Looking for help
Gpz 750 turbo has developed a surge at 3500 or misfire
When off throttle cruising ,it pulls boost strong and doesn't do it when moderate throttle is given, only when the throttle is almost closed and cruising at 3500rpm
Just swapped out the TPI from another turbo gpz and still the same
Brief history, bike was sitting for almost 20 years
And it now has a header
Bike was not showing this issue the first week I started riding it,it just started doing it and its now continuous
Fuel pressure shows only 32psi and when the throttle is opened to 3000rpm it stays at 32 and almost dips below 31 when it reaches 3000rpm
Feels like a misfire or surge at 3500rpm when off throttle cruising
Re: Feels like a misfire or surge at 3500rpm when off throttle cruising
Is it in race mode? ...and make sure your check valve is clear. ...and clean fuel filter.
Re: Feels like a misfire or surge at 3500rpm when off throttle cruising
Not in race mode
Im new to this bike ,where is the check valve and how does it affect the surging at that particular rpm.and closed throttle cruising
Im new to this bike ,where is the check valve and how does it affect the surging at that particular rpm.and closed throttle cruising
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750turboguy
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- Joined: Tue May 17, 2016 12:17 am
Re: Feels like a misfire or surge at 3500rpm when off throttle cruising
My God I am so sick of people suspecting the throttle sensor or other big item. Its been forty years now people.
How many times have I posted this?..... Lets move on........
ITS NOT THE SENSOR!!!!! Its not its not its not....stomping up and down now like a four year old.
Okay...I'm over it......
You need to go through the WHOLE bike. Especially if it's been sitting for a long long long long long long long long time.
You need to replace EVERY rubber vaccum hose you can find. Yes, and even the little short one that connects the boost sensor
to the airbox. Dont just look at them. REPLACE THEM!
Next you might want to actually drop the air box and look at and remove the rubber throttle body
manifolds to inspect for dry rot, cracking and leaking. How's the battery? If it's old...replace it. Dont charge it. REPLACE IT!
These bikes run crappy even if only ONE cell is a tiny bit weak. Did you check the tank? What's it like inside? Flush it out if
its rusty and replace the fuel filter. And remove the fuel pressure relief valve and make sure its rust free and moving up and
down smoothly. There are instructions on here for how to pop it apart and clean it. Check your ground connections. I believe there are three. Under the tank is a ground wire near the coils with a bolt to the frame. Remove the bolt, hit the eye on the end of the wire with a wire brush. Scrap some paint from around where eye makes contact with the frame. There is another ground near the fuse box and a third above the clutch in plain view. Do all three of them. Unplug and plug in any connectors you can find several times to scrape the contact pins clean. They corroid over time.
Now that you got it running you get to spend three hours readjusting that throttle sensor.
How many times have I posted this?..... Lets move on........
ITS NOT THE SENSOR!!!!! Its not its not its not....stomping up and down now like a four year old.
Okay...I'm over it......
You need to go through the WHOLE bike. Especially if it's been sitting for a long long long long long long long long time.
You need to replace EVERY rubber vaccum hose you can find. Yes, and even the little short one that connects the boost sensor
to the airbox. Dont just look at them. REPLACE THEM!
Next you might want to actually drop the air box and look at and remove the rubber throttle body
manifolds to inspect for dry rot, cracking and leaking. How's the battery? If it's old...replace it. Dont charge it. REPLACE IT!
These bikes run crappy even if only ONE cell is a tiny bit weak. Did you check the tank? What's it like inside? Flush it out if
its rusty and replace the fuel filter. And remove the fuel pressure relief valve and make sure its rust free and moving up and
down smoothly. There are instructions on here for how to pop it apart and clean it. Check your ground connections. I believe there are three. Under the tank is a ground wire near the coils with a bolt to the frame. Remove the bolt, hit the eye on the end of the wire with a wire brush. Scrap some paint from around where eye makes contact with the frame. There is another ground near the fuse box and a third above the clutch in plain view. Do all three of them. Unplug and plug in any connectors you can find several times to scrape the contact pins clean. They corroid over time.
Now that you got it running you get to spend three hours readjusting that throttle sensor.
Re: Feels like a misfire or surge at 3500rpm when off throttle cruising
the fuel regulator is a turbo 1:1 type? I think it should be increasing pressure as boost goes up & from what you say it seems a little static, the stuff turboguy says is all good however the earth by the coils is a sham it runs up into the right side of the fairing & finishes as a empty plug next to a white/blue (to be used as a accessory plug) so you could ignore that one.
good luck, I know you have good knowledge on kwack engines but like most (including me) the help over fuel injection & electric problems off this site is priceless
good luck, I know you have good knowledge on kwack engines but like most (including me) the help over fuel injection & electric problems off this site is priceless
Re: Feels like a misfire or surge at 3500rpm when off throttle cruising
I would go and back and find grey wire going in the computer and pull it and ride it around and see if its better.I f not no big deal put wire back in and keep looking.