[JWilliam]

I have been working on my buddies 1985 CB450SC, the previous owner tried to rebuild the carb and put A bunch of incorrect parts. I have already replaced the pilot and primary jet with the correct size. The only part I am unsure of/think might be incorrect is the Vacuum piston needle.
It is 54.8mm long (Needle taken out measured top to bottom) with d329 stamped on the side.

does anybody be know what the stock needle length is? Any information would be helpful.

thank you!

 

[longdistancerider]

I don't have that information. The current needle is an aftermarket one though. It's a shame people replace the brass with aftermarket and throw the perfectly good original pieces away.

 

[JWilliam]

I don't have that information. The current needle is an aftermarket one though. It's a shame people replace the brass with aftermarket and throw the perfectly good original pieces away.

Hello,

If only the last owner kept all the parts they replaced(but they didnt), they dont even have a record of what carb kit they used.

I was looking at another thread that shows needle size and this aftermarket doesn't seem that far off in height which conflicts with my hypothesis that the needle is too long.

I do have a couple other questions, I have been working on this 85 CB450SC for a while now and it still dies whenever throttle is given(most recently started to slightly back fire on right cylinder which is why I am cleaning the carbs again).
So far I have:

• Cleaned carburetors thoroughly (3 times), including carb dip, clearing all passages, making acceleration pump work etc.
• Replaced primary and pilot jets (previous owner installed 108's when it should be 125's, and also had pilot jets with mismatched emulation holes)
• Installed a new gasket kit (previous owner had a pilot screw o-ring in the air cut off valve which does not work).
• Validated float height is at 15.5mm
• Replaced ignition coil (was not getting good spark and now I am)
• Used gravity feed fuel to confirm petcock was not restricting fuel.
• Did Ignition Timing troubleshooting (followed direction on this forum checking ohms).

Question 1: When looking at a new Needle Jet Kit there is a o-ring that is included, this is just for the plastic cap/spacer correct? It doesn't impact impact the needle height?
There is also a brass piece, that I think is still within the slide does this just get pushed out?

Question 2: I was also wondering about the copper bit sticking out in the venturi (seen in attached picture), is this an emulation tube? I have not been able to press it out but havnt tried too hard since I dont want to damage it. I already have the Primary Jet and Jet holder out.

Question 3: Any idea what could be causing this issue? would timing impact this?

I have also included a few more pictures in case you see something that doesn't look right.

I am sorry for all of the detail, I am just at a loss.

Thank you!

 

[longdistancerider]

Looking thru the pictures the only thing off is the slow/idle jets don't match for the emulsion tube sections.
Backfire thru the carbs indicates a lean condition but it can also do that sometimes if the airbox is disconnected and the throttle opened fast.
The O-ring with the needle is for the stopper. after the jet is in, aluminum plug screwed down snug replace the O-ring and push the stopper in, a little saliva helps. Did you buy the Hinda needle kits?
The brass piece sticking up in the venturi is the nozzle for the needle. It's just lightly pressed in and the jet holder actually keeps it in place. If the PO didn't change that when he replaced the needle you're in trouble since the nozzle and needle are calibrated to one another.
Ignition timing is fixed, no adjustment, so if the ignition system tested good there's no issue there.