Valve lapping - Suzuki Z400 Forum : Z400 Forums
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post #1 of 10 (permalink) Old 03-18-2018, 05:36 PM Thread Starter
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Valve lapping

Just got the head off today I’m replacing the valves. My question is the valve seats look fine but should I get them lapped anyways. Here is the pic of the old I take valves that are cupped and valve seats.
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post #2 of 10 (permalink) Old 03-18-2018, 05:39 PM Thread Starter
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Also when doing a valve job should the springs be replaced how much of a benefit does it offer.
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post #3 of 10 (permalink) Old 03-18-2018, 06:07 PM
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do not lap

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03 ltz400,95.5bore,+5crank,P&P,13.7:1,JE piston,spacer plate,RHC +1 intakes valves,RHC #208in&187ex cams,DRZ manual decomp,DID cam chain,no air box,Sredrum TB 42mm FCR,RAT stack,WB fuel screw,EMN needle,quick shot,06 clutch 450r drive plates w/trx400 ex springs,C2HB,ex thumber,trx450r air boot, Barker Performance pipe, trailteck flywheel,dynatek,NOLOGY HOTWIRES ,nerf bars,450r shocks, +4 swinger,lowered front & rear
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post #4 of 10 (permalink) Old 03-20-2018, 01:30 AM
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Springs get tired. I would change them and the seals while it's apart. Get DRZ-E springs or better, that will last longer and allow you cam upgrade and rpm increase when/if you want. Get better valves than stock. I would lightly lap them myself to confirm they are sealing. Could do a liquid sealing test instead, if you wanted.

2007 LTZ 400.. 94mm J&E piston, +4mm hotrods crank, 536webb cams,wiseco valves, 39mm fcr, tokyo mods throttle spring, honda thumb throttle,spring removed. yoshimura full exhaust, honda 400ex intake tube, no air box
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post #5 of 10 (permalink) Old 03-20-2018, 10:10 AM
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Depends on the valves.........
https://www.suzukicentral.com/forums/...alves-not.html

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post #6 of 10 (permalink) Old 03-20-2018, 08:27 PM
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Quote:
Originally Posted by amcf18 View Post
Springs get tired. I would change them and the seals while it's apart. Get DRZ-E springs or better, that will last longer and allow you cam upgrade and rpm increase when/if you want. Get better valves than stock. I would lightly lap them myself to confirm they are sealing. Could do a liquid sealing test instead, if you wanted.
no use that blue dye to check them . if you use lapping compound you risk cutting through the coating

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03 ltz400,95.5bore,+5crank,P&P,13.7:1,JE piston,spacer plate,RHC +1 intakes valves,RHC #208in&187ex cams,DRZ manual decomp,DID cam chain,no air box,Sredrum TB 42mm FCR,RAT stack,WB fuel screw,EMN needle,quick shot,06 clutch 450r drive plates w/trx400 ex springs,C2HB,ex thumber,trx450r air boot, Barker Performance pipe, trailteck flywheel,dynatek,NOLOGY HOTWIRES ,nerf bars,450r shocks, +4 swinger,lowered front & rear
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post #7 of 10 (permalink) Old 03-20-2018, 10:49 PM
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I've used light before.....just hold a flashlight tight on the head over the valve and see if any light is coming through will looking in the ports.

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post #8 of 10 (permalink) Old 03-21-2018, 03:05 AM
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Quote:
Depends on the valves.........
Do I lap these Wiseco valves or not?
I did, twice..We'll see how it runs on Friday..

2007 LTZ 400.. 94mm J&E piston, +4mm hotrods crank, 536webb cams,wiseco valves, 39mm fcr, tokyo mods throttle spring, honda thumb throttle,spring removed. yoshimura full exhaust, honda 400ex intake tube, no air box
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post #9 of 10 (permalink) Old 03-21-2018, 11:23 AM Thread Starter
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I already got kibble white valves and new seals. I was thinking new springs but wasn’t sure how many hours are on them.
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post #10 of 10 (permalink) Old 03-21-2018, 12:19 PM
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Do not lap the Kibblewhites. Get DRZ-e springs
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