Engine running good one day, Shit the next?? Whats wrong!

helitaiwan963

helitaiwan963

New Member
Alright guys, I have a 74 KZ400 and it's been running well for the past few weeks finally. I rode it like 4 days ago and it was perfectly fine.

Today, I saw snow/rain on the forcast for Sunday so I figure it was probably time to ride it to my storage unit and put it away for the winter. I follow my normal starting procedure. Choke on, start it up but it wouldn't turn over. Finally got it to turn over with the choke off. I thought, well ok, whatever. Warmed up and seems to be idling fine. Go to ride it out the parking lot and it just has 0 power whatsoever... I could barely make it down the street... It just was struggling the whole time. Also, when it's sitting there just idling, it doesn't die out or anything. But if I let it idle there and I try and put it on half choke, the bike dies.

Thought it was maybe cuz it rained the night before and I had pod filters and maybe they were still a lil damp. Took them off, figure it may not run well but it would at least go... But the same exact thing happened. I checked my spark plugs and to my surprise, my Right cylinder was really lean... and my left cylinder seemed to have some oil on it... I have no idea why this would be when It was fine before and I had checked my plugs just a few weeks ago.

Could it be the cold air now? I've ridden the bike in colder temperatures before... Could it be the dry winter air is finally here causing my bike to do something weird? I'm going to try it again tomorrow and hopefully it's fine...

Oh, one more thing. When I had the pod filters off, I had tried to put my palm over the carbs to see if maybe something was plugged and not sucking in air. The Carb to the left cyclinder had a MUCH strong suction than the left and when I put my palm on the left carb, the bike wouldn't die or even lower idle... I put my palm on the right carb and the suction was much less and the bike would also just completely die out after that...


What's wrong? Should I be worried about something and check for it? If so, what could it be? Or is it simply just the weather...

Thanks a ton
Eric
 
I have not actually... I supposed that's a good possiblity cuz my bike unfortunately has been sitting outside for awhile... and we are getting some big temp swings from day to night... (50F to 30's) I will check for that tomorrow after I get some new plugs.
 
They could have perished which will seriously effect the running. Hope thats all it is, if so its a quick cheap fix :)
 
Yea I'm 99% sure that this is spark related on your left cylinder. I don't think you mentioned checking the plugs for it.

I had the problem occurring to my left cylinder on numerous occasions but for different reasons each time. A difficult start, idle but no power, and rich vs lean cylinder were some of the same symptoms you are encountering now.

Pull your left plug off, and let it touch the engine while turning it over. If you don't see a spark, that'll let you know. Then you can start working your way up from there. It can be anything from a bad plug, to a bad wire connection to the spark plug, fried coils, or a broken point.

Check the wire connection to your spark plug and replace the plug. If neither of those change anything, inspect your points. If nothing from there, I would start looking for new ignition coils.
 
socalmike_cb72 said:
Yea I'm 99% sure that this is spark related on your left cylinder. I don't think you mentioned checking the plugs for it.

I had the problem occurring to my left cylinder on numerous occasions but for different reasons each time. A difficult start, idle but no power, and rich vs lean cylinder were some of the same symptoms you are encountering now.

Pull your left plug off, and let it touch the engine while turning it over. If you don't see a spark, that'll let you know. Then you can start working your way up from there. It can be anything from a bad plug, to a bad wire connection to the spark plug, fried coils, or a broken point.

Check the wire connection to your spark plug and replace the plug. If neither of those change anything, inspect your points. If nothing from there, I would start looking for new ignition coils.
Click to expand...
Mad Ratter said:
They could have perished which will seriously effect the running. Hope thats all it is, if so its a quick cheap fix :)
Click to expand...
MadRatter: I really do hope that's it...

Socalmike:
You're right... I never checked for spark on the plug... I just assummed it was ok because it has ran fine a few days ago... I'm gonna go buy some new plugs for it later today and give it another go.

If my left cylinder isn't firing, why would that cause my right cylinder to run way lean?

I hope i can get it running good enough today so I can bring it over to the storage unit tonight... It's supposed to snow tomorrow and I have no garage :(
 
You can still check for the connections to see if they are good. Could be as simple as that. I had loose plugs on mine and they would slip off all the time. Check the connections going to the spark plug, as well as the connectors going to the points.

Haha or you can always just run on a single cylinder by rev'ing full throttle and easing into first.. :p

Hope you figure it out. good luck man
 
helitaiwan963 said:
If my left cylinder isn't firing, why would that cause my right cylinder to run way lean?
Click to expand...

Don't know. But don't think that'll matter much right now. Point actually wasn't that you were running lean on the right, but that your left was full of fuel (no spark/not burning). But if half an engine isn't running, wouldn't be surprised if it'll alter your air/fuel intake or combustion dynamic.
 
Well... seems like I figured it out.

Spark was there so I knew the connections and the coils were good. I had purchased new NGK B7ES plugs to replace my fouled plugs and it started right up on choke like normal, but it still wasn't revving up high like it normally does. So I knew something was still off...

Pull the plugs again... Now the right cylinder seemed like it was getting too much gas and a ton of char on it. Pull the Left cylinder plug(this was the brand new one) and it hadn't looked like there was ANY combustion at all in that cylinder as the spark plug was still shiney and looked as it did when i put it in.

At this point, I noticed my fuel filter had no fuel in that fuel line going to my left carb... Pull the line and a ton of red rust came out with the gas... Plugged it in again after I bled that line a lil. Same thing... There was a LIL char on the plug now but still wasn't running great... So i'm pretty sure that left carb is just plugged up with that rust from the tank... To make sure, I pulled the carb bowl drain plug and sure enough, just a tiny bit of gas came out and nothing else... Petcock was on of course. So Looks like I just need to go thru the carb and just spray some carb cleaner thru all the passages to clear everything.


Thanks for all the help guys!
-Eric
 
hello,
i would be drainning the fuel out of the tank, and pet cock. to make sure that the tank has no rust, which is where the problem started. then pull the carbsand pull them apart, clean out the fuel tubes and gallaries.
thats my two cents.
also, if your bike dos'nt already have it, a electronic ignition will help the bike run 10+.
any way, good luck
 
Yea, I got the bike to the storage unit so i have a warm place besides my parking lot now to work on it. But it's finals time so it'll have to wait. I know whats wrong so I'm gonna work on it after it's done.

I did have inline fuel filters... Are those worthless? Cuz clearly my carbs still got plugged up... I'm gonna redo my fuel lines, should i just exclude them from my "to replace" list and just run straight fuel lines?

Also, what do you mean electronic ignition? Is that like a coil pack for modern cars? I'm a college student so this is supposed to be a budget build. It's only an in town cruiser.
 
ya, the electronic ign is a replacement of the points. bolts right up easy to wire. its around 150 but is well worth the money.
as for the filters, i would not run them. if the microns in the filter is not right, then you could starve the engine of fuel, etc....
run it straight, the pet cock has a filter screen in it, if you cream the inside of the tank that is all you really need.
 
a electronic ignition in my opinion should be in the budget of any build. just my 2 cents.
its up to you but the starting and running of the bike will be night and day.
 
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