Dafeimao85
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Hi All Happy 2025
Does anyone know if the busa has a limp mode function?
Does anyone know if the busa has a limp mode function?
Question on Gen 2 busa Limp Mode
- Thread starter Dafeimao85
- Start date
No, the Gen1 and Gen2 do not.
Dafeimao85
Registered
I am having a big headache
Why the bike bog at around 4k rpm... Without giving off any error.
Does the ecm detect fuel line pressure. With this symptoms my bets are now on the fuel pump which I recently replaced
I am not sure, as you have had so many issues with the bike, but if the secondary throttle plates have been removed, it will cause it to bog at lower rpms, and run better at higher rpms.
The bike needs to be tuned if they are gone, but performs better with them in.
Dafeimao85
Registered
Ya my bike is getting more and more badass and weird...
I have done almost overhaul and handful sensor replacement.
Sigh... Spend almost 2k for all these yet it still fall sick
I don't know any of the history of your bike, but if you replaced the fuel pump, did you replace the filter? The big plastic piece the pump fits into, not the sock on the bottom of the pump. The Gen2's are getting old enough the filters are failing. I've seen it more than once. If the bike recovers from the bog and then revs fine, the filter likely isn't the problem.
Dafeimao85
Registered
Hi Dennis and all.
I did not replace the metal strainer. It was not sold separately. Did saw on ebay for after market type. FYI gen 2 2014 onwards the fuel pump metal strainer is on the top (same like gsxr 750) No longer on the side.
So I just open up disassemble make sure everything is okay and reassemble and I also change back my old pump pressure regulator.
By chance I forget to put in 1 O Ring Seal on the pump discharge, which result unable to start. I then re assemble once more. The abnormality I notice is the pump body is hot with that few seconds of priming and running for start. If the pump is unable to suck in any fuel, I could understand. But the O ring I forget to place back was on the discharge. It should just continually recirculate within the fuel tank. The pump should not be hot for that few seconds of running.
Then I took the bike for a test run and was able to Rev past 8k rpm easily. Then after 20miles, it suddenly bog down to limit at 3k rpm.
Hence I believe the fuel pump had sort of partial malfunction and result in high temp which then cause a vapour lock or the suction strainer is badly plug but from the look of it which I don't think so.
I had contacted Quantum Fuel Pump and explain the situation. They send me a new pump immediately. I wonder is it a malfunction that they knew.
Well if thats the case, it means I need to start save up for a Suzuki pump before the replacement pump fail...
Old bikes that have sat around un-ridden or have been left out in the weather can have a multitude of issues. I read your other posts @Dafeimao85 and I see you discovered wiring connectors that were corroded, a classic sign of a bike left out in the weather. Unfortunately that was only discovered after you went and replaced parts thinking they were at fault. Outdoors insects can make homes in unusual places too, blocking up breathers and causing many issues. In the old days I saw a bike with a fuel issue that was caused by an ant crawling into the air-box then down a pressure equalization hose to a carburetor and effecting the float level. It was only found by pure chance.
Your shop also found untold carbon buildup on the valves, (from my experience) caused by running an engine on low grade fuel like 91 and or just putting around town and never taking the revs up high. The same principle applies to any engine, they need to get hot and fast to burn up and blast out the carbon. How you do that in tiny Singapore I don't know but I regularly run in a gear lower than needed, just to keep the engine at a higher RPM. It's a shame you've had these problems, the Gen-II is a super reliable bike, but even the best will have issues if not cared for over time. Let's hope you're at the end of the issues soon. Next time follow the golden rule, Low Mileage
Your shop also found untold carbon buildup on the valves, (from my experience) caused by running an engine on low grade fuel like 91 and or just putting around town and never taking the revs up high. The same principle applies to any engine, they need to get hot and fast to burn up and blast out the carbon. How you do that in tiny Singapore I don't know but I regularly run in a gear lower than needed, just to keep the engine at a higher RPM. It's a shame you've had these problems, the Gen-II is a super reliable bike, but even the best will have issues if not cared for over time. Let's hope you're at the end of the issues soon. Next time follow the golden rule, Low Mileage
Dafeimao85
Registered
Hi Oz22,Old bikes that have sat around un-ridden or have been left out in the weather can have a multitude of issues. I read your other posts @Dafeimao85 and I see you discovered wiring connectors that were corroded, a classic sign of a bike left out in the weather. Unfortunately that was only discovered after you went and replaced parts thinking they were at fault. Outdoors insects can make homes in unusual places too, blocking up breathers and causing many issues. In the old days I saw a bike with a fuel issue that was caused by an ant crawling into the air-box then down a pressure equalization hose to a carburetor and effecting the float level. It was only found by pure chance.
