90e series 91kx125 hybrid project

Discussion for swapping a KDX motor in a MX frame...
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Special
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90e series 91kx125 hybrid project

Post by Special »

First off I'd like to thank everyone here for all the great info I've found already on kdx hybrid & fork swaps .I have a white 1990 kdx e series the power delivery is amazing ! I see what everyone here raves about and I totally agree .I also have a 1990 kx125 I thought this would be an easy swap but I have run into a snag or 2 so far .i test fit the engine already the rear mount/swingarm pivot was a direct swap ! Easy bolt right in leads me to believe the kx swing arm will fit (I will try that later ) the lower mount was a tiny bit to narrow so I removed the double thickness on the mount and boom ! Slid right in front mounts are off and will need new mounts welded . Front head stay will also need fabricated since the e series has a rear head stay that will def need to be removed for tank clearance it looks like it still may not fit (any one know for Shure) I also found that 89 kx250 radiators bolt on with the exception of one tab on the rh side rad will need to be moved a little but they have the exact same coolant flow as the e series motor so I was pretty excited at this point but what do I do with the exhaust? I tried a h series burly pipe and it will need major surgery ! Anyone have any ideas? I actually put both bikes back together then swapped forks and I was pleasantly surprised that it was a direct bolt on swap ! Like it was made for it unfortunately the kx forks are leaking so badly a real test ride would be out of the question I don't think they even have any oil in them anymore so what should I do just a fork swap poss swing arm also I was looking at 1989kx shock and looks to have a similar design anyone have info on that ? Thanks for your help
sarrant
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90e series 91kx125 hybrid project

Post by sarrant »

Marrk_us from this forum did this exact build. E-Series engine in 90-91 KX125 perimeter chassis:
http://www.kdxrider.net/forums/viewtopi ... 0&hilit=90
He linked the DirtRider article for the same build in his thread.

Seems pretty straightforward.
Special
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Re: 90e series 91kx125 hybrid project

Post by Special »

Thank you!!!!!! This is what I need to get motivated on the project again! I was about to pull the trigger on a fork swap on the 90 kdx but I think ima tear into the hybrid project again so u heated the tank for clearance & cut off the pipe and welded a kx stinger on it also do you think my 89kx250 rad will work they fit nice and have propper outlet size and position thanks again
sarrant
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Posts: 463
Joined: 02:47 pm Aug 10 2012
Country: USA
Location: Sac, Ca

Re: 90e series 91kx125 hybrid project

Post by sarrant »

Well i didn't do the build, Marrk_us did. But that sounds about like his description with regards to the tank and pipe.

He used the E-Series KDX radiators, which are very much like the 89 KX250. The lefts are identical (same Kaw catalog part number). Don't know what the difference is in the right, but he also had to weld on a tab with the E-series rad, just like you're proposing.
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