NOT STARTING...PLEASE ADVISE!

I just inherited my dad's '82 xj650j, which i rode for years, after he gave up on it because it wouldn't idle. I thought it might be a vacuum leak caused by cracked carb boots. Replaced them and rebuilt carbs. Nothing! After 15 minutes of starting, holding the throttle wide open and choking it to keep it running suddenly something clicked and it ran like a dream. But once it cooled down after the ride it wouldn't start again. I noticed a sheared off screw, one of four which holds the #2 carb hat on, replaced it...no help! I cleaned and checked each diaphram and needle set too but she still won't fire up. It smells like gas and some dripped out of the air intake boot for #2 carb. Where should i go from here guys?

 

Check float levels. Floats apparently easy to install upside down. Carbs sound like they need bench synch first. Replace air filter. Check petcock to be sure it is OFF when in "ON" and motor not running.

 

Have you got a good healthy spark on all 4?

 

I still have to do a good check of each spark plug. I pulled out one and checked for spark and it didn't seem super-bright but there was a spark. But it's also hard to make a good contact on a bare engine surface since it's painted. Do you have any suggestions for a better way to check for healthy spark? My checklist has "assess the spark plugs and boots" so maybe i'll do that next.

 

I just had my carbs rebuilt by a 30 year yahama master mechanic, it idled perfectly but ran like chipmonk choking on walnut, now, it idels perfectly and runs like a banshee, he told me that there are several circuts in the
fuel path in those carbs that kick in at different times, and some toghether at times, he
said that your problem is the carbs were not correctly rebuilt, that sometimes you CAN NOT reuse the same parts as they were bad to begin
with from the factory and grew out of tolerance with use, he says you need a professional to rebuild them so that problems an ameture would
not catch can be found and corrected, no insulte to your work intended, but
some carb sets are as he stated " carbs from hell " and no one but a master rebuilder can fix them right....

So, hit up wild george , or some other carb pro here, have them fix them right ... my complete rebuild only cost $125 u.s. took 2 days,... was
WELL WORTH THE MONEY.

 

Hi asphaltgecko, beware of the sales pitch, there is nothing in the carbs that needs a master mechanic. With the help of XJ BIKES anyone can achieve top results. Wiz.

 

My '83 ABSOLUTELY WOULD NOT start earlier this fall. Fully charged battery, new air filter, inline fuel filter, fresh gas, petcock on PRI, ran when I parked it. Spark but "watery." Took the '81 to AutoZone and got a BRAND NEW set of plugs. Gapped, dab of antisieze, installed and torqued, and it fired as soon as I TOUCHED the damn button. The old plugs LOOK fine. They came in the bike. Original? Maybe. Bad? yep. And Wiz is right, these things (CV carbs) aren't rocket science. You just have to be careful and meticulous (or just downright anal.) They are Voodoo however.

 

plugs often will break internally and with heat they will "reconnect". it happens often on our race machines. plugs are cheap and easy to replace, good place to start would be to check for spark when its not starting.

 

Thanks Zookie400! I called my Dad last night (the PO) and he said, "Come to think of it after i changed out a bad spark plug cap i think that's when all of my problems started." If one was bad, i'm sure the rest are hanging on for dear life too! Tonight I'm going through the plugs, wires, caps and petcock and tank if i get to it. Someone said these tanks are notorious for rust in the corners and quirky petcock issues. I'll let you know how it goes!

 

I checked each spark plug, cap and wire and they look good and are each sparking. After trying to start the bike for several minutes, i took out the spark plugs to check them and the #1 plug was dry, #2 had a small amount of gas, #3 was soaked with gas/oil as was #4. Next i took off the carbs to check the floats since #2 carb was still leaking gas out the intake boot and i had a hunch there was a fuel distribution problem. I popped off the bowls and #1 float was 80% dry, #2 float was 95% dry and #'s 3 and 4 floats were each 50% (which seemed like a normal fill level). I pulled out #2 float and float needle and there was a piece of something in the float needle seat which i removed. I left the bowls off, hooked up the gas tank to the carbs on my work bench in a pan, and set it to prime to check for fuel distribution to the bowls thinking that they weren't getting fuel equally. A healthy supply of fuel flowed out of each float needle and the floats were each set the same to shut it off. What should my next step be?

 

Since you have ignition, spark, and the plugs are working I'd start looking at Float Settings and do a live test of fluid levels.

Get small diameter clear plastic tubes of equal length, 8-10", insert a tube into each carb's bottom bleed hole. Tape loose ends up to the carb tops. Study the photo.

Place carb rack in a vise evenly; fore / aft / side to side. Use a small carpenter's level to check that the set is even. Level goes on top of the whole rack across the tops.

I used a turkey baster and paint thinner to fill the carb set from the center T or main fuel line. Why thinner? because it's safer than gas or water.

After you have the set filled up go down the line unscrewing each bleed screw until fluid starts to rise in that bowl's tube. The fluid level should rise & stop, then you turn it off & go to the next carb. You may have to add fluid at the T or swivel.

If the floats are set and working properly at 21.5 mm each bowl's fluid fill should be level with the heads of the bowl attachments screws +/- 1 mm. All bowl tubes should have the same fluid level evenly across the set. See the pic below. Remember to drain the thinner out and close the bleed screws.




