TOPIC:

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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Zaddict wrote:

I found photos are not always the best way to compare plugs without a reference plug to compare to in the photo. A dark photo makes plugs look richer, and vice versa. But the plugs in that photo look pretty good to me, compared to what i get out of my gpz's. One looks to have a noticeably darker ground electrode, but other than that, the other three look pretty good.

Yeah, I think those plugs look OK but I can tell you they're darker than I've ever seen them.

Corey, you're correct, everything seems to be running fine now. Just went for another test ride and all seems normal. My impression is as before, a little down on the low-end from the zr550 cams, a little higher on the high-end (to the point where I surprised myself a few times today, as in "oh shit, better put on the brakes quick!"

I was extra careful buttoning everything up yesterday. No problems with idle so far. No explosions while starting.
The bike starts fine hot and cold, and pulls well across the rpm range.
I'll try leaving the petcock on PRI. I just rebuilt the carbs a few months ago, with new float needles and gaskets. Would be surprised if that was an issue.
Engine oil smells normal.
No fuel or oil in the airbox.
Nothing restricting the air filter/box.

mpg for today's 85 mile ride was 35.8.

There's an inefficiency somewhere. I'm guessing the bike is running rich. I'm scheduled for a dyno run Tuesday, if my job schedule allows. Will report back.

I'd put a set of NEW plugs in it and to plug chop. Ride it on the old plugs to a place you can do
WFO blast put the new one's in bust it's ass WFO pull the clutch shut it off stop swap plugs and
ride bach home and look at the plugs.

I'm reading about cam duration and compression. Interesting stuff.

"The most common issues associated with a long-duration cam on the street are a very rich fuel mixture, mild to outright annoying hesitation under light acceleration, an extreme bog under hard acceleration, extremely poor fuel mileage, fouled spark plugs and in general very poor throttle response.

One of the biggest problems with big camshafts is when the cam is added to an engine with insufficient compression. In most cam catalogs, the larger camshaft descriptions include a compression ratio recommendation. For example, COMP’s Xtreme Energy hydraulic flat tappet XE294H cam with 250/256 degrees of duration at 0.050 and 0.588/0.593 inch lift and a 110-degrees lobe separation angle (LSA), recommends no less than 10.5:1 compression when using this cam. This recommendation is often ignored when selecting this cam but it actually is there for a very good reason. As intake duration increases, the intake closing point occurs much later. If you think about it, the engine cannot begin to compress the intake charge until the intake valve is closed. So the engine’s effective compression will be much lower than its static compression ratio because the intake valve closes later. This results in reduced cylinder pressure—especially at low engine speeds. That’s why after a big cam is installed in your engine, it seems like the engine feels sluggish at lower engine speeds.

Proof of this is to perform a cranking compression test before and after the cam swap. What you will find is that the big new cam has reduced the cranking pressure by perhaps 10-psi. The engine has not lost ring seal – the later closing intake valve prevents the engine from creating cylinder pressure until the intake valve closes. The best way to maintain a cranking compression of around 180 to 190-psi with a long-duration cam is to increase the static compression ratio. "

They go on to recommend advancing the ignition as workaround.

Very curious to see what the dyno/gas data look like.

My weekend cam degree test is on hold due to lack of valve cover gaskets. Arrrgh! I always have spare VCG's in my parts bin, but last time must have grabbed the last one.

Sounds like you have checked everything, and the exhaust sniff test at the dyno should tell the story. When you get it on the dyno, and if you will get a recommended change, before you buy any new main jets, I have a bunch of the Factory Pro variety. So you are leaving everything as it is for this dyno to find out what's happening, right? Remember, if you opt to change to pod filters in the future, I still have that good used set with your name on them.

Looking at your pics it seems the timing marks are lining up with the cams in that position - though difficult to tell from that viewpoint exactly, Your chain is not meshed tight on the cam sprockets, Any slack in the chain and your cam and crank alignment marks become meaningless. (If you miss the lines then just turn it over twice to get back again, never reverse it.)

I would check the marks again with the tensioner in place and turn it over a few times to get the slack behind the cams and taken up by the tensioner. It is easy to be one pin or tooth out and they do run ok. If the head has been skimmed before your EX mark may be noticeably below the gasket face line datum.


Adam documented some of his ZR615 development on the gpz550 forum and he had his own zephyr site. I though it odd to run just one of a pair of megacycle cams, and without any actual tested lobe centre numbers I was openly sceptical about it. He had a theory about cylinder head port differences making some gpz cam tuning specs not applicable to his ZR.

I always found it really odd the 92 degree IN cam setting, no other performance cam is spec anything like that...or even the earlier gpz and kz cams. My rpm power cam settings was 108 /112 . It is a pro TTS uk gas flowed zx head.

You may also/and have a flat spot somewhere in your fueling not apparent from a WOT plug chop. Maybe experiment with needle position anti- tamper can be shimmed with tiny washers, pilot airscrews can be accessed under rubber bungs IIRC.
I did quite a lot of trial and error on the main jetting, needle and position and pilot airscrews to get it good. (4-1 / pods ) . Even the factory fueling is quite different between the various similar 550 variants- all running on the same carbs, pipes and airbox.

Well, advancing the intake to the Zx timing would make the intake valve close sooner, restoring compression at lower RPMs. Maybe that is needed more-so with the lower compression of the Zr motor than on the Zx.

It looks like you have two Zr sprockets right now. If you can sweet-talk Corey out of a Z4/IN sprocket, I would try that on the intake just to see what happens.

loudhvx wrote: Well, advancing the intake to the Zx timing would make the intake valve close sooner, restoring compression at lower RPMs. Maybe that is needed more-so with the lower compression of the Zr motor than on the Zx.

It looks like you have two Zr sprockets right now. If you can sweet-talk Corey out of a Z4/IN sprocket, I would try that on the intake just to see what happens.

But then that would increase the overlap by a corresponding amount, correct? Though from what I've read the intake closing timing is the single most important cam setting. Maybe worth a shot. As it so happens Corey was kind enough to give me the ZX sprockets along with the cams, so I just need to find time for the swap.