TOPIC:

dpivas7 wrote: I will fix the kink in the fuel line, just gotta figure out a good solution because there isn't much space with the inline fuel filter and the petcock being so close to the top of the carbs. ..

Regarding the fuel line kink - see www.kzrider.com/forum/2-engine/609132-in...gine-81-kz650#789676 for details on what I used for routing, fuel filter, etc. The images below show how I routed the fuel line with filter and elbow. Ed

dpivas7 wrote: I will fix the kink in the fuel line, just gotta figure out a good solution because there isn't much space with the inline fuel filter and the petcock being so close to the top of the carbs.
The CV's and pods topic has been done to death on many forums and as of yet no solution except stock air box, the bike manufacturers spend millions to get air flow right, if it was as easy as putting pods on i am sure all of our bikes would have them on and the companies would save millions.

I'll check the jets, but I ordered a jet kit just in case. I have genuine K&N pods

After reading some online, I wish I still had my stock airbox because people are saying that CV carbs don't like to work with CV carbs!

I'll save the header wrap discussion for another post...

If not already done, would test ride with fuel cap ajar to eliminate cause as possible tank vent issue.

And make sure fuel level in the tank is well above reserve level.

Good Fortune!

JR wrote: A kink in the fuel line will cause exactly what you described. Happened to me.

I had primary main jets at 70 and secondary mains at 140 when i had k&N pods on my Keihin CV34 carbs 1980 kz750E1 . It ran well.
Stock jets are 60 and 125?

Why did you choose these jet sizes? In the jet kit that I purchased (DynoJet kit Stages 1/3) it only provides secondary main jet sizes 116, 122, 130, and 136 - no primary jets. This is the only jet kit available for my KZ750 LTD H3. I'm wondering if the difference is because you have the E1, but the kit instructions say it is compatible for E models too...

According to the Haynes manual all E H and L model 750s have Keihin CV 34 carbs with stock 62 primary mains and stock 120 or 125 secondary mains and I assume you would be the same. So I doubt there is any difference between E and H models in using the jet kit

When I bought the bike over 15 years ago it came with K&N pods and a Mac 4 into 1 exhaust. According to my notes the jetting it came with was 64 primary and 130 secondary (ala the PO) and it ran reasonably well. To make a long story short wiredgeorge posted here that 70 and 140 was a better combination and so I tried it and he was right. Jets were/are available from Z1 Enterprises.

A number of members have used the dynojet kit and reported good results. I think I looked at a kit years ago and the instructions mentioned drilling the slides so I backed away but I could be wrong. If slide drilling is part of the set up process then I guess dynojet have a different approach. Also some companies number or measure jets differently so I cant tell if Dynojet follow Keihin convention or Mikuni or their own. Their jet numbers may or may not be comparable to Keihin

Not a full answer I know but hope it helps

So I went to install the DynoJet kit, but it turns out that my carbs already have this installed...

The jets are super clean (I've cleaned them out a lot lately) but there is some rust flakes blocking the float bowl valves and there is A LOT of rust in my fuel filter. The filter is only a few weeks old so I now believe that it is the amount of rust in my tank that is impeding the flow of gas thru the petcock & carbs. I guess the next thing to do is to clean out the tank and see how it improves performance.

Just a quick update: I took the bike out for a ride yesterday and it felt quick - like quicker than I've ever felt on this bike. The only adjustment I made was I turned the pilot screws from 2.5 to 3.5 turns out (per DynoJet instructions).

I noticed that it is quick through 1st and 2nd gear, but I don't think I can redline in 3rd even on a flat road. I think my problem with 4th gear is that I'm shifting too early, but 3rd gear doesn't seem to rev as loud as 1st or 2nd (I don't have a tach).

The other thing is that when I come to a stop sign, the bike tends to stay at a high idle until I let the clutch go a bit. If I pull the clutch in @ 2000 or more RPM, it doesn't drop, it stays where it's at which to me signals a fuel flow problem. And no, my throttle cable isn't binding or anything...

