Black deposits on pistons

The springs I bought are for drop in cams and slightly larger. For higher lift, duration, grinding must be done on the head and valve cover. Shim under cam followers as well. The price didn't make sense for my application.
Steve

Got it! thanks

Les

Kibble white springs are on their way.

/ :evil: Though valve springs can test to be good while cold, they can lose their "memory" when hot. Being they are encapsulated by the lifter cup, the bore they ride in and on top of the head, they can lose their properties to some degree. These are 20-40 year old machines and the valve springs are one of the hardest working components in the engine. They are often overlooked just because they "look good" but are not. It is good practice to change them when a top end overhaul is done. The cams on a typical KZ engine are relatively mild compared to the camming required for a 100/200 cc overbore. The use of "heavy duty" valve springs bringing the closing tension from 45/50 LBS to 100 LBS causes the valve train to wear more quickly. Valves, cams etc. and is not necessary for a mildly modified street machine.
I have experienced a "ticking" that comes and goes and when I check the valve clearances while cold, they check out good. I've known about this issue for many years but like most the added expense of replacing the springs was out of my budget. That's why I waited, bought seals, new valves and springs, then put it together at one time. I could have reused the valves but I didn't know the condition of the stems at the time and was prepared to buy new guides if needed. The last time I went through the valve train was after the wreck in 86, when I switched valves, installed new guides, and valve springs from a wrecked low mileage KZ 900 head I had picked up at a motorcycle salvage yard I was working at. I had Z1, KZ 900 and Z2 750 motors to scavenge parts from. My motor had 5000 miles on it when I parked it in 98. During that time the local Meth heads relieved me of my spare cases, heads and barrels for the aluminum while I was out of town working. I still had cranks, cams and transmissions wrapped in garbage bags in my shop that mysteriously burned down one windy summer night. That was in 2010. The shop was on the other side of my property but the fire almost made it to my house. I could have lost everything including my life to these sons of dubious progeny.
If they can't steal it from you, they will make sure you can't have it ether.
Sorry for the tangent, now you have the whole story.
Steve

A couple of quick comments...

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.

Regarding the valve springs, I would NOT use aftermarket (high pressure) springs with stock cams. The seat pressure will be higher than necessary which will cause excessive wear to all parts involved - cams, seats, valves. Most aftermarket springs like Ape and Kibblewhite are designed for high lift cams. For stock cams the stock springs are adequate and recommended.

In this case and mine, the valves were coated with oil because of the old leaking seals. They can be cleaned up and lapped. Like I said earlier, if the valves don't lap in in a couple tries, than new valves are called for. The Kibblewhite springs I was suggesting is a direct replacement for stock springs. They are of higher quality and have about the same pressure as the stock ones. The "heavy duty" ones are stronger and more expensive. Not called for in this application.
Steve

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


Results 1 - 4 of 4 1

i would go with 40-0449 .the 40-1007 probably has to much seat pressure for stock cams.

swest wrote: In this case and mine, the valves were coated with oil because of the old leaking seals. They can be cleaned up and lapped. Like I said earlier, if the valves don't lap in in a couple tries, than new valves are called for. The Kibblewhite springs I was suggesting is a direct replacement for stock springs. They are of higher quality and have about the same pressure as the stock ones. The "heavy duty" ones are stronger and more expensive. Not called for in this application.
Steve

KZchop82's exhaust valves are burned. The seats too. The service limit for seat width is 1.2 mm. The head shown in the photo seems to have WAY more than that. Only way to fix that is to cut the seats.

The stock replacement Kibblewhite springs should be okay. I doubt anyone riding a chopper needs expensive valve springs though.

471-10 .410" 250° 105° Use racing pistons & springs. Road race/drag race. 20 btc/50 abc .006"
.410" 250° 105° Great throttle control. Mid-range and top-end. 50 bbc/20 atc .006"
these are the cams i am running in my 810 cc .i am using APE VS900K springs that are good for .440" lift.

Nessism wrote: I doubt anyone riding a chopper needs expensive valve springs though.

Not quite sure what to make of that.
$65 for peace of mind seems well worth it to me.

KzChop82 wrote: Swest- just ordered the new rings and seals.
Thanks for the advice.
A friend of mine was saying that the buildup of char on the Pistons could also be caused by the timing being a bit off. Do you think this is a possibility?

Before you dump money into rings, Measure piston and bores.
As long as youre changing guide seals in head check the guides also and clean up the valves.