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Bike dies on reserve

MagicMoose

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I have a 1980 Honda CB 750C. When I switch to the reserve supply, the bike dies. Funny thing is that even though the engine doesn't seem to be getting fuel, I can see gasoline flow through the filter when when I twist the petcock to the reserve supply. Once after the bike died after I tried switching to reserve, I tanked it up and it still wouldn't start. So then I drained the carburetors... and it started right up, no problem. The bike also bucks/stutters, is not delivering even power in 2nd and 3rd gears for at least 5 minutes into a ride. Any one have a diagnosis and/or treatment?
 
Rust or water in the bottom of the tank. Switching to reserve draws it in. If rust, it has probably plugged the reserve port for the most part. If water, drain it (through the reserve port) and put some gas drier in your next tankful.
 
agreed with posts above. remove the petcock and fuel screen and clean. while you have it out, take the petcock apart and make sure that the gaskets are intact and passages are open.
 
So I've cleaned the tank out (full of surprises---I'll get into that later), but now the little wings of the gas tank cap won't spring open (they are stuck in---retracted). So the cap is not locked into place; it can easily fall out. Any ideas?
 
Is it key-lock? My '79 F requires a twist, no spring loading. If there is a spring catch, they probably need to be released with the key.
BTW, if you didn't have an inline fuel filter (sock in the tank doesn't count), you no doubt have crud in your carbs now. Any bike with a steel tank that is older than ~10 years or has has ethanol gas in it should have an inline filter.
 
It's a key lock. The key does turn, but it's sticky. I've tried moving the key to different positions, but the wings don't spring out in any position.
 
Might be one of the few good uses for WD40. Gently working the key while fiddling with the tabs until you work the corrosion out, then use some real lubricant.
 
BTW, key inline with bike is usually locked, 90 degrees rotated unlocked. At least on the 5 different Hondas I've owned.
 
I'll try that...WD-40 on the wings, gently work the key. And I have some WD-40 dry lube to spray into the actual key slot.
 
I was also going to suggest the WD40- but not sure what else it could be - is there a spring for the lock tabs that could have broken? I think you might be able to score a new lock from someone here or even on flea bay.
 
I used WD-40 dry lube and was able to get one of the two little wings to spring out. So the cap does stay in the tank now; but it's not as secure as I'd like. I'm wondering two if one of the springs is broken. Doesn't look like it's a piece that can be taken apart. If it's just a matter of corrosion, would submerging and soak the cap in gasoline help?
 
Some good news in brief....
1) I flooded the bottom of the gas tank cap with WD-40, and the 2nd wing sprung out. So it clicks into the tank now.
2) I gave the tank a thorough cleaning (garden hose water flush, hot water rinse, shake with ice cubes, vinegar+salt soak for a few days, neutralize with baking soda, flush with water again, rinse with distilled water, rinse with isopropyl alcohol, heat gun, swish around some gas with oil added to it). It rides like a charm now.

The details:
After I drained most of the gas out of thank, I saw a lot of crud in the remaining fuel at the bottom. I also saw that the tank sealer I had put in a couple of years a go had delaminated from the tank walls in several areas. (This probably happened because I did a poor job sealing it: I forgot to mix the sealer and dumped it all in. Some parts were extremely runny, just liquid, others super goopy. It was so bad I decided to get another can of sealer and pour that in... this one I did mix, but now I was trying to get it to bind to the uneven substrate of the first sealer.) I would speculate that the chunks of sealer that came off the tank were starting to disintegrate and contaminate the fuel or perhaps the large pieces were physically constraining flow out of the reserve port.

I tried to scrape and get as much of the delaminated pieces that I could out, but I couldn't get everything. So.... this could happen again. I'm thinking next year I should drain the tank again and use long pliers to try to remove more of the pieces of delaminated sealer, use a vacuum cleaner to get out more. Any further thoughts on the issue (i.e. feedback on my tank cleaning technique, how to avoid flash rust [I waited at least 12 hours after drying to add swish the gas/oil and I believe I got flash rust... definitely around the tank opening] recommendations on if to reseal and how to prep if I do, getting more of the pieces out, etc.) are very welcome.

Thanks to everyone that responded!
 
If you used Kreem (or several others), you can dissolve it with acetone (takes a week or two) or MEK (use caution it's dangerous).
 
Just get a new tank and don't ever use that sealer. Take your time and shop eBay until you find a clean tank. Once it's regularly filled with gas, you will be fine. Why risk contaminating your carbs?
 
Would you believe 15 months later I still haven't done this? I bought a gallon of MEK and acetone. I sloshed some acetone around for a few minutes, garden hosed it, then MEK, garden hosed it. Didn't dissolve all of the sealer. How long do you think I should have the MEK in the tank?
 
FYI.........the '80 model used the same passage size spigots the rest of Hondas under 750 used back in the day. Meaning they are too small to begin with and any problem with them you get this trouble. Why the later ones upped the size twice but the tank fitting generally changes to to not allow switching. I've had to wait 5 minutes for my 550 to reprime when switching to reserve before, it is slow with low fuel weight in the tank. It uses the same fixture. Not helped by the paper filter I use, we use ethanol here and the rust in tank goes right past the OEM filter tube like it is not there. Only a paper one will catch it.

Another one, WD40 is fine for loosening locks and such but left alone to evap it dries up into a really fine glue that sticks things worse. I'd be taking a fuel cap and toss it in oil for a soak and then drip-dry it a day or so to have true oil left behind in the inner parts.
 
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