What GS camshafts are interchaingeable?

[Buffalo Bill]

Kinda tempted to build a GS650 race bike for AHRMA.
Wondering if I can get GS1000cc cams into a GS650 head?
Those and oversized pistons would make it competitive in it's class; Vintage Superbike Middle Weight.
Anybody with genuine tech knowledge wanna suggest something?
Thanks! BB

 

[Steve]

1000 cams are longer than 650 cams.

I might have examples of each around here to measure, if you want.

.

 

[Buffalo Bill]

1000 cams are longer than 650 cams.

I might have examples of each around here to measure, if you want.

.

Thanks Steve. Am I right; 750cc thru 1100cc 8 valve, all cams are same size and interchangeable?
550cc & 650cc 8 valve, all cams are same size and interchangeable?

 

[Nessism]

Thanks Steve. Am I right; 750cc thru 1100cc 8 valve, all cams are same size and interchangeable?
550cc & 650cc 8 valve, all cams are same size and interchangeable?

This is correct. Megacycle has this info on their website.

 

[Steve]

Ed beat me to it, but yes, that is my understanding. :encouragement:

.

 

[Chuck78]

Precisely, 750 & up 8 valve are all the same general specifications and interchangeability. 550 and 650 are the same but 650g sprockets do not work on the chain drive 650e and 550 engines.

as mentioned, megacycle has several available grind patterns in their catalog. Web cams does also. Both are great to deal with.

My buddy is putting together a 650 E track bike. I might consider one also if my 500cc GS425 cannot keep up!

 

[Buffalo Bill]

Precisely, 750 & up 8 valve are all the same general specifications and interchangeability. 550 and 650 are the same but 650g sprockets do not work on the chain drive 650e and 550 engines.

as mentioned, megacycle has several available grind patterns in their catalog. Web cams does also. Both are great to deal with.

My buddy is putting together a 650 E track bike. I might consider one also if my 500cc GS425 cannot keep up!

Hey Chuck, I'd like to hear more about your friends 650E track bike!!
Considering one myself.

 

[Chuck78]

His track bike project has Fox Factory Shox, Dymags mag wheels, S model fairing, & 37mm GS forks. Engine is stock for now. It looks real nice. It was sitting like that, abandoned at a motorcycle shop, for years, sold off on mechanics' lien rights.

We're hoping to get 5 of us out doing track days & maybe vintage racing this next season. Another buddy just got a kz550 junkyard project, 610cc kit going it, & 1st gen GSXR mags. Another buddy in Chicago has a mostly finished CB350 race bike, high compression, big cams, XS650 cylinder studs & external top end oiler,etc. The 5th guy is doing track days on a Bandit 1200, but racing an EX250. We'll be looking at mostly WERA racing due to geographic proximity. Nelson Ledges and Mid-Ohio Sports Car Course track days

 

[Buffalo Bill]

Track days are open to new bikes, and they're damn good. Vintage bikes smaller than 1L get buzzed too often for me.
Vintage racing AHRMA looks like some classes are popular, some are not. Single and twin cylinder classes are popular and accept new bikes.
I thought WERA was dead?

 

[Chuck78]

No, WERA is definitely not dead! Some vintage classes are not well attended on the grids, but V5, V6, & V7 are. V5 would be 650cc & up in terms of bikes of our interests. V7 is newer late 1980's/early 1990's. V3 & 4 are smaller 2 strokes and small-medium twins.
Vintage classes run only at the sportsman events. I would be able to fit 5 or even 8 vintage races a year with WERA (within 3, 5, 8hrs drives), but AHRMA has higher participation in the popular classes than WERA, but it's geographically not so doable for me coming out of Ohio - only 1 or 2 within 5hrs, 1 or 2 8hrs away.

 

[Chuck78]

AMA Vintage Motorcycle Days is a WERA/AMA joint event as far as the Vintage racing is concerned. It is not nearly as well attended as Barber Vintage Festival in terms of road racing grids, Barber is three times the amount of racers. But the AMA is a much bigger event overall, especially for swapmeet, hare scramble, and vintage Motocross. As well as Camping attendance.

