Topic: 400F sputtering/rich at idle

[DaveBarbier]

Awesome, bike looks great. Feels good to fix an old thing after some hamfisted PO had their way with it.

[minimo]

Thank you, DaveB! Thanks for sticking with me here.

[strynboen]

nov thange the engine oil and filter..before riding it...half of the oil is fuel..and vill be damping avay in the first 10 minuts...leave some sticky glue as rest produkt for the rest of the ride..killing the engine....the rule is..if you had a overrun of a carb...thange the oil...dont bay the most costy oil...better to thange it often...it make the inside of the engine nice klean .as a bonus

[Deltarider]

Congrats! Man, that bike gave me a sleepless night as I couldn't figure out what else could cause the problem. The guy that harassed your carbs, should stick to Lego.

[minimo]

The bike was returned late last night to a very happy owner

There was a lot of work done to the bike, clocking in probably over two weeks of experience pulling off the carbs and putting them back on, spilling gas, pulling out hairs... but in the end it was worth it.

Thanks again, everyone who chimed in here and for the insights.

Deltarider, thanks for sticking it with me. Sorry to have stressed you out :-D I was losing sleep too! The bike is out of my hands and out of my garage and now it’s back to work on my personal 400F! I look forward to your help with that one too. Sleepless nights, more to come ;-)

Thanks for the change oil soon and often tip, strynboen. I mentioned it to the owner and she appreciates it :-)

Well, gonna tidy up the garage in a bit and call that one all done It’s a good feeling.


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[DaveBarbier]

Ah, didn't know you were working on someone else's bike. Nice job and I bet she's stoked.

[minimo]

So, this 400F would come back to haunt me. The owner claims that “the bike shuts off before it comes to a complete stop”. And during this stop, the push-button start is unresponsive and the kickstart works on the second/third try for the engine to finally turn over.

I’m not sure why the push-button start is not responsive after the shut down but does this sound like a running rich condition? Hard to tell without checking the plugs? She did also point out that the engine ran very hot (so maybe a lean condition?).

Thinking back, I did swap out the main jets with some aftermarkets, size 75; I had to use the aftermarket main jets because the old stock ones were inconsistent sizes - a mix of size 75 and 80 as I recall. As it is now, these aftermarket main jets are being used with stock needles, the clip set on the stock 3rd position from top. Could it be that the needle tip profile doesn’t quite mate well with these aftermarket main jets? I suppose I can try to lower (or raise) the stock needle height... Since the carb rebuild kit came with replacement needles and clips, should I try using those to keep it all consistent? Anyone out there have success running these 4into1.com aftermarket rebuild kits on a stock 400f?

http://4into1.com/set-of-4-deluxe-carburetor-repair-kits-honda-cb400f-1975-1977/


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[TwoTired]

Sounds like a new electrical problem.
Battery cable corrosion, loose connections, faulty key switch.

I had one bike that did your described symptoms.

Finally tracked down to corosion on the crimp lug for main power distribution on the solenoid terminal where wire meets lug.

Make sure she knows that new problems to correct aren't grandfathered by previous work.  Otherwise you'll be fixing the bike for free the rest of your life.

Cheers,

[minimo]

Thanks, TT.

I never knew how quite to put it like the way you did Re: new problems but definitely a good point. Thanks.


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