Your shop also found untold carbon buildup on the valves, (from my experience) caused by running an engine on low grade fuel like 91 and or just putting around town and never taking the revs up high. The same principle applies to any engine, they need to get hot and fast to burn up and blast out the carbon. How you do that in tiny Singapore I don't know but I regularly run in a gear lower than needed, just to keep the engine at a higher RPM. It's a shame you've had these problems, the Gen-II is a super reliable bike, but even the best will have issues if not cared for over time. Let's hope you're at the end of the issues soon. Next time follow the golden rule, Low Mileage
Thanks for the following of my busa story
Yea, Singapore road limit speed is only 56mph on the express way and 31mph on the non expressway road.
So usually we ride to Malaysia where they have less speed camera and long distance road. There is where I always get my busa to 186mph
Reliability was the reason why I brought a busa. But so many unfortunately case happens.
I hope once the fuel pump replace and that's the end and let me allocate the budge to modification.
The budget to change a steering damper, r1 fast throttle and brocks clutch are now use for the repair
Dafeimao85
Registered
OK all,
Update. So I have solve my stva issue. I took the bike for a ride and I confirm there is no limp mode for busa even though the service manual mention fail-safe mode and stva is under 1 of the fail-safe item.
So now I cannot Rev past 5k rpm and my fi is not light up. I guess I have to tackle the fuel pump again!
Will update thread in fuel pump replacement.
Update. So I have solve my stva issue. I took the bike for a ride and I confirm there is no limp mode for busa even though the service manual mention fail-safe mode and stva is under 1 of the fail-safe item.
So now I cannot Rev past 5k rpm and my fi is not light up. I guess I have to tackle the fuel pump again!
Will update thread in fuel pump replacement.
Dafeimao85
Registered
Hi Oz22,
I decide to redo all the test once I am free.
Base on manual and sympton, I am 100% definitely sure it's from the fuel system. It felt like fuel starvation.
Quantum fuel pump system send me a new pump and I have replace the O ring. I am left with 1 I did not replace which is the pump discharge filter.
@Dustin02 did told me the part number 12. I only did a back purge with air gun. This round before I redo everything. I will take out the regulator and use carb cleaner to clean and back purge and then rinse with petrol.
Dafeimao85
Registered
The reason I did not replace the discharge filter (mesh type) and only replace the suction strainer (paper type) is because the strainer is more fine then the filter.
On the gen 1 it's reverse (suction mesh, discharge paper) which I understand that dirt can easily pass thru mesh and clog up the paper.
Hence I was very reluctant to replace my gen 2 filter. But since my busa is showing this sympton. I will do a cleaning and if I can Rev past the 5k zone, I will then order and replace a filter.
On the gen 1 it's reverse (suction mesh, discharge paper) which I understand that dirt can easily pass thru mesh and clog up the paper.
Hence I was very reluctant to replace my gen 2 filter. But since my busa is showing this sympton. I will do a cleaning and if I can Rev past the 5k zone, I will then order and replace a filter.
Dafeimao85
Registered
Hi All,
Finally solve. It was part 12 of the the fuel pump pressure regulator strainer.
Retest everything with flying colour but since part 12 is the only item I did not replace, I out of desperation soak part 12 with 2 cans of carb cleaner.
Now my busa roar with power!
After 4 months of troubleshooting and spending. Finally my busa alive again.
Bumblebee
Donating Member
I hate to say this....but, it's something simple that causes issues sometimes......
Dafeimao85
Registered
Yes
I still dun understand why my flow test can pass. I do not have a pressure gauge so I was unable to conduct a pressure test.
And seems like the filter was clog up very bad or fuel tank is very dirty. Even with the 2 cans of carb cleaner didn't work very well. Today test ride, at around 100 miles and it start to bog again at 8k rpm.
I will buy the part number 12. Empty out the petrol and rinse the tank, place new part 12. Hopefully this is the last time...
Dafeimao85
Registered
Haha
The test ride was positive. Can roar with alot of power. But bog again after 100miles. I guess carb cleaner unable to resolve the issue. I will replace the strainer.
Side note @Dustin02 was the GOAT to the issue! He mention part 12 in the very first of my thread 3 months back. I thought using a air gun back purge would have solve the issue. Now with carb cleaner also useless. I guess I really under estimate this small little strainer screen and the suction paper filter can do.
In my understanding, paper filter should have and capture the most fine carbon.
Bumblebee
Donating Member
Chasing gremlins can be very frustrating.......
Bumblebee
Donating Member
One thing about having a bike that's been around for a long time is that anything that can happen probably has and other people have dealt with it already......
Sure makes it handy when you do have an issue......the only downside is that it's hard to diagnose most issues over the internet....
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