Deadspot created by GPZ Cam install

Ok, gents.

I have an interesting carb situation... I recently installed a GPZ cam into a well functioning, well tuned motorcycle and I'm trying to diagnose a lean/rich condition. I'm not a racer and do most of my riding around town, so I don't push the bike to redline on a regular basis and don't hang out there long when I do. (But boy, I love doing it when I get the chance) I only installed the intake cam and left the exhaust cam stock. From what I gather, this should give a boost in hp across the entire power curve rather than shifting all the power to the higher RPM range. Would installing an intake came with longer duration and lift without changing the exhaust cam create a rich condition? Would this condition only occur at certain RPM?

Since installing the cam, have a dead spot that I haven't been able to diagnose. It only occurs after revving the bike approximately 4-5k. Once I've accelerated and held at an rpm, the bike Boggs a little. Then, if I try to accelerate (regardless of whether or not I shift) the engine hesitates for .5-1 sec before pulling strong. It almost feels like I drop a cylinder or two and there is an audible deficit in the exhaust tones.

Any input or opinions would be great! I have already synched the carbs, checked float levels, have a jet kit installed with larger mains and pilot jets (will get specific numbers next time I open up the carbs) and the float needle is the one supplied by the jet kit, 4th slot from the top.

The bike is an 84' kz700 that's bored out to 810, pod filters (the bike didn't come with stock box), bs34 carbs, original headers with high flow mufflers (baffolds in)

Did you install the cam in the correct cam sprocket holes for a GPz?


.

From what I gather, they are installed the same way the KZ700/750 cams are installed. Cam timing adjustment shouldn't be needed unless the head is milled.

If the bike was out of time, would the symptom present across all rpm ranges? The bike idles fine and hauls like a boss once it gets past the hesitation.

Pondering this further, how does installing cams affect carb settings in general? Are there certain rules or general guidelines that can be followed when changing cams?

I'm wondering if maybe my carbs were tuned well for a stock cam but the increased lift and duration put more vacuum on the carbs across all rpm ranges, exacerbating any weak/dead spots that may have been present but unnoticeable with stock cams.

Jekyll86 wrote: From what I gather, they are installed the same way the KZ700/750 cams are installed. Cam timing adjustment shouldn't be needed unless the head is milled.

If the bike was out of time, would the symptom present across all rpm ranges? The bike idles fine and hauls like a boss once it gets past the hesitation.

There at multiple holes[3] on the Hyvo chain KZ650/750s.


.

Jekyll86 wrote: Pondering this further, how does installing cams affect carb settings in general? Are there certain rules or general guidelines that can be followed when changing cams?

I'm wondering if maybe my carbs were tuned well for a stock cam but the increased lift and duration put more vacuum on the carbs across all rpm ranges, exacerbating any weak/dead spots that may have been present but unnoticeable with stock cams.

Cam timing has a big effect on carberation requirements.


.

Wonder about raising the clip on the needles to the 5th groove..... maybe get a second opinion before going to that trouble though.

I'm running GPZ750 cams on my 810. I am running the stock VM24 carbs. When I swapped in the cams the bike needed no additional tuning at all. It simply moved the power up on the RPM scale and pulled a pulled harder above 6000

OP needs to check cam timing.


.

I'll check cam timing and let you know what I find.

I'm pretty sure my cam installation was correct, but I'm definitely not immune to mistakes. If it is off, both the intake and exhaust cams will be off by one tooth, but off together. I will have time to check in the next day or two.

When checking cam timing, should I use degreeing wheel or just follow the cam installation instructions from the manual? The cam sprockets are not slotted and the cam bolts show no evidence of tampering (cam bolts are still held by the white thread lock used from the factory). However, I found a couple of articles that suggest checking Cam degrees even on stock cams due to variations from factory setup and cam chain stretching. Supposedly, cams can be off 2-3 degrees from the factory and timing can get better/worse depending on which side the cams were originally off.

Any thoughts?

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.


.