Joined
·
24 Posts
Hi everyone,
I recently got a 1983 CM450A that has been sitting for about 2 years and I'm trying to get it back into operating condition...
I'm planning on going through the stickied "New to you" Bike checklist, but after getting a new key cut (the originals were long gone), new plugs, new fuel lines, new in-line fuel filter, a new battery, new oil, and fresh gas in an aux tank I tried starting it up to see what I'm working with. To my surprise it started more or less right up with almost no effort, however after the first second or two it immediately raced to full throttle and wouldn't come back down to idle speed. I immediately hit the kill switch and checked the throttle controls and cables and found that the throttle control was kind of loose on the bar, turning it with force makes the whole thing kind of roll on the bar, and it doesn't return to fully closed when I let go of the handle.
I started the bike again while holding the throttle fully closed but once again it raced right up to the redline immediately. This happens regardless of what position the choke is in.
My thoughts are that there is either a problem with the cables or the throttle butterfly valve, or there's a significant vacuum leak somewhere. I inspected the carb boots but they look fine. When I pulled the carb I verified that the butterfly valve cycles just fine and fully snaps closed when not engaged.
I'm going to replace both push/pull throttle cables and the control assembly. I'm also going to clean and rebuild both carbs this evening.
In the past I've had bikes that had hovering idle issues where the engine speed would either return to idle very slowly or not at all after being revved, this was caused by vacuum leaks in the fuel system... but I've never had one that goes straight to redline speed as soon as it is started. I'm scared to run the engine for longer than just a second or two since it is running so I'm nervous to do the old "spray carb cleaner by the intakes" leak test since the engine is running so high.
So, my question is what else ought I be looking at for this? The intake boots look fine from what I can see but that doesn't mean there isn't a small crack on there that is causing a leak that I just can't see...but if that's the case would it have this big of a result?
I thought for sure it was an issue with the throttle cables or maybe the throttle spring on the carbs, but once I got them out and saw just how strong that spring is and confirmed that the throttle is closing completely at idle I'm thinking it must be something else. Would this happen with a leaky or blown head gasket? It's almost acting like a runaway diesel engine but as far as I know that can't happen with these motors....right?
Thanks for any advice on where to go from here... I'm really hoping that this essentially free bike doesn't end up turning into a nightmare!
-Joe
I recently got a 1983 CM450A that has been sitting for about 2 years and I'm trying to get it back into operating condition...
I'm planning on going through the stickied "New to you" Bike checklist, but after getting a new key cut (the originals were long gone), new plugs, new fuel lines, new in-line fuel filter, a new battery, new oil, and fresh gas in an aux tank I tried starting it up to see what I'm working with. To my surprise it started more or less right up with almost no effort, however after the first second or two it immediately raced to full throttle and wouldn't come back down to idle speed. I immediately hit the kill switch and checked the throttle controls and cables and found that the throttle control was kind of loose on the bar, turning it with force makes the whole thing kind of roll on the bar, and it doesn't return to fully closed when I let go of the handle.
I started the bike again while holding the throttle fully closed but once again it raced right up to the redline immediately. This happens regardless of what position the choke is in.
My thoughts are that there is either a problem with the cables or the throttle butterfly valve, or there's a significant vacuum leak somewhere. I inspected the carb boots but they look fine. When I pulled the carb I verified that the butterfly valve cycles just fine and fully snaps closed when not engaged.
I'm going to replace both push/pull throttle cables and the control assembly. I'm also going to clean and rebuild both carbs this evening.
In the past I've had bikes that had hovering idle issues where the engine speed would either return to idle very slowly or not at all after being revved, this was caused by vacuum leaks in the fuel system... but I've never had one that goes straight to redline speed as soon as it is started. I'm scared to run the engine for longer than just a second or two since it is running so I'm nervous to do the old "spray carb cleaner by the intakes" leak test since the engine is running so high.
So, my question is what else ought I be looking at for this? The intake boots look fine from what I can see but that doesn't mean there isn't a small crack on there that is causing a leak that I just can't see...but if that's the case would it have this big of a result?
I thought for sure it was an issue with the throttle cables or maybe the throttle spring on the carbs, but once I got them out and saw just how strong that spring is and confirmed that the throttle is closing completely at idle I'm thinking it must be something else. Would this happen with a leaky or blown head gasket? It's almost acting like a runaway diesel engine but as far as I know that can't happen with these motors....right?
Thanks for any advice on where to go from here... I'm really hoping that this essentially free bike doesn't end up turning into a nightmare!
-Joe