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Xj750 overheating

Discussion in 'XJ Technical Chat' started by Codysc843, Apr 18, 2020.

  1. Codysc843

    Codysc843 Member

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    So I have the carburetors fixed on the bike air box I just fixed but now I've got a new problem so I'm making a new thread

    The bike rides good it's very fast but I do not think it should be as hot as it is after I ride around for about 10 minutes and then park it the motor is hot enough to fry an egg I know if it was sitting in idle for a long time it would get hot but it was only idling for 5 seconds before I took off also an issue I've had off and on which is still here is the oil light blinking and today when I day when I pressed the button to shut it off with it running at some point in the ride it started blinking again up until I parked it seeing as I have changed the oil and put about 2 and 1/2 quarts of new 10w40 oil I don't think it should be overheating or have any oil lights blinking but since it does seem to be hot and the oil light is on considering it's got oil in it what do y'all think could be the culprit and fix for it
     
  2. Jetfixer

    Jetfixer Well-Known Member

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    You are most likely lean , low fuel level is a possibility, your fuel mixture screws maybe lean if you have a colortune plug , would be able to set it closer to optimum if not what color are your plugs if they are white this indicates lean. Your synch could also be off. The other possibility have you checked and adjusted the valve clearance if it is to tight can cause the engine to run hot. Just a few things to check
     
  3. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    Remember it’s air-cooled, not liquid-cooled. After 20 min of riding, it GONNA be hot. Touch it and you WILL burn yourself. Touch the pipes after a few minutes of idling and you’ll burn yourself.

    What else are basing your thought of overheating on?
     
  4. Codysc843

    Codysc843 Member

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    Air cooled so it is in fact supposed to be cool I know it'll get warm but I am wondering if it's getting overheated and if it will tear up if I keep riding it as hot as this bike is in 5 minutes there's no way I could go on a multiple state ride the motor'd be glowing orange by then I'd think. Say it is overheating what would cause it? Thinking there's an oil issue since the lights blinking but it's full so I'd think no light should be on
     
  5. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    you got to get your facts straightened out...
    air-cooled does NOT mean “as cool as the air”. Air cooled engines still get hot enough to give you a bad burn.

    You fire up your engine for just a couple minutes and it’s gotten hot enough you won’t get an accurate valve clearance check till the next day. They get hot. that’s what they do.

    Ever grab hold of your lawnmower engine? Ever grab hold of a chainsaw engine?

    ever check your oil level sensor like we told you to in your other forum?

    “it’s hot” doesn’t mean it’s overheating.

    did you ever do a running sync? Ever do a colortuning?

    you said the bike is fast—yup, the XJ’s can be. How fast were you going? For how long?

    Did you get your brakes fixed? How well you can go fast you can go isn’t nearly as important as how well you can stop fast.
     
  6. Codysc843

    Codysc843 Member

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    No I did not do a running sync because if I'm not mistaken that requires vacuum gauges and I do not have any sure I've used mowers and chainsaws Etc have you? And when I say it's getting hot I understand it's supposed to get a little hot mowers and weed eaters were nowhere near this hot and me posting the question here was just trying to figure out if I am going to tear up the bike or not by running it as it is seemingly overheating as for the oil sensor how do I check that exactly? I can't even see through the sight glass these things should have dipsticks as for brakes I've got back brakes and downshift to slow down I'd like front brakes but can't afford parts right now cheapest calipers I've seen are about $25 each I think my master cylinder is okay so if I go the route of fixing front brakes I'd be ordering calipers once I get enough extra money to pay for them I don't even plan on keeping this bike yeah it runs real fast but I've got another project I'm looking into buying after I sell this one I bought it broke down did some maintenance and got it running I still am going to have to file for lost title if I keep it otherwise when I sell it it will go for a bill of sale if I haven't went about getting the title yet I figure running and driving it should at least be worth about $400 I've got 350 in it
     
  7. Timbox

    Timbox Well-Known Member

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    Hard to work on these bikes without out having of making the tools you need. When you come to this forum and ask for help on something you will normally get a good answer. The followup is doing or trying to do what is given as advice. If you don't do the work and then come back and ask why it is not working, those that give the advice get frustrated.

