Degreeing cams on GS700

[Nicholaschase29]

Hello all,

I've finally gotten around to setting my bike up so that I can degree the cams. My intent is go move the power band higher and increase peak power at higher rpm's as well. Hopefully by degreeing my cams to complement my pipe and pods I can gain some noticeable power increases.

I plan to retard the intake cam ~3-4 degrees from stock or when it was new and then retard my exhaust cam ~7 degrees. By doing this I am hoping to get results as i posted above. This is also where my questions come. As I have never done this before I'm looking for someone who has with either an 83 750 or 85 700 that has experimented with cam timings to save me some headache. I talked to a guy in madison at a shop and he said he had a 83 750 and he put a 700 exhaust cam in and then found specs for a cam made for his bike by yoshimura and put his cams to those specs. Anyone have any information like this?

I also need the stock cam timings so I can compare what I have now with what I should have stock. My thinking is that my camchain stretched over time and I am assuming my cams have been retarded ~3-4 degrees so I think that the only thing that I'll need to do is retard my exhaust cam an additional 3 degrees from what I have now in order to get the desired results. I need the stock timings though in order to see just how far the cams have retarded so if anyone can help me out..

I'm going to take the gears off the cams and grind slots in the holes in order to adjust them also..

Thanks guys
Nick

 

[Guest]

I would try 110 exhaust and 108 intake. If you want even more top end 110 for the intake but don't expect an idle under 1500 rpms.

 

[lecroy]

Sure hope that long pipe and wrench isn't for turning the motor on that side of the crank.

 

[Nicholaschase29]

Sure hope that long pipe and wrench isn't for turning the motor on that side of the crank.

Why? Is there a better way to do it? I don't want to remove the stator cover. On the rotor for the signal generator there was a hex that I assumed was to turn the motor over...

 

[RacingJake]

Hello all,

I plan to retard the intake cam ~3-4 degrees from stock or when it was new and then retard my exhaust cam ~7 degrees.

Retarding your intake will increase your valve to piston clearance. Good thing.

Retarding your exhaust will reduce piston to valve clearance so when the piston is coming up on the exhaust stroke to TDC the exhaust valve may still be open too much. You need to check the Piston to Valve clearance before you start the motor. Need to have at least 75 thou clearance. If it binds when turning the engine over by hand with the sparkplugs out you'll need to stop and see what's causing it, cause you don't want to bend any valves.

 

[RacingJake]

On that side there's a small dowel pin on the crank that keeps the mach advance or rotor timed, if you snap it off you may be in the market for a new crank, if you can get whats left of the dowel out.

 

[Guest]

Plus it's easier to degree with you on the side of the pointers. The other way sucks.

 

[rapidray]

Why? Is there a better way to do it? I don't want to remove the stator cover. On the rotor for the signal generator there was a hex that I assumed was to turn the motor over...

Also, & the BIGGEST reason I NEVER turn the motor on the same side as the degree wheel is that the wheel could MOVE if you are turning the crank with the nut that is on the wheel side. How accurate will the cam timing be if the degree wheel is moving? Take off the stator cover & do it RIGHT by turning the crank with the nut on the LEFT side! Ray.

 

[lecroy]

Yep, the pin could crack and the wheel and slip and if your using a billet rotor you can damage it. I know pulling thos 8 or so bolts out are a lot of work compared to the rest of the job. LOL. I have to agree with Ray on this, do it right. And to Jakes point, make SURE you have enough clearance when your done!!!!

I normally put the dial on the starter side and the wheel on the pickup. I use a couple of large washers to sandwitch the wheel and keep it from moving. I still double and sometime tripple check this part of the setup.

Just my 2 cents on one other thing I see you doing. You have the dials clamping in with a mess of clamps and grips. Looks like a kids erector set. Not that there is anything wrong with that as long as nothing can move but, most people make a custom mount. I used a cobbled mount until last year for some strange reason I looked at the diameter of the cylinder studs and it turns out that the diameter is very close to a standard dial stand. Of course you would need to thread it into the head nut and you may not have enough. But with the aftermarket ones there is plenty. Very solid rig and easy to set up. It almost makes this adjustment fun to do.. But not quite.

Make sure when you slot the gears that they fit flat. Any bind and you could crack the cams when you go to tighten.

Use some brakeclean and wipe it down good, then use a little lock tight on those stupid bolts. You don't want those gears to slip...

One last comment about this, those two little bolts SUCK AZZ!! With the cams I use, they are worse than stock to get at. I have ground wrenchs, sockets, once even looked for cap heads but Suzuki had to use that odd ball size. I thought about drilling and tapping for a standard size but good sense popped in before my rage took over...

Then someone gave me some old junk cams out of some bike that actually have a torx head.
I believe these came from an early 1100 or 1000. If anyone knows, post!!!!

 

[oldschoolGS]

I mount the degree wheel and turn the crank from the right side as well. Space the wheel out and use an open wrench behind it on the 17mm trigger. Be very careful when you turn the motor over as to not disturb the degree wheel. It can be done but I would not use the hex bolt that holds the trigger on.

Mark the wheel once TDC is established and verify it has not moved once the cams are timed. If careful, it can be done correctly without breaking the seal on the stator cover.

