2002 CR125 Hybrid Build with LOTS of pictures

chopper · Post by **chopper** » 12:04 am Jul 06 2011

chopper wrote: Strangely, I didn't need to cut the inside of my swingarm, I guess that Honda changed the swingarm sometime between 02 & 07 although they are all considered Gen III.

Here's what I've determined, 02-03 use the same swingarm, 04 is different and was only used that year, 05-07 are a third design. We know that the 02-03 require cutting and that 05-07 do not. This leaves 04 to be determined regarding the need to cut. For future reference, until the 04 dimensions are determined, it may be wise to use a swingarm from an 05-07 model in order to simplify the conversion.

sixstringsteve · Post by **sixstringsteve** » 12:28 am Jul 06 2011

chopper wrote:On my 07 CR125/KDX hybrid I needed to notch the back side of the downtube also. Strangely, I didn't need to cut the inside of my swingarm, I guess that Honda changed the swingarm sometime between 02 & 07 although they are all considered Gen III.

Ok good, that makes me feel better now. I really only took about 1mm off each side of the swingarm. It was no big deal. I don't think it'd be worth buying a '05-07 swingarm just to avoid sanding it down. However, if you had a choice between an '02 and an '05-07 for the same price, go for the '05 if it's one less step.

sixstringsteve · Post by **sixstringsteve** » 12:45 am Jul 06 2011

Didn't get a ton done tonight, but that's ok.

I got the front forks/bars mounted, and I pulled the head.

I have no clue how I'm going to get those 3 stripped head studs out. They're soaking in PB right now. I wonder if I'm going to have to weld some nuts to them and back 'em out with a wrench. Anyone have any great ideas? I can't double-nut them because they're stripped (I can't even get a nut on them).

The above pic shows a rough idea of where the c/s sprocket is in relation to the swingarm pivot bolt. I think it'll be fine.

I'm still unsure what to do about the radiators. THe CR radiators are about 130% bigger (1" taller and 1" wider) than the KDX rads. In order for the CR rads to clear the KDX head, they'll need to be raised 1/2" (like hybridracing65 did.) Chopper, how did you do your radiator?

Or I could go with the KDX radiator, which would simpler since I have more room to work with them. I'd just need to make mounts to bolt it up. I wonder how the plastics would line up with a smaller radiator.

I'm also toying with the idea of making some radiator supports/guards since they seem like the first thing to break when the bike goes down.

I test-fit the tank and it'll fit fine. The airbox looks good too, but I didn't have the subframe in. The exhaust looks like it'll be good as well.

chopper · Post by **chopper** » 08:49 am Jul 06 2011

Regarding the rads you solved your problem without knowing it! Use the CR rads and buy a set of Moose rad gaurds (MSR, Enduro Engineering, all the same). These gaurds have an aluminum bracket that mounts between the frame and the rad. These brackets are drilled so that the rad mounting bolts pass through and fasten into the frame. Heres how I did it, install a 6x1.00 helicoil into these holes, the rad will then be mounted to the bracket rather than the frame, you will need to use shorter bolts so that they don't contact the frame. Then the bracket can be redrilled to meet up with the frame holes so that the rads can be repositioned. I raised mine somewhat but mainly moved the bottoms forward as the clearence is needed in the same area of the cylinder that caused the need to notch the frame.

sixstringsteve · Post by **sixstringsteve** » 09:23 am Jul 06 2011

that's an excellent idea chopper! Are you running your radiators with the CR flow or the KDX flow?

chopper · Post by **chopper** » 04:07 pm Jul 06 2011

CR flow,most of the CR hoses can be used but I used the KDX hose from the bottom right rad to the waterpump. This hose was used in the same location except I may have cut some off(I can't remember) on the end that fastens to the CR rad.

sixstringsteve · Post by **sixstringsteve** » 04:09 pm Jul 06 2011

Well, I dropped my radiators off at the shop. They're converting my CR flow to the KDX flow. It's not going to be cheap, but it's a really simple setup and it should provide more than enough cooling for the kdx engine. We'll see how it turns out and if they botched it or not.

chopper · Post by **chopper** » 04:21 pm Jul 06 2011

sixstringsteve wrote:Well, I dropped my radiators off at the shop. They're converting my CR flow to the KDX flow. It's not going to be cheap, but it's a really simple setup and it should provide more than enough cooling for the kdx engine. We'll see how it turns out and if they botched it or not.

