GPZ500 Issues

[stephen_o]

Had a problem tonight, bike ran fine for 1st 2 miles pondering along at 5k doing 30 until i reach a double roundabout and the speed limit goes up to 50, Hit the 50 limit still in 3rd or 4th gear before changing up as I did I felt a bit of a missfire, then after going into 5th felt another slight miss...looked at the mileometer and it was about right for going on reserve so I flicked the tap to reserve as I reached another roundabout from where the speed limit goes up to 60. Got into the 60 zone and started to accalerate steadily upto 60 but didn't get there..the revs died off and I pulled over to the side of the road. Now Ive had this before many times on this bike, but the difference this time is it ticked over fine and only stalled on opening the throttle, any opening, couldnt get above 2k revs or would stall. Usually I find its an airlock, so open the tank lid and give it a min, but my petrol lock broke so the tank cap is only taped down. Anyway gave it a min but no joy. could start, idle was fine, but couldnt pull off. In the end (ive had it happen before) I opened the choke up to race the engine for a bit in case of a bit of crap...did that..still wouldnt run right. In the end I did 7 miles with the choke on full and not moving the throttle to get near home. When I got to within a mile of home hey presto it rights itself and I get back home with things "normal"

1st could anyone give me pointers to look at?
2nd the engine when it got home was very hot and the cooling fan has stopped working, my haynes manual doesnt cover it so any ideas what to check?
3rd on tickover with a boiling hot engine my oil light was flashing with increased frequency although this stopped when revved. my oil level is fine...what do i need to address here.

Any sane ideas would be welcome


Stephen
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current scoot 2009 Yamaha YBR250 + Current Pootle 2013 Nissan Leaf

[Vincent]

I'd probably look at the tap first..is it a vacuum tap or gravity fed? Does it run OK again on a full tank? It could be running hot as the mixture is week.
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Space Is Deep

[stephen_o]

I don't know what type of tap it is but will check it out thanks
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current scoot 2009 Yamaha YBR250 + Current Pootle 2013 Nissan Leaf

[Vincent]

[stephen_o]

Mine is on off and res
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current scoot 2009 Yamaha YBR250 + Current Pootle 2013 Nissan Leaf

[stinkwheel]

I'd have a look at your air filter for one thing.

Then, as others have suggested, I'd check the tap and fuel filter. It is a vacuum tap. There is a gauze filter inside the tank, you need to remove the tap to get to it which means either draining the tank or taking it off while fairly empty and leaning it over to one side so the fuel sloshes away from the tap (I rest tanks in an old tyre for this job). Fair chance the bottom of the filter is choked or the hole leading to the reserve position has a bit of muck in it.

It IS a vacuum tap, there should be the fuel hose running between the tap and the carb and a second, thinner one between the tap and the inlet manifold vacuum stub.

Check your coolant level. By removing rhe radiator cap with the engine cold and seeing if it needs to be topped up, not just by looking at the expansion bottle. You can JUST get it off without removing the fairing with the steerig at full lock by using the tips of your fingers (or recruiting someone with small hands).

Check around the area of the oil pressure sender switch. It's on the bottom left side of the engine. A round rubber cover with a single wire sticking out. Make sure the exhaust and bodywork aren't touching it. Anything pressing on the outside of it can make the oi light come on. Any breaks in the insulation of the wire leading to it or on the rubber switch cover which could allow it to short out would also make the light come on.

The fan circuit is very simple. Power goes to the fan motor from the fuse box, the fan motor goes to the fan switch. When it gets too hot, the fan switch allows the fan motor to earth and the fan comes on. Simple, dirty test is to undo the connector that attaches to the fan switch (top right of the radiator as I recall) and short it to earth (any bit of metalwork) with the ignition on. The fan should run. If it does, your fan switch is suspect. If it doesn't, the fan itself or the wiring attaching to it needs checking.

Worth noting Second gen (disc brake rear, 17" wheels) GPZ500s temperature guages over-read by a fair bit. Fan wouldn't normally come on until they actually hit the red.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[stephen_o]

thanks for the replies, plenty for me to be getting on with on a wet day then!
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current scoot 2009 Yamaha YBR250 + Current Pootle 2013 Nissan Leaf

[Kickstart]

Hi

This is exactly the symptoms we had with a GPZ500 when there was water in the petrol tank. Fine until reserve, and when switching to reserve it idled but but died when you touched the throttle.

Add some petrol, switch back to normal tank and drain the carbs. Then try and start it. If that fixes it then drain the tail fully and decant the petrol from the top of the water .

There is a drain hole from around the filler cap (might have to unbolt the cap and surround to see it). Check it is clear.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[pdg]

The GPZ500 I have (for sale ) has 'on', 'off', and 'res' printed on it too.

It is a vacuum controlled tap...

Might be a bit of a rare case, but... If the vac tube is split or loose then it could be opening just enough to supply fuel for idle, but not enough for faster running (leak coupled with decreased vacuum with open throttle - an air leak here will affect the running as well, compounding the situation.)
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Any and all advice given should not be followed - if you have to ask it means you don't know so get a man in to do it for you.

[stephen_o]

Thanks for this info. The bike runs fine on main tank but is often a pig on reserve. Ive often thought water in fuel or starvation through hearing whistling or seeing condensation aon top of tank filler. Ive tried to clear the pipe which I think is a breather (from hole in filler area to a nozzle out the back of tank under seat?) Which had some shit in it and water...then the tank lock broke so its taped down anyway. I didnt fancy a dtripdown as its my only transport but will atempt on sunday.
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current scoot 2009 Yamaha YBR250 + Current Pootle 2013 Nissan Leaf

[groovylee]

if you find that your tap is dodgy, give me a shout, i have a spare one in the shed you can try

one other thing that has been mentioned is the air filter. it is easy enough to change, and just recently there have been a couple of people on the owners forum that have had their air filters disintegrate, causing shitty running. they can be had cheaply enough on ebay when i replaced mine it was looking decidedly crap, and since replacing it, the bike has run much better

good luck getting it sorted.

Lee

edit: if you havent already, join these sites:

https://gpz500.co.uk and https://www.ex-500.com

the latter one being more for the american guys. they are full of useful info
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Past - 1988 honda revere 600, 1996 kawasaki gpz500s, 1999 Yamaha R6

Current - 2002 Aprilia RSV1000R & 1999 Kawasaki ZX6R

[stephen_o]

Thanks, not had chance to look at it yet, I had hoped after the final mile home was ok last night that it would be ok today but had trouble right from the off, I called for petrol and put back on main tank but that didn't achieve anything until I had done another mile or so. Stopped in traffic managed to get it to rev to 6k without the choke on, it then settled down to be ok for the rest of my 20 miles.

Appreciate the offer, got things on tonight so likely to be sat night when I look at it.
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current scoot 2009 Yamaha YBR250 + Current Pootle 2013 Nissan Leaf