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1990 dr350...ran great, now not at all?

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I just got a 1990 DR350s, it ran fine all summer for the guy that I got it from. On the way to my house to complete the sale it died. He said "it just wouldn't respond", "I would twist the throttle and nothing would happen". I brought it to a local reputable shop and had them go over the bike...they said that the battery was junk and it needed a few parts. They put a new battery in and got good spark, compression was at 100 and wouldn't run. They told me that I may need to rebuild the top end to get it on the road. Any other ideas that may not cost so much money? I ended up getting the bike for $200 instead of the $800 he wanted, so I would like to try to get it going again.

Thanks

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They put a new battery in and got good spark, compression was at 100 and wouldn't run.

100 PSI sounds low. I think the compression ratio is 9.5, so if are near sea level, the compression should be north of 130 PSI.

Did you check valve clearance? That can affect compression.

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100 PSI sounds low. I think the compression ratio is 9.5, so if are near sea level, the compression should be north of 130 PSI.

Did you check valve clearance? That can affect compression.

Compression ratio is only one of the keys that equates into actual compression. Valve timing, cam profile, engine RPM, even valve adjustment if it's off significantly or too tight holding a valve open.

If the cam chain has jumped, the intake valves could be staying open too long after BDC causing low compression, or possibly worn valve seats. Worn valve seats will cause a tight valve lash, sometimes no valve lash which will definitely cause a compression issue.

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