2000 GTX bogging @ 3300-3800rpm

[RyanNZ]

Hi all,

I've recently rebuilt the 951 engine and carbs in my 2000 GTX and put it in the water for the first time yesterday. Idles well, has good top end, however if you have the revs sitting anywhere between 3300 - 3800rpm and then gun the throttle, it'll bog down and die within a few seconds unless you let off the throttle. Any ideas? Have replaced all fuel line and cleaned out fuel selector. Could this be an accelerator pump issue?

 

[racerxxx]

When you rebuilt the carbs did you use genuine mikuni hits as did you replace the needle as seats? Did you check the pop off pressure?

 

[mikidymac]

We need to know as racerxxx said.
Also verify the accelerator pump is squirting. And the selectors don’t typically survive cleaning and will leak air. You need to replace them considering they are 20 years old. I have had good luck with the WSM ones for the 951. The SBT ones are junk.

 

[RyanNZ]

Sadly no, I used an aftermarket kit (gaskets, o-rings and diaphragms only), needles and seats were not replaced. I didn't check pop off pressure as don't have a pump but it's looking like this is something I'm going to have to invest in?

Accelerator pump is definitely squirting, however it's very bubbly/lots of air coming out with the fuel at the squirters?

 

[mikidymac]

You have to ditch those aftermarket parts immediately. You will get nowhere with them.

You have to use only genuine Mikuni parts and replace the needle and seats. Also your accelerator pump should not be pumping any air.

 

[SabrToothSqrl]

Inspect the hoses between the carbs and the accel pump for hairline leaks. Although at the speeds you suggest, 3300 RPM+, I don't suspect the accel pump is the issue.