Deadspot created by GPZ Cam install

The sprockets have 3 sets of holes.
1 has a round circle around the bolt head.
Another has a square and the last has an octagon.
Use the correct setup for the GPz.
Don't alter cam timing unless you are willing to check it with a degree wheel.

This.

GPz 550 models have the same six hole cam gear, any one pair, of the three pairs available, gives timing specific to that model.
The 750 is the same.

I'm puzzled why you only used one cam, all the aircooled GPz used symmetrical cams. Even the performance cams, the duration and lift numbers are pretty similar. Looking at the megacycle catalougue for example.

www.megacyclecams.com/catalog/Page45.pdf

Note the caution about 83-84 unitrack cams base circle, IIRC correctly it may be just one of the cams of the pair with the cut base circle -to increase lift. Also they have a whacking 288 degrees duration, quite a lot over the stock cams. I would sort this out first.


You carbs will very likely need upjetting and/or a needle lift too.

I found several documents referring to the 550 cam sprockets but gpz750 sprocket information is proving tougher to find. I might wait to pull the head cover until I can verify what I'm looking for.

I have both the intake and exhaust GPZ cams but I decided to install them one at a time after reading about how the two cams will affect the hp curve. The combination of free flowing exhaust, the 810 kit and the exhaust cam will supposedly cause the bike to loose some of its low end but gain high rpm hp. I figured I would throw he exhaust cam in there eventually, but wanted to see what all the fuss was on upgrading only the intake cam.

I bet you read the same thread on running mixed cams that I did.
www.kzrider.com/forum/2-engine/344859-mi...l=component&type=raw
I also wanted to try this when I put 84 zx750 cams in my kz750. But because of the .5mm smaller base circle on the exhaust cams, (the zx750's had the exhaust valves sunk .50mm to "better increase exhaust flow" so the exhaust valves would have been to long to shim properly from the factory. So instead of manufacturing 4 shorter exhaust valves, they just made 1 cam with smaller base circle.) but once I had my 3 angle valve job done, my valves were recessed in the head so the zx750 cams fit and shimmed up without having trim the valve stems. (My intake valves had to cut down after the fore mentioned valve job) So beware of that IF you decide to install the zx750 exhaust cam.

The kz700,750 and all gpz750's share the same cam timing gears. Just the cams themselves are indexed differently.
So you simply follow the factory manual instructions for timing the cams.
The zx550's had weird intake only cam timing that necessitated having a specific cam timing gear.



MAKE SURE YOU COUNT AND HAVE THE PROPER AMOUNT OF CHAIN LINKS BETWEEN THE CAMS AS THE ILLUSTRATION SHOWS!! IF NOT THE TIMING WILL BE OFF!!
Its VERY easy to install the cams and have the timing marks line up AND yet have the wrong amount of chain links between the cams.
The "sag" that needs to be in the cam chain when timing the cams is hard to gauge by eye. So I made a temporary upper cam chain guide out of a zr-7 guide so I didn't have to eyeball it.


Also, some guys buy the gpz750 Turbo cams, but the turbo cams are only kz650 cams with less lift and duration. I noticed several ebay sellers advertising Turbo cams as being the same as N/A zx750 cams....so beware!

Thanks Daftrusty! That's exactly what I needed to know. That was one of the links I came across when researching whether or not I wanted to make a go at a cam swap. I also have a 550-6spd transmission ready to drop in if I ever get around to pulling the engine out of the frame. If I find the other pages I read about running asymmetrical cams, I'll post them.

When I bought the cam, I did enough research to know all the markings of the zx750 cams and then checked the base circle and lobe measurements when It arrived. I got lucky, too, as the intake cam was a near perfect drop in and only needed one shim on #4 cylinder to be in tolerance.

I'll pull the head cover and double check timing tonight or tomorrow. I know I'm spot on with the intake cam being timed to the exhaust cam (46th link, etc), but certainly want to make sure it's timed correctly to 1&4 at tdc.

I certainly appreciate the info and input. It's my first motorcycle and first build, etc. I found myself doing a lot more work to the bike once I started working on it but I've never felt in over my head because of all the great info on he forum. I'll throw up some pictures when I get a chance.

