Tight Valves on an R16

[g12080]

How would an R16 behave with tighter than specification valves? I am about to adjust valves, and before touching anything, I am measuring about half the clearance than I would expect (.009", instead of .017" hot). My car starts and runs fairly normally, the only undesirable behavior is bogging under throttle tip in. I was hoping slight valve adjustment would improve this condition without any other detrimental effects but it looks like it needs a large valve adjustment on all valves and I want a sanity check before proceeding.

Thanks,
Jack

[g12080]

Yes, I am pushing down on adjustment screw with screw driver when I make the measurement stated above.

[msampsel]

Do you have a stock cam? My valves on an R16 with a Racer Brown grind are 0.012" intakes and 0.014" exhaust.
Supposed to be set with the engine running and hot. The running part make for a big mess and some funny looking feeler gauges

If your valves are too tight, you will burn the exhaust valves IIRC.

[g12080]

Yes, stock cam. (Only my carbs are non stock.)

[spl310]

The bog on tip in is probably because you need to adjust the accelerator pump.

[g12080]

spl310,
Should I use top hole in pump rod (more fuel) or bottom hole in pump rod (less fuel)?

Thanks,
Jack

[spl310]

I'm no expert by any means, but I think that you need a little more fuel.

[Gregs672000]

So long as you have valve clearance at all temps to allow the valves to fully seat and transfer heat to the head, by increasing the valve lash the only result is that you reduce the duration and lift of your cam by that degree. If the engine runs good with the valve lash you have I'd leave it. Check lash both cold and hot so you know if it increases or decreases with higher temps. For example, despite what the manual says, a U20 actually increases valve lash when hot, so I set my valves tighter when cold so they are where I want them at temp.
Agree that the carbs probably need adjustment. Consider investing in a wide band O2 air/fuel meter... If you're serious about tuning the Mikuni well it is an invaluable tool, believe me! Other wise, I would read your plugs and adjust accordingly (black rich, white lean, tan just right). I believe the top hole on the pump rod is richest on those carbs as you said. Have someone drive behind you as you produce the problem to see what the exhaust looks like. Does it happen at all RPMs? What size venturies are you running? That too could cause a bog by being too big.

[spl310]

Greg, what cold and hot valve settings are you seeing

[g12080]

My venturi's are 34mm.

Thank you for all responses.

Jack

[msampsel]

Greg, what cold and hot valve settings are you seeing

Hum ... I plan on doing this myself soon. Setting them hot then checking them
after a cool down. Will post the same, although fewer care about the R16 with cam grind

[Gregs672000]

Greg, what cold and hot valve settings are you seeing

I set them cold at a tight (meaning I have to wiggle and push the blade a bit to get it between the rocker and the lobe) 6 intake, 8 exhaust. At temp they are a tight 8 and 10 respectively. As I have posted before, someone had said they were actually looser at temp instead of what the manual said, and when I tested it myself they were right!

[Gregs672000]

Greg, what cold and hot valve settings are you seeing

Will post the same, although fewer care about the R16 with cam grind

Not so sure about that! Many many R16 owners talk about valve train noise etc. They can be carefully tightened up some to see if they will quiet up. Remember, the thing that MUST happen is that the valve seats long enough to transfer heat or it can burn, especially the exhaust. My cylinder head guy said that racers would often run absolutely minimal clearance to gain just that little bit of extra lift and duration from the cam, but there is a risk.

Regarding the 34mm chokes, they may be a bit big for a stock cam R16. I certainly understand the desire to "go big" but I've also learned that the carbs will be more easily tuned and more responsive with good signal to the jets. If you are unable to get them to work like you want, I don't think you will give up much if any top end performance by trying a set of 32s, and you may find the car is quicker and more responsive everywhere.

[msampsel]

Well I set my valves today, 0.012" intakes and 0.014" exhaust hot after running the engine to temp (200 degrees in 15 min at idle in AZ) . When I initially assembled the new head, I
set the valves at 0.014 intakes and 0.016 exhaust. The valves when hot were a little loose compared to 0.012 but not much from initial, unfortunately I did not take
precise measures before adjust since I thought I would do it cold tomorrow. Well ...

I got a little tired and decided to place the valve cover and change the oil so I will not be checking them when
they are supper cold.

Sorry about that.