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Bad Running 95 750

4K views 32 replies 9 participants last post by  Sabba 
#1 · (Edited)
My 1995gsxr 750 Has been progressively worse.
The idle is terrible and sounds like its only running on 2 cyl. Taking off from a light it terrible.
It has a really bad stumble and basically no power under load untill it hits 4k, then it takes off like a rocket.
Anything after 4k feels great. great throttle response, no loss of power. as soon as I stop the idle seems to sound fine for a few seconds then drops.
Seems to be fine if the choke is on.
I had ran in to this issue before. It was bad enough to the point where the bike would stumble then die while riding. Switched to petcock to prime and completely resolved the issue. now with the petcock on res/on/prime/ it still runs like shit.

I've tested the petcock. Flows free in prime and flows the same in res/on when under vacuum. I've torn apart the petcock, all seals are good and thoroughly cleaned

I do have a slight vapor lock with the tank but still runs like shit with cap
open.

Replaced plugs with new cr9's

Just taken the carbs apart. all seals and orings are cleaned/no nicks, not dried.

emulsion tubes are good. they seem to be stock. they are marked with a serial number.

Needles are not worn.

Haven't checked float bowl height yet. should be able to check later tonight

carbs 1/4 have 110.0 jets. 2/3 have 112.5

I have a drop in K&N filter, stock airbox. no mods/ full V&H header+pipe with a a thinner baffle/

I believe this bike originally came from Cali. I say that because it has the factory sticker on the frame stating that the bike meets the California emissions laws. And has a massive ugly as fuck canister on the left side of the bike. (4th picture down). if that is the case how can I completely remove that system.

Please help me out with this. Anything would be appreciated. if you guys need any more info let me know. will upload video of the bike running and more pics
 

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#4 ·
I'm actually having an almost identical issue as you except my bike is probably at its worst, I'm on my second carb cleaning, I also have a dynojet stage 1 jet kit with 116 main jets. I can't figure it out at all, the carbs are sitting on my kitchen table right now as I'm trying to find anything out of the ordinary, even though there is hardly any wear on my jet kit. Needles have slight wear but everything else looks to be new. My bike only will idle if I have it at 2k rpm, and when I take it out it spits and sputters up to 3500 rpm and after that it will kick out of it do hard that it almost throes you off the bike. I can't find anything bad I got good spark, petcock flows like it should, and I just can't figure it out.
 
#6 ·
:punk Great communication there Adam...you are definitly on the right track to getting it sorted.

You are right, it you have a Cali bike with stock carb parts (you may want a Stage 1 to go with your full exhaust and K&N, but that's another matter).

You say it runs okay with the choke on? That sounds like something in your pilot system is causing it to run lean.

Check all pilot jets to make sure they are clear. Careful not to enlarge the holes if you try to clean them with wire.

Next, check your pilot screws. How many turns out are they at? Put them at 2.5 turns out as a starting point.

Also, be sure to set the floats at 15 mm...
 
#7 ·
Thanks for the quick replies guys.
All floats were about 12mm. Currently now set to 15mm.

I'm going to check the pilot screws, but unable to get the brass cap off. any suggestions?

Also has anyone ever taken the extra emissions shit out of a Cali bike.

Ive looked through the manual and it looks like the only real difference is those 4 purge tubes(1 for each carb) that basically go to the canister. Then the canister has a another tube that runs and connects to the lower right rear of the gas tank. In the tank theres apparently a fuel fume seperator. I have a diagram that ill post up. hard to explain.

But couldn't I technically block off those purge tubes which will cut out the need for that canister?
 
#9 ·
Thanks for the quick replies guys.
All floats were about 12mm. Currently now set to 15mm.

I'm going to check the pilot screws, but unable to get the brass cap off. any suggestions?

Also has anyone ever taken the extra emissions shit out of a Cali bike.
That would have made your bottom end richer, having them set to 12 mm. Anyways, good thing you checked and set them right.

Like Cody said, drill a small hole into eack one, insert a wood screw, and pull it out.

Can't help with the Cali stuff...search through the archives here, I'm sure you're not the first to do this. I would say the vent tubes should not be blocked off, rather vented to the atmosphere (if it's anything like the 38 mm carbs).
 
#10 · (Edited)
Thanks guys. Worked great.
Counted when I turned them in and they were all off +/- half a turn. All currently now set to 2.5 turns out.
I'm going to rip out the all that emissions crap out tomorrow/ reinstall the carbs and try again.
Also sure its been discussed multiple times. but would you recommend DJ or FP.
 
#12 ·
Both are good kits and will cost roughly the same.

In short, the DJ kit comes with new proprietary emulsion tubes. You replace everything with new DJ parts, but slide drilling is required.

The FP kit does not come with new emulsion tubes. You will need to order new OEM tubes to run with this kit should yours be worn. No slide driling requred.

Do a search, this has been covered extensively in the past...

Either one you decide to get, be sure to buy the Cali version of the kit...
 
#14 ·
Placed the carbs in the bike. Connected everything up, and now the bike has no electrical power. The fused connector to the solenoid was melted to the solenoid.

Getting that replaced right now and then I'm going to give everything a try. I let you guys know what happens
 
#16 ·
**UPDATE**

Purchased the correct DJ kit for my Cali bike. Have installed everything correctly and rechecked the pilot screw aswell as the float height.
I have also since replaced the float bowl gasket.

I reinstalled the carbs in the bike and am running into the exact same issue in every way(can take another vid if necessary) The jet kit hasn't made any difference at all.
Now is it possible for the coils to break down under certain rpm?
Can this be an electrical issue? Or should I keep trouble shooting the carbs?

