Suzuki GR650 aka Tempter camshaft timing specs? Per manuals

[Chuck78]

As a rule of thumb, comparing duration at .040in to .050in, you gain around 10deg duration measuring at .040in.
So 245 @ .050 would roughly equate to 255 @ .040in.

Anything around 250 @ .040 is good. Big lifts on this duration give a very strong signal at the carbs which means you can run big carbs and tune them.

Back in the day, I cut 4 or 5 sets of RS's into twin sets. They went mainly onto EX500 Kawasakis for racing here. Not hard to do.
One tip - you don't have to use a Tee for fuel. You can feed into the outside of the fuel galleries rather than the center...
Not hard to tap the galleries and put in a pipe fitting.

THANKS FOR ALL THE TIPS, GREG!

So I'm torn on cam profiles, & I dont want to go too crazy on lift that I've compromised valvetrain longevity... I would like to still run shim over bucket, but just for durability reasons, I might go shim under bucket even if the camshaft profile does not require it (altho I don't have any of the KZ650 type shim under bucket shims, and I have two of the shim over bucket Suzuki GS factory/dealer service dept. shim kits). You never know when you may miss a shift and over-rev...
AND these GR650 cams seem to be very healthy for a stock OEM profile, & would be much easier on the valvetrain... but of course the lobes may have a fairly slow conservative ramp profile, which would make them significantly less effective than the similar Web Cams grind.

Web Cams grind #118:
365"/.365" lift int./ehx.
286°/286° advertised duration
245°/245° duration @ .050" lift
"High performance street profile for stock engines. Very broad power range. Stock base circle."

-versus-

GR650 Suzuki OEM cam specs:
.364"/.364" lift int./exh.
268°/268° duration @ .040"
(258°/258° duration @ .050" approximately, thanks GregT!)


Based on your previous comments, do you think that this stock grind would have enough lift and aggressive enough of a ramp to provide adequate signal to run a set of Mikuni RS34 carbs????


The other grinds I was REALLY eyeing up were:
MegaCycle Cams grind #384-70
.380"/.380" lift int./exh.
261°/261° duration @ .040"
107.5°/108.5° lobe centers
23°btdc/58°abdc int. open/close
59°bbdc/22°atdc exh. open/close
running clearance .004"/.004"
"Use modified pistons and springs. Best all-around street and road performance.
Increased mid-range and top-end. Wide smooth powerband."

-or-

Web Camshafts grind #110:
.395"/.395" lift int./exh.
284°/284° advertised duration
256°/256° duration @ .050" lift
(266°/266° aporox. @ .040")
"Good mid and upper end performance for hot street. Requires Exhaust System, High Compression Piston / Big Bore, and Performance Valve Spring Kit."

What do you all think of these grinds & any estimates on power gain percentages on a 489cc 10.3:1 GS twin with BS34SS -or- RS34 carbs + a free-flowing full-length 2:1 exhaust?
The Web 110 grind seems to be the best choice for my goals, but I'm wondering how much of a difference I would notice between the stock GR650 grind, if it would really be worth the money it would cost for a regrind, and how durable to regrind would be versus the OEM cams?
Ray tells me Web can grind any cam grind that I want basically. Although I have been really impressed with MegaCycle in the past, and just looking at their catalog, they provide a lot more specs than Web does. But... I don't know if they can grind any custom grind imaginable upon request, and ultimately I want the cam lobe faces that will wear the best and longest.

[GregT]

Any of those will work with RS34's. cam life for a build-up and regrind - as I imagine all of the aftermarket ones will be - is very much dependent on the skill of the welder and what oils you use in the motor. Everyone around the world is using the same overlay material now. I've found it interesting to see which oils are recommended by various grinders. Basically, a good high zinc oil is satisfactory.
I'd go with the GR cams - if only to give the rest of us a baseline for how good they are, LOL.
You can always swap in something more agressive later.
In the 450 race bike I built, I used shim over bucket, springs giving approx 75lb on the seat, and a cam grind giving .415in lift and approx 250 deg duration.
Both mine and a full 500 I did for a customer to the same specs were revved to around 12000rpm regularly.

[Chuck78]

Well I just picked up a 2nd pair of GR650 cams, as they were only $28 shipped on eBay, so I can play with one and have one set regrind to a web 110 grind or thereabouts, and run the stock and see how it does on its own. I know that some guys that race GS450 twins in WERA run just the stock GR650 camshaft...I can't comment on how successful they were or how the engine ran, but they seem to be pleased with it and considered it the biggest upgrade of stock cams, even above the GS500 early model camshafts.

As far as oils, I exclusively use Shell Rotella T heavy duty diesel oil, & now Rotella T4, in everything that I own (VW diesels, '62 GMC big block v6, GS's, 2 stroke dirtbikes...).

In general, are a regrind camshaft's lobes going to be less durable in the long-term than a 35 or 40 year old used OEM camshaft?

[Rich82GS750TZ]

Every time I read one of these very technical posts, I realize again just how much I don't know, and haven't ever even thought about how these things work. I sure hope I never need any of the info in this post but I sure am grateful that you guys understand this stuff and are willing to share.
#wayovermyhead

[GregT]

Well I just picked up a 2nd pair of GR650 cams, as they were only $28 shipped on eBay, so I can play with one and have one set regrind to a web 110 grind or thereabouts, and run the stock and see how it does on its own. I know that some guys that race GS450 twins in WERA run just the stock GR650 camshaft...I can't comment on how successful they were or how the engine ran, but they seem to be pleased with it and considered it the biggest upgrade of stock cams, even above the GS500 early model camshafts.

As far as oils, I exclusively use Shell Rotella T heavy duty diesel oil, & now Rotella T4, in everything that I own (VW diesels, '62 GMC big block v6, GS's, 2 stroke dirtbikes...).

In general, are a regrind camshaft's lobes going to be less durable in the long-term than a 35 or 40 year old used OEM camshaft?

I can't comment on the US race scene. GR's always were rocking horse poo out here. I've been told maybe six came into NZ. IMO the late 500 cams are not worth racing with. But we have for a small country, a lot of cam grinders, LOL. The symmetrical cams used here are right in the common area of lift and duration for a lot of engines. The profile I used is a Ford Lotus-Cortina race grind - one of about 20 for that engine in my local grinder's library.
Hard to say re durability. OE cams are chill cast Iron. The overlay is a nickel based alloy. Durability has got better as cam grinders have understood what oils work well with this alloy. When they started using it, my local grinder took the lobes completely off a Formula Ford cam and built up new lobes with the new rod.
That cam was then used for a season of racing in NZ as a test piece. No measurable wear after a season.