Burned Exhaust Valve
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Author:  rmr [ Mon Jan 05, 2015 2:21 am ]
Post subject:  Burned Exhaust Valve

Greetings one and all,

I'm a new member from the U.S. and have had an ongoing challenge with my '92 907ie. With 20,000 miles on the clock about 18 months back, I took the machine in for a valve adjustment only to learn the exhaust side guides were shot. Replaced guides, seals, seats. Everything went back together and it ran great for about 2,000 miles. Then it started stalling and would not idle. Took it back to my mechanic for trouble shooting. Did a leak down test to discover (eventually) horizontal cylinder exhaust valve/guide shot. Valves/guides/seats/seals now replaced with new and bike is now back to my garage, starts right up and sounds healthy. Injectors checked for proper flow. Based on discussions here, I bought and installed a new FBF Stage 1 chip. Pulled out the existing older FBF stage 1 chip installed by previous owner some years ago. The airbox is opened up with reusable filter and have staintune slip-ons installed. I should mention I have put on about 8,000 miles on the bike prior to valve work without any issues.



Author:  paso750 [ Mon Jan 05, 2015 11:19 am ]
Post subject:  Re: Burned Exhaust Valve

Did you do an emission/gas analyzer test ?
If you really want to know what`s going on with the fuel mixture you`ll have to get one of these http://www.ebay.com/itm/O2-SENSOR-BUNG- ... b4&vxp=mtr
weld it in the exhaust header then take the bike to a shop that has an AFR meter or borrow one if you know someone.


Author:  rmr [ Thu Jan 08, 2015 3:00 am ]
Post subject:  Re: Burned Exhaust Valve

Yes, excellent idea G, thanks. The local dyno/fuel mapping guy is now back up and running as he was unavailable for quite a few months. I will be bringing the machine in for an analysis in the next couple of weeks which should let me know if the fueling is lean. If it is, he will likely suggest a Power Commander. I don't suspect they can provide the wiring hook-ups so would have to solder up the connections. But, with most things I have been through with this machine, one step at a time and remain patient.

Author:  rmr [ Sun Jan 18, 2015 6:01 pm ]
Post subject:  Re: Burned Exhaust Valve

Okay so I took the beast to a guy yesterday who hooked it up to a dyno and with a probe, confirmed the motor is running way lean. His program shows about 16 to 1 air to fuel which he say is lean enough to burn valves. He confirms it should be around 13 to 1 at the leanest. Does anyone have experience with getting a power commander to hook up to the fuel injection harness? Does the 907 run Bosch or Marelli FI?

Author:  900streetfighter [ Sun Jan 18, 2015 6:32 pm ]
Post subject:  Re: Burned Exhaust Valve

Maybe ask on the 851/888 forums which run similar marelli brain. Dont tell them you ride 907 tho. :lol:

We have P7 brain, most 888 if not all, have P8, basic difference being P8 can be tuned for seperate cylinders.
Connector block is same tho. Someone on here fitted a P8 to 907 if you do a search maybe some help there.


Author:  higgy [ Sun Jan 18, 2015 6:36 pm ]
Post subject:  Re: Burned Exhaust Valve

907 is a Weber-Marelli IAW P7 ECU.

Weber-Marelli IAW P7 ECU

851, 907 and early 888's up to serial number 000508.

P7s have no rear cylinder offset map. ( not exactly true, it was never utilized due to the limited memory of the P7 which is solvable by the addition of a daughter card)

Weber-Marelli IAW P8 ECU

Later 888's from serial number 000509, 916 Strada, 916SP, 916SPS, 996SPS

Note: The P7 and P8 ECUs turn-on the fuel pump once they initialize via a relay.

The procedure for setting up the P7 is here in the documents folder.

you will need two of the documents found there, The TPS adjustment procedure and the CO trimming procedure.

You can't do the trim until the TPS is adjusted properly

It is often stated that the CO trim cannot be set without an exhaust analyzer, not exactly true but it does take an experienced ear to get it right. Anyone experienced enough to accurately do dyno tuning should be capable of getting it right

Author:  900streetfighter [ Mon Jan 19, 2015 9:43 am ]
Post subject:  Re: Burned Exhaust Valve

I run a similar set up to yours, 2:1 / K+N / open airbox with a Baines chip, I've never had the mixture checked but the bike runs fine and I've done 50,000 miles without problems. 16:1 seems way out, perhaps something else is causing your bike to run lean. Brad the Bikeboy has some good info on our systems.

