Honda CX 500 Forum banner

21 - 35 of 35 Posts

·
Registered
Joined
·
23 Posts
Discussion Starter #21
Okay so just throwing my 2 cents in here...

My '79 CX would do that. Start great in the mornings, but once hot it'd never start. Couldn't even push start the bike. It'd drown the battery after a few cranks...even a new battery. Couldn't jump start it, either. I went through so much trying to sort it out and ultimately I just stopped turning the bike off unless I was REALLY sure I was done riding for a while. I dealt with it like that for over a year.

Then one day while riding I got a nasty puff out the back and no power. White "smoke", oil everywhere, chocolate milk in the oil, just generally nasty. Temp gauge never showed I was overheated. I went to change head gaskets only to find my headgaskets were both fine and unphased. Flushed the engine and she started right up and ran as good as she ever had. No exhaust gas in the coolant. Just real peachy. Except once hot...still...no starty. Totally miffed by this I dropped the engine back out and went snooping around. Someone here suggested that a bad seal in the water pump could be a potential source of coolant in the oil so I popped that cover off...and the impeller fell out. Splines were completely stripped, the inside of it was a mix of polished and tarnished and the hole was rather elongated. It had been that way for a very long time. After replacing a few seals and swapping a water pump over from another bike she ran perfectly...even started right up when hot.

The engine was getting too hot, causing things to start getting sticky. Coolant wasn't flowing so my gauge never really showed the temp spike in the cylinders and head.
OK, I will look at water pump. I have no much hope because it seems not overheated at all. Oil is perfect, no coolant in the oil. Just changed the oil as well.
 

·
Registered
Joined
·
156 Posts
I had no oil contamination either until that one special incident. I even made a 250 mile trip through the mountains doing my best to hang with some sport bikes and never ones did it give me any serious indication of running hot. I thought it seemed warm compared to some other bikes I'd ridden any time I stopped but it was a "feeling" unsupported by anything. The gauge always said normal, oil always clean, never any bubbling, just didn't want to start when hot.
 

·
Super Moderator
Joined
·
13,779 Posts
Mak: I hope you cleaned out the weep hole after that. It must have been blocked because if the impeller was loose coolant would have leaked out between the impeller and the shaft and exited by the drain hole (as happened when my impeller nut came loose - I learned the importance of using a torque wrench on it when that happened).

Inc:
  • Feel the radiator after a ride. If it is hot at the top the coolant is flowing.
  • An accelerator pump is not a fuel pump. It is a diaphragm pump on one of the carbs that is operated by the throttle linkage. When you move the throttle slowly it does nothing but when you open the throttle quickly it squirts a bit of raw fuel into the throats of the carbs to help the engine pick up speed before the slides in the CV carbs react and open more.
  • Have you checked that your chokes are opening properly? It may be hard to start a hot engine with the chokes partly closed.
 

·
Registered
Joined
·
156 Posts
It was many years and motorcycles ago...but the impeller was held in place, just not spinning. It probably would have started weeping eventually. It was the kind of failure that stressed that not all failures are normal failures.
 

·
Super Moderator
Joined
·
3,762 Posts
Have you checked that your chokes are opening properly? It may be hard to start a hot engine with the chokes partly closed.
I would like to know if he has tried a hot restart using the choke. I think that might be something to try as he is able to restart if he add fuel directly to the cylinder.
 

·
Registered
Joined
·
23 Posts
Discussion Starter #26
I would like to know if he has tried a hot restart using the choke. I think that might be something to try as he is able to restart if he add fuel directly to the cylinder.
I am struggling with this for 2 years, so I tried a lot of options - no throttle, full throttle, choke etc etc. Nothing helps. No way to start. As soon as it cools down it starts excellent and idles excellent.
Chokes and accelerator butterflies are in perfect sync, they open as they should.
 

·
Registered
Joined
·
23 Posts
Discussion Starter #27
I had no oil contamination either until that one special incident. I even made a 250 mile trip through the mountains doing my best to hang with some sport bikes and never ones did it give me any serious indication of running hot. I thought it seemed warm compared to some other bikes I'd ridden any time I stopped but it was a "feeling" unsupported by anything. The gauge always said normal, oil always clean, never any bubbling, just didn't want to start when hot.
I just checked the cooling system. All is fine. Thermostat is working, opens when hot. Water pump is working fine and it is in good condition. Coolant looks fresh. Oil is fresh as well. Is there anything more to check on this bike? :)
 

·
Super Moderator
Joined
·
13,779 Posts
OK. It is hard to tell if the chokes are fully opening when you push the button in with everything put together so I wanted to make sure you checked that there isn't something interfering with the linkages.

You say you "cleaned the carbs". How thoroughly did you clean them? Just spraying carb cleaner through the openings may not be enough...
 

·
Registered
Joined
·
23 Posts
Discussion Starter #31
OK. It is hard to tell if the chokes are fully opening when you push the button in with everything put together so I wanted to make sure you checked that there isn't something interfering with the linkages.

You say you "cleaned the carbs". How thoroughly did you clean them? Just spraying carb cleaner through the openings may not be enough...
I took off carbs yesterday, to check water pump, choke and butterfly works perfect. I cleaned carbs recently, replaced all seals and nozzles, from carb rebuild kit as well. it is cleaned with cleaner from inside as well. It is clean.
 

·
Super Moderator
Joined
·
3,762 Posts
I am struggling with this for 2 years, so I tried a lot of options - no throttle, full throttle, choke etc etc. Nothing helps. No way to start. As soon as it cools down it starts excellent and idles excellent.
Chokes and accelerator butterflies are in perfect sync, they open as they should.
Since the bike will hot start if given raw fuel but using the choke will not allow it to start, I'm thinking vapour lock as has been mentioned. Is the fuel hose from petcock to carb still stock and routed as per the factory shop manual? How old is the fuel hose? Could it have developed an inner flap which is affecting fuel flow?
 

·
Registered
Joined
·
23 Posts
Discussion Starter #35
Since the bike will hot start if given raw fuel but using the choke will not allow it to start, I'm thinking vapour lock as has been mentioned. Is the fuel hose from petcock to carb still stock and routed as per the factory shop manual? How old is the fuel hose? Could it have developed an inner flap which is affecting fuel flow?
Not the case, I measured fuel level cold and hot it is the same, just below the rim. Petcock is not in charge, as if I'm removing the fuel tube from the petcock - it is full and nothing flows in carb. It is full. So I assume there is no vapour lock in fuel line till carb. Fuel line is new and transparent, so I can see the fuel flow.
 
21 - 35 of 35 Posts
Top