'74 KZ400 Startup issues...

[helitaiwan963]

Hey guys,

So I just purchased a 74 KZ400 and it's in GREAT shape... Anyway, it was supposed to have been running but the previous owner had it sitting for a few months in a garage.

So we tried to start it yesterday, and it didn't seem to want to turn over. So we checked the spark plugs and they were all good and produced spark. Also all the fuel lines, and petcock were flowing freely with fuel. So today, i pulled the plugs again, cleaned them and sprayed some starting fluid into the combustion chamber, changed out the old fuel with some new gas, and cranked it while my buddy was spraying starter fluid into the carbs. Choke was in the closed position btw. So it would just start up for a few sections, and when we would try and it it idle, it just dies out. Never stays running for more than 4-6 seconds... This is really frustrating for me as this is my first bike and I'm really excited to get on with the bratstyle build...

Is there anything i'm doing wrong? Or stuff I should be checking for in order to get the bike to start running? Right now, i feel like it's only starting up because it's running off the starting fluid and not the gas like it is supposed to...

Does the clutch need to be in to start on these bikes or no? I think i read somewhere that some bikes needed to pull the clutch in?

Any and all suggestions and help would be greatly appreciated!

-Eric

 

[helitaiwan963]

PS: Idk if you guys need more information to diagnose? I'm not sure. please let me know if you need more info and I'll do my best to answer them.

 

[spotty]

hey eric, if it was the clutch thing, it wouldn't turn over at all or fire on starter fluid for that matter
tho there have been many kwakas over the years that have had the clutch cut-out switch. i'd be investigating the fuel flow thru the carbs, if you're getting enuf spark to fire on the starting fluid (theres a brand here in australia called 'Start Ya Bastard')
when you crank the engine with the plugs out is there any smell of petrol? are you getting petrol thru to the carbs themselves? check this by opening the float bowl drain screws on the carbs themselves and see if anything comes out there.
next step is check the jets/passage ways/etc inside the carbs. this will require removal of the carbs /cables and probably the airbox. also worth checking that the airfilter isn't full of crap, if it isn't getting proper airflow, it will run on starter fluid but not keep going
good luck spotty

 

[helitaiwan963]

hey eric, if it was the clutch thing, it wouldn't turn over at all or fire on starter fluid for that matter
tho there have been many kwakas over the years that have had the clutch cut-out switch. i'd be investigating the fuel flow thru the carbs, if you're getting enuf spark to fire on the starting fluid (theres a brand here in australia called 'Start Ya Bastard')
when you crank the engine with the plugs out is there any smell of petrol? are you getting petrol thru to the carbs themselves? check this by opening the float bowl drain screws on the carbs themselves and see if anything comes out there.
next step is check the jets/passage ways/etc inside the carbs. this will require removal of the carbs /cables and probably the airbox. also worth checking that the airfilter isn't full of crap, if it isn't getting proper airflow, it will run on starter fluid but not keep going
good luck spotty

That was my thought as well as far as lacking fuel flow. All the lines to the carbs are free flowing. I will have to check the bowls today and see if the carbs are letting fuel through. I was suspecting the carbs were kinda plugged and I wouldn't be surprised if they were because the old gas looked in bad shape and some crap settled on the bottom of the tank when we dumped out the old gas.

Also, idk if this helps diagnoise anything, but after we let it fire with starting fluid a few times. I pulled both plugs to check them. The left cylinder(looking from the rear) spark plug had some carbon on it. Not like a huge amount of buildup but just a little bit. Then when I looked at the right cylinder(same view), it seems like it doesn't have anything on it and looks as it did when I put it in new. It did produce spark though when I checked yesterday... Could it be my right carb that is plugged up and no gas is getting through the car, thus making the bike not be able to stay on?


Thanks
Eric

 

[teazer]

Clean the carbs. Sounds like a pilot jet is blocked on one side. It happens a lot with modern "gas". Ethanol absorbs water from the air and that water rots and clogs jets after a few weeks.

 

[helitaiwan963]

Clean the carbs. Sounds like a pilot jet is blocked on one side. It happens a lot with modern "gas". Ethanol absorbs water from the air and that water rots and clogs jets after a few weeks.

Sweet, I've been thinking it's the carbs as well. Just really didn't wanna tear into them unless I had to...

I should be able to just disassemble the parts, and shoot carb cleaner thru all the jet passages and make sure it's clear, then reassemble right?