Are you still at this? Very admirable! No tach yet, eh? What about the manual... You surely have gotten a manual by now, right? Just stopped in for a cameo and it sounds like your carbs are out of sync again as evidenced by the stop light fluctuations. I did get my mercury carb sticks off Craigslist and I do believe I stated that you could have for free my old Chinese junky gauges as long as you pay the shipping. They work okay and like Ed stated one gauge was so out of sync with the others you need to be creative but that's just how this goes. Oh, one thing about these junky gauges, they come with junky hoses that have cracked in the year that I've had them. But it won't be hard to replace them with better, less crappy hoses.

Did you sort out the kink in the fuel line.

Also, just reading back through the entire thread and wondering if the timing advancer might nèed inspection and lube ?

dpivas7 wrote: . . . The other thing is that when I come to a stop sign, the bike tends to stay at a high idle until I let the clutch go a bit. If I pull the clutch in @ 2000 or more RPM, it doesn't drop, it stays where it's at which to me signals a fuel flow problem. And no, my throttle cable isn't binding or anything...

A less common cause of fuel starvation at cruising speeds is when crud or foreign matter (such as paint over-spray for example) is suspended in the fuel and especially at lower fuel levels collects around and obstructs the petcock pick-up tube(s), thereby restricting increased flow needed at higher speeds. A fuller tank mitigates the effect of the clogging.

A good flushing of the fuel tank may be necessary. Requires removing the fuel tank so that several partial fills with gasoline or household rubbing alcohol can be swished around inside the tank and fast-dumped out the filler hole.

A "racing idle" often results from air leaks through cracks in old carb holders.

Good Fortune!

JR wrote: Did you sort out the kink in the fuel line.

Also, just reading back through the entire thread and wondering if the timing advancer might nèed inspection and lube ?

I did fix the kink in the fuel line and haven't experience the original problem anymore, but I haven't rode a whole lot since fixing the kink. I think I need to check the timing advancer as you suggested because everything else checks out.

As @Patton noted:

A "racing idle" often results from air leaks through cracks in old carb holders.

but I have no air leaks/cracks in the rubber parts. The "air leak," I believe is the high flow (pod) filters. The racing idle only happens sometimes and since the jets are already non-stock, the carbs are cleaned & balanced, the spark plugs & ignition coils are good, there aren't any air leaks, and the throttle cable isn't binding on anything, I'm lead to believe it is the timing advancer.

I will have to check it out when I have the time. I also cleaned out the tank and am going to use some Metal Rescue to remove some of the rust.

OP: Have you compared battery voltage to voltage available at the coil primaries?

A common problem with these old bikes is excessive resistance across the ignition switch, resulting in less than battery voltage available at the coil primaries. That produces a weak spark from already weak-ish coils, even new ones.

Let's say battery voltage is 13 v, but you measure 11.5v at the coil primary. The reduced voltage cannot produce a robust spark. Why is this important?

Secondary coil output must ionize the gap across the spark plug enough to break down the insulating properties of atmosphere (air/fuel mix) enough to allow the spark to ionize & jump the gap. For our purposes, spark is most easily formed in free air at atmospheric pressure. As cylinder pressure rises on the compression stroke the atmosphere within the combustion chamber becomes much more dense, increasing it's insulating properties, thereby raising the potential (voltage) needed to ionize the air/fuel mix in the plug gap enough to allow the spark to pass. On top of that, as the throttle is opened further combustion chamber pressure rises even more as increased intake charge is drawn in, further increasing the potential needed to produce a robust spark. At WFO throttle, the combustion chamber pressure is at it's maximum. If full battery voltage is not available, the spark may simply be "blowing out" as the throttle is raised. We've seen many motors where they will idle fine and maybe cruise at low loads but, when asked to produce more power they stutter and just won't rev smoothly. More load = worse running.

If full battery voltage is not present at the coil primaries, check and clean all connections & pin connectors from the battery to the coils. If doing so does not produce battery voltage at the coils, consider doing the coil bypass realy mod as appears here:
wgcarbs.com/index.php/using-joomla/exten...-categories/89-coils

Kudos to WG for publishing the coil relay bypass mod. It works. We're running it on all our Z1's.

Good Ridin'
slmjim & Z1BEBE