Valve clearance adjustment issue

[Lantanafrs2]

Originally Posted by Ultramaroon

Oooo! Would reveal itself with some prussian blue, no?

If you want to pull the thing apart again. It's hard to get a good valve job. They're time consuming when done right

[Ultramaroon]

Originally Posted by Lantanafrs2

If you want to pull the thing apart again. It's hard to get a good valve job. They're time consuming when done right

I'm beginning to see the merit of shimming to the high side of acceptable lash and letting the chips fall where they may.

[Lantanafrs2]

Originally Posted by Ultramaroon

I'm beginning to see the merit of shimming to the high side of acceptable lash and letting the chips fall where they may.

Why not. It's what the factory does. When they do it right that is

[Ultramaroon]

Originally Posted by Lantanafrs2

Why not. It's what the factory does. When they do it right that is

Why not? Habit, for example. Maybe shooting for the middle in a misguided attempt to get it perfect. I've never had this conversation with others so it's cool to consider different approaches.

[Lantanafrs2]

Originally Posted by Ultramaroon

Why not? Habit, for example. Maybe shooting for the middle in a misguided attempt to get it perfect. I've never had this conversation with others so it's cool to consider different approaches.

Key word there is misguided. Once the valves have banged their way in you can shoot for the middle lol

[Lantanafrs2]

I used to disassemble bike engines and recut valve seats and lap them in for people years ago. At the time it made a big difference in leakdown. That's back when magazine test bikes were hand picked by manufacturers because they had "good parts" in them.

[NoHaveMSG]

Originally Posted by Lantanafrs2

I used to disassemble bike engines and recut valve seats and lap them in for people years ago. At the time it made a big difference in leakdown. That's back when magazine test bikes were hand picked by manufacturers because they had "good parts" in them.

There is a reason there is a "A", "B", "C" stamp on the cylinder

I never had to do a leakdown on a new bike but I could imagine. On the YZ-F dirtbike engines they always needed the valves adjusted after around 20ish hours. Then, never had to touch them again.

[Lantanafrs2]

Originally Posted by NoHaveMSG

There is a reason there is a "A", "B", "C" stamp on the cylinder

I never had to do a leakdown on a new bike but I could imagine. On the YZ-F dirtbike engines they always needed the valves adjusted after around 20ish hours. Then, never had to touch them again.

Particularly on the 5 valve heads.

[NoHaveMSG]

Originally Posted by Lantanafrs2

Particularly on the 5 valve heads.

Yup. I was always told never to lap the Ti valves in those though. Something about there being a protective coating on them. I lapped the valves on a few different engines anyway and never saw an issue with them

Shit, getting OT

I will be pulling the covers off my spare FA20 to reseal them and I want to pull the valve covers off to make sure sealant didn't go where it shouldn't. I'll check valve clearance on it and see if I can get repeatable readings. That will be either Friday night or sometime this weekend.

[Lantanafrs2]

Originally Posted by NoHaveMSG

Yup. I was always told never to lap the Ti valves in those though. Something about there being a protective coating on them. I lapped the valves on a few different engines anyway and never saw an issue with them

Shit, getting OT

I will be pulling the covers off my spare FA20 to reseal them and I want to pull the valve covers off to make sure sealant didn't go where it shouldn't. I'll check valve clearance on it and see if I can get repeatable readings. That will be either Friday night or sometime this weekend.

My opinion is that the valve height shouldn't change from hand cranking the motor unless something is really screwy

[bobel]

Originally Posted by NoHaveMSG

I will be pulling the covers off my spare FA20 to reseal them and I want to pull the valve covers off to make sure sealant didn't go where it shouldn't. I'll check valve clearance on it and see if I can get repeatable readings. That will be either Friday night or sometime this weekend.

Will be interested to see what you find, and what kind of clearances you have.

I’ve ordered another lot of shims from Toyota, based on my last set of measurements, unfortunately some of them are currently on a 3 week lead time so my build is stalled.

I’ve aimed for the upper side of the spec this time. Adjusting to 0.15mm Intake and 0.26mm Exhaust,

I didn’t want to go for right on the upper limits Incase with some variance I end up out of spec but I agree with the general consensus here that being a little loose on this motor is not going to be a bad thing.

[bobel]

Originally Posted by Lantanafrs2

My opinion is that the valve height shouldn't change from hand cranking the motor unless something is really screwy

I really hope that’s not the case with my motor, I trust the shop I used they are very reputable and build a lot of race engines here in Ireland.

Also I’m seeing a similar thing across both heads, and I think it would be unlikely that all four cams or either of the heads are wonky.

I can really only conclude that the valves with the new beehive springs have seated/bedded slightly after the first turnover by hand. Given that the clearances that changed all narrowed to various degrees would suggest that’s the case, the only thing I noted too was that the lobes towards the front (timing gear end) dropped the most, and perhaps the Timing gear exerts a little leverage force on the cams and they sat down in the cradle journals a little too in the absence of oil pressure.

[fika84]

Do you think it would be worth putting things together, lubing with oil and cranking the thing over 10-20 times with an impact or manually to try and get things to settle down?

If things are changing when you're manually turning the motor over then I would be afraid the valve clearance would grow quite a bit after the motor is fully installed and running for a little while. Do you plan on doing another valve adjustment/check after XXX mi (or km)?

[bobel]

No plan to reopen it once I have it built to be honest,

I’m not a fan of turning over the motor too much without an oil supply, it’s got new rods, bearings, and pistons so I don’t want to glaze the bores by turning over with anything powered.

The one reassuring thing is that the gaps tightened so if anything it’s worst case, if they were getting bigger I’d be more concerned, they will likely only get tighter with running in.