gpz 550 cams in a kz550 or zr550?

Daftrusty wrote:

Zaddict wrote:
These are my current settings:

Main Jet = 112 for carbs #1,4, 115 for carbs #2,3
Pilot Jet = 35
Needle = 0968h-66u, /2 clip position with 2 washers above clip
Float height = 17mm
Mixture Screw = 3 turns out

Those are the same exact settings that I am using, but I am still using the stock main jets as instructed by the Factory Pro setup sheet.
#108 (1&4)
#110 (2&3)

But since you are using a freer flowing exhaust, I would have figured that the #112-115 jets would be needed. But apparently not....very weird.

Well, if I go down one size I'd be at #110 (1&4) and #112 (2&3), so it would be a little richer than stock setup. Though Raul suggested I go down 2 sizes, which would be the same as stock (#108 and #110). It is a little weird. Still not sure whether to take Marc or Raul's advice.

No eBay APP ID and/or Cert ID defined in Kunena configurationAll of this seems correct as you are still running the stock air box, and stock pilot jets. I agree with Lou on the wideband, as Gary Bishop has been using the following on his 84 GPz550.


Side note: Different jetting would be used if you were tracking/racing this bike only. For the street, you are not running the engine as hard, nor do you have the throttle cranked open as much as you would on track, so tune it for the street.

Thanks Mark, for being the Guinea Pig on this experiment.

Zaddict wrote: Well, if I go down one size I'd be at #110 (1&4) and #112 (2&3), so it would be a little richer than stock setup. Though Raul suggested I go down 2 sizes, which would be the same as stock (#108 and #110). It is a little weird. Still not sure whether to take Marc or Raul's advice.

If it was me I would only go down one size, as it is better to run slightly rich than lean. But if you notice that when the engine is nice and rocket hot, that bursts of high rpm's getting onto the freeway dosen't pack the same punch as when cold. Then I would drop down to the stock jets.

But if according to Raul it is running really rich up top, maybe stock jets are the better bet.....remember that if you went to stock jets, you might have to raise your needle because as it is now (according to the dyno) it isn't running rich in the midrange and when you greatly reduce the main jet size, the reduced access to fuel will lean out your current needle settings.

But with carbs you are damned if you do, and damned if you don't. What ever choice you make, you will surely have to jimmy those carbs out from around the airbox boots just to fiddle with the jets a couple more times. ( with pods it took me 2 minutes tops to remove or re-install the carbs for jet changes. )

Thats not even getting into the dark art of setting the float height so the fuel level in the emulsion tubes will be "just right".
I just go with stock 17mm or what ever Factory Pro recommends.

Thats simply not something I will ever be able to figure out for myself.

Here's another cool graphic that helps make sense of a lot of the things we've been talking about

I'm going to go ahead and get the zx cam gears slotted. I want to try advancing the intake 2-4 degrees. Will be a fun project. In the meantime, here's one more informative graphic that shows the effect of advancing/retarding a cam 4 degrees (on a Porsche, but general principle should be similar).

That Porsche graph is interesting. Do you know which cam was advanced? Was it both? I think what is most interesting is the effect on where the power peak occurs.

TexasKZ wrote: That Porsche graph is interesting. Do you know which cam was advanced? Was it both? I think what is most interesting is the effect on where the power peak occurs.

here's the original Porsche thread. Looks like the 944 is SOHC, so only one cam to advance or retard -

rennlist.com/forums/944-turbo-and-turbo-...m-timing-info-3.html

Interesting. I wonder if the results would be different if only the intake was advanced while the exhaust stayed the same.