Author:  rmr [ Mon Jan 19, 2015 4:58 pm ]
Post subject:  Re: Burned Exhaust Valve

Good info here. Thanks all for your thoughts.

Yes, it seems something has caused this lean running and I feel to some degree, I will be treating the symptom not the cause. The Staintune slip ons are fairly new but I don't believe that could make the lean running issue so pronounced. Some say the low quality of our current gas can also negatively affect the air/fuel ratio. Something else perhaps?

Author:  higgy [ Mon Jan 19, 2015 9:53 pm ]
Post subject:  Re: Burned Exhaust Valve

Staintunes by themselves will not do it.
The number one cause is the TPS sensor and new ones are readily available from California Cycleworks. Fuel pressure regulator can also be an issue as can any of the other sensors, temp, airtemp MAF on down the line right down to the injectors may need cleaning

If you are computer saavy there are programs to replace the very expensive and hard to find Mathesis tester to allow you to read the data directly for the price of some cheap adapter cables from ebay

Author:  nickta [ Tue Jan 20, 2015 12:55 am ]
Post subject:  Re: Burned Exhaust Valve

higgy wrote:
If you are computer saavy there are programs to replace the very expensive and hard to find Mathesis tester to allow you to read the data directly for the price of some cheap adapter cables from ebay

Lo Higgy.

I guess more information is required? You were looking a little while back for the Mathesis tester, and missed out. Do you have any links and/or information regarding which cables and the software to suit?



Author:  higgy [ Tue Jan 20, 2015 10:35 am ]
Post subject:  Re: Burned Exhaust Valve

software is here


More in depth info here if you feel the need :fart:

Cables can be found on fleabay You will need both.


Author:  rmr [ Wed Jun 17, 2015 4:59 am ]
Post subject:  Re: Burned Exhaust Valve

So the ongoing lean running issues I have not yet sorted out. Although due to the excellent weather we are having, I am very motivated to get the 907 back on the road.

The TPS was apparently not properly adjusted so that work was completed. I took it back to my dyno guy who confirmed it is still running as lean as before. Roughly 16 to 1. Way too lean. The trim is set about right he confirms. So thinking about what else could cause this issue. Have checked and not found any air leaks anywhere. Injectors flow tested okay. I now have the bike apart and am thinking to change over the MAP, ATS, WTS and dang, while I'm at it, the fuel pressure regulator. Geez, I might throw in my spare fuel pump although a fuel pressure check should confirm the proper service of both pump and regulator. What am I missing as possible causes? I had read in the forum here some years back an Aussie bloke spent thousands trying to pin down a rough runner only to remove the MAP air line into the air box and plug it with a cigarette butt. Sounds like that worked pretty well.

Any more thoughts on this are appreciated.

Author:  Tamburinifan [ Wed Jun 17, 2015 8:26 am ]
Post subject:  Re: Burned Exhaust Valve

Opened airbox as you have gives engine quite a lot of more air.
On a carbed w open lid you go up two sizes in jet size.

Original box is two snorkels w like an inch diameter.
Try to gaffers tape down air inlet quite a lot and see what the
dyno tells you.

Or, the best & obvious, get a chip f your setup.
Not sure but I think FastbyF stage 2 is for free breathing bikes.

Author:  higgy [ Wed Jun 17, 2015 10:30 am ]
Post subject:  Re: Burned Exhaust Valve


Info on JPDiag and GuzziDiag and which cables actually work out of the box :smoke:

Author:  rmr [ Tue Jun 30, 2015 1:50 am ]
Post subject:  Re: Burned Exhaust Valve

Well I spent yesterday working on the beast. Closed up the air box. Installed new FBF chip. Checked the resistance of the WTS and the ATS. They appear okay from what info I have on the expected resistance at around 80 degrees. TPS has been set. New fuel lines. New fuel pressure regulator. Have the tank open and will change fuel pump, clean screen, new fuel filter. Have removed the tube from the airbox on the MAP and partially plugged off the tube to simulate a cigarette filter as mentioned in the forum here some years back. Will install new lines inside tank from pump through filter. I noticed quite a bit of crud in the gas when I emptied it out through the drain plug although the symptoms in my experience, do not really indicate a clogged filter or starved fuel pump. It could be ECU perhaps, but that would be about impossible to pin down without some software diagnostic tools. Should be ready to re-test in a couple of weeks. Will post my success or failure then.

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