The Barzu Bike - XJ750

I tried to do it with mine, but it cuts the engine off Gotta find the switch to bypass.

In the mean time, I wrote Chacal an email with my woes and here's his reply: (I'm off to the garage)

******************************
Well, you've got too much fuel OR NOT ENOUGH AIR getting into your cylinders.

Obviously, just as it's a fine line between pleasure and pain, so also it is between the
"too much fuel" vs. "too little air" issue.


What could cause too much fuel?:

* choke is engaged; choke plungers stuck open and not closing fully, choke plunger valves
horribly worn.

* fuel jets are the wrong size, regardless of how they are marked (they could have been
previously drilled open), or in reversed positions.

* air jets are placed incorrectly, so that the large pilot air jet is in the main air jet position
(and, obviously, vice versa). Please note that although the photo in the Haynes Workshop
Manual showing the air jet positions is a "correct" photo (the jets are physically placed
correctly), the caption which labels which-jet-is-which is reversed.

* the fuel level in the bowls is extremely high, thus it takes much less engine vacuum to
pull a greater amount of fuel into the system....... in essence, your carb(s) are "always
flooding".

* the main fuel needles are incorrect for that engine or are very worn (rare), thus allowing
much more fuel to enter.


What could cause too much air?:

* "Pod" air filters or no air filter.
* Air jets that are much larger than specified.

Now, although it is conceivably possible that your idle mixture screws are too short, that
is not normally an issue. For reference, originally mixture screws are approximately:

Overall length: 20.45 - 20.70mm (20.55 average length)
Length beneath head: 14.60 - 14.90mm (14.70 average length)
Shaft Diameter: 2.93 - 2.97mm OD (2.94 average diameter)
Tip length: 2.30 - 2.50mm (2.40 average length)
Tip bottom diameter: 0.55 - 0.61mm (.58 average diameter)
Tip top diameter: 0.72 - 0.75mm (.73 average diameter)



My first guess would be since you are having difficulties getting the idle mixture circuit to
ever go "lean", even when turning the screws to full closed, would be that for some reason,
you are getting extra fuel either through the pilot circuit or through some other circuit. The
most probably causes of such a situation are that the fuel levels are way too high, or that
the choke system is active even when you think it is "closed".


Also, I assume that the valves have been adjusted and the engine synched? I not, as
much as you may not like to hear it, I would start there.

I would ALWAYS start there.


Let me know what you find.


Len
******************************

 

didn't you put bigger jets in? I am a total noob when it comes to this stuff but earlier in this thread you said you put larger jets in, what about changing those out to smaller ones?

 

I don't think the center stand has a switch... hmmmm. I know the side stand does, but not the center stand to my knowledge.

Your bike was running fine until when?

 

I think you're right, I might have kicked out the side stand by accident 8O Noob.

The Barzu Bike never ran fine since I got it on July 29th.

I'm working through all the issues one by one, as they're all carb related. I AM making significant progress. The carbs are pristine, and there's nothing left to clean on them. But as I cried to Chacal, the friggin' beast has no power when I want to get out of the hole. Tons of hesitation, tons of noise and no power. Plugs are black as night. Rich, rich, rich. So rich that I cannot colortune the orange out of idling. Even with the mixture screws all the way turned in.

I know the bike is getting plenty of air.

I do have a suspicion though, after reading Chacals reply to my email.

Three things I will check tomorrow is:
1. Fuel levels - i set the floats perfectly, but never actually checked the levels live.

2. Do the DIY synch tool thingie with the carbs. They've been bench synched to perfection. (I have OCD about things that I work on,so I can say that)

3. Jet needles - I think this is my issue. Let me explain. In my thirst for power I threw that stage 3 dynojet in the carbs. The stage 3 has you move the clip on the needle by three spaces, maybe like 5mm up or so. Which allows for more fuel to enter the main jets quicker. I bet that's what's causing all the richness. Tomorrow, I'm moving the clip back to "stock" depth and will take it for a run.

Mikegustus, you're absolutely right. If I get better response, but not there yet, I'll switch out the main jets.

Why did I not think of this sooner? Because I would never suspect "Dynojet RESEARCH" to get it wrong. I don't know.I just don't know.

Some of you don't subscribe to the DynoJet thing, but hey, it's my first bike and I wanted to make my first purchase for it something really significant. Something I could brag about.

Hopefully I'll have great news tomorrow. Thanks dudes, I'm glad the forum is here for help!

