Author Topic: CB750f. Parts bike or project? Pic heavy thread. Need opinions. (Read 10894 times)

b1jackson · « **Reply #25 on:** December 10, 2016, 03:06:07 AM »

Look at that bling. Removed the oil cooler and adapter plate. It's not going back on.

Might as well put some fresh oil in the bike too before attempting to start (this won't be happening for awhile!)

This was so oily I didn't realize it was chromed!

b1jackson · « **Reply #26 on:** December 11, 2016, 04:32:54 PM »

Cleanest carbs in all the land!

Paint removed (what kind of fool paints their carbs!) and hellish dirty varnish gone. New kits installed.

Float height all set at 26mm.
I kept the jets in that the PO was using (135) rather than using the stock size ones from the new kits.

Just need a bench sync and they are done!

SOHC4 Cafe Racer Fan · « **Reply #27 on:** December 11, 2016, 05:05:00 PM »

They look good. Even Harrisuluv would likely approve.

seanbarney41 · « **Reply #28 on:** December 11, 2016, 05:22:36 PM »

you using pod filters? If not, those 135's gonna be toooo big

b1jackson · « **Reply #29 on:** December 11, 2016, 05:47:44 PM »

Quote from: seanbarney41 on December 11, 2016, 05:22:36 PM

you using pod filters? If not, those 135's gonna be toooo big

There are a couple of dirty old pods in a parts box that I got with it so assuming the PO used pods. Also the original airbox is long gone so, yeh...likely will try pods as they are probably cheaper to source than an air box. Not sure yet.

Getting the bike running is step 1.

seanbarney41 · « **Reply #30 on:** December 11, 2016, 06:25:55 PM »

Quote from: b1jackson on December 11, 2016, 05:47:44 PM

Quote from: seanbarney41 on December 11, 2016, 05:22:36 PM
you using pod filters? If not, those 135's gonna be toooo big

There are a couple of dirty old pods in a parts box that I got with it so assuming the PO used pods. Also the original airbox is long gone so, yeh...likely will try pods as they are probably cheaper to source than an air box. Not sure yet.

Getting the bike running is step 1.

doubt it on the price...cheap emgo style pods really don't work...period. And k and n's are $120 a set...

One year I was at the Gilmore Vintage Bike Show swap meet. I bought an airbox for $5. Two vendor spaces later I found another in somebodys "free" pile. I suppose if ebay is your only parts source you might have to pay a small chunk for an airbox...i dunno, I got one whole shelf at the shop overflowing with cb750 airboxes, and I doubt I paid $50 for all of 'em.

754 · « **Reply #31 on:** December 11, 2016, 07:51:13 PM »

135 is probably wwwaaaaayyyyyyyyyyyy more than that motor can eat..

b1jackson · « **Reply #32 on:** December 12, 2016, 01:46:09 AM »

Thanks for the input guys. Appreciate the insight and stay tuned. I wonder if since the engine had the performance cam and (maybe) yet to be determined piston upgrade, that the PO didn't up the jetting too. We will see.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #33 on:** December 12, 2016, 09:41:37 AM »

812 kit with Yoshi Daytona cam, no head work, at 6900', stock airbox with K & N, Kerker or stock 4 into 1, 115 mains were slightly rich

b1jackson · « **Reply #34 on:** December 12, 2016, 12:17:20 PM »

It came from a place 50 meters above sea level if that matters. But perhaps it ran like crap? Who knows?

754 · « **Reply #35 on:** December 12, 2016, 01:45:51 PM »

He did up the jetting but too much. Common thought is every change needs an increase it jet size...but in reality it aint so..120 or 125 maybe

b1jackson · « **Reply #36 on:** December 14, 2016, 05:26:04 AM »

I'm thinking for now, I'm best to just run the stock sized jets. No need for "performance" just yet on something I am basically trying to get running again. At least with stock, I should have a decent known baseline for any possible troubleshooting.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #37 on:** December 14, 2016, 11:27:49 AM »

Did your bore scope show up yet?

