Spark + fuel = No start

1982 xj maxim 750. Good alternating spark on all four leads, seem to be getting fuel. #1 cylinder is firing but the others aren't. Have had the carbs off twice with nothing found except the pilot jet and main jet were backwards. Replaced TCI and made sure it's grounded, I'm usig the TCI with the red sticker type TIB 14-06. Had it running intermittently with all four cylinders firing nicely but not running at all now....need advice.

 

Did you properly bench sync? Throttle, air, butterflys adjustments.

Vacuum leak?

I would check the carbs one last time. Are the brass needles, and cylinders that are connected to the diaphragm all free flowing, and offer similar resistance and pushback?

1234 on the spark plugs. There is no firing order. This is a wasted spark system.

Valve clearances?

-Kaya

 

How are you determining that you have enough gas?

How are you determining that only #1 is getting spark? If #1 is then one other cyl should be getting spark, too, since they both come off of the same coil. If you're only getting spark on one coil, then either the second coil is bad, or your TCI is bad, or your pickup coil is bad. In either case, you will also want to check that the rectifier is still good. Swap coil leads and see if the spark changes to the other coil. If so, coils are good. Then look at tci or pickup on end of crank.

Let us know what you find.........
Dave

 

You still have carb problems. " It seens to have fuel" does not mean there is the proper ammount of fuel in the carbs.
You need to ;
Adjust valves
dissamble carbs totally and clean. Remove jets, mixture needles, slide diaphrams, floats/needls/seats,etc. Search the forums for how to articles
Wet set floats
Bench sync

 

How did you determine the jets were reversed?
the air jets or the fuel jets?

 

Hey Guys thanks for the quick replies!

Ok before I answer questions, I should first note that I also have pods on and have installed the Mac 4-2 exhaust.

No I don't believe I have done a proper bench sync, throttle, air, butterflys please advise!

I don't believe I'm having any vacume issues as all the boots are in good shape.

Resistance from needle seems ok.

To clarify about spark; All plugs are getting a nice spark but it's only firing on #1 cylinder. Coils are good 1/4 and 2/3 working together.

I have totally disassemble the carbs, but i'll just have to do it again and make sure my settings and all the jets are correct with my mods.

The main fuel jet had the #43 and the Pilot fuel jet had the #120

Any advice with my particular set-up would be great. I'm having a hard time finding a manual locally but I'm gonna have to get one pronto.

 

This is what i've done so far. Earlier Progress, will add others soon. Also has an ammo box for a battery box and ignition with push button start on the right side.

 

Ok So my valves are perfect. I have done the bench synch on the throttle valves as per the "how to synch your butterflies", list on the forum.

I gues the next step is re-jetting??? I have the stock 120 main fuel and the 43 pilot fuel which I will be changing to a 122 main fuel and a 44 pilot.

I don't know where to buy the jets I need. I found that I can buy a jetting kit from dyno jet website but they are larger than I need, is my only option to drill them out.

Let me know if there is something else I should be doing.

 

Did you carefully and individually wet-set the float levels? GOTTA.

You should also be establishing a working relationship with forum member chacal, proprietor of XJ4Ever and the last place you'll ever need to look for any part you might need. HE HAS THEM.

Click the logo/link in the site banner at upper right; PM chacal, or send an email to "info AT XJ4Ever DOT com" (real symbols redacted) he'll hook you up.

Don't drill jets, you'll only ruin them. If they're still good, keep them in your spares stash.

READ THIS: http://xjbikes.com/Forums/viewtopic/t=14692.html When you get near the end, you'll find a chart with jetting recommendations for the mods you have. Helps cut down on the guesswork trying to select jets.

 

So I'm almost done rebuilding the carbs just waiting for some parts to come in....but I am wondering if I sould change out my main and pilot air jets and my needle.

Does anybody have some experience with these mods on a 82 xj750. I've got pods and the Mac 4-2 exhaust

Stock jets are;

main fuel - 120 (changed to 122)as per my mods with forum formula
pilot fuel - 43 (changed to 44)as per my mods with forum formula
main air - 80
pilot air - 195
needle - y14

 

Gotta do it. 3mm isn't much.

 

Haven't yet but am going to. Just wanna know what jets I should put in before I put it back together.

 

Ok so my bike is officially running and running well!! Did my research and followed the advice of a few. Rebuilt my carbs, Polished the inside sleeves of my carbs, cleaned the heck out of them, new mixture screws, springs, o-rings and washers. I also replaced all of the o-rings on the supply line.

Since I am running a Mac 4-2 and pods, which apparently can't be done well or without having poor throttle response. I swapped my 120 main fuel to a 122.... the stock 43 pilot fuel to a 45.

After reading all the posts I could handle I still could not find out what changes were required for my air jets. I bumped the stock 80 to a 90 and the 195 to a 215.

Then......I wet set and bench synced.

Prior to all of this i checked the valve clearances which were all good. The only thing I had to do was put in heli coils for the valve cover bolts

Fired up first try and idles like a dream.

Hope this helps someone else.

 

Your not finished yet!

Now that you have the carbs done, and the bike running again. You need to vacuum sync, color tune, and plug chops to do to get those carbs dialed in properly.

With the mods that you have on the bike. Finding the proper jetting is going to be a matter of trial and error. The specs in the link you were givien were only a recommended starting point.

Ghost

 

You're a cruel man Ghost! LOL

 

What the hell are "plug chops"? I've been around a while and today is the first time I ever heard of "PLUG CHOPS"!

 

Yeah, but he will appreciate it in the long run. :lol: :lol:

Running a/f miture check at a set speed. It is the only way you can check the a/f mixture in the mid, and high rpm ranges. You basically run the bike at the speed you want to check. Then pulling the clutch, and killing the engine at the same time while coasting to a stop. You then change out/check the plugs for color. color tuning only sets the a/f miture at idle.

With the mods that he has on his bike (pods, exhaust) it will be the only way to get the carbs dialed in properly.

Ghost

 

Edit: Duplicate post
Ghost

 

| will vac sync and planned on it anyway, but as for the plug chop.....I'll just dyno my bike and get a real measurement.

 

Well here she is.... few little things to do. Powder coat the carbs, order the LaRosa bags to match the seat and find the perfect strip of Leather to cover the rear edge of the fuel tank.

I spent $5038.00 cdn from start to finish and that includes a clutch kit. I actually got the bike for a trade for two watches I paid nothing for.

Hers's the before and after.

 

Just installed a new clutch kit. This bike runs like a brand new bike, just grabs the gears like a champ. Throttle response is bang on.

 

I have same bike think if I put those size jets,pilots,and air think it would work I am using jets 130 ,132 and is not running my altitude is 2000below sea level think it would work If i went of permissiotolandfmx changes