79 runability problem.

[whatscooking]

Recently I bought a 79Z knowing it had problems. I removed and cleaned the carbs along with pulling the idle jets, synced them, set screws 2.5 turns and adjusted the valves. Now the bike starts right up and idles very very good, I can lower the idle way below 1000 rpm with no clutch rattle at all and it takes fuel very well. When I go for a test ride around 2.5 to 3000 rpm if I go steady I get a bit of bucking somewhat jerky response. If I keep in it even slightly it is smooth. Above 3000 rpm runs great. I checked compression 120-125, pulled plugs and they are pretty white. It had a K&N air filter, I got a paper= no difference. I has Supertrap 6 into 1, 13 disc was installed I took it down to 7 = no difference. I know it has 65 primary mains, 35 idle and 98 secondary mains, floats set 15.5 and checked with the clear tube. Stock needle jets, new carb boots. Great looking coils and wires.
I have not put very many miles on it yet and if quit babying it in that rpm range it runs real good but before I get a little bigger primary mains ordered I wanted to check with you guys if you think I am looking in the right direction? How much bigger?

[NobleHops]

I don't have much to offer other than encouragement and praise. You did a kick-ass job of baselining the bike and eliminating a lot of common variables. I'm gonna guess you are close.

[daves79x]

Agree - sounds like you are close. Are you positive all the vacuum pistons in the carbs are completely free in their tops? This is often overlooked and one or more can hang up. Other than that, you can go up to #68 or #70 on the primary main.

Dave

[whatscooking]

Agree - sounds like you are close. Are you positive all the vacuum pistons in the carbs are completely free in their tops? This is often overlooked and one or more can hang up. Other than that, you can go up to #68 or #70 on the primary main.

Dave

They were free when I put them together and I checked them before I reinstalled. I can use the brake to lug it down in this rpm range and not get any hiccup out of it. I think I will get another set of new spark plugs and ride it before I order jets.

[daves79x]

I'm not sure what you mean by 'using the brake to lug it down'. Are you saying the revs are hanging up in this range? I understood you to say in the original post that it was just 'bucking' in this rpm range.

Dave

[whatscooking]

I worked in a large car dealership years ago in the tune up department. I found that if you put a pull\lug on a engine at lower RPMs that will make ign problems show their ugly hand, spark plug break down, coil ark, or the wires jump and make the engine miss unlike a fuel problem, most times.
I went into town today to get some spark plugs and to put some miles on and interestingly enough if I forget about the problem that I think I have and just ride it the problem is not that big of a deal, really who keeps the RPM at 2,500 for long anyway. By the time I got home I thought she was doing pretty good. Might of been I got her warmed up good or whatever, might be we are just getting to know each other.

[whatscooking]

I believe I need to dig deeper, went for a extended ride yesterday feeling the jerkiness starting around 2500 rpm and really it is there above but the higher rpms just mask it to some degree. I came home and pulled the plugs. 2 3 4 5 are clean as can be but 1 especially and 6 somewhat are sooty not completely darkened but no where near as clean as the others. Compression is at 120, the clear tube test shows the fuel level right where it needs to be. Since 1 and 6 share the same coil I think I need to look at ignition closer. I put the new plugs in with no change last night so I walked away and called it a day.
Since the bike starts fine and it goes to idle every time when I let off of the throttle and will go way below 1000 rpm with no clutch rattle when I lower with the idle screw doesn't that mean that the idle system is working, when I throttle it hard it does blow a lot of black smoke like It is over fueling or not burning it completely. When I look down into the spark plug hole in # 1 and 6 the top of the piston does look wet.
It has what I think is a Dyna ignition, I sent Terry a picture and he said it doesn't look exactly as other ones he has seen but the wire colors look to be a Dyna set up. I know the wires go directly to the coils from there.
I think I will put on my best pair of glasses and get the ohm meter out and start looking at the coils and wires.

