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1986,Honda rebel 250
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57 Posts
Discussion Starter · #1 ·
Can you run a second gen engine in a first generation rebel.
 

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1986,Honda rebel 250
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57 Posts
Discussion Starter · #3 ·
So all the wiring matches between both generations? It’s as simple as swapping them out?
 

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The Gen2 Rebel 250 has a top engine mount that connects between frame and cylinder head. Gen1 Rebel 250 does not have that. The intake manifolds are different as well. If you google photos of the two engines you will see those two differences.
 

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Most folks who do the engine swap just don't use the top mount. The intakes attach to the engine the same way and are easy to swap out.
 
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1986,Honda rebel 250
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57 Posts
Discussion Starter · #6 ·
Ok dosent seem too hard to do is all the wiring the same?
 

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1986,Honda rebel 250
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57 Posts
Discussion Starter · #7 ·
Can you use the first gen carb too or would you need a second gen carb to go with a new engine is the wiring all the same?
 

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While I've never done this, my understanding is that a first generation carb/intake combo will bolt to a second generation engine. Have no idea about the wiring. Wiring diagrams cause stress and anxiety every time I have to look at one. Soaked Karma would know.
 

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1987 CMX250C AC
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I can't think of any wiring differences with 2nd gen engine in 1st gen frame/wire harness..
The exciter connector may be different but neutral switch, alternator and pulse generator connectors are the same iirc
1st gen wiring must be used with 1st gen CDI, as it doesn't have kick stand safety lockout that 2nd gen has..

minor difference with Ignition switch as 1st gen has park position that lights tail lamp while allowing key removal..


1st gen intake only works with 1st gen carb..
2nd gen intake only works with 2nd gen carb..
either intake bolts to 1st or 2nd generation head..
 
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1986,Honda rebel 250
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57 Posts
Discussion Starter · #10 ·
Will I need to replace the intake bolts or will those be fine? I have a 07 that I’m putting in and have the top motor mount from the bike and the original carb and intake and all wiring and Cdi from the 86 so I should be just plug and play?
 

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IIRC, there is a difference in the intake studs length between the two generations. Seems someone posted recently that adding some washers under the nut was a work around. The exhaust studs are more prone to breaking due to the stress of repeated heating and cooling. Intake studs should be ok, but check them over before using.
 

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1987 CMX250C AC
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The two 2nd gen lower intake studs are shorter (6X40) 90034-KBG-670
1st gen (6X60) 90034-KB4-670
upper 2 studs same lengths for all years..
 
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1986,Honda rebel 250
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57 Posts
Discussion Starter · #13 ·
Ok I’ll get the two lower studs for the intake manifold. Flitecontrol should I buy new exhaust studs for new engine they look fine. Are they easy to take out while there in one piece also how do you remove them? How long would it take to fully switch a motor out couple hours? Thank you all
 

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If the exhaust studs look good, I wouldn't replace them.
 

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1986,Honda rebel 250
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Discussion Starter · #16 ·
Ok sounds good guys how long should it take to swap over and be on the road?
 

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For me, I would plan a weekend. For more capable shade tree mechanics, probably a lot less.
 

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1985 CMX 250C, 1982 GW Remember that you are invisible, treat all others accordingly.
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28 Posts
Hello.
Honestly, I've had to replace the manifold studs after 1 broke. It's a struggle at best(UGGGHH). My bike had 40K when it broke. So.... an awful lot of heat cycles. I had no problems with them up until then. You have to weigh the decision & see what's best for you.
 
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