New Coils, leads and plug caps. Now won't start

[britx303]

Float valves good and fresh? Proper height? It seemed like its dumping fuel. Whats the milage? May be time for new emulsion tubes and just an all around full rebuild with all new gaskets and o-rings. Seems like alot,but its cheaper than a new bike and you will be HAPPY when you get it sorted.

[chris-seed]

I'm not too sure what the float valve height is. Is there a way to check this? They looked to be in good condition when I took the carbs apart.

Mileage is 43k. A full rebuild sounds expensive! But I'm sure it's worth it.

Thanks for the advice.

[britx303]

Ive never seen the emulsion tubes worn so bad as to give the symptoms you have at that extreme,but at 43K you need new ones regardless. Those are what is going to be the worst part of the rebuild as far as the damage to your wallet. I dont know what you have available back in the UK as far as a source for the o-ring/gasket/float rebuild kits. They are'nt too bad usually cost-wise. Me personally,after having many a junkyard fzr600,found its just easier to do the full kits and get the tubes and normally most woes are gone immediatly. If you arent sure how to check float height,then perhaps youve disturbed them in such a way that you didnt realise it when you opened them up to clean them and they are way off and there is little to no fuel flow control.Been there-done that myself, so no worries. I think on the wiki it may have some pics on setting float height......check there and get back to us.We will get you through it.

[buzzawak]

I have done a full rebuild on a few of these babes. I would be happy to help. Chris are you willing to do a few test to rule out some possible cause ?

First up I would check that the bike isn't flooding. You do this by draining all the carbies. Put every thing back. Turn the key to start and turn on the kill-switch but don't turn the engine over. Listen for the fuel pump to start filling the carbies. The pump should stop after about 5 seconds. At this point the carbies will not be filled. Turn off the kill-switch and on again. The pump should again pump and then stop after about 5 seconds. After the 3rd or 4th attempt you should hear the pump slow down as the carbies close their float valves and stop. After this if you try again you should not hear the pump startup.

If you want to give this a go and maybe record ( mainly want to hear whats happening) it I think it would be a good point to start solving the problem from.

[chris-seed]

Many thanks for the help guys. Much appreciated.

Buzzawak - I'll certainly try this method over the weekend/Monday and I'll record it. We'll go from there.

Britx303 - I'm not too sure what's available in the ways of new emulsion tubes etc. here in the UK ether. I can get hold of new gaskets and floats I think. I'm starting to think that maybe I did disturb the floats when I took the carbs apart. I'll check the carbs for flooding as Buzzawak suggested and then move on to float height adjustment after that.

I've just replaced the fuel filter for a brand new one, just to make sure that it wasn't blocked. It hasn't helped though.

The bike is kept under a carport at the moment, and we're having some severe cold weather (severe for the UK anyway) so working on it is quite hard at the moment due to the freezing temperature.

Cheers for the help guys! Always nice to get some good advice from people on the forum.

[buzzawak]

For carbi parts in the UK try here http://www.nrp-carbs.co.uk/shop/index.p ... ESC&page=2

[chris-seed]

Excellent. Thanks for that. I'll try the float height adjustment and then I may just bite the bullet and buy some rebuild parts.

Thanks.

[chris-seed]

Update:

The bike is now running!!

The floats were set way too low, so i raised them up to 24mm (measuring from the edge of the carb bowl to the highest corner of the float). The bike pretty much fired straight up with the choke on and then ran without the choke within a couple of seconds. Previous to this I had to leave the choke on for a minute or so to prevent the bike from cutting out.

So it seems to be running fine now but I still need to take it for a test ride to see if I have the issue with bogging down at mid-rpm like it had a while ago. I'll send another update later this week after I test ride it.

Buzzawak - I filmed the floats filling up like you instructed and everything seemed to be fine with them filling up.

Think I'll still rebuild the carbs soon though for peace of mind.

[buzzawak]

Once you have the carbies rebuilt I found the best way to adjust the float level is as follows

[chris-seed]

Excellent. Thanks for that. It's probably a much more accurate way of doing things compared to the way that I did it.

Thanks.

[chris-seed]

Ok, update on the bike.

I took it for a ride after changing the oil today. It seemed to idle well. When riding it though it still bogged down massively when I pull the throttle anything over a 1/4 turn.

When I returned from the ride I noticed a fuel smell. Took the airbag off and one of the overflow pipes on the carbs had spat out quite a bit of fuel.

I ran the bike with the airbox off and no fuel came out of the overflow pipe. But I did however notice that carb no.2 (on the left if you are sitting on the bike) was squirting fuel into the carb after I turned the engine off. The fuel was bubbling inside the carb. Fuel was also firing upwards from the small left hole infront of the carb (i think it's the top of a jet or something. It's the small hole that you can see at the bottom of the screen on the video below).

Video to show the fuel bubbling: https://vimeo.com/259161742

Also here's a picture of the carb slider after running the engine. The rest of the carb sliders were dry but this one is wet with fuel. The red arrow is where some fuel was bubbling out when revving the engine.

[buzzawak]

If I was you I would be doing the fuel level test. for the 1989 600 it is 3.8mm - 4.8mm above the fuel bowl mark.
It will give you a good idea of the float situation. I find doing it with the carbies off the bike is easier.

[chris-seed]

Quick update on this one.

I managed to get the floats adjusted to a correct height and the bike was running well. But there was still an issue with opening the throttle more than half, which causes the bike to bog down throughout the rev range.

I took it to my local mechanic (a Yamaha specialist), as I had run out of time and effort myself. He had the bike for a few weeks and went through everything including valve clearances, compression, leak down tests, coils, electrics. He also had the carbs off twice for inspection and visually they looked fine.

He confirmed that it is an issue with the carbs. He suggested either getting them sonic blasted or just buying a new set and replacing them completely. I rode the bike today and it still bogs down at anything over half a turn of the throttle.

Not sure what the best options are now really, as I'd love to enjoy the bike to it's full potential after upgrading so much on it so far.

Thanks,
Chris.

[buzzawak]

Hi Chris, I would ask for my money back. a Yamaha specialist bullshit.
So if the bike starts and idles ok but bogs down mid range, does it pick up at the top end ?

[chris-seed]

It wasn't too bad, as I didn't pay anything for his service.

I have recently sonic cleaned the carbs fully and re-assembled them. The bike runs much better and bogs down less, however it is still bogging down at anything over 1/2 throttle. It bogs down from around 6k rpm to the redline. So it's still not fixed but is idling and running much better.

Next I may try the inlet boots from the carbs to the manifold, as one of them is cracked on the outside. I couldn't see any crack from the inside but it's probably worth a shot to change them out, as they aren't too expensive to change.