The stock jet is a 105. Too small for a cam. Hard to say how much up you need to go. Strictly guessing game anyway. Depends on bore, cam, air filtration and exhaust. I'd definitely go up at least 1 size initially with stockish exhaust and airbox and raise your needle 1 notch for that mid-range cam while the carbs are off for starters. If everything is free flowing then maybe a couple sizes on the bigs.

b1jackson · « **Reply #38 on:** December 14, 2016, 11:54:42 AM »

Still waiting for the scope. Slow boat from China I guess? And right now, the exhaust is rotted off so I'm unsure where I'll go with that though likely something not too obnoxious.

b1jackson · « **Reply #39 on:** December 24, 2016, 06:41:47 PM »

Was hoping that the collector part was in solid enough shape to just put a slip on on it but pulled the exhaust today and it's toast. Rusty big time. So I'll be looking for a new one. Looks like the aftermarket ones on vintage CB are about the lowest price for me.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #40 on:** December 25, 2016, 11:02:23 AM »

Look into Delkevic. Very good quality and stainless at a great price. I have one plus a Kerker $$$ too.

b1jackson · « **Reply #41 on:** December 26, 2016, 02:46:14 AM »

I guess no matter what I look into I better be prepared for the sticker shock of it being more than I paid for the bike. The joy of a project after all.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #42 on:** December 26, 2016, 10:21:21 AM »

Delkevic ~ $329 shipped complete unit. 2 different muffler options.

b1jackson · « **Reply #43 on:** December 26, 2016, 01:21:27 PM »

Didn't see that price for Canadian buyer

b1jackson · « **Reply #44 on:** February 08, 2017, 09:57:14 AM »

Update : Scope from China never did arrive

Tried one from Cdn. Tire but it wasn't small enough to fit inside the spark plug holes so therefore all I saw was blackened piston tops and I definitely couldn't read any markings to tell whether or not there were oversized pistons in it.

Think that I am now just going to do a compression test using the kick starter. There is fresh oil in it. Maybe a bit of wd40 down the cylinders?

b1jackson · « **Reply #45 on:** February 19, 2017, 01:20:48 PM »

Ok. Amongst many other tinkerings with the bike this weekend, I decided to do a compression just using the kick starter as the bike is in pieces. The issue I had was when I went back to re-check cylinder #1. My process:

(1) squirted abit of wd-40 down the cylinders a couple of days ago
(2) there is clean oil in the bike as I didn't want to be pumping crap oil throughout the engine
(3) started at cylinder # 1 with my handy dandy guage.

Cylinder #1 gave me just shy of 120 lbs at first check and held pressure but that changed...[b/b]

Cylinder # 2, #3, and # 4 all gave me 150 lbs. Quite pleased with that! [b/b]

When I went back to re-check #1, I could get it up to 150 lbs but the guage would fairly quickly zero. Connections were all tight on the guage so can I assume that this is a stuck intake valve? No doubt will loosen up when the engine actually gets running again.

Also, recall this bike has a Yoshi cam in it and with 150 lbs compression, could there be high compression or upgraded Pistons in it too? That just seems high to me. I'd expect about 120.

b1jackson · « **Reply #46 on:** February 24, 2017, 01:49:15 AM »

Anybody?

754 · « **Reply #47 on:** February 26, 2017, 09:25:11 PM »

Squirt a bit of oil in , if compression holds its rings.

Don R · « **Reply #48 on:** February 26, 2017, 09:52:27 PM »

Re-check the valve lash on No.1 If it's been sitting there could be a little rust of carbon stuck on a valve seat. I wouldn't freak out about those numbers.

b1jackson · « **Reply #49 on:** February 27, 2017, 02:50:48 AM »

Yes. I assume just gummed up. I've squirted some WD in the cylinder and abit around the valve from the access bung. I don't thing the bike has ran since the mid 1980s.

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Author Topic: CB750f. Parts bike or project? Pic heavy thread. Need opinions. (Read 10894 times)