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Poor compression measurements, but it rides well

  • Thread starter Thread starter spenczar
  • Start date Start date
S

spenczar

Guest
So, I checked compression on my bike for the first time today. I got really, really low numbers: around 60-70 PSI for every cylinder. The bike was warm, and I had it at WOT while doing the tests.

The thing that confuses me is that it has great power and has been riding really well. I've done several highway rides, no problem at all. It was really just a lucky coincidence that I was even testing the bike's compression at all (I'm helping a friend work on his bike). Only things I can think of that aren't ideal:
- Very smoky exhaust at startup
- World's slowest oil leak - if I let it sit for around 2 days, there will be a dark spot right under the oil drain bolt. It's an immeasurably slow leak and has been like this for a few months at least; not sure how worried about that I should be.
- I *think* the charging system isn't working right since I've had to put the battery on a charger twice in 4 months, but the problem might have just been that it was hard to start before I did a valve adjustment, so I cranked it a lot and drained the battery fast.

Work done already:
- Carbs cleaned
- New petcock
- Valves adjusted
- New intake boots
 
they won't pop with those numbers...
faulty gauge or you didn't crank it long/fast enough.
runs good?
then don't worry.
 
Valve adjustment is critical. Hope the engine wasn't damaged too much from neglect by the previous owner.
 
1. Try another gauge
2. Probably bad valve guide seals
3. New washer
4. Read the Stator papers - did ypu up clean the connections - get a VOM if you don't have one
 
When you adjusted valve clearances, what did you find? The oil drip could also be from oil filter cover,running back to drain bolt.Have you had to add oil alot?
Those kind of compression readings would make the engine very unhappy, so you gauge/adaptor setup is screwy.
Fix your charging system!!!!
 
Just relax and forget that you ever checked the compression. Ride the thing & enjoy.

... But you want a peek at those valve clearances yourself at the next opportunity.
 
my 850 smokes at wot, drips oil, and has roughly 100 psi cold....it pulls and runs fantastic still....

ride it till it goes
 
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