Cant keep this thing running!?

So now that my electrical mess is sorted out I have another problem. *sigh lol

Its a 1982 XJ750 Maxim. I have never had it running since I've gotten it and its unknown how long its been since it ran good.

When I got the bike the carbs were so disgusting and everything in them was stuck and caked with varnish. Well i tore them all apart and cleaned it all up. I put everything together and have been trying to get it to stay running for a while now. I AM running a petcock without a vacuum line and the vacuum line coming out of carb 2 appears to have been snipped off and is just open at the moment. Not sure if this is causing the problem or not. I have the entire airbox out at the moment as well. The only way I can get it to crank up is if I slightly block a good portion of the intakes with my hand. If i do this it will start up fine but the second I pull my hands away it will almost die instantly even with full throttle. Also my hands will have fuel on them as well but only when i attempt to partially block the carb intakes. Will these motors even run without the airbox installed? Choke doesnt help either. Im lost as it seems there are so many things that it could be, I just want to narrow it down in possible. Thanks guys!

 

Also, the fuel I threw in the tank has been sitting in a gas can for about a year, maybe a bit longer. It looked clear when I put it in but I guess this could be a possibility as well.

 

If you have a vacuum leak then that is something that has to be rectified right off. Yes bike will run without airbox ..but not real well . Have you done a FULL carb rebuild IE taken carbs to church of clean ? What condition are your carb boots in ? Replace the fuel right away !!!!

 

With a vacuum port open you have a HUGE vacuum leak. Plug all ports if you're running a manual ptcock.

The carbs don't like to be open; they need an airbox (or pods if you must).

Fresh gas is best, just to rule that out.

Did you do a full teardown of the carbs, including replacing the throttle shaft seals?

IN THE CHURCH OF CLEAN

 

I did tear them down and clean every nook of those carbs, I just didnt have throttle shaft seals at the moment so they were not changed. I did just order a carb rebuild kit so hopefully it comes with throttle shaft seals. And ok, Ill plug that vacuum port so i wont have to worry about it. It just seems like its either not getting fuel or its getting too much fuel. I tried it will the pods on there as well and it did the same thing. Fortunately for me and my altitude if I switch to Pod filters and do all of the math for my mods etc i end up with the same size jets as i started with. Tomorrow I will change the gas in the tank, plug that vacuum line, and replace the old air box and see what happens.

 

The carb boots seem decent, no cracks or splits. Hopefully its something as easy as just the fuel. lol

 

Thottle shaft seals do not come in any of the rebuild kits. You'll need to order them from Chacal.

Some commonly missed items:
Did you thoroughly clean the enrichment jets in the float bowls?

Did you remove the enrichment plungers when you split the rack for cleaning?

Did you remove the idle mixture screws for cleaning, and replace the 0-rings therein?

Did you perform a bench synch?

Did remove the emulsion tubes?

Did you make sure to put the air jets in the top hat back in the same holes that they came from?

 

Ya, I did all of that, just didnt change the o rings. :-(

 

If the idle mixture screw o-rings were in good condition you probably are OK.

My gut says throttle shaft seals. That and not being hooked up to the airbox could make the mix too lean to be able to start.

Were the valve clearances checked?

Many small things can add up to a no-start condition.

 

is there a way to check and make sure fuel is getting through all of my carbs? Just take the bowls off and see if they have fuel in them? It was seriously so gummed up it wouldn't surprise me if a portion of the fuel rail is super blocked. There was black varnish caked everywhere in those poor carbs.

 

It probably is the throttle shaft seals, my throttle shafts were absolutely horrid and still not the greatest.

 

Chacal! Help! I need throttle shaft seals!

 

http://www.mrcycles.com/oemparts/a/yam/500421def8700209bc78741c/carburetor

Judging from the link I'm guessing its part #27 correct?

 

No. Those are the fuel rail o-rings.

Go to your inbox and start a conversation, or email info@xj4ever.com


There are drains on the float bowls to see if they have fuel (and for checking the fuel levels)

 

OK, I sent him a message, might as well get them anyways. Ill check the drains and make sure its getting fuel in all carbs.