I've just read this topic, and I felt I had to create an account to bring my personnal experience to Zaddict. first of all, be indulgent with my grammar and my spelling, I live in France and english isn't my native language.
I own a ZR550 zephyr for many years now, and I made the same modifications as Zaddict during the winter 2016-2017. If compared to many fellas here, I lack proper equipment, but i managed to get through the painful time of carburation setup after complete engine overhaul and tweaking.
I too, took the cams from 89' ZX to put on my ZR head. I kept the ZR sprockets because I didn't want to have a valve clearance concern, and didn't want to loose much midrange. I had an opportunity to re-bore my block for cheap, so I bought some stock compression pistons with 3mm oversize on ebay. I knew that the longer duration would soften a tad the engine, so I removed 0,1mm from the head mating surface wich is the max you can do before you grind too much the valve seats. in fact there's not that much you can do with a ZR head, so I also polished the intake ports. the head gasket provided with the pistons was looking like a 650z, so I used a wiseco 615 one and discarded the former. I put a Marshall deeptone exhaust, some DR9EIX iridium spark plugs, and a 6 sigma kit for my carbs, the 4 mains being 115 if I remember well.
at first during break-in, the bike was running terrible despite carb sync and experiments with the mixture screw, and most important the mileage WAS terrible. accelerations were soft, and there was no tangible signs of improved performance. at some point after the first oil change was done, I had the idea to just remove the filter from the airbox in order to figure out wtf was happening. that turned immediatly this sick donkey into a racer. un-fucking-believable: the max speed immediatly jumped from around 185 km/h to above 205 km/h without windshield.
I understood the problem was coming from CV carbs drilled slides. with an increase in displacement and duration, the depression increases much at midrange and the slides move too fast, thus making the curve far too rich. so I returned to stock slides, and put foam pod filters from pipercross, after removing the airbox. my mileage returned to almost normal level (but not returned to stock for obvious reasons). now that I rode 5000 miles in this configuration, I can say that it runs like an aircraft.
I tested my bike against some modern bikes. lastly a friend of mine borrowed a brand new 650 CBF from the seller and we had a confrontation on curvy roads. despite the superior power of the Honda, he was unable to leave me far behind. the same happened with an old carb 900 mostro.
however the powerband of this engine is very specific. from 2000 to 5500 rpm, the behavior is very linear but doesn't lack torque vs stock. starting smoothly at 5000, and frankly at 6000/6500 rpm there's a huge amount of acceleration until you reach 11000 rpm. and even there, there's still something after. once the 12000 are behind, there's no point at continuing unless you seek for speed records.
as a result, I experience serious clutch slipping when shifting speeds above 6000 rpm. I don't know yet how to solve the problem. I would like to know if someone here as ever encountered this and found a solution with an aftermarket kit, suggestions welcome.

those little critters need to breathe. I am conscious that my bike runs lean now at iddle in winter.
but Zaddict you should empty the airbox once to check if it runs worse or better, this can give a direction to follow.

That's great information, thank you Roy, and welcome to the forum.
So you used the stock zr550 valve timing? I'm planning to advance the intake a few degrees - just need to get my sprockets slotted. Are you still running 115 main jets? What about the pilot jets? Needle settings? Was it the Cruizer pistons you bought off eBay?

Roy Batty wrote: I experience serious clutch slipping when shifting speeds above 6000 rpm. I don't know yet how to solve the problem. I would like to know if someone here as ever encountered this and found a solution with an aftermarket kit, suggestions welcome.

Thanks for your feedback and sharing your experience.

On the clutch issue, I'd make sure there is play in the clutch cable, and a little free-play at the lever. This would be a tight clutch cable, and not releasing completely.

Higher rpm clutch slippage usually leads to needing a clutch replacement. Cut to the chase, and replace the springs, steel plates and fiber plates. Once you remove the old clutch you might see what it is. I have had great experience with Barnett Clutches, not so good with EBC.

Zaddict wrote: That's great information, thank you Roy, and welcome to the forum.
So you used the stock zr550 valve timing? I'm planning to advance the intake a few degrees - just need to get my sprockets slotted. Are you still running 115 main jets? What about the pilot jets? Needle settings? Was it the Cruizer pistons you bought off eBay?

Yes, I use stock sprockets with zx cams. no timing change on intake, just greater duration. the ZX engine is on the peaky side, and I mostly use my bike for daily commute, so I prefer mid-power to peak power.
the higher the operating range, the lower the mileage and I didn't want a gas guzzler too (FYI, right now gas cost 6,90$/gal where I live).
currently the 4 main jets are 120,
the needles are stock with a 0,6mm thick spacer under the head,
slide where drilled with an additional 0.5mm hole, but this was reversed as it is not manageable in road use.
2.5 turns at the mixture screw.
the pistons are the cruizer ones and they are identical to stock regarding conception and quality. note that under 800 miles of break-in, the engine doesn't deliver as it should. the valve's shapes on the pistons heads are deep enough to allow more aggressive cams profiles. but compression is stock, so removing material from mating surfaces was the only solution to compensate a tad.

If you offset the intake 10 degs, the engine might start to kick 500rpm above and it may be of little use for everyday life on a naked bike. just my two cents, but I may be wrong.