Bench Sync:

Next stop - examine your carb set's butterfly valves. Are they almost closed evenly in the venturis? If not back off the small spring-loaded rack throttle adjust screws until they all closed. The large idle speed adjust screw on the bottom will open them enough for starting.

Leaking Manifolds:

Check the 4 rubber carb manifolds carefully. Are they old, cracked, dry & possibly leaking? If so; its time to either fix them or install a new Carb Holder set.

Check & Recheck:

Check everything in the fuel system very carefully. Make sure the tiny inlet valve clips go over the float's center tongue / tab or it won't operate properly. Are the idle enrichment jets clean and flowing in the bottom of the bowls? I had to replace a Float Inlet Valve that looked good but it leaked anyway. Keep after it ... it will start.

 

While you're messing with the carbs (all of the above is sound advice but the bench synch is a bit more complicated than that) be sure they all pass the "clunk" test. While it won't contribute to starting issues, you don't want to have to pull them again when it refuses to idle back down.

 

Here's the Bench Synch quote from Chacal's recent reply to: "leaking carb after #3 / #4 rebuild"


"CARB" SYNCHING AND OTHER FANCIFUL MYTHS:

Q: I know that you adjust the valves first (valve cover gasket also on the next order) but what is the sequence for the Colortune and Carbtune?

A: Well, it depends on whether you've "rebuilt" the carbs or not....kinda depends. If you've had the carbs off the bike, then the first step is to "bench synch" them, which means getting the butterflies "pretty close" to being all equal in terms of how much they are open at their fully closed (idle) position

"(the butterflies never actually "fully, completely" closed, they always remain open a tiny amount, otherwise the bike wouldn't get any fuel-air mixture in, and thus wouldn't run).

"Synching" on a bench means adjusting the synch screws (there's only three of them, the #3 carb doesn't have one because all of the other carbs are synched in relation to #3) while eyeballing the other throttle butterflies, and getting them "close enough" to allow the engine to start and run."

ACTUAL HOW-TO DO BUTTERFLIES:

PostPosted: Mon Jun 16, 2008 6:57 pm
Post subject: Re: Bench Sync Carbs
Your carbs are off the bike and on a table or bench?

Your #3 carb is controlled by the knob under the carb. You want to close this butterfly onto an object. (paper clip, 1/4 " strip of business card, the wire inside a bread wrapper tie)

With this object trapped in #3, you then shut another butterfly on another carb on another identical object, doing #1 last because #1 "leans" against #2.

When you have everything adjusted just right, a slight turn of the idle knob will allow you to drag these 4 objects out with the same resistance "feel". All 4 butterflies are opened the same amount.

Then, when you get the bike running, you have to sync all over again !!!
even if you get the bench sync perfect. Search topic- - manometer- - carb sync- - plug read- - bench sync

In the pic I used 4 business card slips - they are under 1mm in thickness. Adjust all 3 throttle screws so the slips can be eased out. You may have to "pre-load" the throttle by turning the large Idle Speed Screw IN until it just barely begins to open the butterflies. You can always back it off once the engine is running.

 

Happy Turkey Day,

Thanks to all for the wonderful suggestions. I will be following them to the T, after the carbs are put back together after cleaning them The Whole Nine Yards. A special thanks to Rick for that awesome tutorial!

I will be sure to post my progress as I continue to go. For those who haven't followed RickCoMatics "Clean Your Carbs- The Whole Nine Yards" tutorial, I implore you to read it and follow it. The olive oil and Propane Torch technique worked wonders on a buggered and rusted pilot screw!

Today I'm thankful for XJBikes.com!

Chris

 

Hey Guys,

I just installed a fresh battery which was fully charged. After 10 minutes of kicking over and spraying carb cleaner into it, the bike started - revved high - and died. This happened numerous times until I stopped using carb cleaner, now "nothing" when it kicks over. Bike was fully choked getting plenty of flowing fuel and each spark plug is sparking. For those who are new to my situation, I have already cleaned carbs, clunk-tested and bench-synched.

What else am I missing?

 

Got the throttle & choke cables switched ?

 

How do your throttle shaft seals look? Any chance they could be contributing?

 

Wizard- I thought about the throttle and choke cables being switched but they were fitted back correctly.

Joe- I know the throttle seals should be changed in the near future, but I don't see them as the problem. The bike was running in January and the idle was nice and steady. Unless the seals cracked over the last few months which could be possible.

I had hoped there was something I could check before ordering more parts. Any other ideas?

Thanks guys!

 

Hey Guys,

I just installed a fresh battery which was fully charged. After 10 minutes of kicking over and spraying carb cleaner into it, the bike started - revved high - and died. This happened numerous times until I stopped using carb cleaner, now "nothing" when it kicks over. Bike was fully choked getting plenty of flowing fuel and each spark plug is sparking. For those who are new to my situation, I have already cleaned carbs, clunk-tested and bench-synched.

What else am I missing?

Please help me guys! I wanna ride again.

 

It sounds like you are not geting fuel.
It revs high until the carb cleaner runs out, then dies.
Could be a petcock issue.
You could pull the fuel line turn it over see if you are getting fuel when the bike is turning over.
It will pour right out.
Do you have an inline filter that may be clogged?
Easy things to look at.