[whatscooking]

How can a carb over fuel a cylinder if the float level is set proper and the correct jets are installed along with the correct needles?
I have cut and slid every spark plug wire back on both ends checking resistance everywhere as I went, a lot of them looked like they need some help but no difference. I misted water over the coils and shut off the lights and ran my hand all over them, no difference. Check timing saw it was fast so I dug all the way down into the advancer weights, all look new and lubed and free there, I had to take my cut tool to remove part of the plate to be able to drop the timing just a bit, no difference.
I pulled the plugs and sure enough # 1 and six are blackened\wet. I took off # 1 float bowl to find what I think must be the grease I used, was in the book, on the seals for the float bowl gaskets floating in the bowl, I would of thought the gas would of dissolved it. Cleaned, squirted and blew, BUT when I started the bike and throttled no huge puffs of smoke, turned on the fuel and smoking again.
Where do I need to look for this over fueling?

[daves79x]

No - you are seeing the spark break down above idle. Just went through this with a Dyna - intermittent spark above idle. Sent it away and they found #2-5 igniter bad and replaced it. Sounds like that's what you've got there, apart from finding some wiring issues or a bad coil. But your problem is for sure the ignition for #1 and 6 and with your set-up, is either the coil or the pulser. Fuel is fine.

Dave

[whatscooking]

I have someone good enough to send me a Dyna sensor so that I can pug it in to test things out.

[whatscooking]

I replaced the Dyna with another with no improvement. Since 1 and 6 were showing rich I was able to lower the float levels with the carb still on the bike. That did help with the blackening of those two but I still have the jerkiness right off of idle. What is interesting when I go for a test ride on a stretch of road near me where I can open her up going up a rather good incline, build heat in the engine, for about a mile or two afterwards she will operate without any glitches then I feel like after she cools off a little the herky jerky returns. I was able to get in touch with Mike Nixion and we went over some things but as of yet no improvements. I rechecked the compression finding 130-135, warmed up all plugs out with the throttle held open.
I feel like I need to go back in the carb and look closely at everything again. I have some concerns about the idle jets that I drilled to remove.

[herdygerdy]

Suggest fitting an ignition coil relay on it?

Cheap and quick to do and lots more mumbo at the plug tips.

PM me if you need help to either roll your own or I have a plug 'n play available if needed too.

It sure would not hurt....

[whatscooking]

I wired the coil directly off of the battery when I was doing different test.

[daves79x]

I'd first switch coils around and see if a different pair of cylinders got sooty. My bet is still that, or something ignition related. #1 and #6 is too much of a coincidence.

Dave

[whatscooking]

Today I decided to look into the carbs to see what I could find. They come off even better if the bike is still hot. I came home from another test ride and was ready to get after removing them. Only took about an hour then there they were. I knew I lowered 1 and 6 float while they were on the bike and they really were different when I got them flipped over. I took the tops and bottoms apart and pulled the idle jets again. I got the brake cleaner out and made 110% sure all passages were clear, even the three little holes showed free flowing cleaner coming through, I thought that was where I thought the problem might be. So then I grabbed the idle jets and went to checking. I thought I needed a way to check flow on them as I thought they felt different when I blew air through them and I could see light. The first one I squirted brake cleaner through blew out an ok shot, a nice stream I thought, I grabbed another and give it a blast and it would just slobber a little, I hade one of those moments then I thought I must of plugged it when I re tapped the hole. So I checked the rest but got to noticing a difference in the stream. So I aimed the jet that will screw onto the brake cleaner real easy since we cut new threads into it and started squirting long distance.
I discovered differences in the range I can get out of each jet even though I can run the tool that Mike says to get in his book through the jets. I didn't do any more the first time I was in there to the jets other than run the wire through and blew them out. They are soaking in carb cleaner overnight now.
I might of been fighting two problems, when I took #1 bowl off to lower the fuel level I found a pretty good ring on its float needle so I put another used one in and raised the float level and the wet look simmered down when I pulled the plug, same thing on #6.
I am by no means positive I have fixed anything yet but I do have my hopes up. I have got to know my CBX a lot better the last few days.