Vintage Dirt Bike Q & A
https://vintagedirtbikeforums.alp-sys.com/

cr250 78-79
https://vintagedirtbikeforums.alp-sys.com/viewtopic.php?f=21&t=683		 Page 1 of 1
Author:  2five0 [ Sun Jun 12, 2005 9:42 am ]
Post subject:  cr250 78-79
will a topend off of a 79 work on a 78 bottom end.

thanks
Author:  redrocket190 [ Sun Jun 12, 2005 3:34 pm ]
Post subject: 
Yes. Check that the piston you use is drilled to lubricate the exhaust port bridge introduced with the 1979 cylinder.
Author:  2five0 [ Sun Jun 12, 2005 8:10 pm ]
Post subject: 
if i have a nos honda piston why would they make you drill the holes.

thanks
Author:  redrocket190 [ Sun Jun 12, 2005 9:30 pm ]
Post subject: 
Wiseco recommends some oil lubrication holes for the 1979 cylinder because of the exhaust port bridge which wasn't present in 1978. Honda however offers the same part # piston for both 1978 and 1979 (13100-430-000), so I assume both don't have holes. I use the former, hence the advice.
Author:  william richard [ Sun Jun 12, 2005 10:18 pm ]
Post subject: 
every 78 CR250R ive owned had a bridged exhaust port-the port that is different is the intake port-it has a bridge crossways in the middle of the main intake port not present on 78 CR250R cylinders-if there is something different i havent seen it-anywho the drilled skirt is a good idea on any bridged exhaust port
Author:  redrocket190 [ Mon Jun 13, 2005 1:33 pm ]
Post subject: 
Thanks for clearing this up (and the pictures you sent). I have cylinders with and without intake port bridges. Now I know that they are 1979 and 1978 respectively. I am sure that at one time I had a cylinder with an un-bridged exhaust port, but I let that one go with a parts bike so I can't check. I wonder if some clown ground the bridge out in a "porting" job? Or perhaps I am losing it :) If you have your 1979 cylinder sleeved check the smaller of the bridged intake port(s). I found that the hole in the LA Sleeve was much smaller than the port itself which can't be good for the air-flow. I assume that you drill holes in the NOS Honda pistons you favor?
Author:  2five0 [ Mon Jun 13, 2005 5:00 pm ]
Post subject: 
i can tell you one thing i am not drilling holes in my piston.
Author:  redrocket190 [ Mon Jun 13, 2005 10:16 pm ]
Post subject: 
And there lies the difference between well-intended advice and an instruction.
Page 1 of 1 All times are UTC - 7 hours [ DST ]
Powered by phpBB® Forum Software © phpBB Group
https://www.phpbb.com/