Stumble on 99 yosh slip on, PC ii, stock box w k&n

[Jdesorme]

Looking for some help

Bike surges and stumbles below 4k. I have tweaked the map w assistance of power commander.

Using their recommended map w yosh slip on that is on their web, we tweaked below 4k by enriching mixture. Some improvement but nit cured and I'm concerned because I am 12% north of the power commander map. Just has me concerned that I've gone the wrong direction.

Any advice, wisdom, proven maps available?

 

[dadofthree]

What's it run like with the PC disconnected

 

[karnage]

get it on a dyno.The maps that dynojet has a base map and really dont do much according to my tuner.Its a starting point.Try unplugging it or reinstalling the map maybe.

 

[Strife]

Custom map only way to go. there is no magical map you can download and it work 100% for your motor. EVERY motor behaves differently. Some more then others.

 

[dadofthree]

Before you drop $250-$350 on a dyno tune, drop the PC and see how it runs. I'm thinking your mods had little to no affect on your bikes performance. You've got to remember you're working with a 12 - 13 year old bike. How many miles ? Has it been maintained well ?

 

[Jdesorme]

Maintained well and has 22k on it. The tune seems to help but just seems WAY to rich by the numbers. If I zero out offsets in PC (according to them) it's the same as disconnecting right? Just trying to save some time on diagnosing.

Rode 100 miles tonight. 3500-4000 is awful which is where I cruise based on MI lower speed limits. It seemed better last night but who knows?

 

[dadofthree]

You might be an old pro that builds motors or may have just bought your first Busa and know very little about them.

Fuel, Fire , Air.

Busa's run a little rich. IMO Yosh Slip-Ons wouldn't make a difference in your bikes performance.

You say you know the bikes history and it's been properly maintained. The easy things to check or replace are plugs and air filter. You say it's running rich and stumbling down low so I'll assume you're getting fuel albeit too much.

Plugs could be fouled now and need changing or cleaning. I would seriously drop that PC or have it dyno tuned by a competent tuner.

Harder fixes are adjusting valves and throttle body sync.

I know you're not riding around with the fast idle operated.

Looking forward to seeing what the fix is. Many possibilities.

 

[Johnnycheese]

the problem with pc2's is you are not changing injector pluse you are changing the sensor value to make the ecu change thing.
ie if you map at 90 degrees and then run at 40 your sensor will already be maxed

 

[2Wheels2Live]

Maintained well and has 22k on it. The tune seems to help but just seems WAY to rich by the numbers. If I zero out offsets in PC (according to them) it's the same as disconnecting right? Just trying to save some time on diagnosing.

Rode 100 miles tonight. 3500-4000 is awful which is where I cruise based on MI lower speed limits. It seemed better last night but who knows?

Like DO3 said, busa's run slightly rich anyways, and the mods you have on there aren't going to affect breathing a whole lot. You would most likely be just fine with those mods and no pc. A SLIGHT bit more fuel would'nt hurt, but you should not need near the fuel you're giving that bike. Pull the pc off and try it stock. The pc could be bad/have a bad ground (they do fail), or the map could just be overkill for your situation. When it comes to fueling with minor mods like yours.....less is more
More fuel doesn't automatically equate to more power.....

 

[Jdesorme]

Well it was faster to zero out offsets in the PC map. Took all values to zero for all throttle positions from idle to 4k rpm.

Rode 50 miles after that and it's sooooo much better. A little stumble around 2700 but minor. I'm going after plugs next to satisfy my curiosity.

I think I'm there about dumping PC. Just need to get some time to remove and eBay....

 

[dadofthree]

 

[Jdesorme]

Well the 2500-3000 stumble was too much

New plugs and removal of PC2 all together still has not cured the bike. It's close but not perfect.

Any other ideas to check/test?

 

[jphilipson]

I think it's the k&n over oiled. Is it a brand new k&n out of the box? Has it been re-oiled? This is just the type of problem you see when one is over oiled. Clean the filter and re-oil it very lightly and see if that helps.

 

[Jdesorme]

Serious? I just don't see how a air filter or any facet of a filter could cause an isolated RPM surge or stumble. The bike has 3k on the filter already.

This seems to be common on these bikes. Does anyone have a bike they have cured? If so, is there a hit list of items to check? Sensors or metering?

 

[Jdesorme]

anyone have any information to help? I have the bike torn down to change the color this winter so I have access to every component. Seems like this is VERY common issue with Busas - has anyone coordinated a root cause matrix so we can just go down the list to resolve our individual problems with surging on these bikes.

I am considering doing the airbox mod and Par valve removal - but with the thing surging as-is (even with PCII removed) - I am not sure about doing anything else that may compound this surge issue.