Shiny's 1980 CB750 F...happy with pods.

[shinyribs]

Wow, thank you for looking! I found some needle and seats on jetsrus for $11 per carb. Still spendy,but affordable.

And type away bud. I like to chat.

PM inbound.

[shinyribs]

It was like Christmas at the post office just now.  My needles and seats came in. Also. the jet kit that Hambone so graciously sent to me. Free of charge.
Thanks again! Off to the barn....

[hambone]

awesome! glad they made it..cant see how that beast runs...

[hambone]

I meant cant wait to see how it runs....

[shinyribs]

Hahaha! After im done working on something, sometimes I really can't see how it runs either. I s'pose I just get lucky sometimes. :D

[shinyribs]

Got the Mikuni's on. 130 main ,32.5 pilot, idle mixture at 2.5 from seated.

Has only been bench synched but the first thing I noticed was how smooth the bike starts up and idles now. The typical clutch rattle is nearly imperceptible. I know synch isn't what causes clutch rattle, but its a good indicator of a smooth idle. It really is idling smoother than it ever has, which seems so odd to me.

Anyway, off idle and part throttle feels fantastic. Very smooth and elastic. In 5th gear I can peg it at 25mph and it will accelerate to 100 smoothly.

But....


Ok, so on the first go I used the needless that came with the kit. Which are remarkably shorter than the stock needless. About 6-8 mm, but the profile is otherwise very similar. Not a skinny needle at all.

With these needless the bike would break up at wot in 1st and 2nd. Backing off the throttle slightly smoothed it out. All other gears revved well. Activating the fuel enrichment circuit has no affect on the stumble. Also, puttering around the bike seemed to have a slight roughness when holding the throttle steady to just cruise ( 25-40 mph in 5th) . Rich bogging?

So, I popped the stock needles back in. Longer needle should be a little leaner?? The cruising sputter went away , but wot in 1st & 2 and were unchanged. 3rd gear now stumbles at wot. Backing off still smoothed it out.

I think the short needles were introducing too much fuel at cruise, since the long needles seem to have cured that. But its causing 3rd gear wot to stumble. Shim these longer, stock needles for more fuel? Opinions please.

[TOOLS1]

"Options?"  Here try this  http://www.dimecitycycles.com/vintage-cafe-racer-caferacer-bobber-brat-chopper-custom-motorcycle-carburetors-keihin-cr31-cb750-cb900f-cb1100f-sidedraft-racing-carburetor-016-3051.html
TOOLS

[shinyribs]

Float me 800 bucks and I'll be glad to run those.

I'm guessing I'm running lean? Since backing off the throttle ( closing the butterflies/air) clears it up, would that be a lean condition? But you would think activating the fuel enrichment circuit would show an improvement if this was the case. I dunno, but I'm only on day 1, so I still have hope. It's ooooodles better than it was. Gettin' there...

[hambone]

Shinyribs,im trying to process whats going on here..i know your bike is basically  a 900 so its gonna be slightly different than mine so I can tell you my settings...needle is 2nd clip down ,2 turns out on the mixture,i have used two different slow jets -the ones that are in the kit and the emulsified ones with holes...now the second ones run a bit rich on idle but no hesitation on take off..thats on a stock 750 other than cbr coils..when I had my original needles in I had those 150 mains in there .might be worth a try just to see..i also don't have pods ive got velocity stacks ...im not sure if yours is running lean or rich.i think you should try to shim what you have in there now.once these are dialed in its a very nice pay off..if these needles just aren't doing it...I have another stock euro set that actually has clip positions..very close but not identical to the kit...your there just a combination of the little things,sync ,clip position,mixture...I hope some of this helps

[hambone]

my gut is also telling me those slow jets might not be enough with your engine set up

[shinyribs]

Thanks for the input Hambone. I shimmed my stock needles up and it helped wot. Still not perfect, but it'll rev higher before breaking up, which tells me out so needs more fuel. But, the low rpm cruising sputter returned. Which tells me the needle is too high at that particular point. So I'm guessing I need to bump up the mains for more fuel and drop the needles to correct my cruising stumble.

[shinyribs]

Just documenting things incase I decide to forget...

All of things being the same, I did drop the 110 mains back in. The breaking up is worse, starts sooner and has also moved in to 3rd gear now. So going leaner was definitely a step in the wrong direction.

How is it possible this 823cc Honda needs more jet than the 1100 Suzuki these carbs came from?

[TOOLS1]

It does not create as much vacuum as the Suzuki, so it needs larger holes to suck the fuel through.
TOOLS

[shinyribs]

Woohoo!! Finally found a good,used lift. $150 and thirty minutes from home. I waved at HF as I motored past them....



Wasn't crazy about the bare metal wheel clamp. Too close for comfort to my rims. Glued some rubber sheets on there. Better.

[TOOLS1]

That is a great deal. And it is the older model, which I like a lot better then the newer ones. However I do not know how you went this long without one, and after you use it, you will wonder why you did not get one sooner. Also you might not want to leave that ramp hanging off it. Bad things happen when they hang like that.
TOOLS

[shinyribs]

Yeah, it seemed kinda jouncy. Like it wants to rip the ears off....or rip my knee caps off.

Dude, I'm just incredibly cheap. lol. It just took me this long to find a used one. I've found a few on CL, but they were always gone before I got there.

I didn't know thy had different versions either.

[shinyribs]

Wow, has it really been nearly a month?

Anyway, first things first. Hambone has been totally hooking me up with jets and such left and right. Big props to him! Thanks man, I won't forget that I owe you.

One my favorite sayings: If all else fails, stop using all else.

So, I've been fiddling around with carbs, jets, tuning every which way....nothing. Need to drop the tunnel vision and look elsewhere. Start from the top. Did a compression test. 170psi on all cylinders except #2. It was 120.  Turns out both exhaust valves were super tight. I mean 0 lash. Fixed that and got 170 psi on the hole now. Yippee!

Playing around with timing lead ( ignoring any factory scribe marks) I saw that my wot stumble was progressively getting better and better. If I took lead away it would creep lower and lower in to the rpm range. Ah ha! On to something!

So tonight task is to scribe a true TDC mark and time the engine by light/crankshaft degrees vs cheesy scribe marks. No offense Honda, I still love you.

Gutted a spark plug ( harder then you would ever believe) and made a TDC locater.




That was last nights project. Tonight's project, use it. To the barn!.....

[TOOLS1]

Its amazing how tough the porcelain on spark plugs is. I have dulled hardened punches trying to gut them.
TOOLS

[shinyribs]

Yes, it is.  I ended up using an old torx screwdriver that was boogered up (not sure why I still keep it). I thought ''hey, it's like a mini star chisel!". And it was. I s'pose it's all the little individual points spreading the impact at once. Chewed through pretty well actually.

Went to button everything up but I'm not comfortable with the holes in two of the cam caps that the valve cover mounting bolts thread in to. On hold until I get some proper inserts installed.

Oh, and the factory TDC mark? Dead nuts on the money.

[shinyribs]

Huh. That's a pretty sloppy fitting plug boot. Spark leak? Is that what has been haunting me all along?