Just bought an 85 Maxim X

The kid that I bought it off said that it ran before he put on some individual cone type aftermarket air filters, replacing the original airbox type setup. Now it does not start.
If i give it a little whiff of ether it will run, The fuel line goes from the fuel petcock to the center of the carbs, on the rider side.
He said he did not touch the carbs other than to remove and replace them.

Q1 Any interlocks that would prevent ignition? I presume not as it will tick over on a little ether.
Q2 I would guess that it would be probably running a lean condition if these new air filters are flowing a lot more air?
Q3 any special issues to know about before i pull the carbs?
Bike looks all there, dirty as heck, but relatively un molested. Some electrical issues to tackle once it's running.
(Blinkers, horn, brake lights non operable).
Thanks
Andy

 

Anybody can say “Oh yeah, it used to run great!” To get you to buy.
That said—-
If you want it to give you no hassles-
Get an original airbox
Get the carbs rebuilt with the correct jets
Get the valve clearances back in spec ( if it’s due/overdue.... and this will be your biggest hassle, other than getting an airbox back in)

If it’s firing up on ether, the interlocks aren’t a worry right now. If it fires on ether, she’s trying to wake up! If it doesn’t keep running, the cyls aren’t getting the gas.

take your time and be patient.... she’ll come around.

 

Thanks, I'll pull the carbs and get a rebuild kit.

Andy

 

Wait there a minute now. This rebuild kit - I can't tell you what may or may not work, but unless you get genuine, you might be making things worse - in the States you are vey lucky to have a supplier who understands and will sell you the right bits for these carbs - top right of this page, click on the link. @chacal is on here and is the place to go. Do not buy generic ebay kits.
There we are, got that out of the way.
If your engine runs on ether but not without then the carbs are not getting fuel or the enrichner jets are blocked. And they do block, in fact they are the first things to block.
Pods will potentially cause you all kinds of issues, but they won't prevent your bike from starting.

 

Are you saying you need the ether to get it to run and then it dies or the ether allows you to start and idle and keep idling ? (Big difference between carb start making it run for a few seconds and idling).
+1 on cheap rebuild kits.
re use ALL the brass in the carb if the jets are original.
Needle, bowl gaskets are the 2 main parts you need. idle mixture O ring & Vacuum seals and the O/D rings that join the fuel tubes too.
Cleaning out the jets and all the little passages in the carb like the fuel enrichment hole in the bowl and the idle passages that exit out in front of the butterfly valve are the big ones.
http://xjbikes.wikidot.com/carb-specs

 

When you get a chance get some pics of the bike on here to pls. That would be nice to see. I have no refreshed a "X" model in a while. Main reason is the valves do take a little bit more work to get into spec.

First things, first, get the OEM airbox back in there as stated above. Get the carb back to OEM as stated above. Do a really good job of cleaning them carbs. I mean really good job, and don't forget about that small jet in the bowl. Yes that one needs to be have good flow so the bike will start and run right.

Good luck and keep the updates coming. Pics with the updates if you can.

 

I pulled off the cone air filters and it started up.
Only the left most cylinder was reliably firing, it started smoothing out when I noticed quite the leak coming from the rocker cover in the front of the head spurting fluid onto the rear of the electric fan. Seems like oil that smells like gas.
When it first started the needle slider was bouncing a little, but then settled down.

 

Will this air box fit mine?
1982 1983 Yamaha Maxim Xj750 Oem Air Box Air Filter Intake Lid

Its on ebay at the moment

 

Unfortunately no. You'll have to find one for the 85 or 86 Maxim.
Sorry I don't have any spares.

Tony

 

Thanks for the reply, I am contacting XJ forever...

 

Think I found a couple of reasons why the motorbike wont run,:

1). The left coil was connected to cylinder 1 &3, while the right coil was connected to 2&4. Assuming each coils fires two cylinders at once every time one is at TDC. I would expect 1 & 4 to fire simultaneously and 2 & 3 to do the same.

2). The right coil Secondary has OL resistance on K ohms scale. Both coils have approx. 2.7 ohms on the primary; the left coil has 36 K ohms of resistance on the secondary.

Questions:
1) Am i correct on the firing order and that the left coil should go to 1 & 4 cylinders and the right coil should go to 2&3 cylinders?
2) Any recommendations on where to source a coil?

Thanks
Andy

 

Firing order info:

cyl 1 is at your left knee when you are sitting in the bike, cyl 4 is at you right knee.

left spark coil fires1&4
Right spark coil fires 2&3

 

sources for coils:
1. Len Chacal at: info@xj4ever
2. Other members here ( I don’t have any extras )
3. eBay

 

I’m getting the air box from Len so I may as well get a coil from him too.

