati's valves. - That got to the point
that if I whistled they'd do themselves.

Cheers,

Nick