82' 750sc runs fine for a 1/4 mile then loses power.

[muddygreentj]

My bike seems to run okay for short distances then it loses power and I see smoke out the tailpipe. Not a lot but it's there. There's also some low idle noise in the crank case. The noise is stronger on the left side if you're sitting on it. Also I noticed that the orange gasket on the left crank case cover is sorta pushing out. It's not leaking oil yet but I have a feeling it will. All 4 cylinders are firing, carb was recently tuned. I think it may have 40 weight oil in it though. ooh...on hind sight that may be a problem.  Please help.

[coffee_brake]

This sounds simple. This sounds like a fuel feed issue. Fuel starvation could be a clogged fuel tank cap vent, or a kinked fuel line, or a degraded old fuel line.

Would be worth a look under the tank...

[muddygreentj]

The fuel line is new, but the petcock is not! Yeah the tank had some rusty spots in it. lemme go clean the pet cock and see what happens.

[muddygreentj]

Well, cleaned out the petcock and took it for a ride. doin better but it stalled out about 1/2 mile from my house all uphill. well the lucky part is i stalled out in front of a man named Jim's house. Jim owns Cyclops Cycle in Merriam Kansas. Just outside of KCK. Well actually it stalled in front of Paul's house who has got to be the nicest person i have ever met. Jim is his neighbor. Anyway jim comes stalking up and pretty much yells at me after looking at my bike for a few seconds "man your carbs are full of rust!" I was like how the hell did this guy know that I cleaned a buttload of rust out of the petcock? The wierd thing was that I was just in Cyclops Cycle to ask after some parts on Friday. First time I was ever there. Serendipity is a MOFO. Anyway I need to know how hard it is to clean my carbs. I have a Clymer but it doesn't always say everything, close though. Anything I need to have on hand? Any tips to getting it apart and more importantly putting back together I've busted my ass getting this bike running and I'll be damned if I'm going to give up because of rust!

[coffee_brake]

Certainly if you found lots of rust in the tank, then there is rust in the carbs. Depends on if that fuel filter was installed before or after the rust.
I'd assume after. Then yeah you gotta pull the carbs.

I'm not as familiar with the earlier 750's but you're going to need a manual regardless. I like Clymers. For a bike of this age, I'd pick up some carb rebuild kits. If you can't find the whole kit, then at least get a set of float needles, available from K and L a lot cheaper than from Honda.

Don't despair, cleaning a rack of carbs is not THAT hard, but it does take some time.
You don't need to take the carbs off the rack (take the four of them apart from each other) but you'll need to open all four of them up and clean the jets and air passageways. Sometimes it takes more than one cleaning.
Then, you want to make sure your always have a good fuel filter in place. If your tank is not in too bad condition, it would be very good to treat it so it can't rust anymore. If it's falling apart I'd start looking for a replacement.
But first, get those carbs off. Don't break the old airbox, if the rubber is brittle and hard some WD40 or CLP will help. Also warming the rubber parts with a hair dryer will make them more supple.
I'd get a manual for the bike to give you step-by-step instructions and pictures.

Folks here can likely help with more questions...and your guy at Cyclops may also be willing to answer your questions since you're ordering your parts from him.

[muddygreentj]

Thanks for the tips. I will consult my Clymer and do it. Hopefully I can get her running again by the weekend. We have a parts washer at work, that might speed things up a bit. The tanks not too bad, there were some pinholes that I had to weld. Those were from the previous owner laying it down. There were some small spots of rust that I noticed while welding on it. I thought I got them with paint thinner but I guess not. Besides who knows how long this has been a problem. I've only had the bike since April. Well let's see what happens and thanks again guys.

[coffee_brake]

To de-rust an old tank, I've use Muratic acid (the stuff you buy to clean the concrete driveway). Be very careful as it reacts vigorously with the rust and bubbles out of the tank, but it will get all the rust out and then you dry it and treat it right away.

If the rust is too bad, it will make the tank fail, which is not a bad thing since treating a tank that far gone is pointless.

You should be able to do your first carb clean in a day, so you can still ride this summer....

[muddygreentj]

Got the carbs cleaned in about 3 hours, after the first 2 I quit messing with the vacuum  cylinders. They were all spotless. Actually all the jets and bowls were pretty much rust free. The Air cutoff valve was plugged. Not sure how this ties into everything though. Some guidance would be appreciated. I'm guessing that would shut off airflow to maybe the feed of the jets, not sure though. #1 slow air jet came out, got it beat back in. That was fun....I was all most crying thinking I stripped out the secondary jet threads trying to get it back in. When the jet screwed in fine without it, I figured out what clymer was talking about when it said do not remove. It's back in fine. All in all it went well, no extra parts or anything. Just got to try and get them back on.....This will be fun....."sarcasm"
""

[coffee_brake]

It's not usually something you'll be able to see, it will be a tiny piece of funk in a passageway.

These are CV carbs with the rubber diaphragm?

The float actuates a short aluminum or brass "plug," remove the float and take out that plug, that's the part I'm thinking needs to be replaced if it looks anything but new. Certainly if it's not been done before it needs to be done by now. And the brass seat underneath that plug needs to be polished (aluminum polish on a Q-tip).

While your carbs are off you can check all the vacuum lines and everything that moves fuel and air on your older Honda, checking is free and easy! Hopefullly you will stumble on a bad fuel or air line that is cheaply and easily replaced, and is causing the high-speed power loss....