Issues Starting the Engine

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ccoulon
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Issues Starting the Engine

Postby ccoulon » Fri Aug 06, 2010 7:45 pm

Hello all,
This is my first post so please bear with me. I just bought a used 1980 cb650, that was running but had been sitting for roughly 5-6 years and needed the carburetor cleaned. After cleaning them and re-installing it took me a while to get the bike started (I presume because it needed to be primed) but once it was running it sounded fine and I was able to idle it around 1200 rpms with little trouble. Later that evening when trying to start it again cold, it started for about 20 seconds all the time losing rpms until it finally died. After that I have been unable to start the engine again. It will start if starter fluid is sprayed into the cylinder until it is burned off, so the sparks are firing. And all four float bowls drain gas consistently when drainage plug is loosened, so I know gas is getting to at least the float bowl. Every now and again it will fire and shoot up to about 3000-4000 rpms for about 2 seconds before dying again, and the throttle has no effect. I have also adjusted the choke in many different setting while attempting to start but to no avail. Any advice would be greatly appreciated. Thanks.

Chris

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Re: Issues Starting the Engine

Postby cb650 » Fri Aug 06, 2010 8:38 pm

Did you clean the tank?
Did you clean the tank out?!?!?!?!

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Volker_P
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Re: Issues Starting the Engine

Postby Volker_P » Sat Aug 07, 2010 6:52 am

Welcome here! :D
If it did run at first and now does not get fuel, this in fact sounds like stuff from the tank. You may release some fuel from the petcock into a clean jar to get an idea what you have. There is a filter inside the tank behind the petcock, worth a look, too. You may also remove an outer floater bowl to see what is inside. I think you'll have to clean the idle and maybe also main jets to get it running again. To avoid to repeat this game, clean out the tank and install a fine enough inline filter.
Maybe not directly related to your present problem, but also have a look at your air filter if it is still there, in one piece and not soaked with oil.
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ccoulon
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Re: Issues Starting the Engine

Postby ccoulon » Sat Aug 07, 2010 9:26 pm

Thanks for all the recommendations! I did not originally clean the tank, looking through the top it looks pretty clean; there are some small spots with light rust showing but for the most part looks good. The fuel that is in the bike now was in it when I bought it and the last owner was said he filled it a week or two ago, so it has been in there for a little while. Fuel drained both from the petcock and the float bowls looks normal and contains no debris or discoloration. Do you think I was just unsucsseful in cleaning the carburetor and the jets are still clogged? (but it sounded good the day I cleaned it). When cleaning the carburetor All I did was take off the float bowl and the floats and spray everything down with carb cleaner as well as directly into the venturi and the jet inside that. I also took apart the acceleration pump and sprayed that. There was gas residue in all the bowls and some of the jets were a bit clogged but I freed everything that I saw before putting it all back together.

As for the air filter, it looks new and clean, I have attempted to start it with it all put together, with the air-cover off and even with the filter itself off, but none of these worked. The time that I did get it started was with it all put together.

Any other suggestions of where to proceed from here, or need more info?

Thanks again!

Chris

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Volker_P
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Re: Issues Starting the Engine

Postby Volker_P » Sun Aug 08, 2010 6:49 am

As it works with starter fluid and floater bowls have fuel, it seems to be something blocking the fuel to go to the engine from there. I'd propose to remove the floater bowls again and check out whether you can still blow through the idle and main jets.
Maybe your cleaner solved some stuff that came not out directly but collected at the jets later.
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ccoulon
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Re: Issues Starting the Engine

Postby ccoulon » Wed Aug 11, 2010 1:11 am

Alright, spent nearly 11 hours yesterday completely taking apart the entire carburetor and cleaning everything. After re-installing the bike fired up right away and can now be driven around, as well as idle at around 1100 rpms (down from originally having to stay around 3500). After riding it for about an hour today the bike was very responsive and smooth while the choke was closed, however after opening it it became less even. It seemed to allow an irregular flow of gas to the cylinder while increasing the throttle. I believe that this might be due to the pilot screws not lined up perfectly (I took them out to clean them and placed them back to where they were, but now believe they might not have been at their original factory settings). Also while driving and coasting (usually down hill) in gear there was back firing. Is this normal for motorcycles? Any further ideas or recommendations would be greatly appreciated.

Thanks again for all the help!

Chris

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Volker_P
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Re: Issues Starting the Engine

Postby Volker_P » Wed Aug 11, 2010 1:37 am

Tough work! Hope you have a filter now.
A CB650 is not really known for backfiring. I'd rather guess a too tight valve or a leaky exhaust seal (directly at the engine) here.
If you have a 1100rpm idle, just be happy and don't touch the idle screws for now.
After riding it for about an hour today the bike was very responsive and smooth while the choke was closed, however after opening it it became less even. It seemed to allow an irregular flow of gas to the cylinder while increasing the throttle.
Sorry, I have no idea how to interpret that. Could you describe how your bike behaved on the throttle without choke when warm?
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ccoulon
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Re: Issues Starting the Engine

Postby ccoulon » Wed Aug 11, 2010 9:19 pm

Sorry for the unclearness of the last post. When I cold start the bike with the choke engaged, it starts good and will run good cold (Throttle is very responsive). However as I disengage the choke (usually after about 5-10 min of riding) this is no longer the case, especially starting from a stop. I will turn the throttle consistently but the bike will speed up unevenly. In other words, it will rev up drop for a half second then rev normal again, drop, then sometimes by this point I have been turning the throttle a slowly it will kick in and speed up real fast. I believe this is due to maladjusted pilot screws and a non ideal fuel/air mixture. I have never adjusted pilot screws before, so it is going to be my next project on the bike to learn how. I am also open to other suggestions as to what could be causing the irregularity.