 

So question...I think I've finally narrowed down my "non starting" and "cant keep the bik running" issue. So the starter cranks and cranks and cranks and every 5 seconds or more it will kick once like it wants to start. So i checked the spark (screwdriver into the plug wire and touch part of the block) on cylinders 1 and 4 and got a great blue spark at a good distance. 2 and 3 were a different story. I literally had to touch the block with the crewdriver and got a small weak little yellow glimmer of a spark. When an ignition coil goes bad could it cause this super weak spark? Or would a bad coil cause no spark at all? I already have some newer (used) coils and a new pickup coil on their way. Is there anything else that could cause this? Thanks in advance.


1982 Yamaha XJ750 Maxim

 

2 and 3 have 10 k spark plug caps 1 and 4 have 5 k caps, they will have a weaker spark
have you ohmed out the coils? caps and pickup coils?
when you ohm out the ignition coils clean the connectors and clean the connectors at the tci also use dielectric grease on them

 

did you get the throttle shaft seals replaced ,

 

both things can happen

bad spark plug caps .
bad or under charged battery do a voltage drop test when starting bike
meter to battery what volts do you have ?
press starter button what does the voltage drop to?

have you trimed back your sparkplug wires 3/8 inch due to corrosion? reassemble usesome dielectric grease

 

Well, i guess it could possibly be my battery being damn near dead. Was brand new but after attempting to get the damn thing started and running for a month now its pretty much dead so i use a little jump box and it acts like iy did when the battery was full and the starter kicks right off.

 

Not yet no, but ive tried 2 separate carb sets now and same result both times.

 

do not be fooled by starter what does the voltage drop to???

remove spark plugs and clean them
what about your ignition numbers?

 

I'm not going to address the carb part since I do complete carb rebuilds down to every oring to every bike I build but I will tell you that I have NEVER seen such a weak yellow spark on a bike as I did my stock coils on my turbo. I replaced them with Accel coils and immediately had instant starting and better running under full boost no matter how cold it was!

Bought used on fleabay for 35 bucks delivered:



jeff

 

Ok ill check that sometime today, i need to see if i can charge the battery first. Lol

 

Ok, so like i said my battery is fairly weak but still new. WITHOUT my jump box on her she starts at 11.7 v and when i try and start it, it dips down to 7.6ish. I havent tried it with the jump box on there. Also, i attempted to check the coils with my multimeter and attempted it multiple different ways since i have seen some 750 people say to it one way and others to do it another. But i think my primary coil was sitting at about 3.7ish but couldnt get a single thing to happen on my secondary coil. Nothing at all. If these newer coils and plugs i have coming in dont help then im gonna go ahead and guess its my CDI?

Also, i temporarily switched the connectors around and before i had 2 and 3 with weak to no spark, now i have 1 and 4 with weak to no spark and 2/3 were soarking and popping good.

 

Bad battery. Replace.

The minimum allowable voltage at the battery under starting load is 9, with 10 or better being ideal.

Your resting voltage is well below the minimum for that spec as well.

 

Its a brand new battery though? When hooked up to my battery starter pak it reads 12.4 then drops down to 11.6 when attemting a start and i have the exact same outcome.

 

Even new batteries can fail. We see this happen a dozen or more times every year.
Take the battery in and have it load tested, and replaced.

12.4 volts at rest is only 75% charged. A wet battery should maintain 12.7 volts off of a charger, and a gel battery 12.9; both for several weeks before showing a voltage drop at rest.

 

Ok, I'll check it out. The only thing im afraid of is spending money on another battery that will start out nice and charged but after another long while of attenpting to get this thing started it dies and end up like my current battery. :-(

 

So tell us more about what happens to the starter before the battery started to go flat.
Were there noises?
Have you tried starting it directly from a car battery?
Has the starter ever been pulled off for cleaning and inspection?

 

Ok, so update. Icharged the piss out of my starter pak and was able to get it somewhat going.



Does it sound like it has anything to do with a spark issue or am I chasing the wrong problem? I took this video at abouy full throttle. I can get it to barely idle if i give it full throttle and i notice some smoke ouffing out of my left exhaust. Its so close, like it wants to run. It acted the same way with both carbs too. Uggghhhhhh, some C4 and det cord is sound real nice about now.

