Throttle response goes down as bike gets warmer. - MVAgusta.net
 
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post #1 of 10 (permalink) Old 07-21-2013, 05:15 PM Thread Starter
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Throttle response goes down as bike gets warmer.

Hi all-

I'm about 4 months into owning an amazing yr 2000 F4, #142 to be exact. The previous owner didn't do any of the regular servicing since it sat mostly for years, so I stripped it down and have replaced the fuel system (all ate up), cleaned injectors, new filters, new oil, plugs, etc etc etc. All with help from posts on this board. The bike is running better now, and a stumble it had around 6000 RPM is now gone.

However, it does have a problem with throttle response everywhere below 5000 RPM- you can crack the throttle and it sounds like it's trying to accelerate up a hill at 20mph in 6th gear- real doggy. Then it hits 5K and everything is OK- still not the most power in the world, but the response is there, it revs up and down freely.

I have recently noticed however, that the bike only really does this AFTER it gets warm. When I start the bike cold, the low RPM throttle response is quite good! I can blip it from 2-3k rpm as fast as my wrist can move. As soon as the bike temp gets over 150F or so, that is when the response gets bad.


Any ideas? Bad temp sensor throwing the map off? That is one idea I had. The other odd thing about the bike is the ECU sticker seal is broken and the ECU chip doesn't look stock- it has no writing on it, except a red paint-pen dot on it. The bike pulls ridiculously hard from 9k to redline... so another thought that I have is this is an aftermarket race chip that has really bad fuel tuning below 5k.

Anyone have some suggestions on what to try, what to look into?
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post #2 of 10 (permalink) Old 07-21-2013, 05:23 PM
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Most F4 1000 bikes exhibit this 4600-5000 rpm stumble. It can be tuned out.

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post #3 of 10 (permalink) Old 07-21-2013, 05:48 PM
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Get a good fuel system such as power commander, Bazzaz, or microtech. I'm in the US and I like the Bazzaz, but the key is going to good dyno turner that can get the air to fuel ratio right at each rpm level.


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post #4 of 10 (permalink) Old 07-21-2013, 05:52 PM
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But it's an early 750. TPS reset? If you can watch the TPS readings, try watching for any wild change as it is warming up on the stand.

I.e: set up multimeter to get TPS reading, start bike up, let bike get nice and warm, see if the reading starts fluctuating.

Just a thought

Is everything else on the bike standard? (i.e. exhaust, etc?). Might be worth trying to look around for a stock eeprom chip?

"You live more for five minutes going fast on a bike than other people do in all their life" #58

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post #5 of 10 (permalink) Old 07-22-2013, 12:32 AM Thread Starter
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When I did the recent servicing I replaced the air filter with a BMC version, and just this weekend I did "the" exhaust mod (removing the packing, putting holes into the chamber). Neither of which really changed the throttle response problem, it has had that since I got it.

I eventually want to go the power commander / other piggyback fuel tuning route and have the bike professionally dyno tuned, but I want to make sure I have it it 'right' first.

I'll try checking the TPS fluctuations as the bike gets warm. I'd like to get a known good EPROM in as well to compare- does anyone hav a suggestion for a vendor that make a chip for better than factory fuel tuning with the exhaust mod and an air filter?

It's not the only problem on my table to fix- I currently need to get new tires on it BADLY as the previous owner thought that, since he didn't put many miles on the bike and it had plenty of tread, the tires were fine. The tires are 11 years old. They are rocks. I picked up some new bridgestone S20's but the rear wheel nut is stuck on like nothing I've ever seen.
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post #6 of 10 (permalink) Old 07-22-2013, 06:22 AM
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I had the same problem with my rear on my 2012 F4. I didn't want to but I took it to the dealer and had them break it. Only because if the messed it up they would be coming out big money to replace the hub not me. Once the broke it and took the wheel of I have since fine it myself to replace the tires.


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post #7 of 10 (permalink) Old 07-22-2013, 09:23 AM
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If the rear nut is stick...and you are removing in in a CLOCKWISE direction, then you will need patience and the correctly tapered nut tool and an impact gun......

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post #8 of 10 (permalink) Old 07-22-2013, 05:17 PM
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You shouldn't need an impact gun. Only a breaker bar and torque wrench. Again from the factory having never changed the tire it took 3 people and a huge bar to break it. Now having removed the rear wheel a few times it has been no problems. Just need to torque it back to the correct settings when done. And yes I know it is clockwise to tighten and counter to loosen. It still was on to tight.


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post #9 of 10 (permalink) Old 07-22-2013, 06:04 PM Thread Starter
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I bought the correctly tapered socket, and I've had my mate on the bike standing on the rear brake and me with a 5 foot breaker bar on it, and nothing. I don't have an air compressor that can run an impact big enough.

The TPO socket I bought is some stainless steel, and it is starting to yield the 1/2 inch drive already. I'm thinking of welding the socket (which was rather cheap anyway) to a long pole and trying that, but it is hard to get the rear tire to not slip. The brakes/weight don't hold it.

And yes, I'm turning it the correct direction. Rightey-Loosey.

The tires are so bad, and the closest dealer is across the bay (Munroe)- and the rear tire is factory original (Michelin Pilot Sport- they stopped making them years ago) and spins up like it's on ice. I have ridden the bike around town, tip-toeing everywhere. So I want to try to get that nut off in my garage if at all possible.
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post #10 of 10 (permalink) Old 07-22-2013, 09:02 PM
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Thumbs down nut too tight?

mjedm6;
dagmvagusta;

if you have a problem with the wheel turning while trying to undo the wheel nut.....stick a tie down through the wheel and hook it to the foot peg mounts DO NOT PUT THE BIKE IN GEAR

Saturday a friend brought his 312 over, because he bought my black stars and doesn't have any tools

his wheel nut was put on by a dealer.....
it took my CP-724 about 10-12 seconds to undo the nut
thats with a 425 lbft rating

no lube on the threads

to remove the caliper bolts?......it was suspended from the ceiling..... i stood on the rear stand

they were so tight it took the plating off

to remove the disc bolts???
he couldn't do it with a SnapOn 3/8" Flex head ratchet

CP-724 1/2" air impact to the rescue

some fucktard (thanks col)put green LocTite on them

there are green LocTites that make the usual red #271 seem like KY

another reason i do all my own work

fuck breaker bars, i don't have the time

next time i'll try my baby Swench Wrench, its 12" long and puts out 500lbft.....oh, i have the old Curtiss Wright versions, all stainless and tool steel
i have the 3/4" one too......the extensions are 1.75" in diameter

"Swench Wrench the cure for the breaker bar"
http://www.youtube.com/watch?v=mbnQb2Hp-cI

the Model 1500 puts out 7,000lbft, not a typo 7,000lbft

http://www.powerhawk.com/images/swench_banner.jpg

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