 

Emmer effer. I took the intake manifolds off today because that's the one thing I've not quadruple checked. Under a really bright light...lo and behold, there's cracks on the BOTTOM of the manifolds. By bottom, I mean when they're installed the cracks are on the outside of the manifolds, opposite side of the vacuum valves. I don't know if they go all the way through, they might.

My question is, could these be the reason my idle is so rich? I though if the manifolds were cracked, that would introduce extra air before the gas mixture and the bike would run lean. This is the reason why I didn't think to pull these again to look at them.

Any thoughts on this?

 

Cracked manifolds = intake leak = lean

 

I know. Does not make sense. There's nothing left for me to look at though.

I've rechecked:
Jets - went down to Dynojet 132's from 136's. (per Dynojet)
Needles - put the clip on the next groove up. (per Dynojet)
Float levels - decreased by 2mm (per Dynojet)
Choke - line, valves, plungers, etc.
Jets - pilot and main, everything
Pilot circuit- everything
Throttle cable
Bench synch.

NO matter what I do, I can turn the fuel mixture screws all the way IN and the colortune still burns orange. No blue. I need more air, but I've even got the pods off and still no better.

When I throw the tank on and go for a ride, there's no power. Ever.
I take it around the block and when I pull in the bike dies. Plugs are black.

I've got RTV sealant curing on the intake manifolds now. It's a band aid fix to see if there will be any improvement.

I've never felt so helpless. I've cleaned the crap out of everything. Everything.

 

BTW, what the hell are "throttle plate shaft seals?"

 

The seals on the shaft that has the butterfly on it

What cylinder do you have the colortune in?

 

Ill check the seals.

Cylinder 1. Should I start with 3? The vacuum valve is plugged on 1.

 

Vacuum valve as in fuel valve? If that's the case, you've probably got a leaking petcock diaphragm that is allowing fuel to travel through the vacuum line directly to the cylinder. Remove vacuum line from intake manifold and plug off the vacuum port. If it feels like the inside of the hose is wet, this is your problem. Run the bike on prime and try to tune it again. You can continue riding it on prime as long as that vacuum hose is not connectedto the engine and the vacuum port is plugged off. Order a petcock rebuild kit and ride around to burn the gas before you pull the petcock out.

 

I'm gonna throw this at you cuz I kinda had the same problem on my 85X, loosing power and hitting the throttle and nothing! I had a $#@%ed up fuelcock, and my carbs were overflowing into my motor, bike would run, but like crap. drained the oil, filled it back up and away i went, since i fixed the fuelcock, it worked, until it failed again ... hence i am looking for a custom tank and newer fuelcock.

 

Earz,

Clarification - I'm tuning with the gas tank off. I have a container suspended off the handlebars with one hose running right to the carbs gas "in" valve. The vacuum ports are always plugged off on the cylinder I'm colortuning.

 

I'm right there with you. I'll pull the pc out and take it apart. I'm willing to try anything at this point. Although when the vacuum hose is off and the fuel line is off the pc, it does not leak. Does not that mean that it's good?

 

Gotcha. Did your carbs overflow since your last oil change? I'm with zack - I've had problems in the past with fuel in the oil causing a rich condition.
Also, have you checked valve adjustment? Here's a tread showing how

http://xjbikes.com/Forums/viewtopic/p=152293.html




Zack - you may consider this route instead of a custom tank.
http://xjbikes.com/Forums/viewtopic...der=asc/highlight=petcock+repair/start=0.html

 

Well, after coming to terms with the fact that I might not get to ride this season at all and then something compelled me to check the air jets.

If the Hayes diagram is right, then my air jets are backwards. I put them in exactly as the PO had them. Assuming he had them in right in the first place was my mistake.

This would explain why the bike ran like crap when I bought it.

Rickomatic did mention in another thread the either the diagram or description in the hayes manual is wrong. I'm gonna try and find that thread and see which one it is.

Again, if the diagram (picture) is right, that's exactly my problem...

 

I think this is the link you need:

http://www.xjbikes.com/Forums/viewtopic ... cture.html

or atleast has the info.

 

gameover - yep, mine are backward. Thanks for the link thread. I'll give it a go tomorrow and hopefully put this frustration to rest...and find something else to gripe about.

 

Wooohooo, cant wait to hear about the results.

 

Can anyone tell me where I can get some Unobtanium spark plugs?