81 KZ1000M cylinder backfire carb issue

[red_razor23]

Had this bike for over a year and it was purchased at a steal, but with hordes of issues. Least to say most are fixed but today I am fighting an issue I've had since I've owned the bike. The carbs were in bad shape when purchased and I'm still working out issues:
i have fought for a long time with gas/ richness issues. I have finally ditched the vaccuum system, and modified the stock petcock to allow reserve through the prime setting. There is a seperate shut-off valve in inline. There is no secondary filter and both times I've taken apart the carbs there was a lot of trash in the bowls, so I'm getting an inline filter as well. This is a CDI/pickup ignition system and here is the issue: cylinder 3 is fouling out. Plug wires are brand new accel 8mm, brand new NGK B8ES with .32 gap. I have the air idle screws out to stock 1&1/4th out, and the sync I'm guessing on, as my mercury tuner just gave up the ghost and i'm ordering a new one. regardeless at idle it fouls, backfires, hick-ups on accelleration. after about 4k rpm though it appears that the cylinder is firing, the engine smoothes out, and the tune is even sounding. come below 2k and its vibrating and off rhythm. I can play musical spark plugs and its the same sooty, nearly wet looking. now this USED to be how #2 was, but since i've removed the vaccuum system, its now moved to #3??? now is that since #3 is always capped off... nevermind. Anywho I've adjusted the floate (pushed in tab to lower gas amount in bowl) and it seems to make no difference. other things i should check? I really don't want to take it to a mechanic if I don't have to as i'd like to do this myself. I'm just out of ideas. Stock airbox, 5FL5 needles 117.5 main jet, 18mm (ish) on the floats... again no vaccuum, no antismog.

[StarGate]

Apparently it's not the factory carbs so what carbs are you running. Have you checked compression and checked/adjusted the valves?

[ArthurGoVroom]

It does sound like the #3 carb might be out of sync. You notice synchro problems most at idle and off idle, at wide open it's not as easy to tell.

Could also check to make sure it's not flooding over, leave your float level tool hooked up and make sure it'll maintain the fuel service level for 15-20 minutes without slowly rising in your sight tube. If it increases slowly your needle valve is leaking/seeping, and would require attention.

[kawpaul]

Originally Posted by StarGate

Apparently it's not the factory carbs so what carbs are you running. Have you checked compression and checked/adjusted the valves?

+1
I am thinking this is not a carb issue. Maybe some carbon buildup on the valve or valve stem keeping it from closing all the way or zero clearance on the valve lash. Also with it backfiring it sounds like an intake valve.

[red_razor23]

Originally Posted by StarGate

Apparently it's not the factory carbs so what carbs are you running. Have you checked compression and checked/adjusted the valves?

These are the original carbs, however they were sent in to "Wired George" and apparantly this is what came back. Not sure why the deviation from the 120 jets, but everything else is stock. The possible answer for the smaller (?) jet size is that the original owner lived in Amarillo, TX North of here (here is Lubbock, TX) and they may have set them for higher altitude??? I have no idea....

The sync issue I might believe in, but as it goes 1 [adj] 2 [adj] 3 [adj] 4; I can tell that the adjuster to LEFT of 4 adjusts 4, the adjuster to the LEFT of 3 adjusts 2&1, and the adjuster to the RIGHT of 1 adjusts 1 only. 3 therefore is the "master". How does one sync to a cylinder that won't fire..

Last comment: carbon in the intake valve... I've been rather timid to break into the engine, although it wouldn't be the first one for me to do this with. This bike is my daily rider, and I would obviously like to it to perform reliably, let alone be twisty fun... This makes me just a little nervous to go in and start messing with the valves. I've also been reading lots about valve clearances, and the shims (never had to deal with those on the Honda I owned before). Shims must be made of gold because of their pricing they go for on ebay... and you have to be some sort of masters level mathmatician to add and subtract for this and that!

I want to order my sync anyway, but I'm considering taking the guts of carb #3 and moving it all over to carb #4: jet, float, needle, venturi, the whole 9. good idea? bad idea? i just want to see if the problem follows or not...

[elr658]

Until your valves are adjusted to .006 inch, you ain't going nowhere.

[red_razor23]

Originally Posted by elr658

Until your valves are adjusted to .006 inch, you ain't going nowhere.

Don't i have to get that shim tool though? like one of these boogers?
KAWASAKI KZ / Z1 VALVE SHIM TOOL:eBay Motors (item 260482855873 end time Oct-03-09 19:30:32 PDT)
Then I need to (if I'm reading correctly...) use a feeler guage measure the distance of the excess then subtract the current shim size from the excess size to equal the size of what i need for the new shim size... then do i get to beg and plead for shims??

