Advice on XJ750 Maxim restoration

Hey y'all,
I got an '82 Maxim in pretty good condition a few months ago and just got it running. I have taken down the carbs, cleaned them, got a new battery, changed the oil, did the brakes/brake fluid, the works. But when I get it turned over and give a little throttle and close it again, the RPMs ramp back up from idle to 4k rpm once or twice before settling back down. I am thinking it may just need to be synced because the carbs looked awesome when I took the bowls off. (It was stored in a garage with some other collector item cars) Also, when I shift into first and go to let the clutch out, the engine dies. Any advice? I have checked over everything and its not my first rodeo restoring but I was hoping to narrow down the issues before syncing my carbs.

 

Welcome to the forum, also, congrats on the bike.

We need to know a little info about you. Not to sure how many yrs of riding experience you have and all that. With being said, need to know how the bike is dying? Does it die as soon as you put the bike in gear with the clutch still in? If so this would suggest that one of the safety swx is bad, I would bet on the kick stand swx.

If the bike still runs after you put the bike in gear, does a very small lung or no lung at all and stays running while full clutch is pulled in, that is good. If you have clutch handle in all the way and then as you put it in gear it gives a big lung and then dies, the clutch needs to be adjusted.

If the bike is still running while in gear, and you have the clutch fully pulled in, as you slowly release the clutch than it does, you have to give it more gas. Without getting too much into it, this is called the "friction zone".

 

I have been around motorcycles since I was 4 because of my family, but actual riding years about 3-4 years. Usually I'm helping my dad or uncle restore some bikes but this is my solo venture since moving out.

As for the bike issue, it stays running after shifting into gear with minimal lunge, and slowly letting the clutch out while giving a bit of throttle doesn't keep it from dying. Would this still be a kickstand swx issue? The bike was in the previous owner's garage since about 2017 without being touched..

 

Sounds like the kickstand switch could be it. Could you link out the clutch switch to check the bike pulls away properly?
Otherwise my usual suggestion is to stop guessing, get a multimeter and test the relevant points on the loom (with the help of a workshop manual diagram).
Welcome by the way, the XJ maxim is a nice compact feeling bike for the engine size.

 

Thank you for the tip! And yes its a great bike, I can't wait to put her back on the road.

 

The side stand swx would kill the bike as soon as you put it in gear. You stated that it is running still, that is a good thing. I know you mentioned that you cleaned the carbs. Just to give you a little background on these carbs, they can be very picky when cleaning. I pulled my first XJ carbs out of my bike six times before getting it right. So now, I really take my time and make sure that all is correct before I put them back in the bike.

Can you do a "blip" test with the bike running? In neutral, snap the throttle and see if the rpms climb and drop? Before you try to ride it I would make sure you can make the bike pull through the rpm range in neutral on the center stand, if you have one. You can also run through the gears on the center stand, just make sure you are careful and don't dislodge the bike while shifting through the gears.

Do you remember cleaning the little jet in the bottom of the float bowl?

This is a pic just for reference.
carbs_floatbowl_choke by Tim Brown, on Flickr
If you didn't clean this jet on each carb, you need to get back in there and do it. If the carbs bowls were really gummed up, it will take a thin wire, carb cleaner and compressed air to clean them out. Once you do, bike will start and run better.

 

Thanks for the heads up. I did use a nice thin wire and carb cleaner to clear the small pilots in there, one was pretty jammed up. I did purchase a multimeter and the kickstand switch was testing badly. I also synced the carbs and they performed beautifully and sound great after that. I also tested the clutch switch and that tested normal on the multimeter. My problem now (since I linked out the kickstand swx) is the now the bike dies immediately as I shift into 1st, instead of when I'm letting out the clutch (I can't start in gear anymore either). Also, I think some of the plates are stuck together because I can feel when it shifts down into 1st, N is easy, 2nd feels fine, but up after that it feels kind of clunky and stuck. Should I open up and unstick them by hand?

 

Not sure what you mean by "linked" but if you disconnected the side stand switch and didn't bypass it correctly then the ignition cutoff safety relay will kill the motor as soon as the bike is put into gear.

If you can't get the starter to engage in gear and you could before that means the clutch and side stand switch were working previously because it takes both of them to function to engage the starter while in gear.

