Is it posible that a stock bike needs rejetted?

I have a stock 82 xj650 maxim and when I pull the plugs after a ride the plugs are a little white on the ends. Would it be wise to go up 1 or 2 jet sizes? The carbs have been synced but I don't have a color tune. I would take it that it's leaner off idle though.

 

A stock bike needs a re-jet if you live in the mountains.
You should turn your Pilot screws (4) out 1/8 th turn (that's alot), and look at your plugs again. Fine tune with smaller turns as needed.

You can post pics of your plugs on brown cardboard.
Then you'll get everyone's opinion.

 

i had this conversation with a Wizard member of XJ just last night on the telephone. with the exception of the mountains, the answer is no (with the airbox)

 

Is it bone stock as far as the air filter and exhaust also?

 

I think it may vary with the quality of gas in your area, ethanol blends are pre-oxygenated for cleaner air, they may run a tad lean.

 

Unless you have owned the bike since new or know all the history on the bike the P.O or P.O.'s could have done anything to the carbs. Having them synched only means they are opening and closing properly and operating at peak efficiency.
Are all the plugs the exact same? What about a potential air leak? Is the air filter the actual O.E.M. filter, because some after market filters may breathe freer and lead to lean out conditions. K&N are distinctive with both appearance and feel, but a cheaper paper one might look the same as stock.
Also, if the tips are as white as you say I wouldn't put too many more miles on it as it could lead to some serious motor damage.
As mentioned earlier, pictures would be great.
Hope it gets sorted soon, good luck.


Graham

 

Yeah I'll have to get pics. Yes it has stock exhaust and air box. I got the air filter from Len so it should be fine. I've cleaned the carbs out and am pretty sure all the jets are stock and I've check the float height dry. It seem to run good when warmed up. Just doesn't start right off the bat when cold. Just takes a litttle cranking.

 

stock fuel jets at bottom are 110 Main and 40 pilot. Air jets under the diaphram are 195 pilot and 50 main

 

I got my pictures. The number 4 plug is alittle black but the other look alittle lean to me with some white on the ends.

 

If those Plugs are shown: 4, 3, 2, 1

Leave 4 alone and add some Richness to 1, 2 & 3

Not much.
Visualize a Stop Watch with the Big Sweep Hand on ZERO.

Move the Screw OFF Zero Counterclockwise to: 53~55 Sec.
Just a Tweak ... Out.

Leave the one with color ... alone.

 

I have very similar color ( 3,2,1) on mine and I live at 5000+
ft. I'm currently trying 4.75 on the screws. I should be rich
but they always seem to run too lean. A local yamaha tech
suggested I drop jet sizes, but I'm reluctant as he says I
should be rich.
The valves check out,the carbs are spotless and dead on the
gauges, stock air box,screamin eagles on the collector (plugs
looked the same before).
Only other change from stock is a k&n filter (this will add some-
what to a leaner condition but it was that way with the stock
filter).
SO.......I'm kinda at a loss as to what to try next.
Any ideas would be great.

 

That pilot screw has very little effect beyond 1/3 throttle. If you're truly lean when riding it's more likely to be the float level.

My 650 would blacken the plugs at idle but were still as clean as the cleaner 3 in the pic when it was ridden.

So long as you have some browning of the insulators you are probably fine. Compare then to a new plug, I bet they aren't as white as you think they are.

 

I just tried putting one shim under each needle and now it is WAY TO RICH. So I guess I'll have to go back to where I was. I don't see a in-between.
I think when I shimed it that it moves it up to much because of the little notch where the needle sits. I think maybe the next size jet would work better. Any thoughts?

 

i never heard of anything like that, could you explain which needles and theory n stuff for me?

 

It's an old trick. You put a paper thin washer under the needle jet and it richens things up a bit. That's how it was explained to me anyway.

