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Discussion Starter · #1 ·
Hi I have an 87, got last year, love the bike, ran when I got it…been doing cosmetic and maintenance work.

Petcock was not working correctly so I rebuilt it, and also cleaned carbs and installed new float valves and needles…this corrected the scary siatuation of leaking gas into cylinder while sitting….luckily I never started it this way and had caught it.

i had reset float height to factory when off (they were higher) then it did not start (cranked, sparked, did not think I was getting fuel) ….so I took off again (always fun!) and set back to higher figuring the pilot jets (which sit high) we’re not getting enough fuel.

So then it did start, ran well.

Took it to a bike night on way there it was dying at idle. i turned up idle once I got there. Bike would not re start. It did though with a bunch of guys pushing in second gear.

Now it’s back to not starting. One thing I did notice before is although it was sparking on all 4, it was not bright and blue, but weaker and yellow/orange.

i have a bunch of bikes, have been thru many issues, I am fairly competent as a mechanic, but diagnosis is hard, and I usually end uo replacing lots of stuff before finding core problem….

any ideas specific to oil cooled Gixxers? Am tempted to just replace coils, but OE ones cost $$, and one aftermkt I seem to see on Amazon could be crappy, so any ideas there also appreciated Thks….here is pic of bike too
 

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If it ran but was dying at idle I doubt it's coils, but anything is possible. Have you determined if it rich or lean when it doesn't start? What exactly did you replace when you rebuild the carbs? Are you sure they are 100% clean?
 

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Discussion Starter · #3 ·
The not starting does not appear to be associated with being rich or lean - it has been strange as it does not even bark or stumble when does not start, so I thought it was not getting fuel thru pilot circuit. but later, it would start only with a push and or a jumpsstart from car where starter spin very fast, that’s when I began to suspect weak spark. I was very confident carbs were 100% clean when I out back together….only replaced float needles and valves and a few float bowl gaskets. It is of course possible that since the pilot jets appear to be even smaller than most, that somehow they are getting clogged….there does not appear to be much room for a fuel filter and not sure which one would be best, but could be an issue…
 

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I would start with fully charging the battery then pulling the headlight fuse before cranking again. If no go, unfortunately it's sounds like you will have to pull the tank to troubleshoot. I would first check your spark by pulling the plugs and checking all 4 cranking. You can also check them to see if maybe you are rich or lean.

The pilots can have issues from left over gelled gas. Even if you think they are clean. Find my thread about my 750 running rich from a few weeks back. If you have to pull the carbs, order a set of stock genuine Mikuni pilots just to rule it out.
 

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Discussion Starter · #5 ·
I would start with fully charging the battery then pulling the headlight fuse before cranking again. If no go, unfortunately it's sounds like you will have to pull the tank to troubleshoot. I would first check your spark by pulling the plugs and checking all 4 cranking. You can also check them to see if maybe you are rich or lean.

The pilots can have issues from left over gelled gas. Even if you think they are clean. Find my thread about my 750 running rich from a few weeks back. If you have to pull the carbs, order a set of stock genuine Mikuni pilots just to rule it out.
So pulling headlight fuse eliminates some draw and allows more juice to plugs right? I’ll try that….I got it started this morning by charging/jumping with car…was reading fully charged from wall charger but did not start that way.

When back from ride, it started, but after sitting it did not. battery reads 12.5V.

I am thinking the bike may need 13 or 13.5V.

Ill try pulling the headlight plug or fuse….thks
 

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So pulling headlight fuse eliminates some draw and allows more juice to plugs right? I’ll try that….I got it started this morning by charging/jumping with car…was reading fully charged from wall charger but did not start that way.

When back from ride, it started, but after sitting it did not. battery reads 12.5V.

I am thinking the bike may need 13 or 13.5V.

Ill try pulling the headlight plug or fuse….thks
Does it run normal again after starting or did you still have to play with the idle to keep it running? 12.5v is low while running and could indicate a connection issue somewhere in the charging circuit.
 

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Discussion Starter · #8 ·
Pulled headlight fuse and it started, had been in wall charger but no jump required. i think I need a fresh battery that’s at 13-13.5A at least may have weak coils too but it is interesting that these bikes have light one when you turn key no matter what adding load to battery….of course I had just bought one for other bike, didnt use it as problem was elsewhere….big crank…best battery supposedly….gave it to my friend (he had given me a bunch of parts….now they are sold out😂
 

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Discussion Starter · #9 · (Edited)
Another thing I noticed is headlight goes on when I turn key on, and does not go out when I hit starter….on my CB1100F it goes out when I hit starter, on my GPz900R headlight turns on after bike is started…..seems like the Gixxer puts more draw on the starting and ignition circuits when starting by leaving the headlight on…unless someone miswired it before I had it but does not look like it from wiring diagram I think they are designed that way….
 

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Discussion Starter · #11 ·
Not sure what you mean with your very detailed one word response 😅 but maybe you are confirming that headlight stays on during starting and this is the way it is done on European bikes?
 

