Main Jet confusion KZ1100

Hi Guys

Some years ago I bought an 82 KZ1100 in the USA and imported into Oz. She fired up and I rode it down the road. The bike looked like rubbish so I did a complete restoration of the bike over 4 years but didn't feel I needed to do the engine as compression was good and no smoke and she ran fine off the ship.

Then I decided to get the carbs cleaned and re-kitted (bad mistake)

I too k them to a guy who claimed he knew what he was doing but from then on the bike ran like a dog. So I took them to a carb specialist and he did no good.

I have mucked about with mixture screws blah blah blah - but she is a dog.

So - Fast forward to today. When I bought the bike it had pods. Now it has the standard air box. It had an old rusted out original pipe - now it has a new 4 in one with Vance & Hines muffler.

For some reason - it never occurred to me through all that adjusting and taking the carbs on and off to ever check the main jet sizes but yesterday it did occur to me so I took the carbs off and - wow - instead of 4 main jets at 120 size (as per standard kit I gave the first guy) ) I find 1 at 130, 1 at 135, 1 at 138 and 1 at 145 sizes !!!!!!!!!!!!!!!!! Where the hell did they come from? I gave the original guy a new standard kit to replace the original with.

So - somewhere amongst that pair of idiots one of them has taken out the jets and used 4 different sizes !! (go figure)

I had in my workshop 4 new main jets at 125 size plus 4 pilot jets.

What the heck - I started all over again and put in the 4 - 125 main jets and put the carbs back on the bike.

She started like a dream and rode beautifully - for a bit !!

Then I noticed after a few miles - she starts popping and carrying on and eventually started to bog down on acceleration.

I thought - too much fuel - and the plugs were really black - so I turned down the fuel air mixture screws half a turn and then another half turn.

She took off like lightening and was running great and I was smiling - then suddenly she started running really roughly - for some reason I instantly knew she was suddenly running on only 3 cylinders and so stopped and sure enough - to my surprise the plug on No2 cylinder was broken in half !!! Bizarre I thought. Luckily I was close to home so limped home on 3 cylinders and replaced the plug .

I then took off for a longer ride (about 15 miles) all on country roads - and she flew along and I thought - great - all sorted after months of trouble. Then just as I was getting close to home - same thing - running rough. When I got home I did NOT think it was again 3 cylinders but when I went to pull no 1 plug to check color - broken plug. !!!! Now I knew this wasn't coincidence - so I immed went on line and discovered broken/cracked insulation on plugs does in fact happen and is caused by engine too hot or hot spots in cylinders - caused by too lean mixture/detonating. The plug (or what was left of it) - was white.

So - I put in another plug and turned the mixture screws out to 2 1/2 turns and this time she rides OK but back to popping on deceleration and other minor issues.

Sorry for the long story - but one needs to understand this journey to help - SO my question is - even though it has new pipes and muffler - are the 125 main jets too large or too small and how do you tell? The popping indicates too rich but one turn down and broken plugs. No vacuum leaks or other symptoms.

Can you measure these things or is it just hit and miss? Do I have to buy main jets to try out (and waste if they dont' work) or what? She idles perfectly so I assume pilot jet change not required? Should I drop to original size of 120 and or add a washer/shim to the needle height , or go up sizes ? - I'm lost as to where to turn to start on this.

All suggestions on this issue greatly appreciated thanks. Greg

It's still running lean. Make sure that the standard stuff is done. Proper timing and advancer movement. Proper valve adjustment. Make sure the carb mounting blocks are secure and not leaking air. IDK if Daveo has any of those sweet carb clamps left but those worked great for me. Thanks Daveo! I have pods & a Delkevic and run the standard pilot jet and 145 mains and run the needle 1 clip up. Do you have the ASS (Air Suction System) on yours? That's a horrible thing. I've been lucky to get non-ethanol regular 90 octane and it's a screamer. When I had the 2 1/4 baffle pipe I had to run 155 mains. Not good for mileage, but God it moved. I'm guessing you have BS34's? And they're called BS for a reason. You're close. I think it needs fattening up a bit. Maybe 135-138 Mains. Good luck.

Some days it seems that no matter where you look, all you can see are imbeciles, con artists and thieves.
With stock intake, stock engine and the V&H, stock jetting or something very close should be good. I am assuming the standard baffle is in place in the muffler.........
Since you know that some jerk reassembled the carbs with whatever parts were within reach on his junk pile, I would start by finding out what else in the carbs is incorrect. Are the correct needles still there? Are some of them shimmed? Are all of the float needle and seat valves identical? Are the floats identical? Are the slides?
Once you are sure each carb has the same, correct setup, then check for the proper fuel level using the clear tube method described in the factory service manual. If you do not have the manual, there is a link under the Articles tab on this forum to a PDF version you can download.
Since you do not know the maintenance history of the machine, and two incompetent nincompoops have had their tools on it, it would be a really good idea to perform all of the routine maintenance required by Kawasaki. Valve lash is particularly important and too often neglected. Be sure to check them and adjust as needed.
Good luck. Please do keep us up to date on your progress.

Oh, yes you can measure the mixture. A full blown exhaust gas analyzer would be best, but they are pretty expensive. A decent two or three gas analyzer can do the job, and is much easier on the wallet. Several folks on the forum have reported good results with a Colortune. Easy to use and cheaper than the other options.
Back in the bad old days, reading the sparkplug was very common. It is a bit of a black art, and the crap they sell for gasoline here in the States makes plug reading increasingly difficult and misleading. I would opt for one of the other choices.

