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Discussion Starter · #1 ·
I picked up a kz 750 spectre today. The bike fires up and runs but seems to have an idle problem. When the idle falls really low there is a loud knocking coming from the lower section of the motor. My friend jake thinks it might be some sort of chain maybe. Anyway once warmed up the knocking definately subsides and the bike runs great. "you can still here it but its definately not as bad" I know nothing about a dohc motor. "dont claim to be a genius with any bike really." If anyone could at least give me a place to start id really appreciate it.

Thank You
Brian
 

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If the idle is set too low, the oil pump won't supply enough oil to engine. Check the oil level, make sure it's clean and the correct viscoscity, and raise the rpms.
 

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Discussion Starter · #3 ·
thank you

That makes sense the guy I got it from told me he changed the oil yesterday. tomorrow I will check the oil. he mentioned something about using diesel oil. Im not sure what that means.
 

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The newer car oils for the most part, contain friction modifiers that are not compatable with the wet plate clutches in these older bikes.

An oil with high Zinc content(like in Shell Rotella oil's) will be a better choice for engine lubrication.
 

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Depends on your local temperatures, 20W50 for hot areas like Arizona, and 15W40 for most other places.

I used Bel-Ray 15W40 in my 82 GPz1100 B2 with a 3000 mile oil and filter change when I lived in San Diego Ca.
 

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I picked up a kz 750 spectre today. The bike fires up and runs but seems to have an idle problem. When the idle falls really low there is a loud knocking coming from the lower section of the motor. My friend jake thinks it might be some sort of chain maybe. Anyway once warmed up the knocking definately subsides and the bike runs great. "you can still here it but its definately not as bad" I know nothing about a dohc motor. "dont claim to be a genius with any bike really." If anyone could at least give me a place to start id really appreciate it.

Thank You
Brian
If your 'tickover' is too slow and a little uneven it will cause the clutch 'basket' to ****** backwards and forwards slightly which makes the clutch plates, both friction and plain, 'chatter' in the basket giving a quite pronounced rattle. Ever since the days of the SOHC CB750 a lot of Japanese bikes, especially 4 cylinder ones which have virtually no flywheel effect on the crank, seem prone to this. Does the rattle stop when you pull the clutch lever in ?, if so get your fuelling, carbs or injection system balanced and increase tickover speed slightly and the rattle should cease. Hope this helps.
 

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If your 'tickover' is too slow and a little uneven it will cause the clutch 'basket' to ****** backwards and forwards slightly which makes the clutch plates, both friction and plain, 'chatter' in the basket giving a quite pronounced rattle. Ever since the days of the SOHC CB750 a lot of Japanese bikes, especially 4 cylinder ones which have virtually no flywheel effect on the crank, seem prone to this. Does the rattle stop when you pull the clutch lever in ?, if so get your fuelling, carbs or injection system balanced and increase tickover speed slightly and the rattle should cease. Hope this helps.
Don't know why I got the ******, I was neither rude nor cussing unless the forum regards the word s****h as offensive.
 

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Discussion Starter · #11 ·
by "tickover", do you mean timing or idle speed? we just took the tranny cover plate off and the sound quieted down a bit but is still there, with a stethascope it is more pronounced in the transmission area.
 

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Discussion Starter · #13 ·
The noise isnt as bad at a higher rpm. Taking off the transmission case the noise almost disappears but when the case is put back on the noise comes back. I also found a problem with the shifter. the shifting mechanism is leaking oil at the point where it enters the transmission and has play all around. How hard is it to take the transmission out? Is this something with limited knowlege I can do?
 

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Tick over to me, means very low idle rpm. Try raising the idle speed between 1100 and 1500 rpm and see if the noise is reduced.
Apologies, US--idling, UK--tickover. Raising the idling speed and 'balancing' the carbs should reduce the rattle if it's caused by transmission backlash. It sounds as if that's what it could be and it's accentuated by the engine cover. Laverda had a similar problem years ago and they got around it by altering the clutch outrigger bearing to a separate bracket isolating it from the outer case, obviously not an option in this case.
 

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Before trying to sync the carbs,I'd suggest checking the valve clearances as this will greatly affect any work on the carbs if valves are not fully closing.

Have you done a compression check? It should be done with the throttle wide open and 125-150 PSI for a good power producing engine.

Here's some specs I found:

Valve clearance{COLD} inlet and exhaust= 0.05-0.015MM

Oil capacity= 3.0L {3.7 with new filter}

Idle speed=950-1050 RPM

Sparkplugs= NGK B8ES/Denso W24ESU gapped 0.7-0.8MM(0.028-0.032")
 

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Discussion Starter · #19 ·
picked up the clymer manual today. changed all the spark plugs. the old ones were really bad. im gonna tackle taking off the exaust and getting to the oil pan. is there an oil screen also I should be checking? I also orderd a shifter seal to stop oil leaking from the shifter.
 

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The oil filter is under a cover about 5" in diameter with some fins on it.

To change the oil, get the engine nice and hot(or go for a 30 minute ride)position a drain pan big enough for almost 4 liters of oil, remove the drain bolt, and then the center bolt holding the oil filter cover.

When re-assembling the oil filter assembly, first put the cover bolt through the cover, the spring,the small washer, and then the filter. Check the condition of the large O-ring going on the cover, it should have no nicks or tears as it might leak if it does.

I try to lube the rubber grommets/gaskets with a little fresh oil as it makes for easier work.I've found a thin film of the silver anti-seize on the oil filter cover bolts first few threads makes removal easier next time.

Carefully remove the cover as oil might be retained and be slung around. Cardboard works well to catch the drips. I use aluminum foil on my Kerker 4 into 1 to keep the oil off the exhaust system.
 
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