Absolutely stumped. Cry for help!

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RickTaff
Posts: 21
Joined: Tue Jul 28, 2020 1:49 am
My Bike: zxr 750 1991 J1

Absolutely stumped. Cry for help!

Post by RickTaff »

Meant to MOT bike today, so started her up, let her warm up on various levels of choke, until choke off. Temperature gauge needle was on the first red notch and she was idling ok, nice consistent note. (with choke off) The odd pop in the exhaust when she first started; but nothing out of the ordinary

So jumped on the bike, clutch in popped her into first, clutch out - found the bite point and could feel the bike slowly pulling, but soon as i rolled on the throttle she died. Every single time. I think i even tried opening the throttle first and holding it at a steady RPM, for example say, 4k, and then found the bite, but as soon as the bite was found..... revs dropped like a stone and it cut out again

Anyway I have been told "it's the main jet, blow carb cleaner through all main jets on each carb, and a can of air, and job done" but then got told if the jets were clogged, it'd not idle, or be a very rough lumpy idle.

Now had 2 people suggest it is the sidestand switch. But my thought is - with my CB500S, if the side stand is down it cuts out the minute you put it into gear, instantly. So wouldnt the ZXR do the same? Or would it continue to tick over and find the bite as is happening?

Confused, massively
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banner001
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My Bike: ZXR400 L4
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Re: Absolutely stumped. Cry for help!

Post by banner001 »

Sounds more like the clutch lockout switch than the side stand switch... But it can only be one or the other.

Unclip the sidestand switch and put a paperclip across both terminals of the connector block on the loom, does the problem still happen? (if yes then your sidestand switch is probably OK, if no then the sidestand switch is faulty).

Next Unclip your clutch switch and put a paperclip between the solid black and the black/yellow wires on the connector on the loom, does your problem still happen? (if yes you have some odd electrical problem, if no then your clutch lockout switch is faulty)

But its most likely to be the clutch switch
UK ZXR400 L3 (1993) - Fully restored and on the roads, my green beast!
JPN ZXR250 A2 (1990) - Revs to 19,200rpm... 'nuff said :smt003
RickTaff
Posts: 21
Joined: Tue Jul 28, 2020 1:49 am
My Bike: zxr 750 1991 J1

Re: Absolutely stumped. Cry for help!

Post by RickTaff »

banner001 wrote:
Sat Jan 30, 2021 7:44 pm
Sounds more like the clutch lockout switch than the side stand switch... But it can only be one or the other.

Unclip the sidestand switch and put a paperclip across both terminals of the connector block on the loom, does the problem still happen? (if yes then your sidestand switch is probably OK, if no then the sidestand switch is faulty).

Next Unclip your clutch switch and put a paperclip between the solid black and the black/yellow wires on the connector on the loom, does your problem still happen? (if yes you have some odd electrical problem, if no then your clutch lockout switch is faulty)

But its most likely to be the clutch switch
Thanks! Dont know if this update will help you narrow it down at all, but I have been out to the bike a little earlier and started it up, knocked it into first with clutch in and found the bite, and again, the bike started to crawl forward as it should do.

But soon as i applied throttle it just wanted to die. With clutch pulled in and in first gear, i kicked sidestand down and bike cut out instantly, as it should, - therefore sidestand switch works, right?

However, I cannot start the bike at all with clutch pulled in, in first, with sidestand up. Electric starter button does nothing.

Perhaps due to the bike not being ridden in so long by the previous owner, it just needs an awfully long time to warm up. Because I have noticed when my friend was " quick blipping" my throttle yesterday while idling... it was a bit flat/lumpy. Almost a bogging sound to it. He had to roll on the throttle very slowly for the revs to climb. (i tried this in bite zone and it still didnt help).

Baffling me because about 8 weeks or so ago, I had the bike up on a paddock stand with rear wheel in the air, and went through all the gears fine while opening throttle. Didnt cut out once then & I have not changed or tinkered with anything on the bike since. Apart from tighten a jubilee clip around fuel pipe :smt017 :smt017 :smt017
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banner001
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Re: Absolutely stumped. Cry for help!

Post by banner001 »

Yeah, definitely the clutch lockout switch, bypass it like I said and it should be fine

They all go eventually, quite prone to corrosion.
UK ZXR400 L3 (1993) - Fully restored and on the roads, my green beast!
JPN ZXR250 A2 (1990) - Revs to 19,200rpm... 'nuff said :smt003
RickTaff
Posts: 21
Joined: Tue Jul 28, 2020 1:49 am
My Bike: zxr 750 1991 J1

Re: Absolutely stumped. Cry for help!

Post by RickTaff »

banner001 wrote:
Sun Jan 31, 2021 12:37 am
Yeah, definitely the clutch lockout switch, bypass it like I said and it should be fine

They all go eventually, quite prone to corrosion.
That lockout switch failing would still allow the bike to find bite, and begin to move, but die on throttle?
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banner001
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Re: Absolutely stumped. Cry for help!

Post by banner001 »

Correct, I had mine die on me coming home once, had to slip the clutch the whole way home
UK ZXR400 L3 (1993) - Fully restored and on the roads, my green beast!
JPN ZXR250 A2 (1990) - Revs to 19,200rpm... 'nuff said :smt003
kawizard

Re: Absolutely stumped. Cry for help!

Post by kawizard »

Did you solve this? The clutch issue does sound bob on, ive had this before.... But one other thing I just wanted to mention incase...

Like an idiot I had the gear shift linkage off to clean behind my sprocket cover.... after which I put back on the wrong way, causing me to shift into 6th - thinking I was in 1st gear (what a donkey). This meant I kept stalling on pull off, just wanted to check you arent as daft as me biggrin
kawizard

Re: Absolutely stumped. Cry for help!

Post by kawizard »

Otherwise, check your choke isnt sticking... but you would see higher revs. Sidestand switch can be looped out with a paperclip like the clutch switch if you wish to double check.
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