Short version: bike ran fine stock. Defenseless carbs are subjected to clueless hack. Bike runs bad. Defenseless carbs are subjected to differed clueless hack. Bike runs bad.

Focus on the carbs. Make sure all parts are stock sizes, preferably OEM, and adjustments are set to OEM spec. Make sure floats aren't set at four different heights. Use clear tube tool.


Good Ridin'
slmjim & Z1BEBE

slmjim+Z1BEBE wrote: Short version: bike ran fine stock. Defenseless carbs are subjected to clueless hack. Bike runs bad. Defenseless carbs are subjected to differed clueless hack. Bike runs bad.

Focus on the carbs. Make sure all parts are stock sizes, preferably OEM, and adjustments are set to OEM spec. Make sure floats aren't set at four different heights. Use clear tube tool.
Good Ridin'
slmjim & Z1BEBE

Stock is good and the bike runs perfectly stock. I realize everyone feels the need to "improve" stuff, because the japs are no good at engine design. >sarcasm< They calculate HP , load, air flow, fuel mixture, exhaust completely and then do it again.. Yeah "improved". lol

It sounds like the defenseless spark plugs are being cracked / broken during installation. I have fried my share of engines in my lifetime, and I do not once remember having a spark plug break from a rich or lean situation. I have cracked them by over tightening, using a swivel and a goofy fitting socket, and using air tools before, but NEVER from running like crap.

The mixture screws have practically no effect on higher rev air / fuel, and are in effect at idle and in the lesser throttle openings (under 1/8 open) . .. so YES it does sound like the 125 main jets are drowning the engine on the highway if the plugs are black. The popping is from the broken / bad plugs. Lean motors pop, not fat motors that blow black smoke and have sooty black plugs.

This article explains what throttle openings the different jets effect.

www.atvriders.com/articles/how-to-jetting-carb.html

Pictures inserted into your postings are indeed worth a million words, and it really does help to spot problems, aside from eliminating a bunch of guess work.

I've never heard of a spark plug breaking because of heat or lean fuel mixture. At one time my old BSA was running so lean and hot that the upper foot of the exhaust headers were glowing a dull red, and that didn't break the plugs. My guess is that either the plugs were damaged before they were installed or during installation. Ed

Amazing amount of variables with these old things. I'm no longer surprised that new bike mechanics don't want to work on them. Big PITA at times, but when these engines want to sing you just have to let them. :woohoo:

There were lots of comments and replies to my thread and I thank you all for them but I think Old Kaw got to the centre of it., however I will check all parts are same in all carbs as - you are right - if one of these fools swapped out the main jets - then he could have done anything and I have not checked so will do that.

It challenges my faith constantly in the so called professional bike mechanic sector in Melbourne. I don't know what its like in the USA but we have seriously few honest well trained bike mechanics down here and the attitude too often is take it or leave it - which is why so many of us get on and learn it all when we want to run classics. Carbs challenge the poor mechanics most I've discovered. You see a look of fear when you show up and say carb

So - my central point in all this is - I started with BLACK SOOTY plugs and black sooty tail pipe end. I changed tout all these odd jets sizes to a 4 x 125 set which is 2 sizes above stock size and now the plugs are black and slightly sooty and the tail pipe is less sooty - so unless the world turned upside down recently and I didn't notice - then going UP sizes of jets as one person suggested makes no sense to me - so I will (after checking every other part) go down progressively (there's only one size between where I am at now and stock size)

Yes the baffle is still in the muffler. I have already done the fuel level adjustment on the carbs and only one was slightly out. I have synced the carbs originally and given thats just setting butterfly's to be equal I can t see why I need to deal with that anymore- unless because the main jets were all different I should now - let me know thanks.

All I have to do is wait for the 122.5 jets to arrive. I 'll post results when they do. (seems Oz suppliers so far are out of stock) (Welcome to down under - our small population is a big issue on parts supply but in recent times we discover postal times from the USA are terrible. -- Up to 8 weeks in some cases - whereas Japan is 1 - 2 days !!!!!

daveo wrote: Amazing amount of variables with these old things. I'm no longer surprised that new bike mechanics don't want to work on them. Big PITA at times, but when these engines want to sing you just have to let them. :woohoo:

I had to chuckle at this one Dave. Mine sings a perfect symphony whenever I turn this caged animal loose.

I don't think with the fuel injection now days, that the new wave of "mechanics" KNOW much about carbs. I wonder if they still teach carburetor theory at the trade schools? I had to take it when I was in college, but that was a really looooooooong time ago. I had to take physics and accounting then too. Not so much interested in the accounting semester, but was a required course.

It sounds like our friend from the land of Oz is on the right track. I assume you took a look at the CV carb article link I posted.

A little back story of my own.. I did a tuneup on a old beater once for an acquaintance, and in my rush to get done before dark, I had used my air ratchet to spin down the plugs I had already started in the holes. I ended up cracking a plug. It ran great at idle, but under load it missed and popped.. Since then, I am the most careful spark plug installer dude this planet has ever known. That porcelain can't handle any side loads, and a small crack can happen with out even being able to see it. I would venture to guess that even a new plug could be cracked in the package, from being dropped at some point on it's journey to Oz.

Good luck with your bike. I think daveo posted recently it is best to start on the lean side (stock jets) , then gradually fatten it up as you check plug colors. Tan=good.