GK76A 1992 doesn't idle gone through checklist.

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CHOCOLATEkevin
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GK76A 1992 doesn't idle gone through checklist.

Post by CHOCOLATEkevin » Sun Feb 25, 2018 3:15 am

Hello all, i'm currently in japan rn and picked up a gsxr 400 gk76a (1992) thinking it was going to be a good idea since it ran good when I test drived it, started up cold and ran no problems. . . Shortly after about 3 weeks the problems began. :( Just as I was about to go get my license my valve petcock hose decided to come off leaking fuel all over the ground.Fixed that but we didn't know about the vacuum hose then the bike ran like shit. FIxed that.Then the vacuum petcock it self broke off from the inside .Fixed that. However prior to replacing the petcock, I started noticing the bike wasn't idling so I did a tune up and replaced the oil and spark plugs with full synthetic Motul and Iridium plugs.At the same time also cleaned the carbs and replaced all the jet seals (which were previously fine) on the bike.I cleaned out the pilot jet,adjusted the screws to stock (1.5 turns out I believe), didn't fuck with the float boat height since I read it causes problems, cleaned every single little hole there was with a PLENTY of carb cleaner and shot compressed air into EVERY single hole there was (and checked to make sure was clear with light). After all this I was exhausted and already out a pretty penny with buying tools and what not.But even after all these things, the bike still DID NOT IDLE.So I thought , OK the bike seems to have problems staying on when I have the lights on so I said it could be the stator , Just replaced the stator and rectifier; nearly destroyed the engine trying the get the old flywheel off since the only way to remove it was to use and extractor and an impact gun.I ended up stripping the old 17mm bold threads that were on the inside of the crankshaft and had to go buy 100 dollars of drill bits and taps . Luckily I ended up getting the flywheel on there but the enlarged bolt size made me have to grind out a hole into the side of the crankcase.Bike still doesn't idle . . .Im considering selling the bike for parts or selling it for whoever wants a project bike. If anybody has anymore suggestions id be glad to hear em ill be posting pics on photobucket? I think thats what everyone uses on here.


PB127CU
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Re: GK76A 1992 doesn't idle gone through checklist.

Post by PB127CU » Mon Feb 26, 2018 7:19 am

Does it idle with the choke on? What about after it's warmed up? Did you try raising idle rpm?

moforockband
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Re: GK76A 1992 doesn't idle gone through checklist.

Post by moforockband » Mon Mar 05, 2018 10:05 am

Hi, check the compression is above 150 psi on all cylinders, then replace every o ring in the carbs if they haven't been done before. should be ok then.
Thye problem you may be having is flooding because of failing o rings.

ventYl
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Re: GK76A 1992 doesn't idle gone through checklist.

Post by ventYl » Sun Apr 08, 2018 8:39 pm

Also if it will idle on choke but not without it there can be still one (or many) passage in idle circuit of carb clogged. The jets there are pretty small and it may get many attempts to clean them thoroughtly.

LiteTekBlair
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Re: GK76A 1992 doesn't idle gone through checklist.

Post by LiteTekBlair » Sat Apr 14, 2018 1:08 am

Assuming you have good compression, replacing o-rings won't always do it if you have leaking throttle shaft seals. Test those by spraying WD-40 or similar on each seal to see if it has any affect. Also test all of the inlet manifolds for leaks.
Carb seal kits in viton & other parts
https://litetek.co

CHOCOLATEkevin
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Re: GK76A 1992 doesn't idle gone through checklist.

Post by CHOCOLATEkevin » Sat Dec 08, 2018 12:37 am

Hello all , update and big story time. I ended having to go through the electrical and boi was it a pain in the ass. I replaced the spark plug caps with brand new NGK's and waterproofed the spark plug holes with double rubber.I used the set that came with the new plug caps and the old rubber seals that came with the bike. I found that there were loose wires on all old spark plug caps as the wire inside the insulation receded over time but it was most sever on cylinder 2 and 3. I checked to see that the original coils were working and I continued to cut the wire were it was receding and I bought NGK spark plug wire splicers/extenders. These are super convenient as they allow you to not have to replace the whole coil and simply extend off of the original wire and apply new HV cable. The wire splicers have two sharp needles, one that goes into the old cable and one that goes into the new one. They have a threaded fitting that slides into each side with a rubber o-ring similar to a electrical conduit for circuit breakers.

I proceed to start the bike and worked for a while but I felt the bike still wasn't running right. At that time I thought the idle screw would vibrate out of place/ the engine felt out of tune. After replacing o-rings on the stock carbs , having them cleaned after I cleaned them by a mechanic, and having them adjusted by him the bike ( both jobs ran me 400 dollars) still didn't run right.So me still thinking it was the carbs as all the electrical was good , I picked up a set of FCR's :P. I had them custom spaced, tuned by my mechanic , ran good for a while but then my bike started to die again. Until one day I was riding around and it died and it wouldn't start.One angry phone call later and I asked him what was wrong, maybe elevation change was dropping the idle making the rpm drop below suitable to charge the bike yada yada yada but deep down I knew it could also be the stator or rectifier.

At the time I had replaced the OEM stator and rectifier with a Electrex brand stator and rectifier (MOSFET Based). One of the biggest mistakes EVER was using spades to connect the stator and rectifier. I know a bit of making electrical connections , so I knew that soldering was the best way to go BUT I didn't have a helping hands or a good soldering iron so against all my warnings flashing in my head I went with what I had , insulated spade crimps :(. The spade crimps insulation ended up heating up , melting, and they caused a short that fried both the stator and my rectifier.

Oil change , new stator , new rectifier , yellow stranded copper wire, proper soldering items and brand new custom stator loom later, I had a solid idle.

I discovered that the stator loom for these bike arent 100% copper. Off of the stator connection they use a aluminum to copper joint that goes in the rubber grommet for the loom.The aluminum was not allowing me to solder directly so I had to make a brand new wire loom ,pull the wires out of the stock grommet, and install all copper wires.I used non-insulated butt connectors as I didnt want to twist the wires making them a pain for when I needed to replaced the stator possibly down the road. After I finished soldering I triple insulated the connectors with 2 heatshrink and 1 3M pro electrical tape wrap that comes in a plastic case.I modded the rectifier a bit to get it to fit in the OEM spot and soldered and crimped the connections on the stator and rectifier.To top it off , I used a terminal block to connect the stator to the rectifier. Ill upload pictures of the actual wiring .

Summary of the things that were wrong and hopefully it helps someone:

-Spark plug wires receding/ not making a good connection with plug cap.

-Plug cap old didn't hold on to plugs well

-Fuel petcock broken replace

-Carbs were dirty, clean , replace seals , and apply two good fuel filters that have the nipple the size of the hose to prevent fuel feeding problems and keep carbs clean.

-(Optional but not necessary) replace carbs with FCR's and remove airbox, it allows a TON of space and makes it easier to install fuel filters, and work on bike.(CON is they are expensive and require some modification as Keihin didnt make a set for this bike.)

-When replacing stator make SURE to solder connections as there are a lot of vibrations and limited spaced in area.If you use crimps or the connectors provided it may fail down the road, be sure to clean the wires with a good solvent and use good solder !!

-Electrical wires on old bikes tend to go bad, make sure to replace them if you plan to daily drive them.


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