Idle Speed with choke on

[wildfire]

Ok so my bike is a '92 1200.  I would like to know what the expected rpm's are when full choke is used starting the bike from cold .

In other words, if the warm engine idle speed is 1100rpms what do you guys get when you start the bike cold and have the choke on fully.

Been a long day for me so I might not be explaining my question very well.

[Harvy]

Usually somewhere around 2300.

Harvy

[Pat Conlon]

My '92 starts cold with the choke on and idles at 1200, then after about 20 seconds or so, depending on the ambient temp. as the engine warms up the revs rise to 2300 as Harvy mentioned.

It's important to note, even after the on choke idle races to 2300, the oil temperature is no where near it's proper operating temp.
It takes several minutes for that to happen.

[wildfire]

My '92 starts cold with the choke on and idles at 1200, then after about 20 seconds or so, depending on the ambient temp. as the engine warms up the revs rise to 2300 as Harvy mentioned.

It's important to note, even after the on choke idle races to 2300, the oil temperature is no where near it's proper operating temp.
It takes several minutes for that to happen.

Hmm, I have not started my bike for about 4 weeks until this morning  I noticed that when using choke on start up from cold the rpms went straight to about 2400 rpms.

Before that when starting when cold with choke on the rpms would be about 1400. It never had the usually rise in rpms when warming with choke on. By that I mean it never had the expected  surge of rpm's with choke on you describe as racing.

Vacuum leak maybe?

[Mark Olson]

Your choke system is working properly , no need to change anything .
In the past you may have had a partial restriction in the choke circuit but now it is ok.

It can be common for the revs to go up to 4k at full choke and you push the knob in slowly to achieve around 2k while the engine warms up.

MarkO

[airheadPete]

What you're describing sounds fairly normal.
My '92 starts on full choke at about 1200rpm. I stand there for a few moments, waiting for it to race up to 2500-3000ish. When it does that, I push in the choke to re-establish it at 1200rpm or so, (I'm not about to stand there and let her rev like that cold). I usually then have time to suit up before the revs start climbing again as she warms. (BTW, completely stock except for #40 pilots; she hated starting cold, (read: wouldn't), when it was in the 30's on the stock pilots.) HTH.

[ribbert]

It's important to note, even after the on choke idle races to 2300, the oil temperature is no where near it's proper operating temp.
It takes several minutes for that to happen.

Oil takes a long time to get up to it's operating temp. If you consider the time it takes you car to reach coolant operating temp, treble it for oil. I won't thrash my bike from a cold start until I have done at least 15 to 20 kms, depending on conditions. This varies from engine to engine but is a good rule of thumb.

The bike specific habit, that I've never understood (no one does it in their car) of letting it sit there idling for a period of time has no benefit and it you want to spit hairs, has a down side, it is no good for your engine.
The best thing you can do is start it and ride it off while being kind to the engine until the oil is hot, which is way longer than most people think. Any mechanic or owner with a temp gauge will verify this.
This will also get the oil hot quicker.

Noel

[~JM~]

My stock '89 will rev up to about 3K RPM with the choke on.

My FJ is probably my coldest blooded bike. It takes a while for it to warm up & accept throttle input without gagging & dying. Of course it is my largest bike & my only 4-cylinder.

Good luck.

[jscgdunn]

what you are experienceing is typical.  We have a number of FJs (in fact we are overstocked) and they all are pretty similar.  I would not say they are cold blooded; it is important that the carbs be clean, and for starting the enrichener (ie choke) circuit be clean.   A "warm up" is not really required for normal riding (keeping RPMs below 5000) in my opinion.  Get your gear on, choke it, start it, and ride away.  After about 100 yards you should be able to push the choke off and ride.....

Just my experience,

Jeff

[FJmonkey]

Changing your pilot jets to #40 really helps the cold start issue. I almost don't need the choke to start from cold. With the standard pilots, she needed the choke for more than a few minutes. I had to relearn how start my FJ when I put the 40's in.

[wildfire]

Thanks for all the replies fellas.

[~JM~]

Changing your pilot jets to #40 really helps the cold start issue. I almost don't need the choke to start from cold. With the standard pilots, she needed the choke for more than a few minutes. I had to relearn how start my FJ when I put the 40's in.

That is most likely what is needed. My bike is all stock to the best of my knowledge, with the exception of a K&N filter from the P/O. I know that most bikes were jetted lean to meet USA import standards.

What is usually the best jetting for a stock '89 at slightly above sea level?

How involved is the job?

Thank you.

[Pat Conlon]

It's important to note, even after the on choke idle races to 2300, the oil temperature is no where near it's proper operating temp.
It takes several minutes for that to happen.

Oil takes a long time to get up to it's operating temp. If you consider the time it takes you car to reach coolant operating temp, treble it for oil. I won't thrash my bike from a cold start until I have done at least 15 to 20 kms, depending on conditions. This varies from engine to engine but is a good rule of thumb.

The bike specific habit, that I've never understood (no one does it in their car) of letting it sit there idling for a period of time has no benefit and it you want to spit hairs, has a down side, it is no good for your engine.
The best thing you can do is start it and ride it off while being kind to the engine until the oil is hot, which is way longer than most people think. Any mechanic or owner with a temp gauge will verify this.
This will also get the oil hot quicker.

Noel

***Noel, I agree 1,000%***  My comment about oil temp. should not be construed to mean that you let your bike idle to raise the oil temp.

Never do that. Never.

You will cook your exhaust valves. Our air cooled engines need air. After the choke start up procedure, start riding, get air moving across the cylinder fins.

However, ride gently, let the oil get to temp. before visiting the kookaloo zone.

I have a theory: I believe that the majority of the FJ engine's ring/bearing wear comes from early aggressive riding before the oil comes up to op.temp.
Reason: I have seen street bike FJ engines with only 60k miles on them, showing low compression, needing rings/or reseating the valves....and I have seen FJ engines with well over 100k miles with stock compression numbers, and wondered why?

I think it could be the oil temp issue.

[FJmonkey]

What is usually the best jetting for a stock '89 at slightly above sea level?

How involved is the job?

Thank you.

#40 pilots will be a good size. Regarding how much effort, that depends on whether your K&N filters are the pod type or you still have your air box. If the air box is already gone then you are in good shape. I highly recommend getting or modifying a screwdriver to remove and install jets. Here is my pilot tool.


You want the blade to be a snug fit in the jet, and a close fit inside the cavity, the jets are soft.



Drain the carbs, take the carbs off, turn carbs over. Either buy a JIS Phillips bit or get the RPM SST fastener kit. A regular Phillips bit does not fit properly and the OEM screws seem really soft. A small impact driver was needed to get some screws loose for me. Remove the bowls, remove the old pilots, install the new ones then put it all back together.

If you will be ordering anything from RPM like the jets, consider the UNI dual air filter pods. K&Ns breath really well, but let more dust past the filter and into your engine. The UNIs are reusable as well.

[~JM~]

Thanks for the reply. The K&N is a cartridge type in the original air box. I'm not a fan of K&N filters & usually run UNI filters.

I have some hollow ground gunsmithing screwdrivers that fit jets well, along with the JIS drivers.