Save your money and don't modify the CR rads. If you ever damage one of the rads you'll need to modify again. Piece of free advise, when doing a custom build try to only modify components that are inexpensive to replace, can be easily modified by yourself, and are unlike to be damaged or wear quickly. Use the CR flow pattern from the 05-07, they don't have the twin outlets on the head like your 02, they have the single outlet on the head like the KDX and are easily adaptable and inexpensive to buy on eBay.

sixstringsteve · Post by **sixstringsteve** » 04:28 pm Jul 06 2011

do you have any pics of the '05-'07 flow? Do I need to cap any of them off? I have about an hour before they start cutting into my cr rads.

Do I have to worry about volume? The outlets on the CR rad are smaller than the KDX radiator.

chopper · Post by **chopper** » 04:29 pm Jul 06 2011

I'm sorry I forgot that the hoses that I am using are from a CR250, 2000-2001 work great for the 05-07 CR125 flow pattern on the KDX engine and CR125 rads. Go to a Honda parts web site and look at the breakdown for radiators and you can see the different hose routings and it will all make sense.

sixstringsteve · Post by **sixstringsteve** » 04:36 pm Jul 06 2011

ok, just to clarify. Do I need to buy new radiators, or can I keep the cr125 rads and just route them like the ''05-07 radiators? Am I going to run into issues with not enough flow through the smaller tubes?

THanks for the help chopper.

chopper · Post by **chopper** » 04:38 pm Jul 06 2011

Definitely call them and have them hold off until tomorrow so that you can think this through and do some research tonight!

sixstringsteve · Post by **sixstringsteve** » 04:58 pm Jul 06 2011

Ok, I see now. You just get a T fitting and combine the top two hoses. I definitely prefer the KDX flow. Hm... decisions...decisions.

It's about $100 to modify the CR radiators. I purchased a radiator guard, so hopefully they don't get too messed up.

chopper · Post by **chopper** » 05:12 pm Jul 06 2011

The problem with the KDX routing is that once your rads are relocated there will not be enough clearance by the frame for the large top hoses to pass through. The cooling with the CR routing will be sufficient as I am using this same routing on my 265cc CR250, riding in slow tight woods with no overheating issues.

sixstringsteve · Post by **sixstringsteve** » 05:13 pm Jul 06 2011

ok, thanks chopper, that makes sense. What do you think about running a single tube from the head to the upper left part of the radiator? Then I'd cap off the upper right rad tube.

Just like FRECNDY said here:

http://kdxrider.net/forums/viewtopic.ph ... 7&start=40

FRECNDY wrote: Seems like it'd be pretty clean to do it YZ250-style. One from the head to top of left radiator, two crossovers, and out the bottom of the right radiator to the water pump. The inlet at the top of the right radiator could either be capped or welded. Less pressure loss for a given flow rate than the KDX routing, and should be equal flow through left and right radiators, unlike the Honda which seems like it would favor the right radiator.

chopper · Post by **chopper** » 05:45 pm Jul 06 2011

No reason to stray from the proven Honda routing. Once again to stray from the Honda routing will require mods that will add to the initial build and also future mods should you encounter any crash related damage that requires replacement of the modified part. Keep it as simple and as stock as possible.

sixstringsteve · Post by **sixstringsteve** » 09:37 am Jul 07 2011

I installed the head studs and the head last night. Then I attacked the rear suspension linkage. It's the old 90/10 rule. Spend 90% of your time on 10% of the work. I've been fighting two of the bearings in the linkage. I got one out, and after 20 min of a chisel and a hammer and a vice, the last one is still stuck in there. I'll get it out tonight.

I'll try to get the radiator installed tonight. Once I've got the radiators working, I can start putting the bike back together.

sixstringsteve · Post by **sixstringsteve** » 11:10 am Jul 07 2011

I'm also looking for a headlight and fuel petcock with a reserve on it that'll fit my bike. Any ideas?

sixstringsteve · Post by **sixstringsteve** » 08:38 am Jul 08 2011

chopper, do you have any pics of your hybrid? I'd really like to see how much room you have between the pipe and the frame, where it enters the motor.

sixstringsteve · Post by **sixstringsteve** » 12:10 am Jul 09 2011

I got a lot of work done on the bike today.

cylinder sleeve looks new-ish:

I made my own upper head motor mounts out of the old CR mounts:

KDXRIDER.NET

KDXRIDER.NET

2002 CR125 Hybrid Build with LOTS of pictures