GPz1100A2 afterfire

A couple more.

What condition is the battery in?  Is the charging system working correctly?  Put a voltmeter on the bike and see if it's charging the battery.

The TPS on the throttle body maybe need some adjustment. It´s a little tricky task because a little tiny mis-turn into the wrong direction can go into the way of too lean or fat A/F ratio.

Some technical trouble shot and training guides.

 

rename the DFI Technical Training Notes.rar.pdf to DFI Technical Training Notes.rar to uncompress the "pdf" file.
Had to do the trick due to the file limit (10 mb).

Thanks guys.

Highway Magician - new battery installed about 4 months ago and its been on a trickle charger ever since. Will check out the charging system though.

Scirocco - Thanks for the pdf - I love the first pages of explanation of the DFI system, very clear.

Once I the new fuel pressure regulator is delivered from the U.S. I'll bang it on and check the header temps too. We've just been put back into covid lockdown here in Australia so its hard to get parts at the moment.

 

OK, been a while as I've been waiting for parts to come from the US. 

Fitted a new pressure regulator.

Doesn't seem to have made much of a difference. Still loads of afterfire and won't tick over on its own. It revs out OK above 3,000 rpm, just bogs when it comes back down

Ran it for a couple of minutes and measured pipe temps
1 - 176
2 - 201
3 - 220
4 - 124

So 4 is definitely cool.

Only other thing its started doing now is the control box is flashing long, short, short - which is air temp sensor. It wasn't doing that before.

I've pulled the sensor and its testing OK. Wires aren't broken as I've tested with a multimeter.

I've ordered a replacement air temp sensor in case its that, but I'm not holding out much hope.

Might be tricking trying to adjust the TPS at this stage as its not ticking over very well and I'll probably end up making it worse.

I guess only other thing is completely pull all the injectors again and check they're not blocked or sticking.

 

Has valve-lash been checked recently, and adjusted to meet spec. tolerance?

How did the bike run before you took the engine apart?

wrote:

Has valve-lash been checked recently, and adjusted to meet spec. tolerance?
 

He covered that at the beginning of the thread:

Only thing I can think of is valve clearances are out (although these were set within specs a few months ago and the bike has done hardly any miles)

Thanks guys, bike was in a bad way when I got it, so didn't run well. Its also had loads of parts reconditioned and swopped over from a parts bike I had.
Work I've done on the motor so far.

Rebored and honed cylinder with new wiseco pistons and rings
Lapped valves (leak tested) and new valve seals
New camchain
Valve clearances set
Injectors cleaned and checked working
New fuel return valve
Rebuilt petcock
All fuel hoses replaced
New fuel pressure regulator
Original fuel pump - but it seems to spool up and pump
New coils and HT leads
New battery
Air temp and engine temp sensors checked as working
Leads and plugs replaced on injectors and TPS
Injectors tested with a bulb probe

I'm thinking its something to do with spark or fuel/air delivery on number 4 as that cylinder is running cooler so must be where the unburnt fuel is igniting.

If it was a fuel pressure problem or sensor problem, surely it would affect all cylinders equally?
 

Get one of these to verify spark.
www.supercheapauto.com.au/p/toolpro-tool...-checker/394392.html


 

I didn’t see “replaced intake boots” on your list, but I’ve got to believe you installed new ones at some point, right?

Not replaced the intake boots yet. Although they are pretty flexible.

Going to check for air leaks once I can get the thing to tick over evenly

OK, so bit of an update.

After many hours of stripping wiring harnesses down, checking connectors and pulling out all the throttle bodies and injection set up. I've found these potential causes.

1. Control box was throwing up check 'air temp signal test' error code.
Air temp sensor and all the wiring checked out. Swopped out the control box with a spare and the fault cleared.

But this was the biggy...

2. Discovered an air leak on a couple of the rubber head inlet mounts.
These were right underneath - didn't show up on my first leak tests.

It turns out I had replaced the mounting bolts with slightly longer bolts and these were bottoming out before the mounts were fully tightened against the head. But only on the bottom, as the oil pipe stays had just enough thickness to allow the top bolts to fully tighten. Which is why I couldn't find the air leaks when I was spraying around the top of the mounts.

I was spewing when I found this out as it seems so simple now!

Also there was some slight cracking inside the mounts which would have increased the leaks.

I've ordered some new rubber mounts, so hopefully this will stop the afterfiring and lean running.

I guess it pays to get the simple stuff double checked first!

Will report back with findings once I get the new mounts fitted with shorter bolts - fingers crossed.