 

Sounds like your working it out but i dont like the gas smelling oil thing you mentioned.
I hope your not trying to get this thing running without doing an oil change first.
Anyhow agree with getting proper stuff from xj forever or oem parts in carbs
Good luck

 

Feel like i should elaborate on the fuel smelling oil.
If your bike has been flooding cause of bad carbs, and has fuel in the oil the oil is thin and not lubricating properly.
Seen many a quad drop a rod because of this .
Any 4 stroke is same.

 

For sure I am going to change the oil first. Coils and sparkplug wires arrived from XJ forever. I found the coils were not connected to the right cylinders, so I suspect a lot of cranking in the past has led to gas in the oil.
One set of sparkplug caps were very high resistance. So, oil change, then try to start.

 

I drained an ungodly amount of oil/gas mixture from the crankcases. No more leaking from the rocker cover now.
She fired up with new sparkplug caps from Len at XJ4ever.

However she went right to 4k rpm and would not come down, for testing i still had the airpods on but with most of the surface area taped over. I am getting a price from Len on the standard airbox and assorted rubbers. As soon as I put it in gear it stalled. So maybe a clutch adjustment needed too.

Thoughts on why it went to 4K? massive vacuum leak? Air pods still making it too lean? I did have the hose to the fuel petcock attached that comes from intake #2.

Thanks,
Andy

 

You had the petcock vacuum line attached to the carb boot and not attached to a petcock or not plugged?

 

It is attached to the petcock, and the carb boot. While troubleshooting I pinched it closed with vise grips but it made no difference.

 

You need to get off the "air pods are the source of all my problems" vibe.
Yes they will cause problems when riding, but for starting and idling they will not. Maybe idle mixture will be off, but usually within adjustable range.
If your engine runs away to 4k it's pulling air and fuel in somewhere past your butterflies, or maybe even before the carbs if there is a rich enough mix to ignite it.
Need to start thinking..

 

Re-check the throttle cable, make sure it is not hung up. If you have pots, take a look to make sure your flies are closed in the idle state. If the bike is running 4k at start, I would guess carbs are not at ""rest" or idle position.

 

What do you mean by flies are closed? What does the rest/idle position look like?

Andy

 

He means throttle butterflies (I hope). Bear in mind it only takes one of the four to push the idle speed up, and that one only needs a tiny bit of opening.
Did you do a bench synch? Using the edge of the butterfly and idle hole?
Are all the throttle spindle free to move?

 

Carbs off I think, unless you have vacuum gauges to do a running synch.

 

Sorry about not giving some visual aids, I always work better with some pics. Here is a rack off a 750 Seca but should be that same principle that we are talking about. When the carbs are at rest of the idle state the butter flies should look like this.
XJ750 carbs by Tim Brown, on Flickr

What sometimes happens is that a cable get hung on the top of the carb as the cable has a little holder that it needs to drop down inside the little cup that has a slit in it. If by chance the cable is hung a little it will look like this and the butterflies will be open enough to give you what high RPM.
XJ750 carbs 1 by Tim Brown, on Flickr
I just mocked them carbs up so you can see what can happen. Not that yours are doing that but could be. Normally if you have a higher then normal RPM at start, you have a hung cable or a air leak. Check all your hoses going to the carbs and make sure that the petcock hose is either on the petcock or plugged or blocked off.

 

Thanks for the visuals. I will double check all hoses and cable routing.

 

OMG what a machine!!!! First ride complete!

I pulled the carbs and checked the butterfly positions 1 & 4 were quite a bit more open than 2 & 3. I adjusted them and reinstalled.
Fired right up, made a minor adjustment and she was idling perfectly.

It took me an embarrassingly long time to realize there is an interlock that wont let you be in gear with the side stand down. I thought the clutch might have a problem.

It kept dying whenever I put it in gear, with the clutch in.

I was just about to pack it in for the day, I sat on it, side stand up, and nonchalantly flicked it into first, to my amazement it did not die.

I went for my maiden ride, what a rush, intake noise, seamless acceleration, first time on an inline four!

Wow, what a machine.

Thanks for all the help getting me to this point.

Andy

 

Now get some vacuum gauges or make a manometer and fine tune all your butterflies.

 

Now you're making me jealous...

 

What a palaver getting the air box in. Heat gun and cursing.

 

Yes but the bike will run so much better and less playing with the CV carbs now that the box is back in the bike. Well done, been there don that....builds character.