 

[Chuck78]

I figured I would start small and try to build a really fast lightweight little twin, keep me out of the liter bike trouble as far as the speed potential! Keep it safer at first, I love taking bikes on the tightest twisty roads anyhow, so if I did decide I only want you to race bigger bikes, then my former race bike would be an excellent candidate for all of my twisty road adventures. The tighter, the better. Race tracks are more high speed turns than anything else, the little bikes really shine on the tighter back roads with 15-35mph rated curves...those are exactly the kind of roads that I love the most! Although effortlessly gliding through 35 - 55 mph sweepers is also nice as long as you can get leaning into them plenty far...

There is also a supermoto / kart racing track 25 minutes from me, and they do track days there as well. The small bike will really shine on a tight course like that. It's all pretty flat though, not much bank to any turns.

 

[Buffalo Bill]

I track my GSXF with a 92 GSXR1127 engine. Getting up to speed is a blast, braking is the most intense. My fobia is the liter bike breaking grip in the rear during initial power roll on at apex, but it don't.
I swapped up to 1127 because there's always a newbee on a new liter bike who will sandbag into the corners holding up traffic, then blasting off to the next corner before they can be overtaken.
The only way around them is to stay with them until the braking zone and pass them there.
My CBR600 is my favorite country road bike, for the reasons you mentioned. I'm sure a well prepared GS650E will be just as fun on country roads and racing with bikes of it's own class.

 

[Chuck78]

Kinda tempted to build a GS650 race bike for AHRMA.
Wondering if I can get GS1000cc cams into a GS650 head?
Thanks! BB

Bill, I failed to mention that running GS550 cams would be better than 650 cams if you are wanting an engine that will rev out really high. The 650 cams are a great street grind, 550 cams are like the early GS400 425 and 750 cams, longer duration slightly less valve lift, better for high RPM

Of course an aftermarket grind would be far better than any of those!

 

[Steve]

Precisely, 750 & up 8 valve are all the same general specifications and interchangeability.

Just in case you were still looking at some 8-valve cams, keep in mind that you should check specs for all years available. :-k

I don't know about the other models and years, but I do know that the timing on the intake cam changed on the 850 from '79 to '80. The 1000E, 1000G and 1100G shared the timing specs from the '79 model (850GN). The '80 and newer 850s had 10? advanced timing to close the intake valve earlier for a broader torque curve. Might reduce peak power a bit, but the 850 was not intended to be a race bike.

.

 

[hannibal]

Since the duration of the 79 and 80 850 cams are the same, don't they use the same cam just timed 10? differently?

In other words, couldn't you just advance the 79 cam a few teeth and effectively have a 80 cam?

 

[Chuck78]

Yes, just like the 1000G/1100G models, same cams, various cam sprockets year by year, altering the timing, searching for more low-mid grunt.

 

[Steve]

Since the duration of the 79 and 80 850 cams are the same, don't they use the same cam just timed 10? differently?

In other words, couldn't you just advance the 79 cam a few teeth and effectively have a 80 cam?

You have a plausible idea, it just needs a bit of "refinement". :-k

I don't know if the difference is in the cam itself or the sprockets. The lobes themselves might be offset 10? or it might be the offset between the bolts that hold the sprockets to the cams.

Either way, there are 30 teeth on the sprocket, so moving just ONE tooth will change the cam 12?.
I certainly would not go "a few teeth".

.

 

[TeamDar]

You have a plausible idea, it just needs a bit of "refinement". :-k

I don't know if the difference is in the cam itself or the sprockets. The lobes themselves might be offset 10? or it might be the offset between the bolts that hold the sprockets to the cams.

Either way, there are 30 teeth on the sprocket, so moving just ONE tooth will change the cam 12?.
I certainly would not go "a few teeth".

.

This is not correct. When measuring camshaft timing and duration, the numbers are referring to crankshaft degrees of rotation not camshaft degrees of rotation. While moving the timing chain one tooth on the cam sprocket is actually 24 not 12 degrees of advance or retard as measured at the crankshaft since the cams run at half the speed of the crankshaft. In other words, if you were to retard the camshaft one tooth on the cam sprocket, you would have to rotate the crankshaft 24 degrees to rotate the camshaft to its old position. Dar

 

[Steve]

Very correct, Dar, thanks for the reminder. :encouragement:

.