Maxim X Starts, but doesnt run past 2500rpms.

Hello,

I dont post very often so IU hope I can get some help fixing my 1985 xj700x.

This is my third year owning the bike, and its my first time having issues.

So this is what happens:
I keep the battery fully charged on a battery Tender. The battery is new this season.

The bike will start great, with in a few seconds at most. The bike does idlt at around 1000 rpms when warming up. Even after letting the bike warm up for 5-10 minutes, the bike will begin to sputter out as I pull on the accelerator. To be specific, if I am slow on the throttle I can get up to 3000 rpms before it chokes and dies. If im quick on the throttle it dies at 2300 rpms. This is all while still on the center stand.

The bike ran great last 2 seasons. So I dont know where to start. I was able to ride the bike one time at the very beginning of the summer. It was hard to start then from sitting all winter(of course after a fresh oil change too). Because of such a hard time starting it then is why I put in a new battery.

I thank everyone in advance for advice. Im very mechanically inclined for automotive projects, but this is my first bike and experience fixing one.

I can get video tomorrow if that helps out.

 

After 3 years of riding its time to take the carbs out for a cleaning and adjustment. Most likley dirt and crud buildup in the jets . Might also do the other scheduled mintenance things at the same time. Valves, fluid changes ,carb tuning.

 

Sounds like mixture issues of one sort or another for sure but let me ask a few questions.

Did the bike sit for a long time between rides? Did you recently fuel up? Has it been outside in the rain, or really humid where you are. What kind of maintenance have you been doing the last 3 years? Valves been adjusted? Have you looked at your plugs to see what they tell you? More info and we'll get you steered towards the fix.

 

Thanks for the help everyone, really.

I plan to do what I can after work today. But I can answer some of your questions so far.

When I first purchased the bike, the first thing I did was have the carbs tuned at a yamaha dealer, which they also replaced the spark plugs to at my request. I had the services done just be safe at the time, not that the bike really needed the tune up.

Each year since then I have done an oil change at the beginning of each season. I have never checked the valve clearances because I have failed to find a pair of feeler gauges that would be skinny enough for the tight spaces of this 20 valve engine.

And i honestly admit that I didnt put any type of fuel stabilizer in the tank last winter. I did empty the tank and put in fresh fuel this season.

As for humidity, I'd say it can get pretty humid here in North Central Ohio. I live just a few miles from Lake Erie. Ive read of coil pack problems and moisture, but have not found a good way to test my coil packs. Any suggestions? Thanks!

 

2500-3k is right where the needle and needle jet starts to kick in. Sounds to me like the slides aren't raising (no main fuel). Pull the carbs and do a cleaning on them, I'm betting that's all it is.

 

That; and you can't simply neglect the valve clearances for lack of feeler gauges. Granted, the intervals for the "X" series are significantly longer than on the "airhead" bikes but it is just as important.

How many miles are on it?

 

There is ~19,500 miles. I also forgot to mention that the previous owner has installed pod filters. Everything else is stock with the bike. I still have a few more hours left at work, so I hope to get to the carbs tonight.

 

OK here is an update. I spent about 4 hours cleaning the carbs. I didnt find anything outrageously gunked up.

After putting everything together, put on prime for a few seconds, set the choke half way and she started immediately. I took it off prime immediately. The bike was sputtering a little at idle so I adjusted the Pilot mixer screw and the idle screw. So i go to put all my tools away while the bike is warming up. I come back less than five minutes and its close to over heating, but the radiator fan never kicked on. So i went to take it for a spin to get some air flow going to it. It was like as soon as I left the drive way, it started to die again. Almost all the same symptoms as before.

Because it was late, Im sure my neighbors didnt like hearing the loud exhaust. Im gonna try the bike again tomorrow and take it for a spin before it over heats like it did this time. Last season, I was sure that the fan was still operational. Thanks for the help so far.

 

So I took the bike out today right after work. Rode it around the block a few times. Im happy to say it atleast runs. There is still slight hesitation between 2000-3000 rpm's, but not nearly enough to stall the bike like before.

Now I noticed I was running in the prime position most of the time. When I put the petcock back to its normal position, it would begin to be a lot less powerful especially under 3000.

I'm firstly going to assume that I need to sync my carbs. I've never done this, so I would like opinions. Should I do the colortune thing ive been reading? How do I know what size my spark plugs would be. Unfortunately I do not have a socket that fits the spark plug. Could anyone tell me the size socket I would need also?

Thanks!

 

Is the spark good?
Hi i've never posted a reply before but like to share my recent experience.

I ride an XJ750A which ran beautifully for two years before i replaced the batery with a new one. It started the habit of dying off on the road after few minutes of riding. It starts fine but it lacks power at any rpm range.

I swapped the ignition coils with a used ones and it solved the problem temporarily. After that it never dies off but it misfires sometimes and still lack of power.
With the help of Chacal's diagram (thanks!) i found out that the pulser coil was out of spec and i replaced it with a used one. Now it runs beautifully.

Don't know whether the new battery is the cause of the problem at that time but sounds like your story is similar to mine.