I recently bought a non-running 2017 CB300F with 7500km (5000mi). The bike is very clean and has been stored indoors. It's sat for the last couple of years. The person I bought it from says the bike was running fine when he parked it. I have no way of verifying that, but also no reason not to believe him PO because everything he told me and showed me (paperwork etc) has checked out so far.
I expected this to be a fairly straightforward "re-commissioning", but it hasn't worked out that way so far.
I started with a brand new battery, fresh gas (drained the tank), and clean air filter and air box. Bike wouldn't start, and didn't really sound like it wanted to.
I then replaced the spark plug, using the recommended NGK Iridium, and verified it gives a strong blue spark. Still no joy.
I then cleaned the throttle body and injector. I tested operation of the injector by cranking bike with injector disconnected - I could see repeating "mists" of fuel come out. This all looked OK to me.
From there, I checked compression and found it was really low (50psi). This was with throttle fully open, but engine was cold (obviously, since I can't get it running). I thought I might have stuck rings or a stuck valve, given the bike's been sitting. So I tried a tablespoon of Marvel Mystery Oil a few times over a couple of days. Still low compression.
Then I checked valve clearances. I found the two exhaust valves were a little tight (0.20mm), so I adjusted them to the loose end of acceptable (0.30mm). Compression is still low.
So now I'm thinking next step is that I need to drop the engine so I can open it up and see what's going on. Before I do, I just thought I'd check in here to see if I'm missing anything.
A couple of specific questions:
I expected this to be a fairly straightforward "re-commissioning", but it hasn't worked out that way so far.
I started with a brand new battery, fresh gas (drained the tank), and clean air filter and air box. Bike wouldn't start, and didn't really sound like it wanted to.
I then replaced the spark plug, using the recommended NGK Iridium, and verified it gives a strong blue spark. Still no joy.
I then cleaned the throttle body and injector. I tested operation of the injector by cranking bike with injector disconnected - I could see repeating "mists" of fuel come out. This all looked OK to me.
From there, I checked compression and found it was really low (50psi). This was with throttle fully open, but engine was cold (obviously, since I can't get it running). I thought I might have stuck rings or a stuck valve, given the bike's been sitting. So I tried a tablespoon of Marvel Mystery Oil a few times over a couple of days. Still low compression.
Then I checked valve clearances. I found the two exhaust valves were a little tight (0.20mm), so I adjusted them to the loose end of acceptable (0.30mm). Compression is still low.
So now I'm thinking next step is that I need to drop the engine so I can open it up and see what's going on. Before I do, I just thought I'd check in here to see if I'm missing anything.
A couple of specific questions:
- As far as I can tell from the shop manual, this engine doesn't have anything special with a decompression mechanism and I should get ~180psi from standard cranking of the engine. Is that right?
- Based on what I've tried so far, and the low compression reading I'm seeing, am I on the right track that opening the engine is the next step? I've been trying to avoid this due to cost and hassle. The bike's got such low miles and been taken care of, so I can't see it having major engine issues. But I'm thinking years of sitting without any storage treatment (stabilizer etc) could be causing problems?