Carbs Issues (Barn find 1981 xj650h maxim)

So i finally got around to reassemble my carbs on the barn find 81 xj650h(thanks chacal for the jets and gaskets and the prompt delivery). Gave it a gallon of premium and mashed the start button. Bike cranks and sounds liek it wants to start but it dies within a second or two. My first assumption is that is not getting gas. I placed the petcock on the PRI position and browsed the forums for 5 minutes. Go back and try again, same symptoms. Starts for a few seconds and then dies. Checked spark, all good. Checked drain screws on the bowls, 2-3-4 carbs drain clean gas but carb 1 is dry. What can be the issue? Where should i check next? The pilot screws on top of the carbs are set to 2 1/2 turns of the "tight" position. Is that correct? Im at a loss and i dont feel like taking it to a pro yet since i dont feel like dropping a hundred or two to have him getting it running when i may be able to do it myself. Am I way out of whack here? It simply doesnt feel like im far off from getting it to run , but im seeking some advice. Any will be highly appreciated. Thanks in advance.

 

I just picked my bike up and it wouldn't crank, the guy forgot to put the gas hose all the way back in. He thought I had flooded it, after about 5 min he found the problem.

Also maybe try some of that starting fluid and see if you can get it running. Otherwise it might be something to do with the carbs. Did you sync them? I'd imagine if it sat for a few years that would need doing, but someone with more experience will chime in in a bit.

 

Did you tap on #1 to see if it would free up the stuck float needle valve?

 

No i have not. I will try a light tap with a screwdriver end , but now that i think about it i may simply just take the bowl off number one and try to fiddle around with the float and the needle valve to see whats what. Thanks for the hint.

 

I know i can get it to sustain a "s*****" run wiht starter fluid, but i dont think it would be enough to dislodge whatever is preventing number one bowl from getting fuel without spliting that carb again. dont you think? .... The fuel line is connected and the fuel flow from the petcock is proper. I did not synch the carbs since i dont have proper tools (or experience) yet. I was simply under the assumption that given a equal amounts of turn from the "bottom" on the pilot screws will bring me close enough to at least get the engine to idle.

***Edited by Robert, mind the language please. Thank you.***

 

Idle mixture is different than sync.

Idle mixture controls the fuel/air ratio. Synchronizations makes sure all the intakes are at the same vacuum.

Gotta get fuel into the #1 bowl. Neither idle mixture or sync have anything to do with that.

Open the drain screw and give a couple taps with the handle of a screwdriver (just enough to vibrate the thing, not hard enough to break the bowl). If no fuel flows you'll have to crack it open again and find out why.

If you end up taking the rack off do a bench sync. I like to eyeball them, others like to use some sort of small gauge (strip of business card, small dia drill bit, tube from can of carb cleaner...) to make sure the butterflies are uniformly open at idle.

 

I had a needle seat back out on my '82. The #2 carb would not flow enough to run that cylinder, but I could get it running fairly well with just the other 3 cylinders. Best bet would be to dismantle the carbs and clean the dogsnot out of them, all passages, jets etc. Make sure everything is snugged back up when finished. After the #2 seat backed out, i checked the other carbs and 2 more seats were loose. This was on a set of parts carbs i picked up froma board member. My fault for not checking everything though, the carbs were in great shape. Anyway...use Ricks cleaning methods and make them spotless, then sync the carbs and set the pilots (or vice versa?) cruzerjd

 

Im hoping to not have to break the carb of the rails. Ill just try the tap on the bowl first and if nothing will get the fuel trough ill just gently split that carb again and mess aorund wiht the float and the needle valve ... maybe it got tweaked while it was naked , even though it paid real close attention to the gentle mechanism of the floats ... etc.

 

I would guess that you need to "Re-finish" the Inside diameters of the Float Valve Body's.

Going that long without a steady supply of fuel to clean them has probably "Tarnished" the Brass a good deal.

I make a tight roll of 1500 Finishing Pager and "Stuff-it" into the small cylinder of the Float Valve Body and rotate the Float Body on the rolled-up Finishing Paper.

Once the Body has a NEW shine ... I doubt the Float Needle will "Hang-up" and get stuck Open or Closed.

Since you aren't getting any fuel into the Number-1 ... you need to pull that Body and examine the Filter Screen, anyway.

 

AHHHH YESSS. That little fine screen on top of the valve seat. I forgot all about that.

I'll put my money on that screen. For the life of me I see no way to stick the float on a Hitachi closed.

No need to pull the carbs off the rack. Everything you need to do can be done without removing the rails.

 

Great ... ill take a look at it tonight after i get off work. Thank you all for the hints, inputs and general how to's.

 

GOT IT RUNNING!

runs like a 3 legged dog, but she does run. Idle? ... not so much. The float valve on number one was stuck so hard only part of the rubber cone came out. 2 of the 4 screens did not came out with the brass valve body. So, it looks like im going to call on Chachal again for some more parts ... Cheers all ... thanks for the tips.

 

planning on replacing floats, and the associated valves and the pilot fuel jets ... once i get the parts (which im a week away from ordering ... im a poor bastard) im going too look forward to have some knowledge dropped on me with regards to adjusting the floats and the associated stuff.

PS ... she does sound as mean if not meaner than my old kawi 700. Im really excited.

 

Is that lift raising the bike via the exhaust? I sure hope not.... It's a quick way to snap multiple exhaust bolts from the head... Better to use wood blocks to have the lift rise the bike via the frame instead of the exhaust...

G'Luck!
Rex S.

 

the rear i resting on the center stand bosses ... i do believe the front is resting on the exhaust ... i shall reconsider. Thanks.

 

well ... shes at home now ... it idles, and it runs nice (i burried the speedo on the way home from the shop - approx 12 mile ride). The thing is ... although i've only been playing with bikes for about 3 years and i may not have the vast experience some others do when talking bikes ... i "feel" this bike to be relatively weak with regards to take-off acceleration. It feels way tamer than my old kawasaki 700 ltd. It may be that i have yet to synch and tune the carbs or simply it may be that the thing is just not that powerfull. Anyone in Omaha NE area that can help out wiht the tuning? ... ill buy the beer!

as a recap :

new main fuel jets
new main idle jets
new needle valves
new bowl gaskets
new inline fuel filter
new blade style fusebox
new K&N air filter
new oil change
new rear oil
new brake pads
rebuilt master cyl
new brake fluid
new fork seals
new mirrors
new blinker lights front

I adjusted the air/fuel mixture screws at the top of the carbs to 2 turns out from bottom. At 2 1/2 turns out it felt "lean". Am i on the right track? ... what else need i do to bring the carbs close enough to parameters in order to ride it?

 

If 2 1/2 turns felt lean, 2 turns is leaner. Most of us are closer to 3 turns out on the idle mixture screws. You may be lean out the gate.

I don't have experience with other bikes. I can tell you this, our bikes are heavy for the displacement and the powerplants don't really start to produce until you get towards 4K RPM. I wouldn't call mine blistering off the line for sure.

 

ill move to 3 tomorow and take it around the block ... Thanks for the hint.

 

If the Pilot Jets are Stock ... take 'em out to 3.0 Turns.

Coming out of the hole ... if its Lazy, Boggs-out or hesitates before "Catching her Breath" and running good = Rich = Tweak IN

Backfire = Lean = Out.

Your complaint ... weak ... probably close on the Lean side coming off-idle.
Close enough not to backfire.
But too lean to make good power.