Thanks
Eric

 

[spotty]

when you pull them apart, take note of all the 'adjustable' screw settings, like air mixture, idle etc, then at least you've got somewhere to start from when it comes to re-tuning them after it hopefully starts, thats of course assuming they were somewhere near right in the first place but if the bike was running before it was laid up then you should be alright,
do you have a manual, this would give the basic settings as your starter
good luck

 

[helitaiwan963]

when you pull them apart, take note of all the 'adjustable' screw settings, like air mixture, idle etc, then at least you've got somewhere to start from when it comes to re-tuning them after it hopefully starts, thats of course assuming they were somewhere near right in the first place but if the bike was running before it was laid up then you should be alright,
do you have a manual, this would give the basic settings as your starter
good luck

I will have to make sure to take note of all that. And the bike came with it's original manual I"ll have to check it out and see if i can find the "factory" settings for them.

 

[helitaiwan963]

Ok guys, Good news. Went thru the carbs today and cleaned everything and finally got fuel to flow to the bowl in the carbs. Few kicks with the kick starter with the choke open and it sprang to life

Problem now is, it starts with the choke open. Idles around 3500rpm and has little surges up to about 4000 rpm... Then when we let it warm up for a bit, it was pretty stable, idling around those RPM's. Then once I shut off the choke, it just dies out? What can I do to adjust this so it idles correctly when I shut the choke off?

Also, i should mention the startup today was open exhaust, open carbs(will install stock filter box back on soon, then pod filters)... I'm not sure if that would make a difference as far as the idling, but any help would be greatly appreciated!

-Eric

 

[spotty]

try again with air box and mufflers on as this makes a big difference especially if the carbs are CVs and if you want to put pods on you will have to rejet which includes the idle/airbleed jets as these make a huge difference with any changes to air filtration

 

[helitaiwan963]

try again with air box and mufflers on as this makes a big difference especially if the carbs are CVs and if you want to put pods on you will have to rejet which includes the idle/airbleed jets as these make a huge difference with any changes to air filtration

What do you mean when you say "CVs"?

I did know that i would have to rejet with pods and an open exhaust. The bike never came with a muffler so I don't have it, but I"ll have to stick the stock airbox back on for now.

What about the dying when I close the choke? Does that need to be adjusted or is that directly correlated with my open carbs and open exhaust for now?

-Eric

 

[.Spindat.]

I would say you need to ajust some fueling, the bike sounds like it is probably starving for fuel when you close the choke as too much air is getting into your mixture.

Thats all I can add from my short experience and bit of research i've done on the matter with my own bike doing the same thing.

Get them tuned!

 

[helitaiwan963]

I would say you need to ajust some fueling, the bike sounds like it is probably starving for fuel when you close the choke as too much air is getting into your mixture.

Thats all I can add from my short experience and bit of research i've done on the matter with my own bike doing the same thing.

Get them tuned!

Well this could just be i'm running open carbs and open mufflers right? It's sucking in a ton of air and not enough fuel for the amount of air it's getting with the open exhaust and carbs... I think i should just throw the stock airbox on for now and see how it does... Then go from there? Cuz I think i def need a rejetting if I want to run pod filters and an open exhaust...

any idea what jet to get if i wanna do that?

 

[spotty]

CV carbs are 'constant vacuum' which are usually the sort with flat tops and the cable operating a butterfly valve in the throat of the body. these types are very sensitive to any changes in airflow, especially at low speeds. the slide is operated by the flow of air thru the carb and is controlled by tiny little 'bleed' jets, you'll find these around the throat of the carb as you look at it from the airbox side
'normal' carbs usually have the cable going in thru the top of the carb, the cable attaches directly to the slide. this type of carb is less sensitive to being screwed round with (and easier to tune/rejet) but is not as smooth or economical as a CV. you'll almost never see a CV carb on any sort of race bike as not only are they harder to tune, they're less responsive in just about any comparable situation
not sure if i explained this properly so if anyone else can say it betterer please go for it

 

[.Spindat.]

Well this could just be i'm running open carbs and open mufflers right? It's sucking in a ton of air and not enough fuel for the amount of air it's getting with the open exhaust and carbs... I think i should just throw the stock airbox on for now and see how it does... Then go from there? Cuz I think i def need a rejetting if I want to run pod filters and an open exhaust...

any idea what jet to get if i wanna do that?

I think that would be a great place to start. I'm affraid I am not much more help with specifying jets, but I do know once you get it running properly with the stock airbox it should be a good starting point for when you will need to tune for the pods again afterwards.

If I am not mistaken, with the pods you are looking at more airflow which means at stock settings will be a lean tune. You will need to add fuel to keep the mixture correct and have the bike run correctly. Sorry if I am pointing out obvious facts. I'm just that type of guy.

 

[helitaiwan963]

Well, slapped the air filters back on and wow, idles 1000 rpm lower already! but when i close the choke, it still dies out. I think it's not getting enough air when I close the choke...

How open is the throttle plate supposed to be when the bike is just idling? And how do i adjust it?