Can't get my 1983 CR480 to run right

Corban_White

Well-Known Member
Location
Payson, AZ
I need some help here. I have a 1983 Honda CR480 that I've had for 17 years. Until a few months ago it hadn't been started since 2005. The last time I rode it in 2005 I was cruising along a smooth road and it suddenly lost all power. It would rev up fine with the clutch pulled in but try to get it to move and it would just sputter as the load increased. We threw it in the truck and planned to tear into it and see what was wrong. Well, 12 years later, I finally got to it.

This summer I pulled the reed cage and exhaust off and checked out the lower end. Everything looked good there so I pulled the head and checked it out. Piston, head and cylinder look great. Tons of compression. While I had the head off I added a decompression button. Put it all back together with new gaskets, spark plug and reeds. Cleaned the carb really good. Cleaned the gas tank, changed the oil and she fired right up. Rode it around the block a couple of times and all seemed well. Then I tried getting on it and that's where it gets troublesome.

The bike runs runs fine but is behaving wierdly. When I roll the throttle on under load, most of the time it will start out pulling really well. Then, about the time it starts feeling good it falls on its face and stutters. The rest of the time it stutters from the initial roll on. The manual calls for a 180 main jet and that's what it had in it the several years it was running well. I've gone all the way down to 168 without really noticing any consistent improvement. I've also had the needle in every notch without really noticing much difference. I did a leak down test and sealed up a few leaks in the exhaust and intake but the crank seals were good. After sealing those up it still behaves the same. I changed the spark plug again with no change. I don't know where to go from here. Any ideas?
 

Rot Box

Diesel and Dust
Location
Smithfield Utah
480's are awesome glad your putting it to use! Maybe try checking the float level. My brothers CR5 was doing something similar and the floats ended up being way out of adjustment (weren't sure how they could have moved after sitting through the winter but they did).

Besides that I'm not sure... The kill switches on those have been known to short out intermittently. Easy way to check if it's bad is to unplug it and go for a ride.
 

rholbrook

Well-Known Member
Location
Kaysville, Ut
Does it run fine cold? Does it run hard for a few seconds then fall on it's face? Did you check the float level, did you check to make sure the float needle valve is fine. If that little rubber point on the top of the float needle gets a groove in it it can run similar to what you are describing. Pull it out and see if you can see a little ring around that needle. When those go bad they run like they are vapor locking
 

Corban_White

Well-Known Member
Location
Payson, AZ
I did check the float level when I was messing with the jetting. Adjusted it a little and gas ran out of the overflow so I adjusted it again and it seems good now. It never quite makes it to pulling hard. It starts to then falls flat. Cold is worse but that bike never ran well until warmed up.
 
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