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SC50 stutter at 3k and gets REAL upset after 8k rpm

8K views 116 replies 8 participants last post by  speedcrazy1532 
#1 · (Edited)
So after doing a bunch of tests including all sensors, injectors, new exhaust gaskets, airbox gaskets, plugs, fpreg, IAT, SMOG injection delete, stator and r/r test good. Battery is fine etc.

I still have the same problem. No error lights at all.

The bike stutters at 3k and last night I took it over 8k purposely for the first time as the bike is fairly new to me and I've been hesitant to really get on it because I know something is wrong.

At 8k the bike got REAL weird bucked and popped until I pulled the clutch in.

The only test the bike didn't pass was the fuel pump flow test but I realized after I put the bike back that I did it incorrectly and overlooked disconnecting and plugging the vacuum line on the fuel pressure reg. Results of the test under this condition were about 140cc after 10sec vs the minimum in the manual is supposed to be 188cc.

Bike has no HTEV, full LeoVinci exhaust and a BMC filter which is new. PCIII USB with dYnojet map I was assured by dynojet would be sufficient.

The bike behaves the same with or without the PC connected at least with the low rpm stutter.

Fuel flow test aside I'm starting to think timing issue?

I will redo the flow test asap but until then anyone have any other ideas?

SOLVED:

After putting in a different ECU and changing the fuel pump I still had the same issues.

In the end I changed out the ignition pulse generator located inside the right crankcase cover and the bike runs flawlessly now. I haven't had a stutter or miss in 100miles. Not an expensive part either. About 40 bucks on motosport.com. i didn't even buy a new one. My timing inspection cover was seized and I trashed the crankcase cover trying to free it. The used crankcase came with the sensor attached haha!

It should be noted that testing the sensor on the bike requires a peak hold tool and when using a regular voltmeter it is very hard to see any voltage at all. (>.07v is what you're looking for).
 
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#6 ·
Yes also tested those. Resistance was in range on all coils. Also tested each coil for spark and all were fine.

Doesn't sound like fuel starvation as it's struggling higher up the rev range, sounds more like an electrical issue, have you checked the stator, battery etc.
Battery test good after a ride, after sitting, and while running. Stator wires all test at .2ohm and have no continuity or burnt wires etc.
 
#14 ·
It still could be a fuel problem. I had a gsxr 1000 that didn't have the low rpm stumble but acted very similar in the upper rpms. It also struggled to pull past 8000 without surging and missing. I pulled the fuel pump out and took the actual pump out of the housing. I did a "backflush" on the housing and you would not believe the amount of crap that came out of the housing. Also "backflushed" the pump itself. basically I took a hand pump and forced gas backwards through the housing and pump (opposite of the way the gas usually flows) worked perfect. The very first ride the bike ran right up to redline with zero issues. The bike was immaculate as well and well taken care of, but the fuel these days sucks! I would try that for sure, it only cost a little time. I got the hand pump from harbor freight for about $5.
 
#16 ·
Fuel pump went in no problem but wasn't the problem. I have no red light on with the bike running but shorted the diagnostic connector and got the following codes:
7
8
9
12
13
14
15
34
35

Could someone fill in what these are for me? My manual is in my work bag and not with the bike as I am right now.

I thought 34 and 35 were the servo motor for HTEV which I do not have (full exhaust) and have installed the bypass resistor/capacitor combo.
 
#20 ·
Fuel pump went in no problem but wasn't the problem. I have no red light on with the bike running but shorted the diagnostic connector and got the following codes:
7
8
9
12
13
14
15
34
35

Could someone fill in what these are for me? My manual is in my work bag and not with the bike as I am right now.

I thought 34 and 35 were the servo motor for HTEV which I do not have (full exhaust) and have installed the bypass resistor/capacitor combo.
Those codes will be stored codes , you will need to wipe them by resetting.Then see what codes it kicks up
How do you clear them? I was under the impression that the codes would not appear if there was no issue.
 
#17 ·
I don't know what the other codes are but you are correct about 34/35. Did you backflush the fuel system? If there is crap in the fuel pump canister replacing the fuel pump wont change anything. Went through the same thing with the gsxr. Put new pump in, had same problems. Was advised to backflush the fuel pump housing and once I did that bike was good to go. Good luck getting it sorted out.
 
#18 ·
What is the "canister"? The filter is new and the entire assembly is clean as a whistle. Everything in there is new. All three filters are new now. We have a bag filter, mesh filter and an actual in line fuel filter. The new pump came with a new bag filter and I cleaned the mesh myself.
 
#21 ·
No,these codes are stored ,for reference that's all. To clear them make sure the ignition is OFF, then bridge the terminals,kill switch should be in the run position, turn the ignition ON,Disconnect the jumper wire from the service connector,once the wire is disconnected the MIL should come on for roughly 5 SECONDS, the jumper wire should be reconnected during this 5 SECONDS, the MIL should start to flash when the jumper is reconnected showing the codes have been erased.If the light flashes 20 times the codes have not been erased and procedure started again.Turn OFF ignition and remove wire. Instructions taken direct from the manual
 
#22 ·
Reconnected with my manual. Sorry you had to do all that typing for nothing (hopefully it was copypasta). I will try it in a bit. Headed back to work on the bike.

