Having problems concerning fuel...

[Jboy3219]

Hey guys, I'm new to the FZR scene but not to bikes. I recently bought a 91 FZR600 that had trouble cold starting and starting in general. I replaced all four plugs, put fresh gas in it, and a few other things to get it rideable, but still won't start. The fuel pump only seems to run when it wants to, if I create a vacuum on the carbs it pulls fuel through but otherwise doesn't seem to be getting any. Am I over looking something simple? Any input would be greatly appreciated, you guys will know a lot more than I do.

[pefrey]

What do you mean the fuel pump only works when it wants to? When you first turn the key, the fuel pump will prime the carbs (as indicated by a clicking sound) then turn off then the bowls are full. Have you turned on the gas petcock?

Difficulty in cold starting is indicitive of worn valves. Check valve clearances. There's a write-up in the Wiki.

http://fzronline.com/wiki/doku.php?id=h ... clearances

[Jboy3219]

Two days ago you could here the fuel pump click and prime the carbs, but yesterday it didn't seem to work at all. There are only 15k on the bike, should worn valves be a major concern?

[pefrey]

The fuel pump will only prime the carbs if the float bowls are low on fuel. If you were to turn your key on, let the pump prime, then turn it off, repeat, eventually the fuel pump will not prime at all because the carbs are primed. Did that make sense LOL.

Anyway, valve clearances that are out of spec can lead to big problems so you will want to check / adjust them as soon as possible. Checking is easy. If you have to adjust them, well, that's pretty easy too but you really have to take your time and understand what you are doing.

I also just realized that Wiki write-up is incomplete. There's a manual online somewhere.

Here are some links to the manual. It looks like there are a few of them. (under the heading "Very Useful Sites")

http://fzronline.com/wiki/doku.php?id=tech_books_links

[Jboy3219]

I was thinking the bowls were full so that makes perfect since. Hopefully the valves won't be an issue, and if you have anymore cheaper recommendations feel free to say anything that comes to mind...
Thanks for your help!

[pefrey]

On a 91, depending on mileage and usage / abusage, there's a good chance that the valves are tight. When this happens you don't get good compression and the bike is hard to start. Check as soon as you can. When diagnosing engine starting issues I think about what an engine needs to fire up. Fuel, Air, Spark. That's pretty much it. Sort those out then work from there. Of course there's other subtle details like timing and compression but those don't generally go haywire and cause an engine to suddenly not start.

If you are doing the work yourself it's always a good idea to be methodical so you don't repeat yourself or chase dead ends. Elbow grease is cheap (relatively speaking) and is the least expensive way to get work done on your bike.


Good luck.

[fzrbrandon]

+1 to Pefrey's comments regarding tight valves and poor cold-starting. Ditto on the fuel pump - If the bowls are full, the pump will not... well... pump.

Regarding timing, you really have to go out of your way for it to be off. Assuming everything in the motor is stock, the only way this could happen is if the cams were installed without the marks on the cam bearings being lined up with the marks on the cam caps. Oh, and the crank needs to be in the right position when installing the cams (#1 & #4 @ TDC). The other possibilities are:

1 - There is an offset woodruff key on the crank/flywheel OR
2 - The bike has adjustable cam sprockets OR
3 - The pick-up coil has been physically advanced or retarded

Barring those three scenarios, setting the timing on these bikes is pretty much a no-brainer.

[pnbell]

This will sound stupid but: Try push starting it!

I've had my bike crank and crank and crank (generally after a long rest period) and it doesn't start; ultimately the battery is just weak. Push starting gets her going, and then charges the battery and no more starting problem...

Long story short, before spending time and energy checking the valves, try this out.

Is there back story? Has the bike ever really ran for you? Has it sat for a long period of time?

[Jboy3219]

Update! Alright guys, to answer pnbell, it did run and I rode it but it took a lot of coaxing to get going. The last three days in a row I've got it running fine but it turns over and over and over until finally (after probably 5 minutes of cranking) it will start and idle for a few seconds and then die. After repeating multiple times it will hold idle and then once it idles for a few minutes it will pickup rpm drastically and run and ride fine.
Any ideas??? And there seamed to be a small gas leak at or above the petcock. I'm not sure if this is related but regardless it can't be helping...
Thanks for all the help again guys!

[reelrazor]

you already have gotten the needed advice...

check and set your valve clearances. More than one intake valve is tight.

[pefrey]

If you have not ruined the head already, riding it like that will certainly do so in pretty short order.

My basic understanding i that it is hard to start because the valves are not sealing because they are tight meaning the valves are slamming into the valve seat. Cranking and cranking builds a little compression by way of a cumulative effect and eventually warms things up just enough for the metal to expand and form a seat decent enough to get some compression and the bike started, but not good for the engine.

Riding it continues this effect, however the valves and valve seats are beating themselves to death.

Do you want to spend $ now or $$$$ later?

[reelrazor]

If you have not ruined the head already, riding it like that will certainly do so in pretty short order.

My basic understanding i that it is hard to start because the valves are not sealing because they are tight meaning the valves are slamming into the valve seat.

To refine your understanding, it is just the opposite..there is no lash (gap between cam lobes and valve stem), so the valves do NOT CLOSE. the valve faces do not touch the seats enough to seal. This is where the compression loss occurs. The reason they start after a buncha cranking is that they get wet (with fuel) and start to seal. As they get hot (and they get plenty plenty hot what with no metal to metal contact to allow heat transfer)..the valve heads expand and seal in that fashion

Cranking and cranking builds a little compression by way of a cumulative effect and eventually warms things up just enough for the metal to expand and form a seat decent enough to get some compression and the bike started, but not good for the engine.

Riding it continues this effect, however the valves and valve seats are beating themselves to death.

Do you want to spend $ now or $$$$ later?

Naw, they aren't beating themselves to death, they are getting seriously hot-way hotter than designed. This makes them deform, get brittle and break.

But, pefrey is right...neglecting this now will cost more, lots more, in the future if you keep forcing it to run, then run the hell out of it.

It's not a hard deal. We have talked and instructed many guys thru this.

[pefrey]

Hmmm, that makes more sense since you use smaller and smaller shims as the valves wear. Not to thread jack, how come everybody talks about tight valves, it's just the opposite. Also, how is it that such a scenario creates "tuliped" valve heads? I can certainly see why too big of a shim would cause the valve to slam the seat.

[reelrazor]

Hmmm, that makes more sense since you use smaller and smaller shims as the valves wear. Not to thread jack, how come everybody talks about tight valves, it's just the opposite. Also, how is it that such a scenario creates "tuliped" valve heads? I can certainly see why too big of a shim would cause the valve to slam the seat.

"tight" meaning the lash clearance is tight...not as in: the valve is tight at the seat. Lash is the point at which people deal with valves, so "tight" is what they experience. Valve spring 'seat pressure' is pretty much fixed at installed height and decreases as the valve recedes into the head...this is why getting thin on the shims starts getting scary.....seat pressure starts getting toward the low end and the springs will bounce on closing, running the risk of pitching valve collets.

They tulip because the get waaaay too hot when forced to run. the poor seal (which means poor valve cooling) allows the valve head to continue to expand. so the soft, grown valve hits the seat and the valve deforms under the load. It's kind of counter-intuitive, but a valve with too much lash is much happier than a valve with tight lash.