Unstable and Hanging RPM's

[Warp84]

have you ridden it like this or is all the tuning based on the bike in the garage?  I rehabbed my FJ from PO who let it sit 15 years, I was only able to get it about 90-95% dialed in on the center stand the rest came from riding it and then coming back and making minor adjustments. I can honestly say it took me like 300 miles of riding before I found the sweet spot for my set up. Have you tired fuel mixture screws in between 2.25 and 2.5? Are you using adjustable slide needs or are they the ones with the little plastic donut on them? I'm curious how your slide needles are set.

Also if tuning while idling be sure to put a big fan on that engine to help cool it and even then don't let it idle too long as even a big fan wont cool that engine the way air flow would cool it at even a low speed of 15mph.

We did one test ride when it had the 37.5 jets after the carb stack was put back together with undamaged carb bodies. That ride is when we uncovered the oil pickup screen gasket was cut, when oil started pouring out from the bolt hole just above the exhaust collector, after passing 55mph. That ride had the RPM ticking up and down the 1k rpm, several times a second, instead of the current slow fluctuation it has.

Like you said, it's nearly impossible to get a perfect tune on the centerstand, Since it's running so much better I'm prepping to check a few more things and set out on a test ride in a day or two. Wanted to make sure I dotted my I's and crossed the T's so I don't have another incident like on the first test ride.

-edit- The Slides for both kinds that I have are the fixed type with no clip for adjusting it.

[86FJNJ]

I know you said you have stock intake/air filter, is your exhaust stock too or is it more free flowing aftermarket?

Seems like you have it tuned really close, if it were me I'd put the fuel mixture screws between 2.25 and 2.5 and fill it up with fresh gas and dump half a bottle of seafoam in there and go for a ride and see how it behaves through the rpm range and see how it is when you stop at stop lights and stop signs, what does the idle do then after it's warmed up, what does it do when you ask for some throttle off idle or ask for more throttle at 3k rpm in 2nd gear...make some mental notes and adjust from there.

If your intake and exhaust are stock I don't think you should need to shim your slide needles the stock position should be ok. If putting some miles on it doesn't allow you to dial it in I would probably try the other emulsion tubes and slides you have from the later FJ's maybe that helps smooth things out.

Are the rubber diaphragms in your carbs OEM or aftermarket? Did you inspect them for any pin holes or tears? Do your slides all go up and down at the same rate or are any of them a bit "sticky" and slow to lift or return?

[Sparky84]

I had hanging idle, you'd give it a quick blip and it'd stay up before going down .... Turned out to be electronic ignition module

[Warp84]

Update: Rechecked the floats via a float test. The level in the tube was low, so re-adjusted the floats. Went back to 2.5  turns on the idle's and it's running so much better now. No burbles or coughing. Easy smooth start up. Still having it go up to 4 thousand RPM and not wanting to go passed it. But going to continue doing road test's and tune out the wall.

[red]

Warp84,
No doubt, you are fairly close on mix & tune.  Good show!
Kinda basic, but . . .
 - Are your throttle cables in good condition, and lubed?
 - There should be a slight amount of free play in the throttle cable system. No-slack there can cause a hanging throttle/ RPM issue.
Just a coupla thoughts, shooting in the dark here.

[Warp84]

Warp84,
No doubt, you are fairly close on mix & tune.  Good show!
Kinda basic, but . . .
 - Are your throttle cables in good condition, and lubed?
 - There should be a slight amount of free play in the throttle cable system. No-slack there can cause a hanging throttle/ RPM issue.
Just a coupla thoughts, shooting in the dark here.

What lube should I be using? I replaced the Carb side Push cable with a unit from RPM. All the cables move freely and with no noise. There's a small amount of play on the grip before the pull cable is engaged, so it's not constantly applying pressure.

[red]

What lube should I be using? . . . All the cables move freely and with no noise. There's a small amount of play on the grip before the pull cable is engaged, so it's not constantly applying pressure.

Warp84,
Any light petroleum grease (*NOT* WD-40, which is just kerosene) will do the job there. Get the aerosol can with the skinny red straw.  No Lithium (white) grease, there.
Then this gadget, at most bike shops and Amazon, will make cable lube easy:

Cable Lube Tool

HTH.

[86FJNJ]

Hi Red, I'm curious why not to use WD-40 for throttle cable lube?

[Billy Bananahead]

Back when cable sheaths had a lining of nylon inside then the application of the WD40 caused the nylon to expand in the sheath and "grab" the cable and stop it from sliding.
Whether cables sheaths are made like that now i don't know but i never use WD40 on cables because the problem once happened to me.

[86FJNJ]

thanks Billy, been using wd40 for years without issue but sometimes you don't know what you don't know so I'm open to changing.

[RPM - Robert]

Those cables are pre lubed you won't need to lube them for awhile.

