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| Need Rod advice 1980 cr250 https://vintagedirtbikeforums.alp-sys.com/viewtopic.php?f=21&t=1374 |
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| Author: | Go4Ducks2 [ Fri Mar 09, 2007 4:12 pm ] |
| Post subject: | Need Rod advice 1980 cr250 |
Started taking motor apart with intentions of new crank bearings seals, rod and bearings because I had a seal leak on the clutch side.(Don't know previous history on motor) Now that I got it apart, crankshaft feels real tight, both sides and is smooth on rotation, no noise. Everythings off but cases are not split. So I thought I would just put in seals, BUT, my side to side big end on the rod clearance is .027 and service limit is .028. Rod big end up and down has no play. Do you guys think I can get away with running a new piston through this motor and then when that piston is done, split the cases and do it all then? Don't really wanna split cases unless I have to. This is a back up bike so I was thinking I could get through this summer with it just doing the clutch side crank seal. Gimme you honest opinion, thanks garry |
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| Author: | Moto_Recon [ Fri Mar 09, 2007 4:22 pm ] |
| Post subject: | Side Play |
My inclinination would be to RUN IT! You're still in specification and the maximum tolerances are usually set on the very conservative side. I'd worry about it more if the small end of the rod had a problem. |
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| Author: | redrocket190 [ Fri Mar 09, 2007 4:57 pm ] |
| Post subject: | |
If there is no up and down play in the big ends or the crank bearings, I say run it... |
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| Author: | Go4Ducks2 [ Fri Mar 09, 2007 7:50 pm ] |
| Post subject: | |
Thats what I needed to hear! Gonna go order me some crank seals. |
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| Author: | rocket racing [ Sat Mar 10, 2007 11:36 am ] |
| Post subject: | Rod |
Barry, I have been a motocross mechanic for over 25 years and my opinion is I would not run that rod with those limits. A new piston will put alot more pressure on the rod and will almost always take the rod out. Alot of people don't relize this but it happens alot when they tend to freshen up a top end with not adressing the rod. Later Randy Sorry I know you did not want to here this. 
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| Author: | redrocket190 [ Sat Mar 10, 2007 11:46 am ] |
| Post subject: | |
You could send the engine to http://www.racerstoystore.com. They put IMS hot rod kits in both my engines and replaced the mains and seals. If you are told elsewhere that the crank and rod are only available as a single - expensive - unit, that is true, but a rod kit from a 1984 Honda ATC250R works fine. Send it to someone who has done this before. |
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| Author: | Go4Ducks2 [ Sat Mar 10, 2007 10:41 pm ] |
| Post subject: | |
Thanks for the advice Randy, you are probably right, but we are gonna run it. Chances are it won't get rode much anyway if at all. Then this coming winter, I'll make the changes when I have more time. |
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