Black deposits on pistons

!Seymore wrote:

KzChop82 wrote: Here is what my valve area is looking like:

Attachment IMG_3413.jpg not found

So, I'm just asking because I rarely see this side of the head... looks to me like the plug is far recessed. Does anyone think the wrong plugs have been run in this motor, based on the PIC above?

Arthur... what plug are in the head? ...and, are the plugs fully seated, in the PIC?

TIA...

Dump plugs are you running?
Its a little hard to light off the mixture from down in the hole,could be part of your carbon issue.

In my opinion, the biggest problem with using the original springs that haven't been in operation for thirty years is that some of them have been in a relaxed state all that time while others have been in a compressed state.
replace them +the rings and while you are at it ,any rubber/plastic parts like dampers , rollers, chain guide, tension-er and o-ring.
Anyways that is what I am doing :side:

JD

bluej58 wrote: In my opinion, the biggest problem with using the original springs that haven't been in operation for thirty years is that some of them have been in a relaxed state all that time while others have been in a compressed state.
replace them +the rings and while you are at it ,any rubber/plastic parts like dampers , rollers, chain guide, tension-er and o-ring.
Anyways that is what I am doing :side:

JD

+1

kawi810 wrote: Item #

Type

Description

Retainers

Retail Price


40-0449 Valve Spring Only Kit 0.425" Valve Lift OK, Stock Replacement N/A $75.95

40-1016 Valve Spring Only Kits 0.475" Valve Lift OK 40-1008, Titanium Retainers for Kawasaki® KZ™ 650/750 1976-1985 ($245.83) $75.95

40-1007 Valve Spring Only Kits 0.500" Valve Lift OK 40-1008, Titanium Retainers for Kawasaki® KZ™ 650/750 1976-1985 ($245.83) $75.95

40-1014 Valve Spring Only Kits 0.560" Valve Lift OK 40-1008, Titanium Retainers for Kawasaki® KZ™ 650/750 1976-1985 ($245.83) $142.37


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These figures apply to smaller engines not the Z1/KZ 900/1000's. The ones shown are for a more radical build, not for this application.
Steve

"It's not that our Democratic friends don't know anything, It's they know so much that isn't so."
Ronald Regan

Nessism wrote:
"The photos below show burned valves and seats. This is caused by the lack of proper valve adjustment maintenance. As mileage accumulates on the engine the valve clearances close down. Eventually the valve doesn't close anymore, usually the exhaust valves first, and then the valve and seat burns. This head needs a full valve job to resurface both the valves and seats. You can not recondition those parts by lapping alone."
As well as:
"KZchop82's exhaust valves are burned. The seats too. The service limit for seat width is 1.0 mm. The head shown in the photo seems to have about 2-3 times that. Only way to fix that is to cut the seats."

This is what you should listen to. If you don't have a factory service manual get one. You can find download links for a free pdf version on our web site, I used to have a good link in my signature but that changed a few years ago with the site upgrade.
You should consult a good machinist who knows motorcycle heads. You want to do the job one time, and that's correctly, right?

Once the valves are cleaned and lapped, it's then the issue of being burned will become apparent. It's being worked on because of oil fouling, not something else.
Steve

swest wrote: Once the valves are cleaned and lapped, it's then the issue of being burned will become apparent. It's being worked on because of oil fouling, not something else.
Steve

This is incorrect. Look at the valve face area. It's black and charred. Also look at the exhaust valve seat, it's charred as well. The valve wasn't seating because someone didn't adjust the valves. This is a COMMON problem with engines in general that require manual valve adjustment, and doubly so with shim adjust valve lash. It also looks like the intake valve guide seals were leaking, but that's a secondary issue compared to the burned exhaust valves.

The photo below shows the max seat width you should have - 1.0mm. Compare this photo to the head in question and you can see the difference in the seat width.

Regarding the valve springs again. The service manual has specs. Check the springs against the manual specs and replace them as needed. Some people come up with their own opinions on this and that, but the manual is the bible, and replacing parts that measure to the spec is a waste of money. The point about a chopper surviving on stock valve springs is valid. The main concern with using old valve springs is if they have sagged out (which you can measure). Even if they have sagged that won't cause a problem unless you are racing the engine to redline regularly. Strong springs are needed to avoid valve float at high rpm, otherwise you want the weakest springs possible for long valve and seat life.

The valve seat still has carbon on it as do the valves. Like I said, they must be cleaned and the seat lapped to tell if a grind is called for. The clean head is mine. Your seat looks great. Text book. Not always practical for some.
Steve

I'll say it again. The springs I suggested are a direct replacement for stock springs, just of better quality.
Steve

swest wrote: The valve seat still has carbon on it as do the valves. Like I said, they must be cleaned and the seat lapped to tell if a grind is called for. The clean head is mine. Your seat looks great. Text book. Not always practical for some.
Steve

Steve, honestly man, carbon on the seat and valve face IS indicative of burning. This doesn't happen when the valves have been seating properly, which those valves haven't. Also, the photos clearly show the seat width which is WAY too wide. The valve has pounded into the seat and the material has been worn away. Lapping can NOT fix this stuff. It will clean the carbon, but you can not resurface the valve and seat through lapping.

Regarding the springs, it's okay to install new OEM springs or equivalent aftermarket springs. May not be needed but spending money helps the economy so what the heck? Just make sure the spring pressure is not greater than stock.