1981 XJ650 - Starting (battery drain) and Idling issues

Hello all - its a pleasure to find such an active forum for these bikes, it has already been very helpful for me as I familiarize myself with my new bike.

In short, I am experiencing some issues with starting the bike and once started, there are some idling issues. I'm hoping that someone here is FAR more experienced in these bikes and issues than I am and would be willing to offer some advice to help me get this bike running road ready.

I'll break this post down into several parts so you can skip around to find information that might be able to help understand/diagnose the problem. Any help is GREATLY appreciated!

Background/History of the Bike
I purchased the bike for dirt cheap from a friend of a friend who had it stored in a warehouse for about 3 years. During those 3 years, the previous owner rode it maybe three times and did not start it aside from those times. Also never performed any routine maintenance on it. When I inspected the bike before buying it, I noticed a stain from oil leak right under the filter. The owner before him (so I'm told) rode the bike almost daily during riding season and it had no issues...

So, I bought the bike about a month ago. I knew I was purchasing somewhat of a project but figured this would be a fun experience to familiarize myself with motorcycle mechanics generally. I purchased the Haynes manual and it has been incredibly helpful and informative so far (as well as the countless YouTube videos).

I tried starting it and it would not start. It had a conventional battery that had been sitting for that 3 year period. I purchased an AGM battery from AutoZone that the cashier insisted matched and would fit. So I installed the battery (it was a pretty tight fit) and tried to start it. No luck. Then I did a quick oil change (15W50), replacing the filter as well (filter gasket did not come with the filter smh) and tried to start again. It did start, and sounded pretty decent. However, there was a problem when idling where it would just start increasing RPMs until I hit the shutoff switch.

After some digging, I assumed it was probably the carbs needing to be cleaned. So last weekend I cleaned the carbs (I was careful not to mess with the idle screws as synchronization is currently outside my wheelhouse), but there was some gunk in a few of the jets and using the jet cleaning tool cleared them right up.

I also noticed there was a bit of rust inside the fuel tank. I did my best to clean out the rust (vinegar and some steel bbs to agitate the rust) but it didn't work as well as I'd hoped, yet it did clear a bit of it up from what I could see. I cleaned out the petcock (I've since purchased a new one), and replaced the tubing to the carb.

I then reinstalled everything, put some more oil in it (there has been a consistent leak from the oil filter due to bad gasket) and tried to start it.

Description of Starting issues
The largest and most frustrating problem when trying to start the bike is that there seems to be a huge battery drain. I only get like 2-3 presses of the start button before the battery voltage drops too low and the starter solenoid just starts clicking, then eventually nothing. For example, my most recent attempts I read the battery at around 12.8v and hit the starter 2-3 times until the solenoid failed. I checked the battery again and it was only reading around 10v. So then I hooked my trickle charger up, waited until it was back up over 12, then tried again.

I had to do this process around 4 times before I got the bike to turn over. When it did, I had it idling for a few minutes and the problem I had earlier of it increasing rpms had (mostly) subsided. I did not try to ride it because I want to replace the petcock and oil filter gasket.

My big problem now though is the battery issue. It is a brand new AGM battery so while that would be the easiest fix, it would be the most frustrating. I'm worried it might be an issue with the starter or the starter solenoid, but need some assistance in diagnosing which of the two (or what else) it could be. Ive inspected the two grounds immediately below the battery compartment (one going to the battery the other going to the left side to the frame) and have cleaned the contact points to ensure good ground, yet I guess that could still be an issue.

Even if I get all the other issues resolved, I can't ride it any meaningful distance if I can't consistently start it without the battery draining as it is currently.

Description of Idling issues
When idling, I have to play with the choke a whole lot to keep it running. Even after it has warmed up, if I leave the choke open it will start to increase rpms (not as bad as before), so then I close it a bit. But if I close it too much then it starts lugging along and almost stops entirely, so I open it back up a bit. But then it starts increasing rpms, etc. etc. I can't seem to find a sweet spot where the bike will just idle at consistent rpms for extended period.

