When open throttle up pass 3k engine Bogs or Dies Help!

Not sure what name brand pod filters you have...
The cheap ones have a shoulder (see pic) and if the pods are pressed all the way onto the carb, will severely restrict air-flow to the corrector jets and vent holes.

 

H.

Cheap pods problem! See, even an old dog can learn something new. Never have dealt with cheap pods.                         Let us know if that helps! If not, need  to clear up a few details to narrow it down.

Hi an update on this.Waiting on a set of new K&N air filters.as the ones i have got told to put in bin.Also Changed out the spark plugs for B8ES non resistors plugs as said.
clean carbs again. Tried starting the bike . Started with a bit of choke waited. The choke of ticking over with no choke at 1000rpm ok. 1/half turns out on all four carbs.
rev the throttle only gets to about 3500rpm then starts to die.. stopped the engine took the plugs out and all four are black and wet..
I know i am waiting on pods .but do you think my main jet is to big or small.?

Have you tried dropping the needles a notch and see what effect it has (it appears rich as it goes onto the needles)

Harris1975 wrote:

Hi an update on this.Waiting on a set of new K&N air filters.as the ones i have got told to put in bin.Also Changed out the spark plugs for B8ES non resistors plugs as said.
clean carbs again. Tried starting the bike . Started with a bit of choke waited. The choke of ticking over with no choke at 1000rpm ok. 1/half turns out on all four carbs.
rev the throttle only gets to about 3500rpm then starts to die.. stopped the engine took the plugs out and all four are black and wet..
I know i am waiting on pods .but do you think my main jet is to big or small.?

 

Correct plugs for a stock KZ650 engine are B7ES. Stock jets are 102.5 main and 15 pilot (with air box fitted) All of this info is in the factory service manual.

Plugs look really rich. Did you renew the choke plunger seals? If not the engine will run rich at all rev ranges, even at idle.

You also have not mentioned fuel level in the float bowls, this should be confirmed by the wet tube method. See FSM.



 

Hi thanks. The carbs got sent off for a rebuild Vapor blasted and new parts. I hope i think theses all got change out..Also did buy floor tube and check all levels from manual.and measure the float height.. So Next i think change the needle height what wookie58 said..but still looking into this. Also thinking. Is there a place or someone who can take my bike and get this running right. I am in the reading range . Will pay. Don’t think i no anth on the carbs jetting.

With any engine running issues you have to go back to the four basics - fuel/compression/spark/timing
If you have any issues with one of those items the engine won't run correctly.

If your in the jet size ballpark and you have good compression numbers but your plugs are black/wet then its either too much fuel (leaky choke plunger seals) or lack of spark.
Have you checked spark length/power?
Also check to see that the ignition advancer is functioning properly with a timing light (3K RPM bog) as that is just about where full advance should come on.

Your hot compression numbers for a 650/750 are a bit on the low side, not terrible but low (+180 PSI would be better)
Have you checked the valve clearance lately? Valves close up on these heads pretty easily especially after a rebuild.





 

You need an old school shop to have engine or carb work done. If you can't plug it into a laptop modern bike shops are pretty much lost and often makes things worse not better. Seen it several times with bikes that turn up here.
I'm by Brands Hatch if its of any use and would be happy to take a look for you. There's around a dozen or more SE UK Z owners that bring there bikes round to get sorted. I'm not a bike shop but have been riding, fixing, tuning Z's for over 40 years.
Currently own 2 650's as you can see from my stable pictures below.