Only one Cylinder...

C

campfirestring

New Member
So, I've just started a restore of a 1973 CB450, and right now I'm just trying to get the darn thing running before I really tear into the engine.

So far, I've gotten it to idle, but only the left cylinder/ carburetor is firing and it's idling at about 2k...

i can adjust the pilot screw and idle screw all day long but they don't do anything.

I have spark on the right cylinder and I've done just about everything I can to both carbs: thoroughly cleaned and all gaskets replaced... the right one still isn't firing though.

I'm about to start messing with the valve and ignition timing today, but I thought that that doesn't matter if i just want the bike to idle... I can't get the right cylinder to fire at all.

also, the right one spits a lot of gas out of the overflow, but i suppose that's just because the float needs to be adjusted.

Could this be a timing problem? Is the carb still to blame?
 
campfirestring said:
i can adjust the pilot screw and idle screw all day long but they don't do anything.
Click to expand...

(a) you need to join hondatwins.net

(b) you need to clean your carbs thoroughly.
 
lol thanks for the pointer.

Yeah I thought I've cleaned them thoroughly enough... I disassembled and soaked them in lacquer thinner for two hours and then scrubbed the bejeezuz out of them... but more cleaning can't hurt I guess.
 
lacquer thinner kills rubber parts
adjust the valves
find a factory service manual

~kop
 
Having "spark" doesnt always mean what you think it means. Pull the right plig and see if its wet with fuel.

The coils.on these bikes aren't great. You may see spark but its not enough to fire (especially if compression is low). Try switching the plug wires and see what happens.
 
I guess what I mean by "spitting" is just that it leaks... it's only leaking out of the brass overflow tube.

And thanks for that switching the wires tip. I'm definitely going to try that. very practical... I could potentially switch the carbs too and see if the right cylinder starts to fire. I hadn't even thought of that. nice.

And lacquer thinner shouldn't harm the carbs at all. I know that much - there wasn't any rubber in them to dissolve when I soaked 'em. all the gaskets have been replaced with new ones.
 
campfirestring said:
I guess what I mean by "spitting" is just that it leaks... it's only leaking out of the brass overflow tube.

And thanks for that switching the wires tip. I'm definitely going to try that. very practical... I could potentially switch the carbs too and see if the right cylinder starts to fire. I hadn't even thought of that. nice.

And lacquer thinner shouldn't harm the carbs at all. I know that much - there wasn't any rubber in them to dissolve when I soaked 'em. all the gaskets have been replaced with new ones.
Click to expand...
Spitting has force. Overflow dribbles...You need to get the technical terms right.... ;)

Did you remove the seals at the throttle shaft? One side is metal cap. the other side, where the shaft comes out, has a seal inside. That seal bad can cause a lean out.

I have never removed them, I never soak my carbs. I go through them with cleaner, pieces of wire, welding tip cleaners, etc. Dirt and rust are not dissolved by lacquer thinner, PineSol, or even carb cleaner. Anything strong enough to dissolve rust, will likely dissolve the carburetor metal. The solvents will dissolve gas varnish and deposits, but won't help a physical blockage.
The low speed emulsifier can get its little air holes plugged.

there are videos and instructions on removing them and cleaning them all over the internet, and this site and HondaTwins.

Since you have an issue after soaking, you really need to educate yourself on the carbs, and dig into them to get them right.
 
mydlyfkryzis said:
Since you have an issue after soaking, you really need to educate yourself on the carbs, and dig into them to get them right.
Click to expand...

Well there was a far bigger issue before soaking - it wouldn't even start haha!

But you got me... I did soak them with the throttle rod in. :-[

just because i don't have my manual handy, is the "emulsifier" AKA the pilot or slow jet? they're both pretty clean now...

I'll inspect that next.
 
The slow jet usually has the emulsifier as part of it. Main and secondary have them separate. Some of the emulsifiers ( think of them like aerators on the kitchen faucet) are called jet holders. If your jets screw into brass that bras piece is likely to be an emulsifier.

The emulsifier helps aerate and cause the fuel to be in a finer spray. They look like a tube with tiny holes on the side. They also meter air in. When the tiny holes are clogged, they don't aerate the fuel properly. This can lead to a lean condition despite having excess fuel in the cylinder. The larger droplets don't vaporize well. So you end up with a lean combustion despite excess fuel.


Sent from planet Earth using mysterious electronic devices and Tapatalk
 
You must log in or register to reply here.

DTT Light or Dark

  • DTT Light

    • Spread the Love

    Back
    Top Bottom