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Old 02-21-2007, 04:47 PM
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Default CR80 to 125 engine swap

     

My girlfriend rides a 1998 CR80 Expert. She is small in stature and light weight. The physical size of the bike works very well for her. She feels very comfortable. However the bike cant pull her up some of the bigger hills that she likes to try. I think part of it might be that she rides very conservative and cant really feather the clutch. But thats just how she rides.
So I'd like to add power to this bike.
Option 1: Add one of the big bore kits. Which one? I'd imagine there are overheating concerns. Yes/no?
Option 2: Swap a 125 engine into this bike. I'm a pretty accomplished fabricator and think this is the route I'd like to take. Anyone done this? I'm thinking I might need to buy a whole bike (125) and use what I need and sell the rest.
Whatever way I do this I'd like to build the engine more for low end power as she rarly rides on the pipe.

What do you guys think? Any imput.

Phil
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Old 02-21-2007, 05:03 PM
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Default Re: CR80 to 125 engine swap

CRF150R!

Honestly, I have no idea if you could make it work, but I bet you could buy a 150R for the amount of money it would take to shoehorn a 125 motor into the 80.
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Old 02-21-2007, 05:08 PM
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Default Re: CR80 to 125 engine swap

I understand the need for more power and I realize this doesn't have anything to do with your question, BUT... have you considered adding a flywheel weight?
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Old 02-21-2007, 05:09 PM
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Default Re: CR80 to 125 engine swap

XR200R motor in the CR80 frame. It's air cooled (no rads to worry about), bullet-proof, good power, lots-o-torque, 6 speed trans, cheap, reliable, etc.
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Old 02-21-2007, 07:11 PM
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Default Re: CR80 to 125 engine swap

Quote:
Originally Posted by Faded View Post
XR200R motor in the CR80 frame. It's air cooled (no rads to worry about), bullet-proof, good power, lots-o-torque, 6 speed trans, cheap, reliable, etc.
Originally I wanted to put a XR150 engine in it or just buy her a XR150 or CRF150 but she road a XR150 and hated it. She wants to stay 2 stroke.

So here we are...

Phil
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Old 02-21-2007, 07:24 PM
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Default Re: CR80 to 125 engine swap

Go for it! I had a RM 80 back in the day that had a 125cc engine in it. It flat out ripped! All that power in a little 80 frame. I didn't do any of the conversion. So, I wouldn't be much help in that department. You should be able to find another motor pretty easy if you keep your eyes open.
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Old 02-23-2007, 03:35 PM
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Default Re: CR80 to 125 engine swap

anyone else?
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Old 02-23-2007, 05:53 PM
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Default Re: CR80 to 125 engine swap

There are 2 problems I see here, none of which have to do with it being doable...

1) Though we're not talking about a turbocharged 500 hp motor going into that little frame, thats quite a bit more power going into a bike that already likes to stand up.

2) This has to do with 1. If she rides conservatively, then I don't see how more power will help her, especially in a small framed bike. If she's going up a hill she has a hardtime with with an 80 motor, I think going up a hill with a 125 motor in such a short wheel base/small tires is just going to end up hurting her, both in performance and quite possibly physically.

Heavier flywheels hurtpower if it already doesnt have the power, and are typically a bad idea for 80's and 125s. Honestly, she's either going to need to adjust her riding, or get used to a crf150... or step it up to a bigger bike. I just think a 125 motor in a 80 chassis just wont be a balanced bike...

-Max.
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Old 02-26-2007, 11:46 PM
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Default Re: CR80 to 125 engine swap

you make some very good points. Both things that still need to be considered. So you think the bike is going to loop out a lot? My thinking is the new engine should have more low end power so she'll be able to lug it more if she has to. Maybe un-true
I would like her to get a 150 but she hates 4 strokes and this seems like a fun project.

Phil
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Old 02-27-2007, 09:47 AM
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Default Re: CR80 to 125 engine swap

If I had a cr125 motor handy and wanted it in that frame I would do it. If you don't already have it I would consider the bigbore and going against what Demon says, put on a heavier flywheel. If she is riding conservatively it will help her overall riding, not necessarily her hill climbing, but would keep her from getting unwanted wheelies.

With the 125 you are going to add weight and raise the center of gravity.

Of all the suggestions made, I like Faded's the best, but you say she doesnt like 4 strokes.
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