1982 GPz 750 running poorly when hot

GPzEric wrote: Get out your meter, check out your magnetic pick up coil.

Heat it up, until it starts messing up, then check it again.

I had one on my '79 Kz1000 that would act up when hot.

I had a similar issue early on ended to be Either a coil or the connection when I redid my bike put a different set of coils on new connectors etc...

I still have some carb issues but no dying and having to wait and fiddle to restart. just an alternate theory

GPzEric wrote: Get out your meter, check out your magnetic pick up coil.

Heat it up, until it starts messing up, then check it again.

I had one on my '79 Kz1000 that would act up when hot.

This would be my guess. And a good thing to check. into.

GPzEric wrote: Get out your meter, check out your magnetic pick up coil.

Heat it up, until it starts messing up, then check it again.

I had one on my '79 Kz1000 that would act up when hot.

Are you talking about the output from the Hall effect sensors under the timing cover? Other than checking the timing and confirming that the centrifugal weights move freely, I haven't really looked at it much. It should just be two signal wires and a ground or something, right?

FWIW, the ignition coils themselves are brand new. It seems like I'd be losing both cylinders 2 and 3 if I had an ignition issue upstream of the plug wires and plugs. Not arguing with you, just thinking out loud.

The big brown truck of happiness left the carb parts on my porch a day early, so I'll get the carbs back on and get it running on the aux fuel bottle again tomorrow. Either way, I'll take a look at the signal as soon as I have the carbs back together. Is there a standard test method? What about the IC Ignitor?

Thanks for the suggestions!

So much for getting this done quickly. I finally got some time to work on the bike.

The carbs have been stripped to the castings again, and each carb body spent several hours in the carb dip. To say that they were dirty would be an insult to... dirty things. These were sparkling clean about 20 miles ago, but there was evidently a ton of crap in the tank, and the carbs were disgusting.

The tank has been thoroughly cleaned and de-rusted now, so that won't happen again. I degreased it with a gallon of lacquer thinner and a length of small chain for a few days, shaking it around regularly. Then I used the Yamalube Gas Tank Cleaner and Rust Remover kit. It's basically phosphoric acid, and a neutralizer with a flocculating agent. I also rebuilt the petcock. I haven't used the tank yet because I'm still just running on my aux bottle, but it is now spotless inside.

I installed a K&N factory-style air filter, and I have the V&H 4-into-1 exhaust, so I also installed a DynoJet Stage 1 kit and used the 118 mains. I have no idea what jets were in there because I can't find any markings on the old jets, but the new 118 are visibly larger. All of the carb circuits have been cleaned, blown-out with compressed air, and verified (plug A and B and make sure that the air comes out of C, then plug B and C, and so on). The pilot jets are stock, as far as I know, and are clear. The needles and seats are brand new K&L, and I spent close to 2 hours nitpicking the fuel level in each one before I re-ganged them. Hopefully that will resolve any carb concerns, but we'll see.

I got it good and hot idling in the garage tonight, and it ran pretty normally, but I haven't had a chance to test it under any load. While I was waiting for carb parts, I went to change the fork seals, since they are leaking badly. Unfortunately, some genius previous owner must have cross-threaded the aluminum cap on the right-hand fork leg. The impact gun finally got it out, but the threads in the top of the tube are damaged beyond repair, and the plug that actually holds the spring under tension won't budge, even with 120 psi on my 1/2" impact gun. I've got another set of fork legs on the way (from eBay), so when they get here, I'll finish the fork rebuild and see how it does on the road.

Does anyone have any tips on checking the pickup coils? I'm going to look for my analog multimeter, because I'd imagine the digital-only won't be very helpful.

Thanks for reading all this nonsense. I've got a few pics I'll post to reduce the thread-suckage. Everyone likes pics...

Ohm Checking Pickup(Pulsing) Coils

The pickup coils on the Kawasaki’s with the factory supplied electronic ignition can sometimes fail or become intermittent due to heat and vibration.