Second, there is a pretty noticeable knocking at times coming from the engine (my ear is not good enough to tell me which cylinder it might be coming from). It responds to rpms so it increases in frequency when higher rpms, and decreases with lower.

Conclusion
Once again, I truly appreciate any insight anyone may have into these issues. I really would like to get this bike rideable within the month when the weather here in Western NY starts to cooperate a bit more. I just want to ensure that (1) I will be able to start the bike without the need for immediate access to trickle charger; (2) the bike will run without me having to constantly play with the choke (not sure if this problem will persist if I am actually riding in gear or not); (3) I won't destroy the engine while riding it with this knocking sound.

Also, some of this just might be due to the fact it is a 40+ year old bike, but I'd like to try to restore it to its former glory.

Thanks!
-ShaperSongs

 

I'm no expert but I can see some things here. First, get an inline fuel filter and insert it between the petcock and carbs. Because you didn't clean the tank really well, rust particles can re-clog jets and are not really good for your cylinders. Second, don't charge your battery with a trickle charger. That takes so long you may not be getting a fully charged battery by the time you use it. Also, use a jumper to a car battery while you need to do a lot of cranking. Third, these bikes will increase the RPM's as they warm up on choke (enrichment). It is normal to have to bump the enrichment down when they climb. The engine should eventually be able to run at idle speed with no enrichment. If not, you change the idle RPM's with the main idle screw. Other issues with idle climbing may have to do with air leaks causing a lean fuel mixture. You can check that a couple of ways (search around for discussions), including using propane or carb cleaner or starting fluid spray. Good luck.

 

This is excellent information, thank you! I'll start with the in-line fuel filter as I'm swapping out the petcock this weekend.

I did inspect the intake boots while I was cleaning out the carbs and they seemed really solid (no obvious or visible cracking, still flexible, etc.). But I have seen videos using propane to check for air leaks so I'll be sure to test that out too.

What do you think about only getting 2-3 cranking attempts when starting? I'm concerned if I ride too far away from my house then I'll have to always keep jumpers with me to jump it once the battery inevitably dies, or I'll just be stranded lol. Could it be bad starter solenoid or bad starter motor? I feel like with a full battery, I should be getting more than 2-3 attempts, but maybe not.

 

There are a couple of things that can be causing you to have poor cranking and starting. Your battery might be tired, easy to check. Your local auto parts place will load test it for free. If not the battery then the starter might be dirty and/or worn brushes. Not too hard to clean and Len at XJ4EVER has the brushes. Easiest is dirty connections between the battery and the starter. Solenoids do go bad and have burnt internal contacts without appearing to be bad, that will make poor power transmission. Back to the battery. The ignition systems require good voltage to make a spark. The battery can easily have enough strength to crank the engine and nothing left to make sparks. Generally 10 volts while cranking is the thresh hold. While these bikes are pretty bullet proof when "right" they are sometimes sensitive to the little things but when they are right they are AWESOME. Good Luck!
Re-reading your post.....new batteries are not always as good as we would hope. When you get it running check the voltage at the battery terminals to see if the bike is charging the battery.

 

So battery is definitely charging once it is running (reads around 13-14v when running). I'll bring the battery to get it load tested to ensure that even though its brand new it is in working order. I'll also check the voltage drop when attempting to start - I've seen that if it drops below 10v when attempting to start it usually indicates poor battery. I'll also ensure good connections between battery and starter.

 

If you bought the battery new and it wasn't fully charged, and you started using it, it might not last for many cranks. Using a trickle charger to recharge may not fully charge in the time you give it and the cycle starts again. Make sure you start with a fully charged battery and if you need to crank a lot while working on the bike, jumper another larger battery to it. I just noticed you are from my home town of Canandaigua.