Vintage Dirt Bike Q & A

Finally got the beast running. This is a 1983 CR480 R that I picked up, it has a fairly recent 1.5 os piston installed. It had a cracked stock pipe that i replaced with a new DG pipe. Here's the problem; it has tons of hit down low, but the mid range falls flat and theres no real top end. Is this normal with a dg pipe? Should i weld up the stocker and re install it? It has the stock kiehen, the plug looks a little dark-not bad. Could the reeds be shot? How do you tell? They are probably stock, I didnt change them...
Thanks!
Mike

The DG pipe is said to increase the top-end over bottom and mid-range. I hear from CR480R owners here in SoCal that the PFR pipe and silencer are the way to go. It is difficult to provide jetting advice without knowing what you are running now. In warm SoCal I am two main sizes down from the 172 that itself I think is leaner than stock. I also moved the needle clip to #2 from the top to lean out the mid-range. I am running the DG pipe and have absolutely no problem with power (compared to a 1979 CR250R). You should check the reeds. If they are chipped I would recommend Boyesen replacements.

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Michael Stiles
1979 Honda CR250R Elsinore | 2006 Husqvarna SM510R | 2007 Service Honda CR500R-AF

Thanks for the info, I'll try a new set of reeds and see if that changes anything. Has anyone tried a later year carb on one of these? Would that disqualify it for Ultima if you ran a 85 or 86 500 carb?
Mike

I would expect to raise an eyebrow at AHRMA tech inspection if you ran - say - a flat side carb, but at "independent" historic events you would be fine.

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Michael Stiles
1979 Honda CR250R Elsinore | 2006 Husqvarna SM510R | 2007 Service Honda CR500R-AF

The 83 CR480 i had didnt seem to gain much from the stock pipe to the DG pipe other than maybe a little less hit-i didnt see much difference.Stock jetting is way rich on the main which hurts the stock topend pull.Also you mentioned yours being bored 1.5mm over-well remember this lowers port height all the way around which will favor lowend power-a little can make a difference and these bike were very mild in the size of the ports.also a larger bore increases your compression ratio because of the increase in the volume of the cylinder but the volume of the cylinder head is the same-higher compression ratios hurts topend power on any 2 stroke

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1979 Honda CR125RZ
1982 Honda CR125R
1979 Yamaha YZ100
2003 Kawasaki KX250

Thanks for the input. I just got a set of FMF reeds, I'll pop those in and try rejetting it to clean up the mid range. Boy, getting the angle on this thing to kick start it is tough. I'm 6-2, 230#, and it aint easy...I've heard of a guy making better kick starters, anyone seen one?
Mike

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Michael Stiles
1979 Honda CR250R Elsinore | 2006 Husqvarna SM510R | 2007 Service Honda CR500R-AF