K6 GSXR Jerky throttle solutions (tried tps,tb sync, and tre already)

Hey guys, first off I appreciate you taking the time to give this a read. I have a k6 750 track bike (leovince slip-on, BMC filter, pc3 w/ orient tune, flashtune ECU (only for TRE and ECU base QS, no fuel tune w/flash) that has the infamous throttle jerk when picking up the throttle after rolling off. This only occurs when you roll off the throttle for braking and then try to pick it up in the apex, the bike will jerk and it upsets it mid corner (as you could imagine). I have had an rc51, r6, and 600rr track bikes that I did not have this problem with. I have tried almost every remedy out there for this problem EXCEPT for a dyno tune. This issue is easily replicated below 7krpm in gears 1-3 even if your cruising at a steady speed and focus on just a smooth roll into the throttle from 0%. Set valve is gone. I have tried adjusting the TPS (upper/middle/ just till it goes to the upper line, by volt meter as well), I have removed the STVA butterflies (which helped a little at the expense of a few mid-range ponies), synced throttle bodies (on separate occasions trying to experiment with them vacuum synced at 2k,4k, and 6k to see if it would help smooth it out but no dice). Usual suspects are not the issue i.e. chain tension, throttle play, has new plugs/clean air filter etc. Some people have mentioned a dyno tune has taken care of their issue while others still had the issue after a dyno tune which makes me hesitant to take it to a tuner and still have this issue persist. The only thing that truly cured this issue was cranking the idle speed to 2.5-3k rpm which just seems like a bandaid but may be what I have to end up dealing with as the "fix". Has anybody experienced this to be the case with their GSXR? If so what tuner would you recommend that does a good job tuning low throttle RPM ranges near North Carolina (I am willing to drive out of state). Any insight/experience with this issue is greatly appreciated. Thanks!

 

All stock ECU? Flashing the ECU to disable the fuel cut on decel helps, assuming it's just the normal amount of jerkiness, but might as well get a full on tune while going through the trouble.

 

Thank you for the reply! I just edited the post for some info I forgot to include, unfortunately it has been flashed for QS, TRE and fuel decel cut already. (Was my first attempt to calm it down).

 

Kyle,
You removed the STVA? like removed the secondary butterflys? have you removed the exhaust valve too?

a little trick I use to smooth on/off throttle is to add fuel in the map area 0%-20% throttle from 4k rpm to 12k rpm.. Do you have o2 sensors on your exhaust? if so you need to get Dynojet o2 eliminator. If you have a power commander, delete the generic map on it and replace all the cells with 0's

 

Doh, I forgot to include set valve is removed completely, butterfly gone with hole welded. Yes the secondary throttle butterflies are gone, two members on n2 track forums had done this and they reported it helped out a bit. Their dyno showed a few HP down in the mid range but this was a sacrifice I/we were ok with to improve ride-ability. No o2's. Also, are you saying to delete the generic map and then add 0-20 between 4-12k on zeroed out map?

 

Clear the fuel table in the PC3/Bazzaz etc and in the 0% to 20% throttle between 4k to 12k rpm add 10 or 15.. this will help keep the cylinder wet and keep chassi compliance between on/off throttle.. you will have to mess with the amount in that range - less is better so pull fuel until it gets harsh again and wha-laa

 

one other thing, the clutch basket springs wear (actual basket [not clutch springs]), this can create slop between on/off throttle too & cush drive cushions..

 

Awesome thank you. I will zero the map and try that and report back. Any reason for not running any specific map (besides the fact they probably suck)? I will throw some new cush drive cushions in there and grab a set of replacement clutch basket springs if the fuel adjustment doesn't help at all (hell, I might just do it anyways to be sure).

 

theres a big difference between the average guy that can run a bike on a dyno and the guy that actually knows what they are doing. one will know how to fix throttle and fueling issues, the other isnt worth giving your $$. those friends that reported minimal change after a dyno tune probably didnt pay the right tuner.

 

That was pretty much my point with me being hesitant to get a tune, and asking for suggestions. Do you have any recommendations competent tuners in the southeast region that you would give your money to?

 

sorry, im on the other coast. someone will chime in with a recommendation.

 

A good tune will help but not cure. I also added a motion pro eccentric throttle that helped more. Took care of about 80% of the jerkiness.

 

Had the exact same issue with a TLR. Have you checked the base filter inside the fuel pump? One of mine looked like a tobacco pouch and once I changed that same exact problem was gone. Your pump is going on 14 years so it might be worth pulling out and checking. It’s the filter under the cylinder pump.

 

2006-2007 GSX-R 750 and 600 with a PCIII can have this problem. Something to do with "duty cycle" I'm not a scientist this is just what Dynojet said. When you wack the throttle the ecu, much like an accelerator pump, increases the duty cycle. Combined with the PCIII which is already doing the same thing it can max the injector's duty cycle. The ecu reads that as an injector being stuck open and cuts fuel completely, then it picks back up.
You wack the throttle WFO and the bike totally dies then slams back on. Not fun. What Dynojet came up with was to add negative values at 80-100% throttle between 5500-7250 rpm. (The secondary injectors are working at this rpm range and more than make up for it. It's not even noticeable in the curve.)

 

You can't replace the clutch basket springs, you have to replace the clutch basket.

 

Thank you for all the replies, you guys are awesome. I will take the fuel pump out and have a look as well just so all my bases are covered. Steeltoe, thank you much for the email! I will let you know how it goes once it stops thunder storming as soon as I get home from work.. and wheeliest, I will replace the basket if none of these other things cure it, considering I probably need new frictions as well.

 

Well, back from the track (CMP). Zeroed map with added fuel in the lower rpms didn't do much, a custom dyno map didn't change much either. I also re-adjusted the TPS as well, cush rubbers are new as well. At this point with 26k on the bike I'm considering a new basket/frictions just to see what happens. Only thing that really helped was cranking the idle up to 2500rpm made it feel how normal bikes feel.

 

Have you looked for solutions on the Gixxer.com forum? I seem to remember a few big threads about this issue, even for street bikes.

Good Luck

This forum changing terms for you- sort of irks me.

Mods- why can't you take that off?

The G I x x e r . com forum?

 

Welp that 's a bummer. I suppose you could swap the throttle bodies and see if it that solves it.

 

I've looked at the other forums as well, all the same things concerning TPS or pc3 tune.

Also what do you mean replace throttle bodies steeltoe? Was that an issue in some of these bikes?