 

the needles he speaks of are what wee call metering rods when applied to automobile carbs. The shims change the seat position of the rods in the jets. when the slides open the needle jets lift allowing more fuel to pass, the shims change the position of the needles within the jets more shims more fuel. chacal has an assortment of shims available from .10-.40mm they run $6-10 bucks a set. It does not change the overall jetting size I mean a size 110 jet isn't going to flow as much as a 112 at wide open throttle but it changes the mid range, they are more for dialing in the carbs than to fix an over lean condition.

 

OK, first off, you shouldn't need to re-jet a completely stock bike except maybe for regular high-altitude use.

Setting float levels dry is only a starting point, they must be verified using the "clear tube" method and fuel. MiCarl is right, if your float levels are off even a bit too much either way it will affect how rich or lean that carb runs.

Once everything is right; correct float levels, carbs sync'ed to within a RCH of each other, color-tuned to perfection, starting instantly, idling like a sewing machine and running the way it did when new---

You may notice a nearly imperceptible "turbo lag" effect to throttle response at certain RPMs.

Back in the day, the fix for that (and virtually all of the major motorcycle magazines of the time did it to their test bikes) was to slip a .010" washer (or .020" depending) under the needle clips to raise the needles just a tad.

It's a very valid tuning tool; the Amals on my Norton (and a lot of mechanical and aftermarket carbs) have slotted needles for the same purpose, being able to raise or lower the needle slightly.

All that being said, it's NOT something you want to add to the equation until everything else is 100%.

NO SHORTCUTS. That's going to be my new mantra, I chant it enough.

 

this shows what adjustments change what part of throttle opening
it's not exactly for our carbs but the idea is the same, the adjustments overlap
putting shims under the needle would move that line to the left
next thought
the little post that sticks up in the well where you dropped the shim will raise the needle the thickness if the shim +the height of the post if you didn't notch the shim to fit over the post
the starting point of the needle height is the top of the pin
did that make any sense ?

 

Yep you are right. that little post down there is the problem. Does the shims Len sells miss the post? I guess I need to try the float height then. That means you check them with the clear tube on the bike,then take them off readjust and put them back on right? And the fuel should be level 1mm lower then the top of the bowel?

 

Mr chacal's shims, i don't know, i filed a slot in mine
final check, yes on the bike preliminary check on the bike to get what one goes up or down but you can adjust them off the bike but you have to use gas and that can get messy
hint: a little bend in the tab goes a long way

 

The rack needs to be level, front to back and side-to-side.

I find it easier to mount the rack in my vice and level it up than to try to level the bike. The on-the-bike check is more for maintenance, to see if anything's changed drastically. Initial adjustment is much easier with the rack off.

 

Here's a post with the diagram from Rick I mentioned: http://xjbikes.com/Forums/viewtopic/t=23490.html

 

I have not got a clear tube to check the float height yet. Does the float height really make the difference in it running a little lean or running richer at speed?

 

think of a fat guy with a bunch of hamburgers..like that guys stack of burgers, the gas is being constantly used. so the float is like the cook, the more he puts on the table the more he eats. too little and he dies as he inhales his food. Its the AVAILABILITY..

BigFitz, you arent kidding, getting that rack LEVEL. i didnt believe it at first, then i moved the rack the tiniest amount, it made a significant difference, i do not see how one could possibly get an accurate reading on the bike... must do while on the bench, such a PITA easily my least favorite job
oh and thanks for that link to rick's picture, i hadnt seen that, but its really nice,

 

ok I got my float height set wet and yes they were below the screw head,but it looks like it's still lean. I'm wondering if I have bad choke seals. Because if I give it any choke at all it normaly dies,but I can richen the idle screws.

 

ok I've put 114 jets in and it made a big difference. Plugs look pretty good now after a ride. I just need to get the idle mixture right now. I don't have a color tune. If you leave it idle awhile they get pretty black right now and it doesn't start up as fast as it did. Might need new plugs now also. One of them the white is blistered probably from running lean earlier.

 

hhh