1.Trace back from where the pick up coils are mounted,(under a right side CD sized cover) locate and disconnect a small 4 pin connector. Using a multi-meter set on OHMS and range of X 100 check between the BLUE and BLACK wires(#1 and #4 sparkplug wires) for between 360- 540 OHMS.

2.For #2 and #3 sparkplugs the wire colors will be YELLOW and RED, again 360-540 OHMS.

3.If the pickup coils are suspect of failing due to heat, they can be stressed using a hair dryer without the need of the engine running.

4.A replacement set of pickup coils might be obtained from a dealer who serviced the police Kawasaki’s.

5. If replacement pickup coils are not available, your next choice would be to order a Dyna “S” electronic ignition system from www.z1enterprises.com It replaces the IC igniter with a smaller module located where the mechanical ignition advancer was mounted.

6.Checking with Kawasaki.com website has determined that the Pick up(pulsing) coils are available . The pulsing coil # is 59026-1133 and replaces the older # 1002, 1012 which were used from the MKII motors until the 2005 P24.

Now you've got a Gpz 750, so the wire colors may be different, I wrote this for the Kz/GPz 1100 engines, but checkout should be the same.

Thanks for the guidance on the pickup coils. I've tested them cold, and I've put some heat into them with the heat gun, but I haven't been able to cause a failure yet. That said, the bike is running pretty well right now, but I've only put about 10 miles on it. I'm going to put some more miles on it, and get a longer ride in, and see if it acts-up again. Today should be a good test in this damn Texas heat.

My biggest headache right now is that the pilot jets seem to be perpetually clogged. Those tiny orifices aren't very tolerant of even the slightest varnish or debris, and I seem to be pulling the carbs to clean the pilots regularly. Is this common with these Mikuni CV carbs? I've got Keihins on my Hondas that will sit for 6 months and happily fire-up and idle immediately.

If you do not have an inline fuel filter on the bike I recommend you install one. I installed a Golan Super-Mini (see 70-312G 5/16 Barbed Fittings in link) on mine. Link gives specs. It's very small (see image below) but works great. Ed

www.golanproducts.com/filters.html

I've got an aluminum Russel inline on there, now. Hopefully it helps. it's got a replaceable brass element, but it is fairly big. The one you posted definitely looks smaller. Nice!

I'm waiting for my new mechanical petcock to show-up so I can get rid of this leaky vacuum thing. I've rebuilt it and it still leaks, so I'm scrapping it.

all that surging and ildling down fits the sighns of fuel starvation. If the petcock is plugged, the cap, or
have any fuel lines running parelell under the tank, the fun starts at just under half tank, :ohmy:
Sounds like #2 cylinder may had a plugged pilot jet or passage. If you don't have any luck can double
check compression by watching the reading first two times around (in case that cyl. has lower compression)
Ive had engines that wouldn't idle on one clinder because 2cyl. share the same carb and one had low (90)
lbs. comp. I just rode a Yamaha xs11 yesterday and the motor did exactly what yours did, turns out
I was running out of gas.

I'm happy to report that she got about 100 miles in yesterday, and ran flawlessly. I think the issue all-along was crap clogging the carbs (repeatedly, since I hadn't cleaned the tank the first time I cleaned the carbs).

I've got a TrailTech cylinder head temp gauge on the #3 spark plug, and she cruises around 375F, with brief excursions up just over 400 on hard runs. That seems fairly normal to me, for an air-cooled engine. Does that raise any red flags to anyone?

Of course, with this 1982 gearing for the national 55 mph speed limit, cruising at a more reasonable 65 is likely to generate more heat than originally intended. Since she could use a new chain, I might as well convert to a 530 which opens-up a variety of sprocket choices. Does anyone have any front/rear sprocket suggestions for a little taller cruising speed without giving-up too much acceleration?

Thanks for all the input so far. You guys are awesome. She's an absolute blast to ride!

I'ld invest in some in line fuel filters, & for sprockets & chain, call Z1 enterprises, tell them you want to drop your RPMs on the highway a little bit, & they'll hook you up right
Pete

You can have a look at the Gearing commander .