    To your question of heat or being hot. If you don't have a IR temp gauge to tell what temp the engine is what is hot? You can now pull your plugs and see what color they are. If they are white, you are running lean and yes will be warmer than it should be. If light brown, you are good and will be normal temp. If black too rich and can run into issues there as well.

    There are links on here to make a home sync device, if you want to take the time to build it.

    The money issue in fixing these bikes is always an issue. Each person is will to pour money into a project at a different rate. If this is a issue you might want to look at different projects and let the bike go to the next person.
     
  8. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    Ok, so-
    No, didn’t do that even though we’ve suggested it time and time again

    A LOT

    remove it and flush it. That would give you a chance to check the wiring to it, too.

    So you still didn’t fix them. It’s still unsafe.

    so you’re riding illegally. With no title, it’s a parts bike until you have a good title. Either get a replacement for the lost title (with those likely hassles, or go through Vermont with requirements and expenses), or you have a parts bike. $400? If you’re lucky.

    Good luck with everything.
     
  9. Rusty81

    Rusty81 Member

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    There’s guides on here to make a running sync tool with some tubing, a vacuum gauge and some golf tees. Worth the 20 bucks. Get a manual (or find drawing online) for the oil sensor.
    If you’re friends with your local FD, ask them to check your engine with their thermal camera. May also show what your exhaust temps are looking like and if you have cylinders working harder than others.
    But I’d leave it parked til you get the brakes done and safetied/titled. Anything happens you’re up a creek....
    My bike needs a safety/plate/insurance but is parked til everything opens here again. It sucks, but better than the fine.
     
  10. tabaka45

    tabaka45 Well-Known Member

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    Air cooled engines get very hot. In fact, Harley makes heat deflectors to deflect the heat away from the legs and seat when at idle. I've had Harley riders tell me that they can't stay on the bike at idle when it's fully hot. If you have enough oil and the carbs are not very lean you should not be too hot. By the way, what do your plugs look like? Riding without front brakes--whoa, that's dangerous.
     
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  11. Simmy

    Simmy Well-Known Member

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    Brakes are overrated, I’ve found all they do is slow me down
     
  12. Polock

    Polock Well-Known Member

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    ,.,,,.,,.,.,.,.,.,...,.,,.,
     
  13. Jetfixer

    Jetfixer Well-Known Member

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    Parts bike ,or organ donor ...Saftey first and foremost...Brakes are not an option it job #1
     
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  14. Pizzaman

    Pizzaman Member

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    never mind
     
    Last edited: Apr 19, 2020
  15. lostboy

    lostboy Well-Known Member

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    The best way to keep an air cooled engine cool is to keep moving. If the air temperature cooler than the engine the engine will disappate heat.
     
  16. SQLGuy

    SQLGuy Well-Known Member

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    Just did some riding with the main intent of exercising most of the range of the engine to capture data for fuel injection tuning. After 30 minutes or so, with some idling mixed in, back of the block is about 280F. Top of the block, intake side, is about 215F. Oil is 185F.
     
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  17. XJ550H

    XJ550H Well-Known Member Premium Member

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    i measured temp at base of sparkplug 3 and 4 got 312 to 317 degrees f my temps front and back of motor with similar to yours I didn't record them these types of what I've been getting on this bike for a year without any issue of overheating you're fine
     
    Last edited: Apr 19, 2020
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  18. Codysc843

    Codysc843 Member

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    Well in sc a bill of sale gets you a temp 45day tag so no I'm not riding illegal although nobody's business if I were
    Ok oil sensor how do I get to it where is it I've extensively went through this bikes wiring not sure exactly where it that sensor is. If it's an oil sensor common sense says its somewhere in the motor but with jap bikes who knows maybe yall do I've never torn down motors on a bike just about everything else yea but not any motors

    I'll be selling the bike after it's more up to par and moving to another bike project.

    Appreciate it yall atleast those who are helping not arguing like keyboard gangsters. There's a few of yall tryna help figure this bike out thanks
     
  19. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    Underneath... round plug in the pan with wires

    31FBD1C1-CCC8-4196-AB73-F7D61921ED72.jpeg
     
  20. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    Locations is top left corner of pic
    B2CF8847-7704-43A9-9950-16E5CB74F22A.jpeg
     

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