gpz 550 cams in a kz550 or zr550?

Wouldn't hurt to take the valve cover off and visually check the cam timing. The difference in the duration from these cams, would definitely not the cause of your change in gas mileage. With just a cam swap, and the air box still on, you shouldn't need to rejet. Pod filters, then yes, rejet for sure!

Is it starting cold and hot OK?

Seems like it's coming from the front of the bike. Maybe ignited fuel in the headers?




Exhaust valve opening a bit early ? inlet closing too late ? I really think this is a cam timing/phasing issue. If this was high compression pistons and lumpy cams things would have gone wrong before now, just there are quite generous clearances on these.

Either an assembly or parts comparability issue, or maybe something else?

If you had this right it would be F@~:>?<Kn' Hell, this bike is mental. Those late gpz cams are really strong rpm power.

Remember the late Adam Wade (R.I.P.) he had a zephyr 550 and had issues with using megacyle x3 cams...I was sceptical about this , and actually bought them from him, then loaned then to Corey for a season, then back in my garage now.
He said the ZR / GT 550 head ports are different from the zx....not sure about this, but the cylinder block fins are definitely bigger and squarer,
At the time I questioned his lobe 'actual' centres, but he had timed from the factory sprockets. What if his "reversion" theory about long duration cams being unsuitable for a ZR head was more about some difference with the ZR head and setting a gpz cam timing? Perhaps slotted timing sprockets required.? This z550 kz GPz ZX cam swap is not uncommon, the ZR to ZX cams more so...

Check your lobe centers now . If in doubt dial-in somewhere between 105 and 110 degrees.

CoreyClough wrote: Wouldn't hurt to take the valve cover off and visually check the cam timing. The difference in the duration from these cams, would definitely not the cause of your change in gas mileage. With just a cam swap, and the air box still on, you shouldn't need to rejet. Pod filters, then yes, rejet for sure!

Is it starting cold and hot OK?

Starts cold and hot just fine (aside from the occasional explosion) . Will doublecheck the timing this weekend.

Tyrell Corp wrote:
Remember the late Adam Wade (R.I.P.) he had a zephyr 550 and had issues with using megacyle x3 cams...I was sceptical about this , and actually bought them from him, then loaned then to Corey for a season, then back in my garage now.
He said the ZR / GT 550 head ports are different from the zx....not sure about this, but the cylinder block fins are definitely bigger and squarer,
At the time I questioned his lobe 'actual' centres, but he had timed from the factory sprockets. What if his "reversion" theory about long duration cams being unsuitable for a ZR head was more about some difference with the ZR head and setting a gpz cam timing? Perhaps slotted timing sprockets required.? This z550 kz GPz ZX cam swap is not uncommon, the ZR to ZX cams more so...

Check your lobe centers now . If in doubt dial-in somewhere between 105 and 110 degrees.

What kind of problems did he have? Just wasn't performing as expected?

Tyrell Corp wrote: ,
Check your lobe centers now . If in doubt dial-in somewhere between 105 and 110 degrees.

Alright gentlemen, I'm going in. Just to be clear, I don't have a way to dial-in lobe centers between 105 to 110 degrees without slotted cams, correct? I'm limited to the predrilled holes in the sprockets which translate to 104/104, or 94/104 in the case of the ZX sprockets. Going to 94 for the intake seems like a bad idea in any case as that would increase the overlap.

Timing looks good visually.

Valve lash is all within spec. Can't find anything wrong...

You are correct. Visually everything looks correct. The timing marks line up (as good as they ever do) and the 44 pins of cam chain lines up with the right teeth.

But....when you rotate the engine and stop dead on the top-dead-center mark on the ignition rotor, does the exhaust cam timing mark line up???
(Remember if you overshoot the TDC mark even by a tiny bit, you can’t turn the engine back because it will add slop in the chain and the results will be skewed.)
If the exhaust timing mark is lined up when at top dead center and there is zero slop in the chain down to the crank...then the intake will be also correct. (assuming the 44 chain pins are correctly placed.)
If not, then you need to start all over and reindex the sprockets.

Hope that makes sense.

Daftrusty wrote: You are correct. Visually everything looks correct. The timing marks line up (as good as they ever do) and the 44 pins of cam chain lines up with the right teeth.

But....when you rotate the engine and stop dead on the top-dead-center mark on the ignition rotor, does the exhaust cam timing mark line up???
(Remember if you overshoot the TDC mark even by a tiny bit, you can’t turn the engine back because it will add slop in the chain and the results will be skewed.)
If the exhaust timing mark is lined up when at top dead center and there is zero slop in the chain down to the crank...then the intake will be also correct. (assuming the 44 chain pins are correctly placed.)
If not, then you need to start all over and reindex the sprockets.

Hope that makes sense.

Not sure i understand. What more am i looking for beyond what's specified in the diagram?

TDC here (pics attached). Is this what you mean? Like shifting everything a link if this was off? I think it's good, though second opinion would be appreciated.

Your photos show the gasket in place. That means when you sight down the valve cover deck, you should not actually see the EX line mark.

Also, if you have the pin count correct, the Z/5 line mark will only be level with the valve cover deck if there is a little droop in the chain between cams.

Yours appears to be correct as long as the T mark coincides with the EX line mark, as Dafftrusty said. (The EX line mark tends to be a little bite above the deck surface as the chain is usually stretched a bit). You really don't have anything else to do beyond that.

(And of course, remember to release the chain tensioner before installing the valve cover.)

So based on everything you have shown us, and you have tested, you state it is not about a running issue, but a fuel mileage/consumption issue. Starts fine hot and cold, pulls good through the rpm range.
- I'd recommend leaving the petcock on PRI, engine off, and see if you have fuel dripping/overflowing somewhere from the carbs.
- Does the engine oil smell like fuel?
- Is there fuel in the aribox?
- Is the air filter and/or air box possiby restrited by something?
- We had the carbs removed from the intake and air box, with cables connected, moved off to the left side at an angle. Maybe a stuck float? We did not remove the vacuum slides or anything else with your CV30 Carbs, just vacuum lines and fuel lines removing the tank.
***Don't adjust the mixture screws. Leave them as you had them set, but you can check them to make sure they have not moved. You are using aftermarket mixture screw adjusters from Factory Pro:
www.factorypro.com/Prod_Pages/prodk55.html

Tyrell Corp wrote:
Remember the late Adam Wade (R.I.P.) he had a zephyr 550 and had issues with using megacyle x3 cams...I was sceptical about this , and actually bought them from him, then loaned then to Corey for a season, then back in my garage now.

Adam only used the X3 Intake Cam with the 615 kit. I have the Factory Pro Dyno Sheet from when he tested it somewhere. Photobucket is now raping us to house our share our photos on any forum, so I'll have to dig for this one. I have sent Mark an e-mail with Adam's Dyno from back in 2001.



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