Re-Seating Valves

[GPZCarlos]

Hi, Its me AGAIN with the bag of shit GPZ400. I have just had a call from the garage who has my bike, i took it in to be tuned and get the carbs set up. He said the carbs aren't the problem, its loosing compression and i need the valves re seating or maybe even new ones which could cost up to 3 of 400 quid. I have already put £350.00 into this bike and am not spending anymore. Anyone got any ideas? Can i do it easily myself, i am quite competent with stuff like this but have never done anything so serious. Also i dont have a manual for this bike. What do i need to do? Any help would be great before i dump it in a lake.
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Carlos

[hmmmnz]

you'll have to pull off the head by removing the cam shaft ect, remove the valves replace or regrind the valve seats, clean up or replace the valves depending on condition.
its a bit of a mission, but if you have a wee work shop and dont mind getting your hand dirty then go for it, but defenitly buy a manual, that will make things a whole lot easier.

if you cant be fuct with all that, then either try and track down a new engine, or just ride it as it is, and just deal with the rough running.
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the humans are dead
I kick arse for the lord
Wiring Diagrams BIDNIP it bitches

[Yoshi]

Assuming you're not a fuckwit, and are able to follow a manual, it shouldn't be too much of a hard job, just take your time, and ask if you're not sure about anything.

Easier if you drop the engine out, have a friend to help with this.

You'll need a bit of space, and somewhere where you can leave stuff without it being disturbed.

Tools required: Torque wrench, Valve spring compressor and Valve seat grinder

Also worth doing the clearances whilst your at it, so you'll need (well this depends on the type of adjustment, if it's shims you will) a Micrometer and Feeler gauges

You'll also need a new head gasket for the engine.
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Present: GS650 Katana - Getting ready for summer touring!
Past: TS50, RS50, ZXR400, LT80, TS250

[stinkwheel]

Well, a top end gasket set for a GPZ500 costs the thick end of £70. I don't know about the 400 but I'd imagine a bit more, if you can get one at all.

Factor this into your calculations.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Walloper]

https://cgi.ebay.com/ebaymotors/SIOUX-Valve-Face-Grinding-Machine-w-Stand-Cylinder-Head_W0QQcmdZViewItemQQcategoryZ63700QQihZ014QQitemZ330122563899QQrdZ1QQsspagenameZWDVW

To repair valve sealing you have to re-cut the valves and seats.
There is no short cut. The garage will use a machine like the one above to grind the proper angle onto each valve then use a profiled stone to grind the opposite angle on each seat.
Each valve is then 'Lapped' into it's very own seat using the grinding paste and the 'Valve Grinder Tool' listed in the earlier post above. This gives the valve the 'Gas Tight Seal' the engine relies on for good compression.
You could take out the valves and lap by hand but this would last about 1000 miles then deteriorate to what you have now and could end up in disaster and burn out the valves/seats.
If you remove a head disassemble valve system and do not use the opportunity to 'Re-Cut' then you are just wasting your time.
Let the garage do it or find a pal with a grinding machine.
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W-ireless A-rtificial L-ifeform L-imited to O-bservation P-eacekeeping and E-fficient R-epair

[teampots]

Theres a breakers with a GPZ 400r in if thats any help to you might be able to get a top end off them heck they are selling a GPZ 400 so you could just buy that and use yours for spares if you can get to em to pick it up
linkage

https://mcabreakers.com/14.html

https://mcabreakers.com/16.html

phone them on

Tel: 01254 77 77 09

M: 077 22 00 99 68

[Odie]

Get it home and do a compression check on it, just to put your mind at rest.
It might not be the burnt out valves, it could be some garage trying to fleece you.
Not saying it is but some times its better to check some-thing yourself before spending money!
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You are so ugly when you were born the doctor said "I?m gonna drop it, if it falls is a rat, if it flies is a bat."

[sickpup]

[stinkwheel]

I'm not buying any at all. If something goes so badly wrong the top-end needs taking off, the whole engine is going in the bin and another one is being fitted in it's place.

For a kawa 500 twin, you can get a decent second hand engine for a couple of hundred quid. It can be changed out in a day and you're back on the road.

Life's too short to be fucking about in the guts of liquid cooled Japanese engines. Been there, done that, can't be arsed. Certainly not for a saving of maybe £50-100.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[GPZCarlos]

Many thanks for all your replies. I am really stuck as to what to do about this. The bike has supposidly only done 15k miles. I have just called the garage again to explain to me a bit more in depth about what he's done. He said to do the compression check he used a liquid then checked each cylinder and they were all bubbling, he then mentioned valve timing??? Could this just be the problem if so how the hell do you do that? The reason i'm asking so many questions is i dont have a manual and cant find one anywhere on the web.... Think i'm screwed!!
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Carlos

[sickpup]

Get a leak down test done on the engine. It will show you whether its the valves, and which ones or the rings if those that are defective.

[GPZCarlos]

Hmmm, leak test? as you can tell i'm going to be hard work coz this is all new to me. Although i'm not a complete idiot!
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Carlos

[Barry_M2]

Never heard of using liquid in the cylinders to check for leaks!?

I have a leakdown tester, which you screw into the spark plug hole, it then puts in around 100psi of pressure and the losses are shown on a guage on the tester. You dont want any more than 7% leakage really, ldealy none, but you usually see around 2 or 3%.

I dont think the timing is adjustable on the GPZ (although I could be wrong) so it cant go 'out of adjustment'.

You could just get away with lapping in the valves, but that all depends on how badly they are leaking, if at all.

Sickpup advice is good, its a shame you live so far from me as I have all the tools to do this job for you.


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CBR1000 RR4 - For the track.
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[bugsy46]

Are you sure he didnt mean checking the valves for seepage when the head is turned upside down? ie place a small amount of petrol around each valve and check to see if it seeps through to the other side.
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[Barry_M2]

[GPZCarlos]

Yeah i think i definatly need a second opinion. Someone else as mentioned that it could be carbon build up on the valves??? What the mechanic is saying doesn't make too much sense either. The bike was running pretty well last week and has slowly got worst and now after running it for about 10 to 15 minutes it will cut out as if flooded then if i leave it half an hour it will start straight back up again. Does this change anyones opinion on the fault?
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Carlos

[Barry_M2]

That sounds more like a fueling issue than anything to do with valves etc..
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CBR1000 RR4 - For the track.
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[GPZCarlos]

Well i'm all out of ideas Barry_MC21 have you got any more things i can try before i take the head off? Cheers
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Carlos