Topic: Valves seated deeper after serdi job

[danyo]

I have question regarding valve height after valve job. I'm currently rebuilding 1971 cb750 engine which came to me partially disassembled. PO started to rebuild top end but decided to abandon project years ago. I bought all his parts and decided to completly  rebuild engine due to poor storage (I found nails in uncovered crankcase ). Some surface rust can be found in cylinders and valve seats - but looked like some porting was done to the head before. I left the head for serdi job and cylinders to be honed and measured. Valves and springs were labeled. Machine shop performed valve job and assembled valves/ springs telling me it's ready to install. I didn't expected any problems so I installed pistons, cylinders, head. Next towers and cam. Everything went smoothly to the point when I installed rocker arms and started to set valve clearances. There is almost zero clearance on intake valves even with adjusters backed off completely. Basicly valve stems are touching rocker arms on intake side no matter on crank position. I was able to install all intake rocker arms and shafts with not much effort but there is almost zero clearance between stems and rocker arms. I started looking why this is happening and measured spring height. Looks like all intake valves are 1mm higher then exhaust side. They grind all tops of the valve stems a little ( just to flatten them)but looks like serdi dropped intake valves significantly and they did not take this in account. I'm now considering my options:
1. Try to grind valve stems around 1mm to bring them to the same hight as exhaust stems (possible without removing head??)
2. If ^^^^ doable, do I need to install any shims to adjust spring pressure or leave it alone. I assume now they are 1mm less compressed so provide less pressure on valve seat.
3. Grind only underside on back of the rocker arms to provide more clearance for adjusters and leave stems untouched. This for sure leave me with different than stock times of intake valves openings and closings but is there a way to tell how badly it will change characteristics of the engine?
This will be stock motor and I'm not shooting for top power. Hoping just for good, stock, rideable motor.
TIA for any input from more expirienced engine rebuilders .

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[danyo]

Can't edit title. Should be serdi job.

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[danyo]

Picture for reference.

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[J-Rod10]

You'll not want to even try to grind anything with it still on the engine. That dust, not good for an engine.

[demon78]

Eww If it was me I would measure valve length against stock spec then seat depth before you go any further. It would make me nervous as hell, valve stems do get stretched and popping a valve head at any rpm would ruin more than one day, so I would say off comes the head out comes the measuring tools, some body may have a better solution just that I know from years of working on things like bikes or A/C engines you shouldn't take chances as far as grinding any thing on the engine wash your mouth out with soap.
Bill the demon.

[Yamahawk]

I'm with Bill,
    Pull the head back off, remove the vales on intake side, and see if the machine shop didn't botch the valve job on those valves, also as was stated, measure overall length of valves to see if they may have stretched. Perhaps the seats were cut at one time for larger head valves, and the PO hadn't got around to installing them yet.. Or maybe the valves were cut at the head to clean them up, so they drop into the head farther... Could be just about anything, but you won't know until you check it.
Charlie

[danyo]

Thanks for waking me up guys. Yeah, I was thinking more about it and realized that I need one step back now. Head will be removed and measurements taken.

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[demon78]

Roger that.
Bill the demon.

[KayOne]

I just went through the same scenario with my K1 top end refresh. A simple Guide and seat refinish turned into this:

I must admit it looks much nicer than the stock setup.

[danyo]

Those are new seats installed? How much did you pay for it.

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[KayOne]

Yup, new custom seats. I supplied new Honda cast guides to the machine shop with the understanding they would install, hone and re cut the seats. The young pup machinist messed up the installation of them, then proceeded to ruin the stock Honda steel seats. The shop owner admitted full responsibility and in house machined new guides and seats.

They do a lot of performance work and make all their own guides and seats out of solid stock. The best thing Is that he only charged me $500, which I consider very reasonable. I don’t know whether machine shops down your way would be able to do it for that price though.

My seats were high mileage and my valves were pretty deep in the head.