Suzuki GR650 aka Tempter camshaft timing specs? Per manuals

[Chuck78]

Does anyone have a GR650 Tempter service manual?
Can anyone post up a photo of the camshaft timing diagram for me? ImIjust trying to figure out the stock camshaft valve opening duration without having to dig out the degree wheel, v-boocks, dial indicator and magnetic base, etc...
I know it is the biggest lift of cams that will fit in a GS400/425, GS450, GS500 head, but I suspect the duration to be on the shorter side due to the intended nature of the GR650 model.


I had contemplated at one point using a GR650 engine and frame as the base for my lightweight GS twin (well ,GS & its cousin the GR) canyon carver build, but I like the early roller crank engines far too much and want to try & build the 77-79 GS twin into a thoroughbred racer/canyon carver with resleeved cylinders, 72mm pistons for 489cc & 10:1, & likely a RapidRay porting job on the head and most likely a moderate street performance camshaft regrind by MegaCycle or Web Cams.

Trying to determine the potential I can reach with this stock cam profile for now, vs a regrind to Web #110 .395" lift or #218 .418" lift

Thanks!

Chuck

 

[Chuck78]

This is from the GS Twins Wiki thread started by Mekanix:

"Intake cam lift: 0.364"
Exhaust cam lift: 0.364"
Intake Duration: 2XXdegrees (Center @ 98' ATDC )
Exhaust Duration: 2XX degrees (Center @ 99' BTDC )
That explains the low torque curve."

With that much lift out of a stock camshaft, I'd be tempted to just run them, but my pistons are approximately 10.2:1 with this stroke, & if the duration is fairly tight, that will build some immense cylinder pressure and will require 91 octane minimum and possibly lesser timing... I wish I would be better awesome out for more lift and more duration in a high-performance hard weld regrind camshaft profile...

 

[Chuck78]

I'll be having a stock set of cylinders resleeved to GS850 sleeves or perhaps GS450 sleeves if I can get the tapered bottom of the sleeves turned down thinner for better crankcase clearance (less grinding on the crankcase top half to fit, thin them to 72mm bore GS850 thickness below the bottom of the jugs). Running some old MTC Engineering 920cc GS850 pistons in them.
Stock 400/425 sleeves are goid for 449cc Wiseco K844 GS750 pistons (you can buy a half set of these 4cyl pistons for a 2cyl build) & be able to run big lift cams and have high compression, or you can also use GS850 +1.0mm overbore (870cc) pistons ans stock-ish cams for 462cc.
I think I determined that 71mm into a 400/425 sleeve may be pushing it for reliable street use. I'll have some in my hands in the near future to check again.

Hoping to diet this bike down to a target of 325lbs, while drastically increasing the little twin's engine output, & substantially upgrading the suspension. GS500 forks and Tokico brakes on a 310mm 98-99 CBR900RR rotor, Fox Factory Shox, billet fork brace, narrowed GS1100E alloy swingarm, rearsets, semi-custom exhaust, clip-on bars, etc... Guiliari seat & GS450S knee dent tank to top it off in serious racer looking trim, as well as GS400 badged side covers... Have to sneak a little of the "sleeper" element into the ol beauty!

 

[Gorminrider]

Chuck- diagram of cam chain GR650..

 

[Chuck78]

Gorminrider,

Thanks a million for posting that up, but do you by chance have the diagram/drawing from the service manual that shows the actual canshaft lobe timings? That's what I was after. This diagram is just the camshaft chain installation and timing procedure with the cam sprocket markings.

I'll see if I can dig up the photo of other GS's from the manuals, illustrating the valve opening/closing timimgs in degrees.

 

[Chuck78]

This is a GS1000ST camshaft/valve timing illustration from the service manuals, I'm looking for the same type of diagram/illustration for the GR650 cams, from a GR650 service manual, if you by chance have that available.
Much appreciated if you are able to post a photo of these specs.

