Rough Carburation

So, after spending a few weeks restoring Pop's Z1 (1975 Z1B with K&N's and a Kerker, 49k miles, re-jetted when modifications added 30 years ago), I finally fixed the oil leak caused by the stripped oil filter drain screw, and got her running. She's always been a little cold blooded, but after first startup, purrin like a kitten. I took it up and down my street at half choke to try and blowout the gunk (I did tear down the carb's during rebuild and simply cleaned them without removing anything but the bowls and top covers). The following day, she started up and again just fine, but when slipping the clutch, and running up until about 4-5k RPM, it's spitting and sputtering like crazy, with about half power. After that range, runs like a top. If I full choke the thing, it will run quite a bit better, whether at idle or when putting the engine under load. Before storing it 2 years ago, it did have a rough time idling all together, and I had replaced the points the previous year. I suspect 1 of 3 things, or a nasty combination of all 3:

1- When disassembling the carbs, 2 of the top end gaskets had splits in them right where the screw was. Thinking that Air does not flow through here, I didn't think much of it, and would replace them when winterizing. But could this be causing a mixture issue on those 2 carbs?
2- Perhaps just spraying the jets to what I believed to be clean with gumout wasn't enough? Should total disassebly be warranted? I'm concerned here, as I have limited experience and resources when it comes to tuning and balancing. The thing had a top end and carb tune up in '98
3- I still need to replace the fuel valve, as the lever snapped from the tab that operates the nylon closing valve, however when testing, fuel seems to be flowing fine. Seeing as it runs fine at the top end, fuel should not be the issue, right?

Another post I read pointed to possible coil problems, but wouldn't that cause bad firing at any range?

I haven't pulled the plugs since the problem started (installed fresh plugs before starting), but certainly will this afternoon, and report back. Any thoughts and/or input would be much appreciated!:huh:

First place I'd look is clogged pilot jets. With it needing to be choked to pull away it's not getting enough fuel at the bottom end. Pull the carbs off and open up the bottoms, pull the pilot jets out and either make sure they are perfectly clean or replace them (only cost a couple bucks each). While you have them open pull the main jets as well and make sure that the passages blow clean, use compressed air for this after cleaning them really well with carb cleaner (some guys also use a small wire or guitar string to make sure the passages are clear).

toolman5774, welcome to the KZR nation. Great to have you here.

As has been observed many times by members, these old gas tanks typically have fine rust and debris which is persistent and repeatedly fouls freshly cleaned carbs. It also steals away precious riding days.

Many have eliminated the symptom by adding a good quality inline fuel filter (don't ask how I learned this) and replacing it each season.



Best of success.
Bill

PS,
Please add your year, model and location to help members help you... and it's considered real friendly too.
Bill

When I bought my bike, it had been sitting for about two years and I had to remove and clean the carbs numerous times before it even ran on all four cylinders. I also had to use muriatic acid in the tank to remove the rust. It took a lot of time, but I finally got it running right. Make sure your timing is correct too, but since you said it ran good on the top end, I doubt it is very far off.

I buy my fuel line by the box from Jeff. On these old bikes and my lawn mower i use about a foot too much line and make a big"U" in the line. You will get a idea real quick of how much trash is in the fuel system.

I have been cleaning carbs for three days. Two sets. Run one set and clean the other. Finally got them clean. Really clean. Roy

Thanks guys! I think I'm going to take all of these ideas and run with them. I had to drain the tank before working on the carbs this year, but the gas didn't really have any debris in it. Nontheless, I have thought about putting an inline filter on it anyways. Pops agrees too that the pilot jet or even main jet could be clogged, so of to complete tear down I go.

One more question though. I've never actually removed the jets, will they need completely retuned/balanced after, or is there a way I can mark them before removing them to put them back as is? Thanks again!

Doug
Second Generation Z1 owner
1975 Z1B 900 with 49k miles
K&N Pods
Kerker 4-1 header
Corbin King/Queen Seat

Just remove jets,floats,and float needles. Clean and blow out air passabes. The cracked gaskets could effect carb balance. Roy

toolman5774, just an observation, you say you are not currently using a good quality inline filter... statistically that makes you eligible for the keep-recleaning-my-carbs club. :dry:

I have not heard of or experienced any de-tuning due to removing a jet and putting the SAME jet back into the SAME carb (with the same washer or same gasket or same O-ring)... but, time permitting, I personally would re-check all tuning to assure best performance.

On the other hand, if there was debris/stuff in the jet and the PO had done all adjustments based on the dirty/partially clogged jet then yes, I would expect to have to re-tune the carb.

Similarly, if an old and or worn jet were replaced with a new or good old jet then again yes, I would expect to have to re-tune the carb.

IMHO, Roy makes a very good point about sound gaskets. You may want to get a new set for each carb as troubleshooting this type of fault is very hard to do the logical way.

Best of success.
Bill

Thanks a ton guys. Yea, replacing all gaskets is on my list. If you're going to do something, do it right, right? So while I'm at it, I'll be replacing the aging peckock as the lever actually snapped out of the nylon, adding an inline filter, which will take some plumbing as it has 2 outlets, replacing all gaskets on the carb, removing the jets and more than thoroughly cleaning them, possibly replacing them, then going from there. If rebalancing and tuning is in order, then that is next, but I think I'll see if I can have somebody do that for me, as I don't have the pressure tubes, nor the experience to really get it right. Might help to learn though, as I might put all the stock parts back on for show next year, in which I'll need to re-tune to make up for the 4-4's and stock air box. Again, thanks for everybody's help!

By all means you are smart to keep this bike stock. The price is going out of sight.

You have the stock exhaust? I have seen some sets go for $3500.00.

We would like to see some pictures. Roy

I have all of the stock parts: Airbox, headers, grips, and seat, which were the only parts changed. If I do want to switch to pure stock original, the headers will need some attentions, as they've been in storage since 1980 when my dad put the kerker on. They just need cleaned up for the most part, but one of them has a rusted through spot near the end of the megaphone. I have a friend who is really good with welding, so I might be able to get it looking new, and either clean them really well, or get them re-chromed. I even have the original baffles, which pops so rebeliously removed the day he brought it home


Here's one for you other Z1 buffs that I'm torn on:

The 75's were known for having the top of the tank fade out the maroon and show the green primer underneath from what I'm told, and mine is no exception. I can get ahold of original paint, but don't know if I really want to get it painted, or leave the "weathered" look. I definately need the side covers and tail painted, as the paint has cracked, but the tank has faded so evenly, it looks like a starburst just below the cap. I'll include some pics as soon as I get home.

Oh, and I have some pictures in my gallery for ya roy-boy. I'll surely be adding some more now that she's back in one piece.

toolman5774 wrote:

Thanks guys! I think I'm going to take all of these ideas and run with them. I had to drain the tank before working on the carbs this year, but the gas didn't really have any debris in it. Nontheless, I have thought about putting an inline filter on it anyways.

Only way to go. Without it, you will have endless problems as the junk drains down into the carbs.