We use tri flow to lube ours. Has a little bit of teflon in it and that helps them slide in the plastic tube liner.

The pull cable might a have a bit of slack but is the push cable adjusted properly?

Positive you don't have a vacuum leak somewhere? Depending on year the igniter box had a vacuum timing advance that can fail and cause a vacuum leak.

[Warp84]

Those cables are pre lubed you won't need to lube them for awhile.

We use tri flow to lube ours. Has a little bit of teflon in it and that helps them slide in the plastic tube liner.

The pull cable might a have a bit of slack but is the push cable adjusted properly?

Positive you don't have a vacuum leak somewhere? Depending on year the igniter box had a vacuum timing advance that can fail and cause a vacuum leak.

Greetings Robert,

This bike was pretty neglected by it's P.O. There's a solid chance there might be something wrong the ignition box. Do you have a testing procedure I can run through on it?

The intake boots were just replaced due to vacuum leak around the brass nipples on the previous set. Also replaced the caps and vacuum petcock line. (Also rebuilt the petcock with the RPM kit) I'll have to double check the line that goes from the boot to the box here soon.

[red]

Hi Red, I'm curious why not to use WD-40 for throttle cable lube?

86FJNJ,
WD-40 is mostly kerosene, not a lubricant. If it works at all, it's because the solvent is just re-locating some lube that was already there. Then the kerosene evaporates, leaving a sticky, gummy mess that attracts dirt. Spray some WD-40 on a glass pane, and see if you like what you find there in a week.
The solvent can also deteriorate the inner lining of some cables, bad plan.
Besides all that, I get pissed when stuff that I can buy in gallons is being sold by ounces, for more money.
All IMHO, of course.   

[Pat Conlon]

Do you have a testing procedure I can run through on it?

There are 2 vacuum lines on our Early FJ's. Cylinder #1 port vacuum line goes to the petcock and cylinder #2 port goes down to the ignition box. The purpose of the #2 vacuum line is to advance the ignition timing *upon closed throttle* (for emission reasons)  as discussed here:
https://fjowners.com/index.php?topic=11690.0

On the early FJ's ('84-87) the vacuum diaphragm is internal in the TCI ignition box and is non serviceable, non replaceable and the later '88-95 FJ's have the vacuum advance as a stand alone module, separate from the DCI ignition box. As our bikes age, this diaphragm can become cracked, thus leaking vacuum...causing a hanging high idle, what Robert was referring to....

How to test? We call this the suck test. Disconnect the vacuum line at the #2 intake port, clean the end, and suck on the hose. Put your tongue over the end of the hose to hold the hose under vacuum. The vacuum hose should stay under vacuum...if it bleeds off or if you can draw air through the hose, either the ignition box diaphragm is leaking or your hose is leaking. The hose replacement is easy, not so much the ignition box internal diaphragm.

Solution: Cap off the #2 intake port, use the heavy rubber oem Yamaha vacuum caps. It's hot in this area in front of the heat shield.
As discussed above there will be no performance loss with this vacuum feature disconnected.

Cheers....hope this helps.

Pat

[Warp84]

Do you have a testing procedure I can run through on it?

There are 2 vacuum lines on our Early FJ's. Cylinder #1 port vacuum line goes to the petcock and cylinder #2 port goes down to the ignition box. The purpose of the #2 vacuum line is to advance the ignition timing *upon closed throttle* (for emission reasons)  as discussed here:
https://fjowners.com/index.php?topic=11690.0

On the early FJ's ('84-87) the vacuum diaphragm is internal in the TCI ignition box and is non serviceable, non replaceable and the later '88-95 FJ's have the vacuum advance as a stand alone module, separate from the DCI ignition box. As our bikes age, this diaphragm can become cracked, thus leaking vacuum...causing a hanging high idle, what Robert was referring to....

How to test? We call this the suck test. Disconnect the vacuum line at the #2 intake port, clean the end, and suck on the hose. Put your tongue over the end of the hose to hold the hose under vacuum. The vacuum hose should stay under vacuum...if it bleeds off or if you can draw air through the hose, either the ignition box diaphragm is leaking or your hose is leaking. The hose replacement is easy, not so much the ignition box internal diaphragm.

Solution: Cap off the #2 intake port, use the heavy rubber oem Yamaha vacuum caps. It's hot in this area in front of the heat shield.
As discussed above there will be no performance loss with this vacuum feature disconnected.

Cheers....hope this helps.

Pat

Pat,

Low and behold that was part of the issue. The Diaphragm in the DCI had failed, as instructed, I put a cap over the vacuum nipple.  A bit more fiddling with the needles and it no longer stops at 4k rpm either. Both on centerstand and under power. Thanks to you and Robert for your input and solving the vacuum leak.