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Old 04-01-2010, 01:05 PM   #1
Chris Mccall
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Default 1983 Honda 750 Magna

Please can someone help
My Magna 750 has a cold start problem. I have checked everything i can think of from the fuel system to the electrics, stripped and cleaned the carbs and chokes. It has a new battery and the starter motor has been stripped and checked over...all seems ok. I can eventually start the bike, on full choke with no throttle. The bike runs and idles sweetly. After letting the bike idle for a while, switch off, and when it is completely cold, it will start first time....however, as soon as i take the bike for a ride and then let it get cold, it battles to start IE , it takes at least 5 to 10 minutes to fire up. A test on the battery shows that the bike is charging fine, 14.5 volts at 2 to 3 thou. revs. The bike runs superbly and idles fine, no backfiring or missfiring...As i mentioned, the problem only occurs after i have RIDDEN the bike for about 2 miles or more. When she is hot, she starts fine, but let her get cold...non starter.
Please, any advise on what to check would be gratefully appreciated
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Old 04-01-2010, 01:18 PM   #2
The_AirHawk
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Sounds like a misadjustment in the enricher/choke. Possibly the choke-passages are still cruddy? (I know you said they've been cleaned, but still........)
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Old 04-01-2010, 10:48 PM   #3
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I've been rethinking it.

Did you double-check your float level on all-4 carbs when you had it apart?

How about the airbox? Is it sealed-up completely? All the boots and screws are in place?

Have you re-jetted the bike (or a P.O.)?

What about idle-mixture screws? 2 to 2-1/2-turns out for each of them?

Did you synchronize the carbs after having them apart?

Some bikes are just cold-natured, and require choke every time they've sat for more than 30-40 minutes.




One quick clarification: You're having trouble getting it to actually fire-off without choke for first start of the day, and any subsequent starts where the engine has cooled substantially, right? Not a cranking problem (just checking here, some of your post was a bit murky).
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Old 04-02-2010, 01:16 AM   #4
Chris Mccall
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Hi, thanks for the input. I have checked everything you have mentioned, the carbs have not been re-jetted and are set correctly. I never separated the carbs and the carb ballance is ok.

This is the problem. i can go to the garage where the bike is parked and it will start this morning (full choke), no problem. I can do the same thing tomorrow morning and it will start (full choke). However, if i take the bike out for a ride, and then try to start it an hour or so later/the next day/a week later....it will really battle to start. Eventually after 5 to 10 minutes of trying to start it, it will reluctantly fire up and start. Following this PROVIDING I DO NOT RIDE THE BIKE, it starts first time, everytime (full choke). Just to clarify, if I ride the bike, stop, switch off and immediately restart the bike, it will start no problem without the choke. Problem only occurs once the engine is cold after riding it.
The bike is cranking over fine and as ive mentioned, the battery is new and i have done checks verifying that the bike is charging the battery correctly. Everything seems to be in order. Im starting to wonder if there is not an electrical component that gets warm/hot when i ride the bike and then not re-setting itself later when the engine is hot? One thing i forgot to mention, when im having this "no start" problem, the bike backfires badly while its trying to start, i only give it full choke (no throttle) when attemping to start..as mentioned in the workshop manuel

Last edited by Chris Mccall : 04-03-2010 at 02:13 AM.
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