Cb750 with pods help...

cbrianroll

Member
1974 sohc...It's pretty close I think, I'm deaf so maybe not...and I suck at troubleshooting carbs in general. Right now they are on the bench, choke plate are way out of spec, havent cleaned them yet. Elec ignition so that's good, will be adjusting valves,etc...

Problem is pods...eventually gonna get stock airbox but want to ride until then. Its main is bumped up 2 sizes, needle is shimned also.
4into1 exhaust.

These carbs are new to me, I'm used to gl1000s. This rack has the single slide adjustments on top and air screws on the body. The slides should be easy enough but the air screws are bugging me. They are 2.5 turns out. Book says that's bad with stock setup. I'm guessing that's out the window since its altered but should I be changing any other jets to bring those to 1.5 turns? Does that matter?

Many thanks, please pardon me if my terminology is off...
 
Last edited:

teazer

Well-Known Member
DTT BOTM WINNER
SOHC or DOHC? It makes a difference.

SOHC with slide carbs, the idle mixture screw allows air in, so 2.5 turns means the pilot jets are a size too large.

on a DOHC with CV carbs, the idle mixture screw allows more fuel-air mixture in, so 2.5 turns means the pilots are too small. DOHC hate pods - even good pods. Cheap pods also tend to obscure the air jet inlets and totally mess with jetting.

edit: I found your thread. SOHC. I'd take the pods off and see if they are the problem. I also have a MAC muffler that might work with your pipe. Unused. I bought it to try on a project and went a different way.

BTW, stock airbox includes a set of four beautiful plastic bellmouths. I use them on some of our race bikes with K0 carbs which are basically the same carb. What size jest are in the carbs? Maybe the PO fitted jets which were a bigger size or even worse, maybe they were drilled out. I'd fit new brass, without pods and see how it runs.
 
Last edited:

cbrianroll

Member
Po said 2 sizes bigger, I'll be stripping them down to clean and verify jets tonite/weekend. Wheres a good source for good jets? Been a while since I ordered some. Pods are garbage....cheap, along with all the other cheap crap on it lol
The pipes are wrapped , kinda scared to unwrap them and see how bad they are....
 

irk miller

You've been mostly-dead all day.
DTT BOTM WINNER
Editing my response, since i reread through Teazer's post and recognize better what he's saying LOL. Wish we could delete posts when we're stupid.
 
Last edited:

cbrianroll

Member
Sorry irk, still learning what's what on this thing, guess I should read up before posting....engine is a 74, guessing the carbs are also. There is only the air screw on the body and one screw on top that moves all slides up and down. You can see it above the intake boot. I think I have the wrong manual.....it shows the mix screw to the left of the air screw.
20200506_214434.jpg
 

cbrianroll

Member
Thoughts on foam uni filter? Be better than pods till I get airbox? I'm getting irritated now, maybe u should just get the airbox...
My other thought was make something like, was it the "breadbox" for cx500s? Might look cooler than a stock unit and work very well?
 

teazer

Well-Known Member
DTT BOTM WINNER
350cc with custom pistons machined from CB350 but with squish bands and low crown. Special cam designed as a drag race unit but works really well. lightened cam sprocket. Ported head. Very light valves, rockers etc. 5 speed NOVAS trans, Dyna crank mounted ignition, Suzuki 4 electronic tacho. CB750 carbs - same as yours. lightened and braced frame and swingarm. Custom footpeg mounts. So basically stock... :) It took years to develop with many changes over the years. Clutch was a mix of different plates and a set of super special CB750 springs. Longer than stock but lighter so they had a light pull and lots of pressure.

Back to your bike. Forget about teh filters for now. Mine ran fine without filters and so will yours to get it running. Get new jets unless you can compare the flow rates to be sure they are all identical and all right where they should be in terms of flow. You could use an optical comparator or a set of jet drills to check the size. Keihin jets are size rated - not flow rated, so a #40 should be 0.40mm 120 should be 1.20mm. The needle jets are 2.60mm Needle is probably a #27201 and slides are #2.5.

Make sure all the air passages and air jets are clear and that the pilot jet bypass is also clear.

Have you checked the fuel level in the float bowls? It should be roughly 3mm below the gasket face.
 
Last edited:

teazer

Well-Known Member
DTT BOTM WINNER
Carbs: Floats still work but will tend to leak if the rubber seal is less than perfect. They will also weep into the pilot jet circuits if the gas is left on

Cbrian: looking at your carb picture. The air screw is close to the filter. That other screw is just to seal the vacuum port for balancing the carbs.

Irk: no worries mate. I have reacted to posts before and then realized that what I thought they said wasn't actually what they said.
 

cbrianroll

Member
Thank's....project went south...found bad frame rust under engine...bike is now completely unassembled and waiting to be sand blasted...
 

DTT Bike Of The Month Gallery

DTT Light or Dark

www.cognitomoto.com
https://www.townmoto.com
www.speedmotoco.com
www.jadusmotorcycleparts.com
www.lostapostle.ca/
www.sparckmoto.com
Top Bottom