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Discussion Starter · #1 ·
Hey guys. I've been looking for potential motors to swap into the grom for a wile. I have landed on the cbr500. People have done the cbr250 all the way up to a 1200. I was originally going to go with the cbr250 but the 500s seem to be a lot cheaper. Also they are probably around the same size just the 500 being wider. Just wondering who has had experience with swaps and what to look out for. I've done many ridiculous things with bikes and cars over the years so fabbing isn't an issue. I would just like to hear some other people's experiences with swaps. Also it seems almost cheaper to do a full motor swap if you know what your doing compared to a big bore by the time your done buying all the necessary things you need.
 

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Look out for the total height of the engine- most big swaps require either modification of the throttle body/intake, frame backbone, swingarm mount, or any combination of the three. My cbr250 swap involved #1 and #3.
 

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If you get a complete totaled bike it may be cheaper, but getting all the parts from eBay separately is often more expensive than buying and putting together a BBK, even ones that require splitting of cases.
 

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Discussion Starter · #7 ·
I was planning on getting a smashed cbr500. Figured it would be easier and cheaper. Also I would imagine that the cbr250 and 500 motor would be very similar. I would imagine Honda would just slap another cylinder on the side of the 250. I think a lot of the electronics are the same to. I Know the cluster is pretty much identical as well.
 

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The cbr250 and 500 are completely different motors. The 500 was designed from the bottom - up to comply with European A2 licencing regulations (below 48hp) and provide extraordinary MPG.
There's a guy who shoveled a cb500r engine to a single cylinder crf250 frame. I believe I've seen the build report on advrider.
 

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Fox. How did you like the 250. How long and how hard was it to get in? I was going to do the 250 but figured it wouldnt be a big enough reward for the work. How's the 450 coming along?
The 250 is great, probably 80-100 hours of fitting and total build. I have less than that, probably half that time but the previous owner had done a few things I didn't have to redo. I currently have it for sale to finance my 450 build (I need to find a donor bike) but I may pull the ads so I can ride the 250 at the crawl.
 

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The cbr300 would be a great build, if I were to do it over I would get the later model 300- same cases, more power
Yeah. The new 300 is actually 283 I think. For the 250 version there's a few BBK's out, a 283, and a couple 305's. Also, if someone else is considering the CBR250, a wrecked CRF250L will work as well. The CRF250L uses same motor and tranny as the CBR250. The CRF's powerband is different, but it's the same motor.
 

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Discussion Starter · #17 ·
The cbr300 would be good. But there still a new expensive bike. Less of them out there. Only thing I'm worried about with the 500 is the width. Sense it's a parallel twin and not s v twin. Did you have a build thread or pics of the work in progress 250?
 

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An also two cylinder 670cc (from an NC700) engine uses a single throttle body and a single exhaust header (these are joined together in the cylinder head) - and the cylinder positioning is a lot closer to the original grom engine (being 62 degree forward leaning) also.
On the other hand it is even heavier than the CB500 motor- although I could not find exact values.
 
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