Cold Start stalling

[sixpack577]

Those 2 visible pistons show no witness marks on them, where valves would have contacted them, which is the only way valves can bend, from jumping timing, and if the bike ran well once warm, the engine was in time.
Did the bike smoke when running?
It looks like the valve guide seals were leaking on at least 2 of the cylinders.

 

[Dafeimao85]

Those 2 visible pistons show no witness marks on them, where valves would have contacted them, which is the only way valves can bend, from jumping timing, and if the bike ran well once warm, the engine was in time.
Did the bike smoke when running?
It looks like the valve guide seals were leaking on at least 2 of the cylinders.

Hi Sixpack577

They are still in midst of taking the engine apart

The bike only smoke when warming up. After it warm up the smoke stop. I can smell petrol during that time.

Thanks for your analysis

I am concern about the valve because they told me the valve couldnt seat back. So valve guide seal will cause the same issue?

 

[sixpack577]

Hi Sixpack577

They are still in midst of taking the engine apart

The bike only smoke when warming up. After it warm up the smoke stop. I can smell petrol during that time.

Thanks for your analysis

I am concern about the valve because they told me the valve couldnt seat back. So valve guide seal will cause the same issue?

Bad valve guide seals can leak oil into the cylinders...and cause smoke on start-ups.
Carbon build up on the backs of the valves and/or valve seats can prevent the valves from closing too.

 

[Dafeimao85]

Thanks bro for the info.

Learn something new again from you!

Riding the bike for 30k mileage only to realize I know nuts about hayabusa

 

[Dafeimao85]

And so I receive the update

Work shop suspect that the engine cleaner addictive I pour into the fuel tank dislodge the carbon and result the consequence

Piston 1 & 4: exhaust valve unable to full close due to carbon deposit

Piston 2 & 3: carbon stuck behind the valve resulting the valve exhaust valve unable to full close and hitting intake valve

Total damage 7 valve. The rest are able to clean up and re use.

The only luck I had was piston was not damage by the valve.

I was told by the work shop that the engine cleaner addictive should not be use on extreme high mileage engine or else my bike would be a classical result. I was told that to have use it every 5k miles. For a high mileage engine valve clearance is the only way

Is this true? I refer to the bottle packing, it did mention that should be use every 10k mileage.

I try to maintain a clean engine and end up I blew it

 

[Dafeimao85]

Hi All,

Just to share what happen to my bike.

After extensive rework on engine. With everything re hook.

I still get cold start issue plus c28 and c29 due to workshop did not known stva should not be remove from the throttle body.

Use finger to simulate secondary flapper close still get cold start issue which leave everyone puzzle. As i had replaced the ISC valve and all sympton to ISC valve, did a recheck on isc valve and wiring and all is OK and fuel Pump relay also changed.

So me and the mechanic sit down look thru C40 and C41. So C40 step 2 on the manual mention if wire is OK, faulty ecm.

Look at C41 step 1, I had 12V between ecm to ground which proof wiring is okay.

The solutions then mention replace fuel pump relay which I did, wire are okay = faulty ECM.

So seems like my next and only steps is to replace ecm...

 

[Dafeimao85]

Hi everyone,

Happy 2025

BIG UPDATE! Because all the sensors data is correct. Shop suggest to contact clean every single connector and try start the bike.

Turns out fuel pump relay connector was "dirty" which it's not visible to eyes. Once contact cleaner in. Bike start like without needing warming up the engine.

Spend 1.5k to rebuild engine because of a connector issue... And during this time, shop created new problem.

Shop did not known stva should not be remove from the throttle body. End up throwing c28/c29

Read thru forum that as long as stva stops open will be ok. Did a test ride was okay.

Shop later tried their best to adjust back stva and stp and manage to clear it. However c28 pop up the next day and bike will not Rev pass 4krpm. C29 does not exist.

I open up the air filter box and confirm butterfly valve was wide open. But why won't it Rev last 4krpm? It hesitate at 4k rpm... I am guessing it's because stp still sending a "butterfly valve is still close signal" to ecm and hence ecm restrict the injector spray rate. Is that possible?

Miss out my new year ride because of this. Waiting for shop to re open after their new year breaks...

 

[Dafeimao85]

I hope anyone with sensor problem can take a look at my case for reference...

Sensor problem is really a pain in my ass!