110 degree centers for both intake and exhaust should give good upper mid/high rpm results

Good luck, Ed

 

[Mark M]

I mount the degree wheel and turn the crank from the right side as well. Space the wheel out and use an open wrench behind it on the 17mm trigger. Be very careful when you turn the motor over as to not disturb the degree wheel. It can be done but I would not use the hex bolt that holds the trigger on.

+1 on this, it worked fine on my 1100E. You shouldn't need anything like that snipe to turn the engine over, I had no troubles with a standard 17mm combination wrench on mine. When you are moving slow, it doesn't take a lot of force.

Mark

 

[Nicholaschase29]

I found this looking through my materials

So the exhaust cam lobe center is at 110 and the intake is at 102. I'll go get the measurements of where My cams are at later today and post them.

 

[Nicholaschase29]

I only used the pipe to more accurately control the position of the crank, there isn't much force involved in turning the engine over. The intake cam has a center of 105 degrees. The intake valve was 50 thousandths off the seat at 9 degrees BTDC and 40 degrees ABDC. Yielding the center i listed previously.

 

[Nicholaschase29]

Exhaust is the following. We measured 42.5 degrees before BDC at .050 and 3 degrees after top dead center.

42.5+3+180= 225.5

225.5/2= 112.75

112.75 - 3 = 109.75


Intake,

9 degrees before top dead center and 40 degrees after bottom dead center.

9+40+180= 229

229/2= 114.5

114.5-9= 105.5

Exhaust centerline = 109.75

Intake centerline = 105.5

Do those numbers sound correct?

 

[rapidray]

If you want more top end move the intake cam to 107.5. You will be close is the exhaust cam is 2 numbers bigger. This will help it pull the exhaust out of the cylinder better too. Ray.

 

[lecroy]

I forgot to bring this up (how do you make the measurement because there are a few ways) but I agree, using 0.050 is good. Make sure its always turning the same direction (that it runs in) otherwise you would have the hysteresis to deal with. If you go to far, back it enough to reset the chain then try again. Just basic stuff but all of it adds errors and with you getting into 0.01 degree readings, that's pretty tight.

I have no idea what you bike would have been shipped with but yes, I would buy those numbers.

I don't understand why anyone would attempt to degree cams but be reluctant to pull the stator cover. It takes all of a couple of minutes, but its your engine.

 

[oldschoolGS]

I don't understand why anyone would attempt to degree cams but be reluctant to pull the stator cover. It takes all of a couple of minutes, but its your engine.

My reasons:

1. its not really necessary
2. did not want to drain the oil (with bike on rear stand) After installing cams I like to run it first before changing oil to wash out all the moly lube.
3. why disturb the gasket on the stator?

your numbers look good to me. I never indexed stock cams on my '83 750 but did have 2 sets of aftermarket cams set at 110/110. Power was peaky coming on hard at around 7500rpm. I experimented with 104/106 and this did give it more midrange at the expense of top end.

Good Luck, Ed

 

[Nicholaschase29]

Ok I was doing some thinking.. I just counted the cam gear teeth and there are 34 teeth on each gear. I think I can do this but I'd like you guys to double check my thinking.. If there are two revs per crank per one rev of the cams then if we move the chain one tooth we'll gain what we want. 360/34= 10.588 then devide 10.588 by 2 because per one rev of the crank the cams turn once so it would be 5.29 degrees right? 5.29+105.5 will put us right around ~110 lobe center..

 

[rapidray]

Ok I was doing some thinking.. I just counted the cam gear teeth and there are 34 teeth on each gear. I think I can do this but I'd like you guys to double check my thinking.. If there are two revs per crank per one rev of the cams then if we move the chain one tooth we'll gain what we want. 360/34= 10.588 then devide 10.588 by 2 because per one rev of the crank the cams turn once so it would be 5.29 degrees right? 5.29+105.5 will put us right around ~110 lobe center..

Do NOT guess! Move it & recheck with the degree wheel. Make SURE you know where it ends up. I wouldn't set the intake any more than 108. I have done enough of this (and dynoed them) to know what works. You need to remember something,this is NOT a DRAGBIKE! You will be spending most of your time riding in the midrange. If your bike has all of the REAL power from 8-10000 RPM you will find yourself re-doing this. I applaud you wanting to do this but think realistically about where the engine will live most of it's run time. Ray.

 

[Mark M]

Do NOT guess! Move it & recheck with the degree wheel. Make SURE you know where it ends up. I wouldn't set the intake any more than 108. I have done enough of this (and dynoed them) to know what works. You need to remember something,this is NOT a DRAGBIKE! You will be spending most of your time riding in the midrange. If your bike has all of the REAL power from 8-10000 RPM you will find yourself re-doing this. I applaud you wanting to do this but think realistically about where the engine will live most of it's run time. Ray.

I second that. Measure what you HAVE, not what you SHOULD have.

As for not going beyond 108deg, Ray has experience to say it's not a good idea. If you want to try anyway and don't mind going back in if you went to far, then try 110deg and be prepared to redo it back to 108deg if/when you find it is too much. There is nothing like firsthand experience in these matters and trying something just to see is how you get it. If you only want to do it once, listen to Ray.

Mark