EDIT - I forgot to post the image!

Thanks!

Chuck

 

[Gorminrider]

oh, ok. This one?

 

[GregT]

Looking at those specs, the stock cams re-degreed to maybe, 106 inlet, 108 exhaust would give a performance gain pretty well everywhere.
IMO the stock CV's would still be within the range of normal adjustments too.

 

[Nessism]

My KZ runs the classic 30-60, 60-30 degree timing for both intake and exhaust and it runs fantastic.

 

[GregT]

My KZ runs the classic 30-60, 60-30 degree timing for both intake and exhaust and it runs fantastic.

I built a Z650 with a 750 top end - and rods - a few years ago. 750 cams timed up 104/106, Z1 carbs and a pipe. Runs with TZ350's. Quicker in a straight line too.
The Suzuki heads like a slightly wider lobe center figure size for size in my experience. Full house GS450/500 likes 107/109.

 

[Chuck78]

oh, ok. This one?View attachment 57864

YESSSSSS!!!!!!! That's the one!

Thanks!

GR650 camshafts are 288 degrees duration intake & exhaust based on these service manual specs, & it was reported on here in years prior that the valve lift was pretty substantial, higher than any of the GS twins including the newer GS500 1989-2010...
EDIT - .364"/.364" lift intake & exhaust via the GS Twins wiki thread, and now 268 degrees duration at .040"/1.0mm valve lift (I believe that is the baseline for the factory specs on valve timing).

These GR650 Tempter camshafts should really help out with making this big bore 489cc 10.2:1 ported head GS425 REALLY SCREAM!!!!!!!
"GS400," I mean!!! (I have GS400 badged side covers to swap onto the little sleeper, but the GS450S tank, Guiliari seat, Hayabusa rearsets, clubman bars or clipons, CBR900RR/twinpot brake setup, & snarling 2 into 1 exhaust note may give it away that this bike is no slouch...and a force to be reckoned with!

Storm64 once told me I need to make my next bike a CB200, so that everyone else has a chance to keep up with me in the twisties for a change!
Ripping around test riding some modified GS550's I rehabbed for others, I was amazed at the cornering ability ease vs my highly modified 77 GS750 (460lbs after all the mods), 30 or 35lbs made a big difference on these 550's with fairly stock suspension (I was making corners on city streets scraping my boots on the ground on 1st test rides!), so I cant wait to see what dropping down to a featherlight mean snarling 330lb thoroughbred GS twin will feel like when leaning it over into corners!


I'll keep those lobe timing specs in mind when installing these once I get the head ported and the cylinders resleeved & overbored for this soon-to-be 489cc '79 GS425 little lightweight twisties/trackday play bike! Possibly WERA Formula 500 racing, but not this year sadly, due to shattering my kneecap & the surgery that followed (plate/screws & 2 big pins!) upcoming physical therapy... 6 weeks out now & my knee only bends 25-35 degrees!!!! Geez... And zero quadricep/patellar strength from 6 weeks of immobilization.

 

[GregT]

Do the math again. 268 degrees duration @ 1.0mm lift - roughly equal to .040in lift.

With that duration, you'd normally expect at least .400in lift - so they're long, low cams.
Kind on the valve train, but could do better...You can go to .418in lift and still safely use shim over bucket.

 

[Chuck78]

Do the math again. 268 degrees duration @ 1.0mm lift - roughly equal to .040in lift.

With that duration, you'd normally expect at least .400in lift - so they're long, low cams.
Kind on the valve train, but could do better...You can go to .418in lift and still safely use shim over bucket.

Ahhhh yes...mathematical error! 35+53=88, 88+180 = 268!!! Not 288!!!
Thanks Greg!