[zoro]

Originally Posted by red_razor23

Don't i have to get that shim tool though? like one of these boogers?
KAWASAKI KZ / Z1 VALVE SHIM TOOL:eBay Motors (item 260482855873 end time Oct-03-09 19:30:32 PDT)
Then I need to (if I'm reading correctly...) use a feeler gauge measure the distance of the excess then subtract the current shim size from the excess size to equal the size of what i need for the new shim size... then do i get to beg and plead for shims??

Howdy Matthew, go to<kzrider.com> and there you will find a clearly explained,easily understood procedure on how to check and restablish proper valve clearances. These are metric bikes,stick to metric dimensions! 0.05mm is the minimum tolerance,anything less than that is going require a thinner shim. 0.15mm is the maximum tolerance,anything between those two measurement readings is good.Dont waste your money on that Motion Pro junk especially if you dont know how to use it! The tool you want is still made by Kawasaki and sold by Z1enterprises. Its the valve lifter tool#57001-113. Its pricey but worth every penny! They also sell the shims for about $3 a piece. You need to address the valves before going any further with the carbs! Youll need a set of feeler gauges that are marked in metric,and that have a blade that is at least,0.04mm thick.Be vary careful removing the valve cover so as not to damage the gasket. Carb work is meaningless if you have tight valves so check those clearances first! Say howdy to Wired George!

[StarGate]

Here is a link to the tool and shims from one of the best suppliers I've found.

Z1 Enterprises > Make > Kawasaki > Large Fours > KZ1000 81 and up > KZ1000-M1 1981 > Engine > Shims

With mine, I've found that I could use the shim from one cylinder that was out of spec and use it on another cylinder to get it in spec. That meant that I only had to buy 1 shim to correct 2 cylinders. I was even able to switch some shims around to get one cylinder that was almost out of spec back to the loose side of tolerance. Yes it took some calculations and planning but in the end I only needed to buy a few new shims to get all cylinders back to the proper specs (loose side of tolerances). And since the tool and shims come from the same source it saves on shipping cost, and the tool is cheaper here than the one you posted.

P.S. OK, that would explain the smaller main jets but if you are running anywhere near sea level that means you are 4 sizes below stock size on that main jet you listed.

[red_razor23]

ok finally had some time. re-fiddled with the carbs, and got things to run a smidge better, however still no #3. but it's backfiring now! I was given a cylinder compression tool today to measure the PSI (Thanks Don Meloy) and wow. what a depressing moment: #1=95 #2=140 #3=70 #4=120. Soooo... ok ok ok I give. I've ordered a replacement valve gasket and I'm eyeballing a shim kit on ebay, but i'm not above just contacting Z1. I know that 1/3 are on the same stroke, would #3 be effecting the performance of #1? the bad part is that i'll have no real time available until a week from this weekend. SO my next question:
What level of risk is there in continuing to run things the way they are? What chance is there really of me bending rods or valves or blowing the tops out of cylinders or having the side of the engine explode and take out my leg at 55mph... or having some lady driving a denali yukon smash into me cause she was texting on her phone while yelling at her two kids in the back seat. Wait that last one isnt compression related... anywho, i'm just concerned that there is possibility for extended damage, which i know the answer is if i were doing this for MONTHS then yes, but i wonder about a week or so....

[ArthurGoVroom]

First off, did you check the compression of all 4 cylinders with the throttle held wide open? The throttle must be open so that there is air in the cylinders to compress.

Second, squirt a little oil into each cylinder and rotate the engine with the kickstarter a few times, then recheck the compression. If the compression improves, you are dealing with worn/broken compression rings. If the compression stays about the same, you have valve(s) not closing, and you are going to be needing to adjust the valve lash as discussed above.

If you run the bike with a valve not sealing completely, the hot combustion gases are going to leak past the valves under high pressure, and eventually melt/burn the valve seats and/or valve faces. I have no idea how long "eventually" is, but it can't be good.

[StarGate]

+1 or Yea, what ^ he said.

[Kawasaki_Boy]

just out of curiosity, how attached to this bike are you? if it has "hordes of issues" like you said, i'd be shopping it to see what you can get for it to put towrds a running bike...
...however, if you are attached fixing it all is the only way to go.

btw, with such low and inconsistent compression, i'd think rings and/or cylinder damage.