Check for air leaks. Did you have a boot come loose?
Hi there,
I recently purchased a clean 09 Blast with 1800 miles. I was planning on doing a full service on it but wanted to ride it a little to see how it ran. It started and idled well. I checked the oil when cold (I later read where it should be checked hot) and it was about 2/3 qt. low so I topped it off with Mobile 1 20/50 and took off on some errand running.
Temp was about 60 degrees f. I drove it about 100 miles and the bike ran strong and flawlessly. Just as I was getting close to home at about 60mph the bike started losing power and then died all within about 45 seconds. No weird noises or anything. I pushed it on home. I still had gas to the carb, had good spark, and battery still had juice. I put a compression tester on it and with the throttle open i had 30psi on the first crank which worked itself up to just shy of 120psi by the 7th to 8th crank. I injected 1/2 oz of oil and got a final reading of about 160-170 psi. I then placed the plug in it and it started and ran about 45 seconds then died at which time the compression readings were back around 120psi. What has happened? Thanks for the input.
Check for air leaks. Did you have a boot come loose?
No problems that I can tell in that area. There did not seem to be any symptoms of an intake leak mentioned in other posts. Thanks
120psi is too low, likely lost a ring from running too lean.
Pull the head and check the bore for scratches.
Thanks much, that seems to explain the quick turn of events. I'll be getting a new boot to be sure.
After seeing what is going to have to be mended in the top end...
I pulled the head, jug, and piston today. To my untrained eye everything looked okay except the top of the piston and the combustion chamber had a lot of carbon build up (in my opinion). The cylinder lining looked good but I will have a mechanic check it out. At 1800 miles do you think this is worn rings from running lean or maybe a stuck ring? The boot had some cracking but didn't appear to go all the way through. Thanks for the input.
Any cracks go all the way through and caused your lean condition. Replace it.The boot had some cracking but didn't appear to go all the way through.
After it is inspected, ask for a light hone and new rings. Since the oil brought the compression test up to spec, I suspect it was a ring.
I appreciate the info and will do. You guys are golden for your time and effort :)
Well this was a discouraging day. The other day I had a mechanic look at the cylinder and head. He said with the old rings everything was in tolerance and the valves were both good. He gave the cylinder a hone and cleaned up the piston, valve seats, etc. I put the bike back together with new rings, gaskets, etc and bought a super boot as well. I did a quick inspection of the bottom end of the carb and sprayed some carb cleaner through it. Finally got everything assembled and started it and it ran for a minute or so and then started the same nonsense. It would barely idle then die. I didn't even get down the driveway. Now I'm banging my head.