I can see you have done a lot of homework and have a good idea of what to do.
Just things to know when setting the cam timing,
Make sure the cam tensioner is removed from the cylinder block just for good practice. That way you know it is not interfering with the position of the cam chain.
Also, make sure that the cam chain from the crankshaft up to the exhaust cam is tight, like tight as a drum. If there is any slop in the chain to the exhaust cam, it will throw off the rest of your timing setup. It helps to put the bike in gear, so you can't accidentally turn the crankshaft as you pull the chain tight. When you tighten down the cam bearing caps the exhaust cam will have a tendincy to turn and then turn the crank, thus screwing up the timing position. Slop in the chain between the intake cam and the crankshaft is not a big deal when setting the timing. But do not try to turn the motor over without the tensioner in place. You can jump a tooth that way. Also the cam chain tensioner ALWAYS has to be installed AFTER you install the valve cover. If not, serious damage will occur to the chain and the tensioners.
Lots of food for thought.

Again good advice from Rusty above, I'd also replace your M6 cam bolts with new high tensile steel -they stretch and can break. Also tighten by feel unless you have a very accurate low tourque tourque wrench. Drilling snapped bolts out of the head to helicoil is a thankless task and easily avoided.

Tyrell Corp wrote: Again good advice from Rusty above, I'd also replace your M6 cam bolts with new high tensile steel -they stretch and can break. Also tighten by feel unless you have a very accurate low tourque tourque wrench. Drilling snapped bolts out of the head to helicoil is a thankless task and easily avoided.

Red Loctite on the cam bolts and make sure you clean the holes and the bolts with brake cleaner first. Do not put it together without the red loctite.... I'd have no problem using the stock bolts. I use them all the time.

Rusty, you were right on the money. The cams are mounted to the sprockets correctly but the exhaust cam was mounted one link off from the crank shaft and the intake was timed to the ex cam. I cranked it up and it sounded great. However, it started a little too easy for being cold so I'm thinking its still on the rich side. Its raining for the next several days so I won't have a chance to get out and see what the power band feels like until monday-ish.



Also of note, I used to have my carb vacuum ports linked (1&2, 3&4) and the bike ran better that way before I installed the new cam. Now that the cam and exhaust cam are asymmetrical, the little bit of idling I did in the garage today yielded a much smoother running engine with the carbs isolated rather than linked. Ill look into this a little further as I get the carbs dialed in.

LarryC, Tyrell - Are you referring to cam sprocket bolts or cam cap bolts? I try to torque all bolts to spec, especially internal engine bolts.

Rusty, I a manual cam chain tensioner which I feel simplifies working any cam related tasks. It also drastically reduced the amount of cam chain noise coming from the engine.


Since I have a few knowledgeable eyes, can anyone identify these carbs? The carb throat measured 36 or 37mm. What carbs are the next step up from here? I hear tons of carb names thrown about from form to form and Im trying to get a gauge of what to watch for.


And this is how the bike sits at the moment.

Nice work finding the problem. Now you will be a pro the next time you go to adjust valves or help a friend with a KZ. I struggled with resetting the cam timing my first time around. Now I know exactly how it can get screwed up, so I know exactly what precautions to take to ensure I did it right.
(Hint: When adjusting valves, just zip-tie the cam chains to the cam gears. Then you can lift one cam out of the way at a time, re-shim the valves and then reinstall the cam and your timing never gets messed up. Cut off the zip ties when you rotate the engine of course.)

That appears to be a Kreiger manual cam chain tensioner. I use Kreiger adjusters on both my zr550 and my kz750. Takes away all the guess work out of adjusting or fixing an auto-tensioner.

Your carbs are Mikuni BS34's. Measure the inner throat of the carb that attaches to the intake boots on cylinder head. It should be 34mm.

Ok, so the timing has certainly helped with the dead spot but the issue persists.

I do believe the pilot circuit was a bit on the rich side before the addition of the GPZ cam and maybe I was unaware of the main jet and pilot screws ability to mask the maildly rich condition. I'm still leaning toward the asymmetrical cams creating a richer afr.

I contemplated rigging up an o2 sensor setup to help dial the carbs in but I can't justify the added $$ for it at the moment. I went ahead and ordered a couple sets of pilot jets to start testing. I'll definitely update when I get a chance.

Question: I'm familiar with how a lean condition will damage an engine and that a rich condition robs performance. Can a rich condition damage an engine?

Also, Rusty, you were spot on. The carbs are Bs34s.

Too rich can "wash out" the rings causing oil burning and lower compression. Then you have to jet leaner to compensate.
Steve