Just Because

[Urban_Legend]

One of the best thing about the FJ is how easy it is to work on. So after a little discussion on Facebook tonight about fuel economy and jetting,  I get to thinking.  I have a new set of bigger than standard jets and the bike has always felt a bit sluggish at low rpm and a bit surgy (if that is a word) at higher revs.

So here I am Monday evening,  long day at work, dinner is done. And now bike in bits. Lucky I know every bolt on it. Will finish it tomorrow.

From This


To This in 30 mins

[fj1289]

Do you find it helps to filter the cooling air to the head?!   

[Urban_Legend]

Do you find it helps to filter the cooling air to the head?!   

Had to sit them some where, but filtering the air to the head might not be a bad idea. Plenty of bugs in there.

[Urban_Legend]

Ok tech question.  I have just changed my pilot jets from 40's to 42.5's. So my issue is I went from being lean to really rich. The new pilot are not genuine mikuni,  and I have heard the the non genuine items are bigger.  So should I spring for genuine mikuni jets or is there a way to lean it out without changing jets again.

[movenon]

No expert here but I would stick with Mikuni jets. I assume you readjusted your fuel/air screws and rebalanced your carbs?  From reading your first post I can't determine which problem you are trying to solve. The pilots are most effective 0 to around 1/4 throttle.  How are your carbs set up ?
Air Pilot jets......................
Fuel Pilot Jets....................42.5
Needle position................
Main Jet.........................

That info might help another member to help.  Nice looking bike by the way . POD's sure make it a lot easier to do carb work ! Now if the throttle cables had a quick disconnect .

I have a 1200 with 42.5 fuel pilots, air pilot jets 155, needle in mid position, 117.5 mains, My fuel air screws are out about 2 1/2 turns.   I have been getting 46-49 mpg (using GPS for mileage calculations).  I am rich on the top end and since have backed down my mains to 112.5's.  I would have used 115's but I didn't have any on hand.  Haven't had time to run it since the jet change.
George

[Urban_Legend]

Hi Movenon. Sorry about the lack of info. My aim was to liven the bike up a bit. It has always seemed doughy at low revs, and with 17/40 sprockets, I am told it should be wheel standing out of corners (which the bike does not). I had forgotten about the needls and you the carbies have been balanced. I was thinking the bike was running lean, so I decided to play with the jets (might be a bad move , but I ave to learn somehow)

No expert here but I would stick with Mikuni jets. I assume you readjusted your fuel/air screws and rebalanced your carbs?  From reading your first post I can't determine which problem you are trying to solve. The pilots are most effective 0 to around 1/4 throttle.  How are your carbs set up ?
Air Pilot jets...................... 155
Fuel Pilot Jets....................42.5
Needle position................It's in the 3rd (mid) groove
Main Jet......................... 115
Fuel/Air screws are 2.5 turns out

That info might help another member to help.  Nice looking bike by the way . POD's sure make it a lot easier to do carb work ! Now if the throttle cables had a quick disconnect .

I have a 1200 with 42.5 fuel pilots, air pilot jets 155, needle in mid position, 117.5 mains, My fuel air screws are out about 2 1/2 turns.   I have been getting 46-49 mpg (using GPS for mileage calculations).  I am rich on the top end and since have backed down my mains to 112.5's.  I would have used 115's but I didn't have any on hand.  Haven't had time to run it since the jet change.
George

[Pat Conlon]

....I am told it should be wheel standing out of corners (which the bike does not).

Who told you that?

[movenon]

No problem on the information. Your jet numbers look good or at least close enough for a good running FJ.  The proper way to work with the jets is to start with the mains and work down.  Reading your comment about surging would lead me to believe you are lean in the mains BUT with 115's you should be good.

If it were me:
I would do a plug reading "just because"
Then make sure the floats are in spec, parallel and not binding,
Check for any air leaks associated with the intake manifolds, cracked manifold, O rings etc..

There is some good info down in the files section the carbs and tuning that might be worth a read.

"...I am told it should be wheel standing out of corners (which the bike does not)."  Well mine doesn't either .  Might be a bit optimistic for a 100-130 hp bike weighing 580 Lbs plus or minus with stock gearing anyhow.  I think of my FJ as more of a train with a little bit more power.  Now if you can get 200hp and the weight down to under 400 lb ... (and if I lost 150 lbs  ) The above is just an opinion. There are some high hp/TQ FJ's out there that will get your attention. Those members can enlighten you more than me.

Hope some of this helps more than hinders.
George

Gives you an idea of what effects what at what throttle position.

[Urban_Legend]

Thanks for the info George.
Pat it is entirely possible I dreamed it all after inhaling too much petrol fumes while pulling the carbs off.
I might try lowering the needles.  The carbs were rebuilt at the start of the year and it got all new seals and o rings and float Heights were good.
When I started the bike last night it only seem to be too rich at lower rpm, but haven't taken it for a ride to confirm.  Plenty of black smoke when giving it a rev from idle but cleared when held a 4000 rpm and reved.

[the fan]

that sounds a lot like worn emulsion tubes. Factory pro makes replacements but I am not aware of anyone who has tested them. I believe RPM also markets replacements, which I am sure are well tested.

[rktmanfj]

that sounds a lot like worn emulsion tubes. Factory pro makes replacements but I am not aware of anyone who has tested them. I believe RPM also markets replacements, which I am sure are well tested.

I think emusion tubes were a part of the FP Config10 kit.   

If so, I have a set in the '89.

[Urban_Legend]

that sounds a lot like worn emulsion tubes. Factory pro makes replacements but I am not aware of anyone who has tested them. I believe RPM also markets replacements, which I am sure are well tested.

The emulsion tubes and the diaphragms are the only things I haven't replaced.

[Bones]

Your diaphragms are easy to check Mark, with the air filters off just lift the slides up with your finger and put a another finger over the big elongated hole at the top, if the slide stays there or at the very least creeps down very slowly their ok, it it drops quickly they've got a tear or hole in them.

You say it's doughy down low, but what's it like at high revs, does it pull hard, have you ever done a compression test on it.

The 4 deg ignition advance mod adds a little bit of pep down low, doesn't take long and easy to do.

[Urban_Legend]

Your diaphragms are easy to check Mark, with the air filters off just lift the slides up with your finger and put a another finger over the big elongated hole at the top, if the slide stays there or at the very least creeps down very slowly their ok, it it drops quickly they've got a tear or hole in them.

You say it's doughy down low, but what's it like at high revs, does it pull hard, have you ever done a compression test on it.

The 4 deg ignition advance mod adds a little bit of pep down low, doesn't take long and easy to do.

Hi Bones. The diaphragms seem ok, just old, and they have been patch, so new one wouldn't hurt. It pulls hard between 5000 and 7000ish rpm then seems to run out of legs and struggles 9surges up to 9000 (not that I get up there very often).

I have not don't a compression test on it. The motor is as I bought it off Timbo. I have been thinking the it probably needs the valve shims done, but I don't have the gear for that.

I have not done the ignition advance. All these reason are why I would like to get to a shed day, but my contractual (and family) commitments are making that difficult, and I feel I have donated enough money to the local bike shop.

Speaking of contractual commitments, there is a very real chance that I might not be able to get to the FJ Rally now either. Bugger. I was looking forward to it too.

[Urban_Legend]

I suppose my next big question is - Are the emulsion tubes and the diaphragms/slides interchangeable between the 1100 and 1200?