Carb Sync???

Ok, gotta question about carb syncing. So got this bike tuned in pretty good, it has 785679kms, don't know what it would be in miles any how when I was doing the sync, the manual say's get it to 22 mercury centimeters, but for some reason I can't get it past 20.. I know th bike has alot of miles on it, but it seems to have developed a knocking which sounds like the Cam chain rattle that was there before but not as present. I've rebuilt the tensioner, checked valve clearance, new intake boots no leaks, compression is good, just can't seem to get it to sync above 20?
Is this normal or am I not doing something right? And because it's not quite 22 on the Carbtune, would this cause a knock? It seems to be audible in the exhaust. The bike is an 84 KZ750.
Thanks

Stock pipes and all?

Is there a way to check calibration on the gauge?

I can't see how slightly low manifold vacuum could make an engine knock.

Yup, all stock. There is no way as far as I know of to check calibration. It's the Morgan Carbtune II, so it's pretty easy to use. I'm guessing it's probably cam chain rattle, but it's gotten alot louder since the sync. It only happens at idle or when I come to a stop. I've been trying to narrow it down but I can't seem to locate the demon. The only thing that confuses me is that when you go to the back of the bike and listen to the exhaust, which is a 4 into 1 stock, you can head the knock through the exhaust. I've heard chain slap before but not quite like this. I'm baffled.

I always thought that the most important thing was to have all the readings in the same ball park. I also have the Morgan Carbtune and usually see the readings in the 20 or maybe 21 area. My bike is a few years older but a little less km at 65,000.

Regarding the noise the primary chain will make quite a racket at idle if the carbs are out of synch. The racket goes away when running. Best way to check this is with a mechanics stethescope on the gearbox. I use a long screwdriver and put the blade to where I want to listen and put the handle against my ear. Thats the easiest way I know to pinpoint where a noise is coming from. If from the gearbox at idle then probably primary chain and good synch should clear it up.

Good luck

you could also be experiancing some noise out of your clutch basket the damper springs on high milage motors can start to work them self loose in the back of the basket. how hard was this bike ridden in the past? on most air cooled carbed engines i personally am happy from 15-16up to 20 on a set of sticks for engine vacuam really the most important thing is that they are even and it wants to idle properly.

If the carbs are out of synch or dirty and causing the rattle, proving this is the case would be the next step. So I'd like to ask what is the idle rpm it rattles at? How far off is it from the stock setting. 650 and 750 carbs are lean and need to be clean clean clean before you'll get anywhere they must be .... well i already toldya. Even if you've just taken them off. I just cleaned some from a 650 and they were clean, had to do it 2 more times for a total of three, and I've cleaned many of them. This is actually where the water spray on the pipes test while it's warming up can be tell tale what the heck is going on, along with idle rpm. Even though these tach are not real close everyone knows when somethings WRONG. Only other cause of rattle thats not clutch or chains related is damage to piston rings or valves. Compression tests should be done in a manner that focuses on the readings the first couple times around, these are the most telltale other than a leak down test it's the best it gets. If you have low comp. in a cylinder it's gonna rattle like it's gonna blow up. I give OMR the torch from here, before the rocks start flying.

timebomb33 wrote:

you could also be experiancing some noise out of your clutch basket the damper springs on high milage motors can start to work them self loose in the back of the basket. .............quote]

Good idea
I never thought of that

It's good to have pro back on the board

Hey thanks everyone for the answers. As far as how it has been ridden previously, I have no idea. I got it out of someones garage cheap, and had to do the top end, valves, gaskets, exhaust studs the whole deal. Bike ran good last season, but wasn't perfect. So after carb sync and valve check which I checked again last night, #1 on the exhaust is a little tight but the rest are in spec. Would this be the culprit? Also after the first sync I did bike ran better than ever, but just with the noise. As I increase RPM's it goes away. Idle is around 1100, but I may increase it if it helps. I'll check the clutch basket, is this something that can be tightened up or will it have to be replaced?
Thanks again for the input.
BD

Quote
idle is around 1100



On my 80 750/4 the recommended idle is 1300 or 1400 and I have to admit I like it like that. Better take off. No noise

JR wrote:

Quote
idle is around 1100



On my 80 750/4 the recommended idle is 1300 or 1400 and I have to admit I like it like that. Better take off. No noise

Really, the service manual I have which is a Haynes I believe says idle should be 1100rpms. But I guess thats for a new bike. I'll raise the idle and see where that goes.
Thanks JR

You are correct sir !

I was sure I had seen the higher figure so I went back and checked the Kawasaki shop manual and darn it you are right.
I guess I've been doing it wrong for the fast 7 years. :laugh:

Oh heck. I think I'll just leave that idle knob where it is as 1300 seems to work best for me.

Thanks

does the rattle go away or ease up when you pull in the clutch.