fluttering vacum gauges

I am so close with this bike I can't stand it.

The bike is a 1981 Kawasaki KZ750H2 with keihin CV34 type carbs. (according to the book)

I found the bike sitting in a garage with some of the pieces removed and paid $400 thinking it would be a good fixer upper to use for a work bike. (back and forth to work and short trips) It has turned into alot more work than I thought but it is almost ready. The bike will start on command with choke and warms up fast. (too fast on two cylinders) The number 2 and 3 cylinders heat up very fast (exhust will burn your hand in seconds) the 1 and 4 cylinders run cooler but do heat up. I think they are the ones that are right.

I bought a cheap set of vacume gauges from Z1 to try and fine tune the carbs. But when the bike is running the gauges just flutter all over the place. (wish i knew how to post video so I could show you) I was just wondering if anyone else had this problem with these kinds of gauges. I guess the good news is that all the gauges seem to flutter about the same as each other.

For the record.. I did not use the tubes that came with the kit. I attached the hoses directly to the carbs vacum ports.

The temptation to take this girl for a ride is real strong. But the thought of burning up those two cylinders and ruining this bike and all the work I have done pevents me from doing that.

I believe the 2 & 3 are running lean and that needs to be adjusted. I checked the float levels using clear tubes and they are all good. The pilot screws are still set as they were from the factory. There are new boots or carb hangers (between the carbs and engine) and no change in idle speed when sprayed with wd40 or carb cleaner. I also replaced all the vacume lines and fuel lines. The boots between the carbs and air box are old but seem to work alright. (no change in idle speed when sprayed with wd40 or carb cleaner) I have replaced the air filter. (as well as all the others)

As a thought...The 2 & 3 cylinders run from one coil and the 1 & 4 run from the other. Could the coil be making the cylinders appear to be running lean? How would I check the coil other than a multimeter? What should the coil be reading? Does the bike need to be running to check the coils or would the readings be the same running or not? I will run some voltage tests and see if there is a difference between the two coils.

Sorry for the length of the post. Frustration brings it out of me I guess. Any help would be great.

For the record.. I did not use the tubes that came with the kit. I attached the hoses directly to the carbs vacum ports

Did you set them up with the restrictions? You need these to tone down the vacuum pulses to get an accurate reading. (went out and took this pic for you...)

Thanks for the tip. They did come with the kit but I didn't use them. That did fix the fluttering.

coils won't make it run lean but partilly plugged pilot circuits will i hate to tell you this but the carbs might have to come back off again also double check your air or fuel screws to make sure they are set as close to the same as possible.

Are the air fuel screws the same as the pilot screws?

yes on your carbs they are fuel screws make your idle adjustments there.usally about 1 1/2 turns out

Quick question if those screws are all the way in then the bike shouldn't run right? but I just tried and the bike starts and runs the same as it did with the screws out.

burkmanofgod wrote:

Quick question if those screws are all the way in then the bike shouldn't run right? but I just tried and the bike starts and runs the same as it did with the screws out.

Where turning pilot adjusting screw makes no difference, there's likely something wrong in the pilot circuit, such as obstructed passage or pilot jet or defective pilot jet, but could also be something else like a damaged adjustment screw, improper assembly, etc.

Good Luck!

burkmanofgod wrote:

...bike will start on command with choke and warms up fast. (too fast on two cylinders) The number 2 and 3 cylinders heat up very fast (exhaust will burn your hand in seconds) the 1 and 4 cylinders run cooler but do heat up. I think they are the ones that are right...I believe the 2 & 3 are running lean and that needs to be adjusted....

Actually, imo the number 2 and 3 cylinders heating up very fast whereby exhaust will burn your hand in seconds are the better functioning cylinders (as all 4 exhaust pipes do on both my bikes), and the slow heating 1 and 4 cylinders are exhibiting poor combustion for whatever reason.

The best test is using water spray on the headers which should immediatly sizzle and vaporize within a few seconds after starting a cold engine. The water spray will just run down the headers from non-combusting cylinders, which sometimes feel warm due to proximity to engine head and hot pipes from properly combusting cylinders.

Would never touch headers with hand or finger to test for heat. Spit on 'em if necessary, but don't feel 'em.

Good Luck!

Thanks for the tip you may be right since this is the first bike I have ever owned and worked on I am just guessing at most things. I have worked on cars and trucks most of my life but I am learning that bikes are a whole different creature.

The coil may not make one pair of cylinders run hot, but the ignition timing might. You may have electronic ignition, but this may still be relavent: Cylinders 1&4 run off 1 coil and 1 set of points; cylinders 2&3 run off the other set. If one set of points is not set correctly it will affect the corresponding pair of cylinders. I would use a timing light and dwell meter (or the appropriate tools for electronic ignition if that's different) to check the timing. If the timing is off it can make the engine (or 2 cylinders) run too hot. Do you have the factory service manual? If not, it's the best money you'll ever spend on your bike. Get one from eBay for your specific model & year. Ed