Idles with choke open but stalls on acceleration

[Ebme Geek]

Did you check your fuel tank for any water, that contamination came from somewhere.
And if you have any water sloshing around the bottom of your tank you will get a little bit picked up every now and again and  it's going to be a recurring problem 
 
Check the drain tube is clear that drains the area under the filler cap.
 
and check the face that the rubber seal of the cap goes down onto is not rusty, mine was, cleaned it with scotch bright pad, treated it with loctite rust converter, let it dry and put a light smear of silicon grease on it - happy days 

[110%]

That's a very good point. The filler cap is beginning to rust which would indicate the presence of water. There's currently 10l of fuel in there which I might try and drain to inspect before considering to put it back in. Thanks for the tip on the filler cap, I will go out and buy myself some locative rust converter!

[darrsi]

Could also try 300ml of Isopropyl Alcohol per full tank of fuel a few times, that stuff binds with any water and it then it gets burnt off as fuel.
It's cheap on EBay.

I use it a few times every winter, it doesn't do any harm at all.
Saying that, if you were to have a lot of water in there it would need draining anyway and then the leak fixed.

[110%]

I've just taken it out for a spin now and the problem hasn't fully gone away.
It seemed fine revving it at the kerbside but then 1 min into a journey the engine randomly blips and begins to stall. If it leave it idling for a while it ticks over fine, until i get going again and whilst accelerating it runs like crap.

I think I'm going to have to completely drain the tank, and then the entire fuel system again to rule out any fuel contamination. The only other component in the air/fuel system that could be at fault is the fuel pump, but other than that I might be looking at an electrical fault from the coils??

[darrsi]

Have you done a TPS check at all, when they go kaput the bike runs ropey?

[110%]

Ita got a brand new tps, air filter, fuel filter and spark plugs.

[unfazed]

There is probably to much water in the fuel to do anything other than drain it.
I would suggest you remove the tank Drain the fuel out of it, than remove the fuel tap and clean the tap filter .
With the tap out drain every drop out of the tank. Refit the tap, put the tank back on but do not fit the front bolt yet.
Put about 1 gallon fuel into the tank and connect up the petrol pipe to the tap, remove the pipe from the outlet of the pump. Fit a long pipe onto the outlet and direct it into a container.
Turn on the fuel tap, turn the kill switch to run and turn on the ignition switch, the pump should pump the fuel into the container. This will do two things, prove the pump works and pump fresh fuel through the pump and filter. Refit the original petrol pipe to the pump, connect the fuel sender and  lower the tank

Drain the carbs and with the the drain screws open run the pump to let fresh fuel flow through the pipes. tighten the drain screws and switch on the ignition. When the pump stops, turn the ignition  off and on again, continue this until the pump stops pumping, this means the float bowls are full. Refit the tank bolt.
Now start the bike and try it.
Let us know how you get on.

[110%]

Unfazed: that's my Saturday morning taken care of! Thanks for the method you've suggested. I'll let you know how I get on.

[110%]

I'm now back on the road.
I completely drained the tank, filter and pump and then finally the float bowls; took the filler cap apart to get rid of the rust and tidy it up, filled it up with some fresh petrol and away it went. One hiccup within 30 seconds but afterwards was running cleanly for 10 miles.

Does anyone want to buy 12.5l of what I assume is water contaminated petrol??!@

[unfazed]

Leave it rest for a week, water will sink to the bottom and then put it the 10 litres in  Lawn Mower and take the rest to Recycle

[sblar]

I'm now back on the road.
I completely drained the tank, filter and pump and then finally the float bowls; took the filler cap apart to get rid of the rust and tidy it up, filled it up with some fresh petrol and away it went. One hiccup within 30 seconds but afterwards was running cleanly for 10 miles.

Does anyone want to buy 12.5l of what I assume is water contaminated petrol??!@

Thank you so much for this very old thread. I had the exact same problem, with the exact same solution 

After testing the pump and taking the carbs apart, I found this thread.
I simply drained the tank and fill a few litres of new petrol in it. There was quite a lot of hickups still, since I didn't drain the fuel pipe, filter or float chambers, but it finally swallowed all the bad petrol and got back to normal operation.

Learning: Don't leave the bike in heavy rain for a long period with only a few litres in the tank 

[Gnasher]

Learning: Don't leave the bike in heavy rain for a long period with only a few litres in the tank 

Better still replace the filler cap seal 

[sblar]

Rigth, except that the seal isn't sold separately and the complete filler cap is around $350 

[Gnasher]

Rigth, except that the seal isn't sold separately and the complete filler cap is around $350 

Try these

https://mtp-racing.com/Fuel-Tank-Cap-7-Holes-MTP6626__Yamaha-FZS-600-N-Fazer-RJ021-022-1998-2001_1
or
https://www.wemoto.com/bikes/yamaha/fzs_600_fazer_sp/01/picture/fuel_cap_with_spare_key

You could also try these, you need to measure the rubber and email them. Like many parts they aren't always model specific in that they use off the shelf stuff and fit the same parts across many models to cut cost.
https://www.ncjetski.co.uk/products/yamahagenuinefuelcapseal-yamahamarine-yagp7u78320100
   
or use a universal and cut it to size, you just need to make sure it's big enough and the same thickness. 

https://www.ebay.co.uk/itm/402352153009?_trkparms=amclksrc%3DITM%26aid%3D1110006%26algo%3DHOMESPLICE.SIM%26ao%3D1%26asc%3D20201210111314%26meid%3Dcbde3ce84a1a4a2ca0afd1e7bed05454%26pid%3D101195%26rk%3D2%26rkt%3D12%26sd%3D254523940092%26itm%3D402352153009%26pmt%3D1%26noa%3D0%26pg%3D4429486%26algv%3DSimplAMLv11WebTrimmedV3MskuWithLambda85KnnRecallV1V2V4ItemNrtInQueryAndCassiniVisualRankerAndBertRecallWithVMEV3CPCAuto&_trksid=p4429486.c101195.m1851&amdata=cksum%3A402352153009cbde3ce84a1a4a2ca0afd1e7bed05454%7Cenc%3AAQAIAAABUObhgc4Nk8%252BdtAwOww4FKLaj%252FQ5qqgDlQCuqZA43WcPFUWDERCUugbbOk7XQv0JXlBfqCg2xKF3WcPghxGMFw2oSlXvfExEaMYr7I7LmrHcP6czY1wIMt0ORyKiCWt95xldincyyBx3g%252BNDW%252B%252FhWUgTaBhK6xAm%252BJIbCOMehu%252Bdwgrp%252FutCPvyb8KO9h4rrJ0zH9wH4QobXz71MGkE0ROQ1Hp%252FQIAyDYcoPyas31Fsuv%252FllmciFPrIzkYqBWNCaOlryzNJ6lf5z0%252Fm9kz5D7yymukXtC3i3DDxtPo74rqDWM1sOOWuJNnXvNL1cOWxu%252FfHQ7Nly2YFBr4k0CGFy5XUwSBBMOSVDsInvUk7n9PDPSGz0ZDz0k9TnESn%252FeaOdLHPSlfno9o6QmA%252BL47hQ0q4BoAb%252BZUBqKJYExpVSLPrJrvXn50CIVRiEvw4qgkxT%252BGw%253D%253D%7Campid%3APL_CLK%7Cclp%3A4429486

It's also possible it's not the rubber but the tank neck that's the issue, either repair it, if possible or replace the tank, for an undamaged one.


 

[sblar]

Thanks Gnasher, the link to ncjetski looks promising