Author Topic: '71 350 twin electrical issue?  (Read 2273 times)

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menzelg

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'71 350 twin electrical issue?
« on: August 13, 2008, 09:54:57 PM »
I have a '71 Honda 350 twin that was running fine until I got it far enough away from my house to be properly screwed and then it started having issues. It started by not having power until it hit about 4K RPM and then it would dump like switching on the nitrous, but going up hills it was still pretty gutless. Then it started to stutter like it was losing power until finally it died and I was rolling down the road with nothing but gravity powering it. Pulled over and it started up and I was going again but shortly it did the same thing and died again. This continued with the time between death and restart getting longer until finally it just flat wouldn't start and I had to push it home. It will start after giving it a bit of starter fluid but won't stay running long. I suspect an electrical issue but don't really know where to start (if this is indeed the thing) Any and all advice is desperately welcomed!

Quick aside, I've been out of the loop awhile, did the honda twins forum move, die?

Thanks!
Greg


Offline scunny

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Re: '71 350 twin electrical issue?
« Reply #1 on: August 13, 2008, 10:00:46 PM »
I'd suggest it's a fuel delivery problem, why do you think its electrical
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Offline tbpmusic

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Re: '71 350 twin electrical issue?
« Reply #2 on: August 14, 2008, 07:20:54 AM »
First, is the battery good - is it strong enough to allow use of the electric starter??

The Honda Twins forum did die, but is in the process of being reestablished - no qword on a time frame.

bill2
"If you can't fix it with a hammer, then it's an electrical problem"

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 '71 CB450 Mutant/ '75 CB200/ '81 CM200/ '71 C70M

Offline JeyLux

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Re: '71 350 twin electrical issue?
« Reply #3 on: August 14, 2008, 08:32:27 AM »
open your gas cap next time it dies down.

vapor lock perhaps?  I had a similar issue on mine.   The flat spot up to 4k sounds like a timing issue too though.

1973 CB500k
1972 CL350

Offline .RJ

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Re: '71 350 twin electrical issue?
« Reply #4 on: August 14, 2008, 10:06:28 AM »
I had a similar issue right after I bought my CB350 - the floats were hanging up and not letting fuel into the bowls.  If I stopped and waited for a while the bowls would slowly fill, then I could continue for a little while.  Wash, rinse, repeat - it was a long trip home.

I rebuilt the carbs after that.  And then the ignition coils packed in.  I love old bikes sometimes...

The K&L kits DO NOT have new o-rings for one of the main (#68) jets.  You can either order the jet from honda, or a jet from a keihin supplier and it will come with a new o-ring.

menzelg

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Re: '71 350 twin electrical issue?
« Reply #5 on: August 14, 2008, 07:12:56 PM »
I rebuilt the carbs back in may, had the timing set by a shop here in june, replaced a broken starter clutch in july and had planned to ride in august/september before the Western Washington winter made going outside generally horrible. Alas.

It was suggested to me previously (I think on the twins site) that the surging at 4K could be due to one of the coils not firing and since I really hated doing the carb rebuild I latched onto that as at least something new. The battery turns the starter over and fires up the bike but only once or twice and then it doesn't really like to. I am suspicious of the charging system because I have been able to ride it for some distance but if I stop it doesn't like to start again. But ultimately I have no idea. Being new to motorcycles, my diagnostic skills are a bit poor as yet. But every day I get the opportunity to speculate about something!

I did pop the cap to release the vapor lock, which worked once, but not the other times so while that may be a part of the problem, I don't know that it is the one solution.

Thanks for the replies

Offline JeyLux

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Re: '71 350 twin electrical issue?
« Reply #6 on: August 15, 2008, 05:41:44 AM »
you definitely have some sort of charging system issue.

My experience with my coils going bad, it wouldn't run on 1 cylinder below like 4k, then, like yours it would scream like a bat out of hell above 4-5k.  but it wouldn't rev very high (only like 7k max) top speed about 50mph.

do you have a timing light?  just put it around the spark plug wire, and see that you have continuous firing.  if your light pluses aren't constant, you've got an issue... maybe a coil, or a point not firing or something crazy.
1973 CB500k
1972 CL350

menzelg

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Re: '71 350 twin electrical issue?
« Reply #7 on: August 17, 2008, 09:44:16 PM »
I do have a timing light and I will give that a try, it is the "something crazy" that I worry. When your coils went bad, were you able to find replacements or did you have to search on ebay?

Offline JeyLux

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Re: '71 350 twin electrical issue?
« Reply #8 on: August 18, 2008, 05:20:58 AM »
I do have a timing light and I will give that a try, it is the "something crazy" that I worry. When your coils went bad, were you able to find replacements or did you have to search on ebay?

i replaced them with a set of Dyna Single output 3ohm coils.

I don't buy vintage electronics if i can help it.  It wasn't worth the risk on a used set the same vintage as the ones i had.

1973 CB500k
1972 CL350

menzelg

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Re: '71 350 twin electrical issue?
« Reply #9 on: August 23, 2008, 10:30:43 PM »
I hear that I was worried that they wouldn't be available, however at $150 they are almost as much as I paid for the bike!

Offline JeyLux

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Re: '71 350 twin electrical issue?
« Reply #10 on: August 25, 2008, 09:05:28 AM »
I hear that I was worried that they wouldn't be available, however at $150 they are almost as much as I paid for the bike!

I felt the same way.

but, having ordered them and installed them, they work and it was worth it.

here's a link on how different people have installed them because they're a little different fit than the original coils.

http://www.caferacer.net/forums/topic.asp?TOPIC_ID=7372
1973 CB500k
1972 CL350