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HiCam Oil Pressure, Gross Stupidity and why you should always listen to Chuck


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Thanks Tim

Looking at some of the comparisons, I think the valve in the bike as of now isn't as good as when I conducted the first test. Whether this is because this valve isn't preloaded (allowing some, or more, float), because the PRV clearances aren't as good or something to do with the lower setpoint I don't know.

Hopefully I shall find out when I change the oil and replace the current valve with the TLM valve and Griso spring (still awaiting the new spring to arrive) which I will preload to 2 or 3mm. The idea being to mess with the valve internals as little as possible

Looking at the first test and the most recent comparitive results are below, obviously nothing is exact here so a little latitude in reading the results is required.

The main points I'm interested in are the 80C readings at elevated RPM. The second test valve has a lower setpoint and given that is the case (around 66-68psi) the idle results are all pretty much in line and way more than required. However the results at 80C 3&4k rpm are pretty stark around a 15psi difference. From what I see pretty much after 2.5-3k rpm oil pressure is constant with revs

Same oil and same cooler (a 13 row, but smaller area, Setrab, with -8 hose and full flow fittings) so the only variable is the PRV. Motul 300V 15/50, full synth lube.

20C/idle 80psi 68psi

40C/idle 70psi 66psi

60C/idle 60psi 62psi

80C/idle 38psi 40psi

80C/3k 75psi 60psi

80C/4k 75psi 62psi

Even as is it stands though its a big improvement over say the 43psi reported on @Lucky Phil thread page 5 by @Kevin_T . If I could get that 13-15psi back I'll be a very happy bunny, but for now at least I can rev it a little without fear of damage

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This is a long sad saga on how one person can be so stupid and how you should always listen to Chuck. I purchased a low mileage Australia 98 from Japan a few years back, HiCam engine and running

Here is what happens when the engine was run with the Griso spring in  

Well bet you were all thinking this was dead and gone. So after removing my OEM V/V with Griso spring to try to lower the presssure a little I then couldn't get the valve to seal well  again.

Posted Images

I think I've now about reached the end of this but wanted to post some more prelim data for now and some more test results tomorrow. Who'd have thought I could spin out a 4 page thread on a bloody spring.

So here's what I've found as a rough guide regarding shimming the OEM valve with the Griso spring. 

Below are 2 results, the first colum is static test data. In other words putting the valve in an oil tester or pumping up the valve on oil, if you use air the results will be different, probably lower from what I saw.

I gave up on using air as a medium the leakage was so bad I couldn't obtain repeatable results. The oil I was using was a 15-50 full synth room temp 18-20C, cold oil for both the static test and the crank test.

When static testing the valve just starts to crack then around 5psi later is well off the seat so it's difficult to pin down an exact lift value, but easy to get a ballpark within 5psi for when the valve lifts

All results psi, shim numbers in mm.

On all of these there was no crush washer or shim on the spring retaining nut on the PRV top, some have these installed others not. IMHO they serve no purpose, however, if they are in place they will subtract from the shim value as the nut will not penetrate as deeply into the valve body and compress the spring

Shim  Static  Oil Pressure

None  80-85     68

1.5     105-110    82

3       125-130    95

I think the results were pretty well linear in behaviour, so as a "Rule of thumb" for every 1mm of shim compressing the spring you'll see 14psi increase in static lift pressure and approximately 9psi on the oil pressure.

Can only base this on my own anectodal evidence, but knowing that no shim gave me 68 and 3mm shim gave me 95, a 27psi difference, 1mm equated to 9psi. 1.5mm should give me pressure in the bike of somewhere around 80-83psi. When I crank tested it was somewhere between 80-82psi.

If you have a facilities to static test by all means do it, you may get different numbers to me, but be aware that the static lift values are higher than what you'll see inside the engine.

The figures here are just what I saw and posted up as a rough guide and starter for anybody mad enough to try it

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