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 Post subject: Re: Joyner 250cc Quad/ATV JN250DA
PostPosted: Sun Dec 18, 2016 9:39 am 
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Now take the removed head and send it out and get it ported and cleaned up. That will wake that 250 up. As for the plug, some have it some don't, I suspect it is part of the casting process that some manufactures use and some don't.

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09 250SV Joyner Polaris 500 (SOLD)
here-we-go-again-joyner-polaris-500-swap-t46499.html
HH GTS150 stk 250SS wheels
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 Post subject: Re: Joyner 250cc Quad/ATV JN250DA
PostPosted: Thu Dec 22, 2016 3:59 pm 
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Location: Royse City, TX
What price range can I expect a port job to cost? That is if the head is still good.
Reason I replaced the Jug, Piston and Head is due to excessive water in the oil. as you may or may not have seen in my previous posts I've already replaced all the water pump seals and was still getting water in the oil. Was told that this was the only other thing that could cause that. Person that had it before me (nephew) overheated it really bad. Will know tomorrow when I fire it up for the first time since the top end rebuild.


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 Post subject: Re: Joyner 250cc Quad/ATV JN250DA
PostPosted: Thu Dec 22, 2016 5:29 pm 
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Got a price from a local ATV performance shop. It starts at $200.00 for porting a head. Not sure I want to do that considering this is only a deer hunting lease ATV.


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 Post subject: Re: Joyner 250cc Quad/ATV JN250DA
PostPosted: Thu Dec 22, 2016 6:00 pm 
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Talk to Tom at SycPowersports. He is familiar with these and knows how to make them run better. Part of what he does is mill the head surface with will true that up also. Which will also bump the compression. BuggypartsNW also can do a head for you but the cost is a little more.

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09 250SV Joyner Polaris 500 (SOLD)
here-we-go-again-joyner-polaris-500-swap-t46499.html
HH GTS150 stk 250SS wheels
Polaris Dark side ride


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 Post subject: Re: Joyner 250cc Quad/ATV JN250DA
PostPosted: Sat Dec 24, 2016 4:18 pm 
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Location: Royse City, TX
Need help.
Got the entire engine back together. New piston, new rings, new jug new cylinder head original valve cover. Got Spark, Got fuel but won't start.
Checked compression, very low to hardly any compression at all. Won't even register on compression tester.

Tried adjusting valves, got a little compression but still wont' start.

Tore the entire engine back down to ensure that the piston rings were set properly. Set them at 180 degrees from each other for the ring gaps. Put it all back together still really low compression and wont start. I am totally stumped.


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 Post subject: Re: Joyner 250cc Quad/ATV JN250DA
PostPosted: Sat Dec 24, 2016 6:41 pm 
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Either the valves are not set correctly or one is not seated from the factory. Pull the valve cover off, the carb and the exhaust. Now make something so you can blow air in the intake and exhaust port to see if the valves are seated. If they are then it is valve adjustment. One way of doing this is get some putty and a piece of hose. Put the hose in the port and block the rest of the port with putty and blow in the that port. You should be able to pressurize the port with your mouth if the valve is seated.

Another thing I have found is if you are using the original acorn nuts on the head bolts you may not be getting a true torque on the head bolts. I have seen the studs stretch and the nuts bottom out on the stud and you think it is torqued when in fact it isn't.

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09 250SV Joyner Polaris 500 (SOLD)
here-we-go-again-joyner-polaris-500-swap-t46499.html
HH GTS150 stk 250SS wheels
Polaris Dark side ride


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 Post subject: Re: Joyner 250cc Quad/ATV JN250DA
PostPosted: Sat Dec 24, 2016 7:24 pm 
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thanks Papa Rich, what about simply pulling the valve cover off and pressurizing the combustion chamber through the spark plug hole? It would seem that if the valves are truly seated I should be able to pressurize it that way right?

I didn't even think about the acorn nuts for the head, what if I were to replace them with regular nuts instead of the capped type. Would there be an issue with me doing that?