Thanks again!

Chris

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Volker_P
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Re: Issues Starting the Engine

Postby Volker_P » Thu Aug 12, 2010 2:02 am

Again, this is not idle screws.
Probably your accelerator pump does not work or your carbs might be considerably (visibly) out of sync.
Accelerator pump could mean misadjusted mechanism or cracked diaphragm. The diaphragm is beneath the small bolted cover at floater bowl of carb#2. For the mechanism, see e.g. the threads '80 carb issues or how to adjust accelerator pump, 1981 standard model (the carbs are upside down in this picture).
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ccoulon
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Re: Issues Starting the Engine

Postby ccoulon » Tue Aug 24, 2010 10:28 am

Thanks for all previous advice! I managed to get the bike running pretty well; however, yesterday while taking it out on the freeway it died on me. This was not the first time I'd taken it on the freeway, and it has done quite well before. This time as I was accelerating in 3rd gear the throttle became unresponsive, as I shifted back down to second it seemed to fix the issue. I thought that perhaps the bike was still a bit cold and pulled the choke out a bit, which seemed to help somewhat. However, about 2 minutes later the throttle became completely unresponsive as the bike died. I managed to coast over to the shoulder and push it to the next exit. When trying to restart the bike now, it seems as though only one piston is firing (the engine is running very unevenly), it is putting out a lot of white smoke, and will only stay running with the throttle pulled back (it will die as soon as I let up on it). One person has suggested that I might have ruptured some seals. I'm not really where to start on this one, so any suggestions would be much appreciated. Thanks again!

Chris

PS: If I left out any info that would be of use just let me know!

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Volker_P
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Re: Issues Starting the Engine

Postby Volker_P » Tue Aug 24, 2010 11:04 am

Seems like you are no lucky guy. As it sounds a bit like fuel starvation, start with leaving fuel from the fuel cock through your inline filter (hope you have one meanwhile) into a jar and get an idea if the fuel flow looks sufficient. If yes, check your tank cap vent for being free.
Also check your oil level and smell for possible fuel in your oil.
Sorry, no more ideas for now, but I will think about it a bit.
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ccoulon
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Re: Issues Starting the Engine

Postby ccoulon » Wed Aug 25, 2010 12:05 pm

Today I went out to work on the bike and it started up normally (weird) and if anything was running better than it used to cold. I took it out for a spin and it was responding very well (possibly just do to the fact that I let it warm for a while before riding it). At one point while riding I got it up to roughly 7000 rpms (in first gear) to see if it was getting adequate fuel/air ratio, sounded good then switched into second gear and back to about 4000 rpms where it suffered the same problem as before, I shifted back to 1st and it seemed as though only half the pistons were firing again as it was very un-smooth and jerky. I turned the bike off and started to push, reached a hill, waited a few minutes and for fun tried to start the bike again, it again started normally and rode it back home.

I am not sure if it would be related at all but there may be a chance it is running better in the lower gears and this occurs as I rev up high and shift to higher gears. (?)

I no longer am thinking it is a ruptured seal as compression still seams to be good when it is running normally. And as for the fuel flow, also seems adequate as it was riding fine for a while, then cut out then ran again.

Now my guess is that it is an electrical issue and that only one pair of the pistons are cutting out. The main culprit that I can think of is the Spark Unit (a.k.a. ignition control module) seems to be oozing a black tar-like substance. I have not been able to find any in-depth description of the workings of this device, however some have recommended using epoxy to refill the oozed out sections and thereby re-seal it.

I do have an in-line filter and had just changed the oil and oil filter the day before the bike broke down the first time.

Thanks.

Rocky
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Re: Issues Starting the Engine

Postby Rocky » Wed Aug 25, 2010 1:26 pm

Could be the Ignition Coils. how do the plugs look after you take it for a short ride?

The way you are describing the problem, I would suspect the ignition system.

Spark units if they look melted then fill them back in and seems to usually work for everybody else.

ccoulon
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Re: Issues Starting the Engine

Postby ccoulon » Thu Aug 26, 2010 1:40 am

Thanks Rocky,

As for the Spark unit, should I try to get some of the melting tar-like substance back in? And if so how? (seems like heating it up might make is less viscous to the point of re-filling the unit. Or should I cut off what has already come out and partially refill the unit with epoxy?

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Re: Issues Starting the Engine

Postby Volker_P » Thu Aug 26, 2010 6:08 am

Right, once soft, that stuff won't get hard again. I just did put it back (as it probably has the required thermal and electrical properties) and then covered it with epoxy to keep it inside. Often the spark units survive melting of the stuff, but possibly one of your spark units already got damaged.
If you can identify the not working cylinders (header temperature?), you may try to swap the spark units between 1+4 and 2+3 to see if also the bogging cylinders will swap.
Another idea: next time starts bogging, close the petcock and stop the bike (in that order), then try at the carb bowl release screws if you have fuel in all four carbs now.
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