I was contemplating having Ray (who will be porting my head and resleeving my cylinders) run them down the street from his shop to Web Cams and have them reground into a more performance oriented grind, but as it is now, they'll be a fairly substantial upgrade over a stock cam which may have a touch more duration but a fair amount lesser lift than the GR650 cams. So as is, they'll be a great & reliable performance upgrade, BUT... I AM trying to build this GS425 into the quickest old school GS twin possible, but also while still maintaining streetability and a nice broad power curve...

At any rate, even a Wiseco K844 (GS750 piston) bored into a GS400/425 for 449cc + these cams, K&N pods, and a free flowing 2 into 1 exhaust should be a vety fun bike to rip around on. Bump that up to a resleeving job and 10.2 or 10.3:1 @ 489cc, & in a 330lb little twin, & the fun factor goes up significantly, especially with a street-ported head.

Ultimately I may as well just go ahead and have these cams reground into a more performance-oriented profile, might as well just do everything at once so that I don't have anything else to be tearing it down for in the near future...and I can put the appropriate valve springs in right now.

Also, these GR650 cams are a bit more unique than most of the GS cams, and that they are hollow core like the Yoshimura billet factory race bike cams! Otherwise, I would just have a set of GS400 / 425 or GS450 camshafts sent in for a regrind, get the smaller cams beefed up and have this hotter OEM factory cam still on the shelf.... but the hollow core factor and the nature of this build, intending to be as light and powerful as possible, definitely fits the bill to use the hollow cores!



Looking to make a custom tee and throttle shaft as well for a set of RS 34 carbs that I have that I got four pocket change due to one having a broken slide. Re-racking a 4-cylinder set into a 2-cylinder set. Just have to plug off the fuel rail on the side of probably just one of the two if I recall (die to the accelerator pump being on one of the middle carbs). The GS425 came with Mikuni BS34's stock, & the ports are 33.8mm or so as-is, stock, so this seemed nearly a no-brainer.

As far as cams, Ray said Web can grind basically any profile I wanted, but looking at the GS1000 8V offerings, the 110, 218, or possibly 109 grinds would all be considered heavily...

Grind #110:
.395"/.395" lift int./exh.
284?/284? advertised duration
256?/256? duration @ .050" lift
Good mid and upper end performance for hot street. Requires Exhaust System, High Compression Piston / Big Bore, and Performance Valve Spring Kit. Price Per Set (2).

Grind #218:
.418"/.418" lift int./exh.
280?/280? advertised duration
242?/242? duration @ .050" lift
High lift short duration cam produces good overall power. Requires Exhaust System, High Compression Piston / Big Bore, Shim Under Followers, and Performance Valve Spring Kit. Price Per Set (2)


Grind #109:
.418"/.418" lift int./exh.
286?/286? advertised duration
260?/260? duration @ .050" lift
Strong mid and upper end performance for racing engines. Requires Exhaust System, High Compression Piston, Shim Under Followers, and Performance Valve Spring Kit. Price Per Set (2).

 

[Chuck78]

BUT...
The base model Web Cams upgrade camshaft, one level above stock type cams, is nearly identical to the GR650 specs...

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. Price Per Set (2)."

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

Nearly identical lifts and very similar duration specs but they are measured at .010"/.25mm different starting and stopping points, so we can only assume they are somewhat comparable. The GR650 cam may have a touch more duration? It's hard to conpare without setting up the dial indicator and v-blocks and measuring for oneself...

At any rate it it quite an impressive cam profile for a stock Suzuki engine of the mid 1980's, especially considering it is a hollow core!

It wouldn't be out of the question to just run with it as is on slotted sprockets... I think it'd give a very pleasing street power curve, very broad! Lots of cylinder pressure vs a higher duration high rpm high hp grind, but that could be a bad thing as far as octane requirements with compression over 10:1...

 

[GregT]

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 suppose I cut four or five 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.
My EX500 - pictured on here elsewhere - uses plug in fittings on the outside of each carb. They can't fall out as they're tight against the frame, LOL.
Not hard to tap the galleries and put in a pipe fitting.

 

[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.