[IndyBob]

OEM valve springs:
Outer: free height: 43.0 mm
Wire ga: 2.83mm
Turns: 7.5
OD: 23.48 mm
ID: 17.9 mm
Bind height: 21mm (approx)
Pressure @ 31mm: 35lbs, 9 oz

Inner: free height: 38.31 mm
Wire gauge: 2.0 mm
Turns: 9.5
OD: 16.0 mm
ID: 12.0 mm
Bind height: 20mm (approx)
Pressure: 15 lbs 6 oz @ 29mm

so, combined pressure at installed height: 51 lbs

Bob

 

[IndyBob]

Speedstar valve springs
Outer
free height: 43 mm
Wire gauge: 3.01mm
Turns: 7.25
OD: 23.79 mm
ID: 17.84 mm
Bind height: 22mm (approx)
Pressure @ 31mm; 46 lbs, 8 oz

inner;
Free height: 41.08 mm
Wire gauge: 1.98 mm
Turns: 9.625
OD: 16.04 mm
ID: 12.06 mm
Bind height: 18mm (approx)
Pressure @ 29mm: 18 lbs, 4 oz

so, combined pressure at installed height:75 lbs

 

[IndyBob]

Orient Express springs
Outer
Free height: 37.57 mm
Wire gauge: 2.89 mm
Turns: 6
OD: 25.14 mm
ID: 19.46 mm
Bind height: 17mm
[email protected] 30mm: 26 lbs, 0 oz

inner:
Free height: 36.64 mm
Wire gauge: 2.35 mm
Turns: 7
OD: 18.45mm
ID: 13.71 mm
Bind height: 17 mm
[email protected] 28mm: 33 lbs, 0 oz

so, combined pressure at installed height (with shims included): 59 lbs

 

[IndyBob]

Here are some of my personal observations and opinions:

The Speedstar springs do indeed have higher pressure, but don’t allow for any additional lift. So, they’re great for stock or Speedstar cams. And also for higher compression setups, that might suck the valves open a bit on the intake stroke, with weaker springs (I don’t know that for sure, but read it somewhere.) But wouldn’t work for Orient Express or Patrick Racing cams since they’re higher lift. ( See my correction a few posts down, after receiving Gilly’s comment)

The OEM springs look pretty safe with the Speedstar cams, given their modest increase in lift. Maybe some risk of float at sustained very high operation, but I doubt it. I have been running who knows how many miles with Orient Express springs that are broken on the inners, with no float. Which, means they had dramatically LESS pressure than stock springs. Maybe think twice with higher compression, but that wouldn’t break anything.

The orient Express springs fit poorly, in my opinion. The diameters are too big for the stock retainers. In my opinion again, that’s why the inners broke. They DO allow much higher lift than either type of yamaha spring, but fairly negligible increase in pressure. They were cheap to buy, expensive to fix the problem after.

I don’t have measurements of the Patrick Racing springs. I’d bet they fixed the problem of fit, by including appropriate retainers. I waited 5 months, and could never get them. Ended up with some NOS Speedstars. So, my 110 ci, Speedstar cam’d bike lives to ride another day.

Bob

 

[arizonawarrior]

This is possibly the most patently applicable technical thread here in some time. It's going to take time to evaluate, but with the raw data alone I pretty much agree with your observations and findings, it makes sense looking back at prior conversations posted over the years. My initial thought is that if anything is in error then it has to be some minor and inconsequential point. Very nice work brother.

Made STICKY in Technical Forum.

 

[Gilly]

I have run speedster springs with Patrick racing cams and high compression piston for a long time so far with no problem. Just lucky I guess.

 

[arizonawarrior]

@Gilly I always say it but can't help myself, your sled is mean lean and nasty you do good work me brother.

 

[IndyBob]

I have run speedster springs with Patrick racing cams and high compression piston for a long time so far with no problem. Just lucky I guess.

Thanks for that info, Gilly. I stand corrected. Sounds like Patrick Racing cams might also, then, be a relatively modest increase in lift over stock. Now that you say that, it seems that I remember reading that. Their benefit over Speedstar cams may be more in the area of duration and timing, instead of even more lift.

One of my surprises in this exercise was that the Speedstar springs do not offer a benefit in bind height, and that the stock springs are very nearly the same. The second surprise was that the Orient Express springs don’t offer much benefit in pressure, but they do allow more lift. The third is that the design of the Orient Express is not optimal/ reliable, given their diameter.

My measurements were taken with a digital caliper, not practical to use a micrometer. But, I think the necessary info is there. Also, the spring pressure was measured using a setup with a drill press, and a small scale.

Bob

 

[random_guy]

I was curious how you did the force/length measurements but presumed you had access to a force tester or something. Ingenious setup!