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 Post subject: Re: Joyner 250cc Quad/ATV JN250DA
PostPosted: Sat Dec 24, 2016 7:37 pm 
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Yes you can pressurize the cylinder.

I usually replace those with flanged nuts.

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09 250SV Joyner Polaris 500 (SOLD)
here-we-go-again-joyner-polaris-500-swap-t46499.html
HH GTS150 stk 250SS wheels
Polaris Dark side ride


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 Post subject: Re: Joyner 250cc Quad/ATV JN250DA
PostPosted: Mon Jan 02, 2017 3:20 pm 
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The BEAST Lives!

So I was able to pressurize the head and discovered that the valves were not closing on the new head. Removed the valve cover and the valves closed and pressurized. Apparently there is a difference in the two heads. The valves springs sit about 1-3 mm higher on the head without the allen head plug in the center. So we put the old head that has the allen head plug back on and sure enough problem solved. Now I had to test it to ensure the oil in the water issue was resolved. Sure enough everything is working. No water in the oil. So it must have been the Jug or Jug gasket that was causing the leak.

I did spring a leak in the radiator during testing and also found that the radiator fan was not working consistently. Also heard some serious clunking when starting the ATV. Cranking would halt with a clunk then resume to crank over and start. I assumed this was the starter so when I returned the new head I traded it for a new starter and new carb.

New carb was definitely needed and a major plus but the starter was not the issue with the clunking noise. Only other thing I can figure is causing it is the starter clutch. Thoughts?

So I removed the radiator and flushed it all out and then using a propane torch and solder I braised the hole and was able to successfully seal the leak. Engine starts and runs great, brought it up to temperature and so far so good.

We then proceeded to put my newly re-wired wiring harness back into its proper placement. In doing so I broke the bracket on one of the electronic modules that I have now discovered has something to do with how the engine runs. Without the module the engine bogs down horribly, with the module plugged in the engine runs fantastic throughout its power range. Still have no idea what this device is as it’s not part of the normal electronics I have found on these type of ATV’s. Picture attached, maybe someone can help me figure it out. It is definitely needed or the ATV runs like crap. I just don’t know what it is. It also has a potentiometer built in for some kind of adjustment.


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 Post subject: Re: Joyner 250cc Quad/ATV JN250DA
PostPosted: Mon Jan 02, 2017 4:39 pm 
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Polaris runs a controller that when it reverse keeps the engine rpms down so that it doesn't get out of control in reverse. That controller looks just like what Polaris uses.

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09 250SV Joyner Polaris 500 (SOLD)
here-we-go-again-joyner-polaris-500-swap-t46499.html
HH GTS150 stk 250SS wheels
Polaris Dark side ride


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 Post subject:
PostPosted: Mon Jan 02, 2017 5:18 pm 
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Location: Royse City, TX
Thanks for the reply Papa Rich

doing a quick google search turned up no results that looked like mine but I will keep looking.
I guess one way to test this theory is to put it in reverse and unplug the module to see if anything happens. The only thing I noticed so far is that the engine would bog down moving forward when this module was unplugged and would really open up when the module was plugged in.

Maybe I should rename it the FrankenQuad. Seems like they built it with parts from Honda, CanAm, Polaris and Kazuma


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 Post subject: Re: Joyner 250cc Quad/ATV JN250DA
PostPosted: Tue Jan 10, 2017 1:35 pm 
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Location: Royse City, TX
The Beast Lives,

Had it running on New Years Eve ripping up and down the street and took it into a nearby field. It runs really well but obviously some fine tuning are still required.

Proceeded to toast in the new year with my Brother and family.

I have now proceeded to tear into the right crankcase cover to replace the starter clutch. Need to order the special flywheel removal tool (07933-KM10000) and starter clutch. Did find the equivalent tool on ebay for around $25.00 and a Starter Clutch for around $40.00. Have to wait until next month to order the parts.

Not sure if any of this helps anyone out there but it is nice to record everything I am doing so I can see my own progress.


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