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Old 11-03-2012, 11:55 PM   #1
Todd0001 OP
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Handy Hack, my style. Engine questions...?

I'm the winner of the 1978 CB400a Hondamatic, Handy Hack giveaway.

I have the bike home and licensed but having one small issue, I'm 250 pounds in my wheelchair and the hack is heavy as well. The bike has a 1978 400cc engine, it's a Hondamatic so 2 gears, 1st takes me from 0 to 50 mph, when I try 2nd it falls on it's face. I noticed the bike had aftermarket open exhaust thinking less back pressure maybe causing lack of low end. Added collector (h-pipe) and mufflers, also went down a tooth on front sprocket, at 50 mph I have higher RPMs but not enough to pull 2nd gear, just slows down until I need 1st.

STRANGE PART, is now I need a tach, so buy a generic one and it idles around 1,000 RPMs but as soon as it goes over 3,500 RPMs or close to it the tach jumps all over. Sent back to manufacture and they tested OK. Thought I'd check the basics and when I got to timing the it idles fine but when I rev the engine to check advanced timing the timing light goes out just before I get to max advance timing. This has to be related.....so...

Do I have a weak CDI or coil? It's just too strange that the Shop Manual and other book show the exact same instructions for timing and it will not light the timing light past 3,000 to 4,000 RPMs. Appears to run OK, very hot even when cool out, can't pull spark plug until you let it cool, a long time even the wire is hot. I use this same light on my car and get light at 4,000 RPMs for advance timing. I need the tach working so I can buy a custom rear sprocket in hopes it will allow 2nd gear to pull.

I've bought another set of cylinder heads, thinking I can put 450 or 500 pistons in, port and rebuild to increase overall power, use the second set of carbs, up jet for the larger displacement. Just fix with brute power, 2nd will have to pull then.

Do I just get it geared right so I can drive at highway speeds then start the new generation of Handy Hack? Or do I put money into the engine to get more power out of the old CB400a?

That's right I want to get this Custom Classic running good so I can build a newer style off a CBR, FZR, GSXR you get the idea a shifter 750 or 1000cc class Handy Hauler. So the more money I save on Handy Hack 1, I spend that on Handy Hack / Hauler 2.

I'm in the shop working on a Motorcycle, haven't done that since the summer of 1988, thanks again everyone who helped or sent parts, you guys are great
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Old 11-04-2012, 12:28 AM   #2
Leaf
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A common problem that put many of these bikes in the boneyard was the exciter coil in the stator going bad, at which point the spark won't advance (though they'll still run), and they won't do more than 40 or 50 mph.

When you say the timing light isn't doing the right thing, is it not advancing, or did you mean it's not lighting at /all/?

Then again, I'm running a hack on a 400T, and it won't go any faster than that on a relatively steep hill, anyway. XD
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Old 11-05-2012, 10:36 PM   #3
bmwhacker
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The little 400cc engine is pretty "taxed" pulling that much of a load.
Don't expect too much from it.
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Old 11-06-2012, 08:11 PM   #4
Todd0001 OP
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sure your right and need some gear.

Thanks, kind of what I was thinking. Gear it right and she should pull second, will try and check back. Winter time for me good time to work on bikes but good time to ride sleds too:)
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Old 11-08-2012, 03:36 PM   #5
argentcorvid
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the CDI's, coils and stators are known weak links in these bikes.

Head on over to this fine forum (specifically the SOHC Twins subforum, at the bottom of the page) and grab the factory manuals.

I'd start with resistance testing the coil, as it's the cheapest item to replace if bad. a $30 GM DIS coil will fix you up. the stock spark plug wires are molded into the coil, so you'll have to replace those too.

Then I'd do the test for the stator next, Those can be re-wound if bad.

Then do the resistance checks for the CDI. If the CDI is bad, you can take your chances with one off of e-bay (there is no NOS out there), but some guys are trying aftermarket suppliers. IgniTech out of the Czech Republic is the most popular one right now. one guy is attempting a fuel injection conversion as well.

The Stator and the CDI are specific to the 400A, but I think the standard versions can be swapped in with some extra work.
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Old 11-08-2012, 08:24 PM   #6
Mechanista
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Whoa!

I think you guys just helped me figure out an annoying intermittent problem with my 400T!
Sometimes it will not go over 50mph, and other times it will run 80. It feels like an ignition problem, and I have looked at everything!
Thanks!
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Old 11-09-2012, 04:38 PM   #7
XL-erate
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I wonder if you wouldn't be better served to do a semi-resto on this bike, sell it and use the profits to invest in a larger and more suitable bike for a tug? Have to figure there is a point where anemic performance can be a threat to personal safety and then add that to the overall happiness factor.
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