Note that the 82 Maxim is a DPST switch for the side stand switch, and one half provides status for the CMS dash, and the other side operates the side stand relay

For troubleshooting you can disable the ignition cutoff safety by disconnecting the B/W wire bullet connector near the TCI. It is highly recommended though to repair any faults with the safety circuit after troubleshooting and not leave it disabled.

My guess is they are not stuck, but just a guess based on you stated you had it running before and could put it in gear, but could not get it to move with throttle and clutch manipulation. It may be that it just isn't running good enough to go, which I think is why @Timbox asked about blipping the throttle to get feedback on just how well the motor is running.

Are all four header pipes heating up (careful you can leave skin here) - I like to check them after a minute or so from a cold start to make sure all cylinders are firing. If you have a cold one you can then check later after letting things warm up a bit.

How many miles on the bike? Any other history like valve lash adjustment? Carbs are cleaned how about the tank and fresh gas? In line filters are usually recommended after cleaning the carbs unless the tank is just pristine inside.

 

It was starting in gear before so I will reconnect the kickstand swx. I had bypassed it as a test. Before I synced the carbs, headers 2+4 were running hot while 1+3 were much cooler to the touch. After syncing, I tested the throttle and it has a great response, kicks up and back down as normal. And pressure readings were good. As well as all the headers feeling the same temp. There's about 25,350 miles on the bike. The engine got a full workup in 2011, and was ridden seasonally until 2017 before sitting/being moved around in a garage. The tank was empty when I got it, the old plastic fuel filter leaked all the fuel out over the years so I cleared the tank and put a new glass and metal filter on it. There was very little debris left behind which was nice. Not sure about valve lash adjustment though, I'll double check the paperwork I got on the repair history.

As far as the engine not running well enough to go, I haven't tried shifting and riding yet after tuning it up so I will reconnect the swx and give it a go and update here with questions. Thank you @Timbox and @Rooster53 for all the advice. Y'all are great!!

 

Great news @Timbox and @Rooster53 I reconnected the fuse for the kickstand swx, and the bike started in gear, and I was also able to shift without killing the engine. On top of that, the bike tries to roll forward in first (with a small touch of throttle) before it dies so I am closer to getting this on the road. Any pointers on what I should look at next? The bike idle is nice and smooth, and throttle behaves as it should with both short and long blips on it.

 

If the bike is rolling a little when you are in gear and the clutch if pulled in fully, you need to adjust or bleed the clutch MC. You have not mentioned the model you have or have any pics of the bike. Don't know if you have a cable only for your clutch or a MC for the clutch? The bike might jump forward a small bit but should not be rolling out of control with the clutch fully pulled into the bar.

 

Not the kickstand switch……that will instantly kill the engine if it’s shifted into gear.

 

It is hard to read that and know just what is happening. If you have the lever pulled all the way in and the bike is moving then an adjustment might solve the issue. If the bike is not moving and stalls when you try to engage the clutch with a bit of throttle then my first guess is either a poorly running engine or maybe you need a bit more practice to get it going?

But this earlier post reads you know just what to do to get it going, and for some reason it is not cooperating.

Perhaps if you were to use some leg power and get it rolling and then put in gear and see if it bogs / stalls as soon as the throttle is opened, which might point to a carb issue. How far did you go on the carbs? Details like removing jets, breaking the rack, what parts if any were replaced could be helpful?

Here is the adjustment if the clutch is dragging and the bike is moving when the clutch is pulled all the way in, The lever on the clutch side cover is also adjustable, but you shouldn't need to go there unless the side cover or lever have been removed.

 

Sorry for the confusion, the bike is a 1982 Yamaha XJ750 Maxim with YICS. It tries to roll forward as I'm slowly letting off the clutch in first, before dying. Its like the bike is trying to go before it bogs down. I will see about the clutch today using the locknut, since it's pretty loose up on the handlebar.

I haven't removed the side cover or the clutch. And when I did the carbs, I mainly focused on cleaning the bowls and the jets, I didn't take them apart fully. I did replace the gaskets just to make sure the seal was good.

https://photos.app.goo.gl/voZ9u7vENZDoRqAQ6

https://photos.app.goo.gl/MtX8rzmJqgLZnUQG7