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Old 04-18-2013, 06:07 PM   #16
81cr450 OP
Gnarly Adventurer
Joined: Jul 2011
Location: Piute ATV trails Utah , Dreaming of Baja
Oddometer: 100
You do realize this is ADV not better homes & gardens right?
When I was a about 5 I watched a guy build a harley trike in his front room. Getting it out was another story. You cant really call yourself a wrench if you've never washed parts in the tub either.

Anyway its coming along , I've thought of a couple points on the motor I forgot to mention. The 1995 & up bottom end has 8 ball main bearings , the same used in the CR500. I replaced the mains with factory honda parts . The 1993 has the same main on one side but the other side got a smaller less beefy piece. Seems like a good deal for longevity.
The case also has a pocket in it that can hold a little more oil if you ditch the gasket & drill 2 holes. The bike only holds 650ml so I think its worthwhile to get some more fluid in there. I did have to run my crank side clearance on the minimum to make up for the .010 gasket thickness. The trans still was good on clearance.

You can see the largish pocket here

On this side you can see where the oil will come out of the trans into the clutch , then theres a built in scraper that will put the oil back in the transmission. I'm hoping this will generate circulation through the pocket. I also went kinda small on the holes so the trans couldnt be over scavenged

I also heard that the latter RMX powervalves could fall into the motor if a spring broke, this motor is not like that. There are 2 springs that should be replaced, but if the do go bad all that will happen is the second stage of the powervalve will flutter.

I also read that the powervalve rod clips break when you take them appart but mine were good so I just used them over

I also changed the carb from a keihin pk that "barely" idles off the choke, to a mikuni 36mm tmx which fits the 92 rm boot perfect. I figure if a cr500 can make 65 hp off of 38mm a 250 should be fine with 36mm & have better throttle response. Alot of people think tmx mikuni's suck, the problem in my opinion is the jetting table out of the oem manuals. This carb calls for a 35 pilot from honda, but from experience the thing takes 4 sizes leaner down to a 25 , some even say a 20 is the ticket. I like em I had a bored out 38mm tmx on my kx550af & they work. Scared me leaning it down that far but...

I need to mention how tight the head is to the top of the powervalves, I had to clearance a bit & I will have to build a new mount but it's worth the squish, trust me.

You can also see the $8 a foot 500 degree silicone hose, it should be leak proof I hope. Which reminds me ... I need to flush the radiators.
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