I'm at a loss right now. Any help would be greatly appreciated.
 
#17 ·
Does the bike stall when you try and start off? Do you smell gas? Pull the plugs see if they smell like gas. It really sounds like the bike is running rich and causing your bogging issues.

Just to be sure with spark have you removed the spark plug books and re sat them to ensure a good fresh connection.

You mentioned it sounds like it starts on two cylinders. Have you checked the coils with a multimeter? Or at least checked all four for a good arcing spark?

I'm leaning towards the carbs even though I've never dealt with a Cali model. I had the same issues with my 94 but I replaced everything from wiring harness to battery to plugs to rebuilt carbs etc. I just got it running perfect. You are close just start simple and go from there.

Is there anything you have done to the bike besides what you have told us. Not trying to come off like a dick or second guessing your work. Just trying to help. These bikes are damn picky! Keep at it and hopefully something I said helps!


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#18 ·
If you know your carbs are set to the T, I would move on and look elsewhere (at least rest knowing you won't have to do the carbs again!)...

Like already mentioned, check out your ignition system next. I saw you already have new plugs, good place to start. Time to take out the voltmeter and manual...

Like JSarget said, these bikes are damn finicky. They require constant TLC to keep them running right...once they have been neglected (as most of them are), it's a bitch to get them back on their feet...
 
#19 ·
thanks for the quick reply guys. Really appreciate it.

I will take the volt meter out tomorrow and check a few things. Aswell as I'm going to hang the carbs off the bike with the fuel and vacuum lines connected. Just to make sure the pilots are completely clear.
 
#20 ·
Any luck with your issues?


Take the time to clean the carbs and soak all the jets while you have them out anyway. You never know;) blow them dry with compressed air!


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#21 ·
Take the time to clean the carbs and soak all the jets while you have them out anyway. You never know;) blow them dry with compressed air!
Well, he did just get a new jet kit! And I would hope he checked the pilots while he was in there... :shifty
 
#23 ·
A possible contributer to this issue is the fact that plug #2 has intermittent no spark. Was turning the bike over with a slightly dead battery and plugs 1/3/4 all had good spark, but #2 did not. Now when the battery was charged more it did produce a spark on #2, but looked weak compared to the others.

So I'm going to be replacing coils and wires.

Now the carbs right now are not fully sync'd but I have set everything on the carbs exactly to spec. And have triple checked everything. Still runs the exact same as before when the carbs specs were out of whack. This leaves me to believe that it's not a sync issue.
 
#24 · (Edited)
A possible contributer to this issue is the fact that plug #2 has intermittent no spark. Was turning the bike over with a slightly dead battery and plugs 1/3/4 all had good spark, but #2 did not. Now when the battery was charged more it did produce a spark on #2, but looked weak compared to the others.

So I'm going to be replacing coils and wires.
You have two coils: One feeds #1/4, the other #2/3.

Since #3 had a good spark, and #2 did not, the coil is likely not the issue!.

Check downstream from the coil. You wire connections at both the coil and spark plug cap ends, the spark plug cap (and rubber insulator), and spark plug. Cut a 1 cm piece of the wires, and refresh the connection at the boot. Your issue will lie somewhere there...

You can replace your wires with new 7 mm cooper-core ignition wire. However, when you remove the stock wires, the brittle plastic clips in the coils WILL break. I ended up JB Welding my new wires into the coils, figured it would be the last time I would be replacing them anyways...

This is what I bought, works great:

http://www.ebay.ca/itm/7mm-Copper-C...h=item35c6e310cf&vxp=mtr&_uhb=1#ht_1256wt_952

Edit: A weak battery will make your bike run crappy as well. Do a load test on it. Buy a new battery if it's weak, you will just have to do it anyways down the road... :dunno
 
#28 ·
Interested to see what's going on too.... I'm having similar issues I had to order another fuel pump assembly which souls be here soon. I do have a question I have a 96 GSXR 750 SRAD are their any hoses that go on the two hose ports that faces the handle bars on the tank? Mine didn't have any

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#29 ·
Honestly I don't know with the srad. I would check in the srad section. I know CCMhunt has posted hose routing pics many times. Check over in that sub forum as you have some of the most knowledgable people there who know your bike in and out.


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#30 ·
**UPDATE**
Big thanks to Jsarget52 for hooking me up with correct ecu/coils/wires!!
Since my last post I have rechecked the carbs and had a buddy ultrasonic clean the carbs. Still had the same issue once reinstalled on the bike. Just wanted to make 100% sure.. And it was free anyways.. :punk

I have also rebuilt the stock petcock for good measure.

Rechecked the spark after trimming back the wires and found out that plugs 2/3 were both getting weak spark. Re-installed plugs and wires and ran the bike at about 5k and tested the header heat with a gun. Confirmed that cyl. 2/3 were running MUCH cooler than 1/4.
Ohms at the coils confrimed the issue aswell.....

so with the parts I got from Jsarg installed on the bike, she fired up instantly and purrrrrrrrrrrreeedd perfectly.
To say the least I'm fucking ecstatic

Ran a bit lean but I didn't have the airbox on. So shouldn't be an issue with everything completly installed.

So hopefully this helps anyone with the same problem. It was mainly a coil issue but keep in mind I replaced quite a bit to get to this point.
Thanks a lot for all the help from the forum.

May start another thread later on to show the next complete custom resto of the bike.
 
#31 ·
Glad to hear it man! Congrats on getting the bike running! Love to see another WC on the road.


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#33 ·
:cheers
 
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