# 4 cylinder is cold.

[Kfreak]

Now I have read about this before but can't find the post. I just did a major suspension overhaul and re-painted my header. After completing the assembly I noticed # 4 cylinder pipe was cool to the touch. After cracking the throttle open a few time it got hot. After a cool down the same thing happened. What the heck is that all about? I know someone else had the problem but i can't find them. I need guidance.....

[md86]

Means that cylinder ain't firing for some reason . Time to dig deeper . At least you know what cylinder is the troublesome one .

[Kfreak]

That was easy. Three out of four smoked. But now the remedy.

[tminus3]

let me take a shot at this guys, after all the advice you guys have given me...

I'd start with the plugs.

(How am I doin, MD86?)

[eddie]

it might be the float sticken in the carb

[The CyberPoet]

It's not getting hot as fast for only one of three basic reasons:
A bit too much fuel in the cylinder (richer mixtures burn cooler), such as if the pilot screw is turned out too far, or the o-ring under the pilot is eaten up; OR
Way too little fuel in the cylinder (insufficient to even detonate), because the pilot jet is blocked by debris or the o-ring under the pilot jet is eaten up and blocking the passage; OR
the cylinder isn't getting a consistent spark (bad spark plug, bad plug wire to cylinder #4, spark plug boot not seated firmly).

Are you getting any after-fires (i.e. - booming out the exhaust, or burbling in general at idle, or burbling on deceleration)?

Cheers,
=-= The CyberPoet

[Kfreak]

Yes, I did get a backfire then the pipe started to get hot. I am assuming the wire connection or the plug is bad. I have to pull the fairings off and pull the plug to see if it's firing. I am trying to trace my steps to see if I had disturbed any of the wires during re-assembly. All I did was pull off the header and swing arm. I wasn't anywhere near the top of the head. I did re-jet the carbs and the bike ran fine after that. That was done about two weeks ago. In other posts I just thought guy's were being careless when this stuff happens but it just happened to me. I am one to check and re-check my work. I am off to check it now so I will be back.

[md86]

let me take a shot at this guys, after all the advice you guys have given me...

I'd start with the plugs.

(How am I doin, MD86?)

Nice try , but if he knows which cylinder is cold , he'll already KNOW which plug is fouled ...... but then , there ARE different types of fouling . Oil AND/OR fuel .
Ok , I'd do a few things for starters (yes , cecking the plugs is one ) . Pull the one plug and wire brush it off . Have another plug ready on standby . Keep it under the seat as a spare if you don't need it NOW . Check plug boot wires is good (twist and push wire into boot) . Of course ,pay close attention to the wire at the cold cylinder . Your jetting could still be off even if it ran ok for a little while . Fouling CAN take some miles if it's just a little off , and often not all cylinder will like the same mix . Can PROBABLY rule out the air filter , unless the other plugs look dark , in which case may be worth a look ...... what am I forgetting ? It's late , and I'm tired .....

[Bright Wire]

I thin you were reading my post about having the same issue. Here are my suggestions in rough order on what to check. Let me know what you find since I'm still chasing this down myself.

1 - Make sure you have gas in #4 carb.
2 - Make sure you have spark in #4 cylinder & check the condition of the spark plug in comparison to the other 3. Fouling? (Wet/Black)
3 - Make sure you have pressure/vacuum in #4 with a carb synch. The petcock vacuum line is fed from the #4 carb. Spray carb cleaner around it and see if your idle jumps up. It could be sucking air.
4 - Look into a possible weak spark. I mention this because of the pop/pop/pop. It sounds like it's catching but not as well as it should. It may be a coil or electrical line that needs to be replaced.
5 - Things are now getting nasty and we may be looking at a compression issue within the engine valve. Start to pray.

Let us know what you find out.

For a proper comparison of what the spark plugs should look like do a search for NGK spark plug comparison chart. CP posted a link to it awhile back and I don't have it handy at the moment.

[The CyberPoet]

There is one other possibility that just came to mind -- that you're leaking air at the header (missing header gasket, or header not seated correctly at the cylinders), but if that were the case, when the cylinder actually started firing, you'd hear pthhh- or bang- noises coming out at the header/block connection.

Cheers,
=-= The CyberPoet

[Tokalosh]

I got the same problem on my friends Bandit 600.
After doing all the above checks and cleaning the carbs thoroughly by taking them off, the problem was still there. We then discovered that if we ran the bike with the fuel tap in the prime position the bike ran like a dream.

What gives, is it a faulty fuel tap?

Tok

[Newbie2it]

I got the same problem on my friends Bandit 600.
After doing all the above checks and cleaning the carbs thoroughly by taking them off, the problem was still there. We then discovered that if we ran the bike with the fuel tap in the prime position the bike ran like a dream.

What gives, is it a faulty fuel tap?

Tok

Faulty or no vacumm line hooked up/improperly hooked up. Prime will flow regardless, the other positions need vacumm to open the valve.

[Tokalosh]

I checked the vacuum line between the #4 carb and the tank and all looked good and snuggly fitted. Could it be a busted something in the fuel tap, I've never taken one apart or know how it works. I'm guessing something like a 3 port valve.

Tok

[The CyberPoet]

http://katriders.com/vb/showthread.php?t=65006

Let's see if I can make this petcock thing make more sense for you.



Behind the pick-up screens (green in my pictures) are two tubes, one short (the reserve/prime tube) and one tall (the standard ON tube).

The petcock acts as a three position switch comprising two pick-ups and two fuel passages.

In position "ON", the system selects the taller fuel pick-up tube, and routes it through a passage that only gets opened by engine vacuum pulling a rubber diaphram open (the rubber diaphram is normally held closed by a weak spring).

In the position "RES", the system selects the shorter fuel pick-up tube, and routes it through the same passage with the vacuum diaphram.

In the position "PRIME", the system selects the shorter fuel pick-up and shunts the fuel through a straight pipe that by-passes the vacuum diaphram.

The engine doesn't produce sufficient vacuum to open up the diaphram until the engine is turning at least 500 RPM or so. This vacuum is created by the intake valves to the cylinder opening while the piston is moving downwards, which causes the air to be sucked through the carb (which is also where the vacuum pick-up is located). When the engine isn't spinning, there is no vacuum in the line to the petcock; as the starter turns the engine, it produces low levels of vacuum, and once it fires (sucessfully catching), the vacuum levels climb.

Since the carbs normally had fuel when you shut the bike down, there is normally no immediate need for additional fuel flow at start-up, unless the fuel in the carbs has been evaporated or emptied somehow. Thus, the fact that the petcock is in the ON or RES position when you start is normally irrelevant because there's enough reserve in the carbs. Once the engine starts, fuel will start flowing through the petcock and refilling the carbs as their levels drop. In cases where the carbs are empty or low on fuel for whatever reason, it makes sense to use the PRI (Prime) setting to flow fuel to the carbs to refill them before trying to start, then to switch back to the ON or RES position.

Generally, if it isn't opening, you're not building enough vacuum, OR there is rust in the diaphragm parts (spring, plunger) of the petcock.

Cheers,
=-= The CyberPoet

[Tokalosh]

Cyber THANK YOU so much.


Tok