Power plateaus

[Bryce]

Hi there, it's been a while since I first posted here.  Finally got my collector's plates approved last week, so I took the bike out for a full day's ride yesterday.  Here's what's been done to the bike so far since I bought it:

-new rear brake pads/rear brake dust cover
-new gear shifter dust cover
-greased speedo cable
-new tire stems
-new grips
-adjusted suspension settings
-new valve cover gasket/grommets and a valve clearance check

All in all the bike ran pretty well yesterday.  Needs some of the backlights in the instrument cluster replaced, and the fuel petcock needs some of its rubber bits replaced (it's stuck open) but other than that the bike has no life-threatening problems.  It did over 500km yesterday no problem.

With that said, I have a couple questions.  Are FJ's reluctant to start when hot?  It's not 'hard' starting, but it does take a bit of throttle to convince it to come back to life.  It sounds good once it's running again though.  More importantly though: does the FJ create power evenly throughout its RPM?  I feel like my bike hits a few plateaus of power before it gets into the 4000+ RPM range and really comes to life.  I realize a sport bike isn't going to be a tractor down low, just wondering if maybe it should be smoother.  Maybe the carb diaphragms are getting old?

If anyone has any ideas (or can let me know if this is normal for an FJ) I'd appreciate it.

-Bryce

[FJmonkey]

1. fuel petcock needs some of its rubber bits replaced (it's stuck open)

2. I feel like my bike hits a few plateaus of power before it gets into the 4000+ RPM range and really comes to life. 

1. Stuck open can be a problem, if any of the 4 needles holding back the fuel in your tank leaks from a little crud, you have a potential flaming mess. If you are lucky enough to have it leak in the carbs then your case will fill up and possibly hydro lock when you start it. That is bad as well.

2. Are your pipes stock or after market? Aftermarket pipes normally come with jetting and that can cause some flat spots in your power band.

[Steve_in_Florida]

Bryce,
I'm glad you got your bike out to shake off the cobwebs.

My stock `92 starts right up when hot. The power is smooth throughout the RPM range. No flat spots that I can sense.

Any tiny pinholes or worn spots in your carb diaphragms can be patched with a product called "Plasti-Dip" or liquid electrical tape (or replaced with NEW from RPM Randy, if you have loads of spare $ $ $ ).

As Mr. Monkey said, you need to address the petcock "open" issue before it consumes you (...in FLAMES!).

Look carefully at the tires for signs of cracks or dry rot. A blowout or tread separation at speed is devastating.

Check the chain and sprocket condition, too. Replace if you can. Broken chains do LOTS of damage, too.

It sounds like you're well on your way to having a trusty, loyal steed.

Steve

[Arnie]

Bryce,

All engines have power plateaus.  Some are more evident than others, and lots of factors can affect this, including intake system design, exhaust system characteristics, valve timing, cam lift and duration, etc, etc, etc.  The FJ engine is 'pretty' linear in its output (ie; no great holes in the torque curve) but it does have some 'steps' as the revs increase.  Wait till you pass 6,000 rpm with the throttle wide open and experience that step :-).
I rarely ride below 3,000 rpm because that is where the engine becomes smooth.  
I'd suggest you spin your FJ's engine a bit higher, its not a HD after all.

If hot starting is a problem, try opening the throttle just a bit.  You may need a new battery or to service (clean and lube) your starter.

And get that petcock seen to.

Arnie

[Bryce]

1. Stuck open can be a problem, if any of the 4 needles holding back the fuel in your tank leaks from a little crud, you have a potential flaming mess. If you are lucky enough to have it leak in the carbs then your case will fill up and possibly hydro lock when you start it. That is bad as well.

2. Are your pipes stock or after market? Aftermarket pipes normally come with jetting and that can cause some flat spots in your power band.

I'm just waiting on parts to fix the petcock.  The vacuum shut-off worked fine the first time the tank was off, so it was only discovered a couple days ago.  Exhaust is completely stock.

Bryce,
I'm glad you got your bike out to shake off the cobwebs.

My stock `92 starts right up when hot. The power is smooth throughout the RPM range. No flat spots that I can sense.

Any tiny pinholes or worn spots in your carb diaphragms can be patched with a product called "Plasti-Dip" or liquid electrical tape (or replaced with NEW from RPM Randy, if you have loads of spare $ $ $ ).

As Mr. Monkey said, you need to address the petcock "open" issue before it consumes you (...in FLAMES!).

Look carefully at the tires for signs of cracks or dry rot. A blowout or tread separation at speed is devastating.

Check the chain and sprocket condition, too. Replace if you can. Broken chains do LOTS of damage, too.

It sounds like you're well on your way to having a trusty, loyal steed.

Steve

Yeah I was thinking I'd take a look at the carbs just to see what kind of condition they're in.  The previous owner said a shop went over the carbs but I'd like to make sure.  Tires are actually brand new - but they're from the 90's.  No signs of dry rot or cracks, but I'm taking it easy (I know old rubber can lose its pliability).  Chain and sprocket are good.

Bryce,

All engines have power plateaus.  Some are more evident than others, and lots of factors can affect this, including intake system design, exhaust system characteristics, valve timing, cam lift and duration, etc, etc, etc.  The FJ engine is 'pretty' linear in its output (ie; no great holes in the torque curve) but it does have some 'steps' as the revs increase.  Wait till you pass 6,000 rpm with the throttle wide open and experience that step :-).
I rarely ride below 3,000 rpm because that is where the engine becomes smooth. 
I'd suggest you spin your FJ's engine a bit higher, its not a HD after all.

If hot starting is a problem, try opening the throttle just a bit.  You may need a new battery or to service (clean and lube) your starter.

And get that petcock seen to.

Arnie

Don't worry, I'm not trying to lug it at 2000 RPM.  I ask because it felt more noticeable than I expected it to be.  Hot starting isn't really problem, like you say a bit of throttle is all it needs.  Just wanted to make sure this was normal for the bike.