You mention that 23K is high but not excessive and I have been wondering what that figure might for other nighthawk models. My 84 650 has about 26K (Ihave had it only one season) is beginning to show a little blue smoke at startup after sitting all day but over runs very well. Is the end near? Thanks
On 11/2/08, Dennis Hammerl <[EMAIL PROTECTED]> wrote: > > Your intentions are good but your methods need a little refining. > Testing on a warm motor is preferred. Your measurements are all quite low > and that tells me some about your situation. First off, both plugs out to > reduce effort of starter. Check and adjust valve clearance before checking > compression. 23K is considered high mileage for one of those but not > excessive. When taking a compression reading, open the throttle completely > and have the choke open as well. (if you can't get air into the engine, > there is nothing to compress.) This alone should result in a higher reading. > I would be quite happy with about 150lbs each. A Honda engine will run OK at > as low as 100lbs. Below that figure, expect poor running. The difference > between cylinders is important. That should be no more than 10~20lbs. > FYI: compression tests are cumulative (longer you crank, the higher it gets > up to a point) They are considered to be a rough indication of condition. A > leak-down test tells far more and diagnoses problems. Operate the starter > for no more than 5 seconds. That's more than enough to get results. > Your running problems are indicative of carb problems more than engine. You > didn't say what year 450 you have, earlier ones (80's) have drivability > issues from lean carburation. > Happy wrenching > > --- On *Sun, 11/2/08, Redtail <[EMAIL PROTECTED]>* wrote: > > From: Redtail <[EMAIL PROTECTED]> > Subject: [Nighthawk Lovers] Compression Testing > To: "Nighthawk Motorcycle Lovers!" <[email protected]> > Date: Sunday, November 2, 2008, 4:23 PM > > I bought my first bike, a used CB450SC back in the summer and have > been riding it ever since. It has 23000 miles on > it. The engine > coughs and spits and backfires sometimes, but starts and runs every > time. I had a quick look at the carbs and gave them a quick clean at > the time but plan on going at them again as soon as I quit riding for > the winter, (which will be soon.) I borrowed a compression tester > from a friend to check it out in case I have to perform a little > engine work. I'm not necessarily good at diagnosing a problem, but > once I know what is wrong, I can fix just about anything. > > A couple of questions: > 1) Should the test be performed with the engine cold, warm or both? > 2) What should a normal reading be? > 3) Should both spark plugs be out at the time or does it matter? > > So far I have only checked it with a cold engine. The left cylinder > tested about 80 to 85 each time, whereas the right one was down about > 55 at first, but increased to 100 after checking it the forth time. > (I used a spare boat battery > so as not to wear down the bike battery > and I let the starter cool for 10 minutes in between tests.) > > My thinking is that the oil was being circulated and coating the > cylinder walls and increasing the pressure in the right cylinder, but > what about the left one? Is there a problem with the rings in that > one? > > Also, I read somewhere once that if one cylinder is low and you squirt > some oil into it and then check the compression again, if the numbers > increase the rings are worn, and if they stay the same, the valves are > leaking. Is my thinking correct? > > Any help would be greatly appreciated. > > Paul B. > > > > > > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Nighthawk Motorcycle Lovers!" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/nighthawk_lovers?hl=en -~----------~----~----~----~------~----~------~--~---