I have thought it wired that the bike has had problems at the two points the HTEV would change positions. I've thought about switching the map in the PC to one that specifically says HTEV deleted.
 
#24 ·
My apologies, I have never taken apart the 954 fuel pump assembly. Most of the other sport bikes I have worked on have a big plastic housing that the fuel pump goes into. I just looked at the miscrofiche for the 954 and it is not set up that way. Sorry about that. I attached a fiche of the gsxr for example to show the housing that I was referring to. 2001 Suzuki GSX-R1000 FUEL PUMP (MODEL K1) | Ron Ayers
 
#26 ·
So after the fuel pump wasn't the issue I did some more digging.

A different ECU is in my possession; I also changed the PCIII map to one that specifically implies HTEV is deleted and also updated the PC firmware just for shits and giggles.

However, when I was going to check the timing the timing cover (which the P.O. had damaged) refused to come off and ended up costing me the entire crankcase cover because it was so seized. It's in the mail as we speak.

The sensor inside the crankcase cover is the ignition pulse generator correct? I do not have my manual on me at the moment.
 
#32 ·
Hi , I wouldn't even think of buying one of those (actually 2 needed) , you would be talking close to $2000, but at least you can check the voltage at the TPS to make sure that's working OK, but before that check the connector by pulling apart and having a look at the pins , can get corroded
 
#35 ·
SOLVED!!! SC50 stutter at 3k and gets REAL upset after 8k rpm

In the end I changed out the ignition pulse generator located inside the right crankcase cover and the bike runs flawlessly now. I haven't had a stutter or miss in 100miles. Not an expensive part either. About 40 bucks on motosport.com. i didn't even buy a new one. My timing inspection cover was seized and I trashed the crankcase cover trying to free it. The used crankcase came with the sensor attached haha!

It should be noted that testing the sensor on the bike requires a peak hold tool and when using a regular voltmeter it is very hard to see any voltage at all. (>.07v is what you're looking for).

So problem solved! Kind of nuts that I've read threads where people have sold bikes because they could figure out the low end stutter.

Hope this thread helps someone out.

I've spent probably 60 hours and poured over the bikes electrical system looking for a solution.
 
#40 ·
Re: SOLVED!!! SC50 stutter at 3k and gets REAL upset after 8k rpm

In the end I changed out the ignition pulse generator located inside the right crankcase cover and the bike runs flawlessly now. I haven't had a stutter or miss in 100miles. Not an expensive part either. About 40 bucks on motosport.com. i didn't even buy a new one. My timing inspection cover was seized and I trashed the crankcase cover trying to free it. The used crankcase came with the sensor attached haha!

It should be noted that testing the sensor on the bike requires a peak hold tool and when using a regular voltmeter it is very hard to see any voltage at all. (>.07v is what you're looking for).

So problem solved! Kind of nuts that I've read threads where people have sold bikes because they could figure out the low end stutter.

Hope this thread helps someone out.

I've spent probably 60 hours and poured over the bikes electrical system looking for a solution.
Nice one matey glad you got it sorted, never give up! ,that's my motto, yes the peak voltage adapters are expensive , but if you look in my cbr400 build post, there I have got a post on how to make a Peak Voltage Adapter for under £7, the parts are so cheap so I don't know how they can ask the price they want for one, would have suggested using one but their not in everyones tool box
 
#36 ·
SOLVED:

After putting in a different ECU and changing the fuel pump I still had the same issues.

In the end I changed out the ignition pulse generator located inside the right crankcase cover and the bike runs flawlessly now. I haven't had a stutter or miss in 100miles. Not an expensive part either. About 40 bucks on motosport.com. i didn't even buy a new one. My timing inspection cover was seized and I trashed the crankcase cover trying to free it. The used crankcase came with the sensor attached haha!

It should be noted that testing the sensor on the bike requires a peak hold tool and when using a regular voltmeter it is very hard to see any voltage at all. (>.07v is what you're looking for).
happy you got it sorted out and really appreciate you coming back to let us and any future users know what the solution was.
 
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#38 ·
yeah it can be frustrating. if everyone did as you have things would certainly be easier for people with similar issues.

i wont say i dont often see people resolve their problems in threads, but it can be a lot of work for someone with similar symptoms to come in and read through 18 pages to find it. :) often people join up and make a post asking for help, there is some back n forth on possibilities. then they just disappear and we are left wondering if one of the suggestions fixed their problem, or maybe they were abducted by aliens etc etc...
 
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#42 ·
*Bows*

Yes it is odd. Probably why two different people gave up on the bike.

However I am quite stubborn and also have had many straaaaanngge problems with past cars that make me suspect unusual things.

I did think it was important to report back with the result. It was extremely frustrating reading so many threads with no conclusion.
 
#44 ·
AWESOME!! And again, great job on coming back to update to possibly help someone else in the future. I hate when people come on forums, ask questions, and people take time to try to help them out. Then when the problem is solved (usually due to help given on the forum), you never hear from them again. Thank you!!
 
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