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you can install euro controls and have a lights off function, switch off before starting, they had those up to what just guessing 05? you also might get a yellow flash to pass switch for the high beam? love those
 

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Discussion Starter · #13 · (Edited)
Aha got you thks, I would actually like to have that light off option if I could source it….but I assume one might need to add certain other wiring or relays, etc so it’s unlikely plug and play….any further experience or advice regarding that is appreciated….meantime I’m just gonna get a new battery, has an older water filled battery anyway, worth running a good AGM….
 

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clean first gen!

sounds like a carb issue. i like these bikes, but not carbs. hard starting is probably a carb issue. like prix mentioned, it could be many things, but carbs are finicky. any passage or something not working, will cause issues. i'm thinking it is carb related. i'm dealing with two bikes with carb issues at the moment. carbs problems suck.
 

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Discussion Starter · #15 ·
clean first gen!

sounds like a carb issue. i like these bikes, but not carbs. hard starting is probably a carb issue. like prix mentioned, it could be many things, but carbs are finicky. any passage or something not working, will cause issues. i'm thinking it is carb related. i'm dealing with two bikes with carb issues at the moment. carbs problems suck.
Thks I do love the bike, so light and fast, and love the looks - it’s my newest bike year wise….

I really think I have it isolated to the voltage/battery resultant weak spark as like I said, starts with headlight due out, not with in….but yes even though I have had carbs off twice I still could have some issues, I still have to such them so I will get my fresh battery and assuming it starts consistently do that next…

I got back into bikes 4-5 years back and hadn’t touched a carb for many moons….now I have 9 vintage bikes and 25 carbs to deal with! It can be a PITA…and the carbs on mine are the BS34 which are CV type which I find the most finicky, and these are the most complex CV carbs of any I have too….
 

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It sounds like you still have carb issues related to the idle circuit. Also, for further consideration it's unlikely both coils would fail at the same time. Maybe time for a good battery use a tender too, freshen up the spark plugs, check the wires, boots, and where they go into the coils. I ran a superbike '86 750 for years, push start only by me, 36mm Flatslides, small battery, no charging system it was a total loss electrical system. Always started on the first bump in 2nd gear.

Good luck.
 

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Discussion Starter · #17 ·
It sounds like you still have carb issues related to the idle circuit. Also, for further consideration it's unlikely both coils would fail at the same time. Maybe time for a good battery use a tender too, freshen up the spark plugs, check the wires, boots, and where they go into the coils. I ran a superbike '86 750 for years, push start only by me, 36mm Flatslides, small battery, no charging system it was a total loss electrical system. Always started on the first bump in 2nd gear.

Good luck.
Thks Nick, yes I have new strong battery coming and I do use tenders, good point re coils…Wire and boots checked, plugs are new….I think it’s just the combination of a weak battery and these bikes keeping light in during start bcuz as I said above starts right up when headlight fuse pulled, nevertheless the idle circuit could be imperfect seems to be a wierd circuit and the pilot jets seems smaller than any other I have seen….sounds like your old 86 was cool, these bikes are just the best….another pic of mine
Tire Wheel Land vehicle Cloud Vehicle
 

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Great looking bike.

When you say weird size pilot jet, what do you mean? It should have a 35 stock. You have to run the exact style for these to work correctly and be aware, the wrong styles will fit and have the same numbers, but will be wrong. I just went through this, its was a giant PIA. Just make sure you get the 100% correct genuine part and don't let any parts guy say you can substitute. I have almost 30 years wrenching experience and learned a lot from these carbs. The lesson was never trust what the previous owner did or even that the factory got it correct.
 

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Discussion Starter · #19 ·
Great looking bike.

When you say weird size pilot jet, what do you mean? It should have a 35 stock. You have to run the exact style for these to work correctly and be aware, the wrong styles will fit and have the same numbers, but will be wrong. I just went through this, its was a giant PIA. Just make sure you get the 100% correct genuine part and don't let any parts guy say you can substitute. I have almost 30 years wrenching experience and learned a lot from these carbs. The lesson was never trust what the previous owner did or even that the factory got it correct.
Actually that was poorly stated on my part. I went back thru my pics and I can’t see the size but I’m pretty sure they were correct as I looked it up, I have the factory service manual. What I meant was that they struck me as being particularly small (as if one can tell that by eye or by blow thru feel🤣). I agree with what you are saying on all fronts, I have been thru many instance of crazy and wrong stuff happening to old bikes before I get them….I have a little CL200 Honda I modded and it had the wrong rotor with wrong TDC mark! This Gixxer had many poor cable and hose routings, wrong carb to airbox outer boots amongst other things I have discovered and am still discovering….but for now I am going to put new strong battery in, and then assuming it continues to start well, sync the carbs….
 

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I had a similar issue and it turned out to be a blocked vacuum pipe that opens the fuel tap (why not just use a regular fuel tap?). Anyway, solved by unblocking the pipe, allowing the vacuum from the carbs to the fuel tap to open the tap. Was intermittent because when the vacuum did work and the tap did open, it would fill the carbs and run for a while, then stop randomly.

To check, pull the vacuum pipe off the tap, put a large syringe on the pipe (I have one for bleeding brakes) and turn over the engine, the plunger should suck in to the syringe.
 
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