 

That sounds like it could be spark, but not knowing what else has been done to the bike I can't say. She's definitely not hitting on all four.
My first inclination is to visit the carbs.

 

I looked back at your post history and merged your threads so we can work on the problem with a full set of data.

Did you ever replace the throttle shaft seals?

 

No not yet, still waiting on them and my rebuild kit for my carbs. I have 2 sets of carbs, one that was super gummed up and one that is actually in decent shape and everything looks good on it and im having the exact same problem with both sets. I guess it is possible both sets could have the same issue. Lol. Also, on carb set 1, it leaks fuel out of the overflow holes on 1 and 3...on carb set 2 it leaks fuel out of 1 and 2. I know there is probably a float needle sticking or something (this will be fixed once my rebuild kit comes in).

Just found something else out as well, if i use starter fluid spray she kicks up quick and revs nice for a tiny bit then tapers off and dies, which to me kinda indicates a fuel issue.

Oh, and spark plugs 2 and 3 are soaked with fuel and black, which would mean no spark is happening correct? Which goes back to one of my coils not properly working?

 

If it runs nicely on starter fluid, it's not a coil.... it's lack of fuel.

Did you ever cap the vacuum port?

Check your crank case (smell at the oil fill cap) and see if you smell gas there--- you may be filled right up with gas-polluted oil

 

Ya I capped it off. I just changed the oil 2 days ago and there was no fuel in the oil then. Crankcase doesnt smell like oil now either. And I might have misspoke, i wouldnt say it runs nice, it just reacts to the theottle and acts like it wants to run nice.

 

This guy here. This spring. Brand new out of the box. . . . lemon. Took it back to NAPA, they put it on their tester. Gave me a replacement no questions asked - without a receipt!

 

Unfortunately i got mine from Amazon. :-/

 

I had good luck with Amazon, contacted the he seller of a large outdoor light (magnum base fluorescent) they sent a replacement without me returning the old one.

Doesn't hurt to ask the seller . . . Explain the battery is not holding voltage and see what they say. Anyone with a bit of integrity would stand behind their sale.

 

No more trying to start it until you tend to the carbs. The battery is dead because you killed it.
Despite the tone that might be inferred, these are both good things.
Mistakes are how we learn, so you can count two successes today.

 

Contact the seller. The battery warranty is still in force and they will take care of it, because if they don't Amazon will drop them from their site.

 

I agree! Ill wait until my new ignition coils and theottle shaft seals come in, then ill rebuild the carbs and report back. Im kinda at a stand still now. I just hope that the motor isnt totally screwed. Thanks for the help.

 

It's not. An XJ engine is very hard to kill.

 

Well, im saying as far as valves etc go. I was hoping to get her up and running somewhat decently without having to get a valve adjustment done. Id like to save that for this winter when i repaint everything anyways.

 

unless you have an X model valves are easy to check and do . you must do the valve check and bring them into spec before you can start adjusting the carbs

AIRHEAD VALVE ADJUSTMENT with Pics

AIRHEAD VALVE ADJUSTMENT Part 2: The Tool vs. ZipTie -w/pics

 

+1
Easy job, and they should not be left-go without at least checking the clearnaces. Valve adjustments are the most-often neglected of all the maintanance items, and you've already seen how well the prior owners have kept up with the maintainance schedule.

 

Ya thats true. Ill have to know k that out as well.

 

Ok, so update. New plugs and coils made it start absolutely gorgeously! But as you guessed now there is another issue. I finally got the idle about where it needs to be and i can slightly rev it, but as soon as i rev it a bit more than that the throttle takes off and sounds like it will climb until it hits redline! :-O Why cant i just have this thing run good? Lol

Below are 2 videos. I have yet to get my theottle shaft seals in yet, could this possibly be the reason why? Everything else is basically new or like new. Please tell me my entire motor isnt shot!?

 

Yes.

Old, worn throttle shaft seals allow air to leak into the carbs, too much air and you are running lean. Running lean will cause a throttle twist to rise and rise and rise on the RPM's.

 

^What he said.