[Alfalfa]

Hey guys,

Me again. Well the bike seems to be running fairly consistently now (that is when there is gas in the tank, this jury riged petcock w/ no reserve is killin me!). Anyway I adjusted the throttle stop screws because it was idling really fast. I noticed while adjusting them that the left throttle stop screw will only adjust so low the "hammer" (for lack of my terminology) rests a mm or two above the carb body while the right stop screw sits all the way down. I tried taking off the throttle cable to see if it was just keeping it from resting all the way down but no luck. Is this normal? Am I just adjusting the throttle stop too much? Here is a pic to help illustrate my problem. (the piece of paper in the background is just for contrast)

'75 Honda CB500T


Thanks for your help again guys. Don't know what I'd do w/o yalls knowledge and experience.

 

[MNellis]

Did you take the carbs all the way apart including the butterfly valves? If so then you might not have gotten the butterfly valve centered. I had a similar problem with my 350 and had to loosen the two screws and work the valve around until it closed completely.

 

[Bird76Mojo]

I did that exact thing on my original carbs too. It's easy to get that butterfly off just a tad bit, and they don't close all of the way after that.

GB :mrgreen:

 

[Alfalfa]

I didn't take the butterfly valve out. But that's not to say the previous owner didn't. How would I go about adjusting this?

 

[66Sprint]

First, be sure there is slack in the cables....They may be holding up the "hammer".... (I assume you took the throttle cable loose at the handlebars... BUT, IT is likely the problem lies right where the cables screw into the carb brackets)

 

[MNellis]

I didn't take the butterfly valve out. But that's not to say the previous owner didn't. How would I go about adjusting this?

I don't have a good picture but maybe this one will help. You can see the butterfly valve that is held by two screws. The metal plate slides through a slot in a shaft. Just loosen (don't remove) the screws and move the plate around until you can see that it closes securely. You can probably do this by just removing the air cleaner without having to remove the carbs, but I'm not sure.

The comment about the splitter is the best place to check first. I had a problem there as well.

 

[Alfalfa]

First, be sure there is slack in the cables....They may be holding up the "hammer".... (I assume you took the throttle cable loose at the handlebars... BUT, IT is likely the problem lies right where the cables screw into the carb brackets)

I thought this might be part of the problem so when i removed the throttle cable I removed it from the carb bracket. So I don't believe it is a slack issue. With no throttle cable attached to the carb whatsoever the problem persists.

 

[66Sprint]

... Normal idle on a 450/500T is between 1100 and 1300 RPM......If it is "faster" than that, Check the condition of the rubber intake "boots" for cracks and air leaks.....make sure the "sync" tubes are sealed as well....( Hint: Carb cleaner spray will cause the idle to drop slightly when sprayed on a leak)
The throttle plates are the ones nearer the engine, not the choke plates shown in Mike's pic.....Make sure they are fully closing, (re-center by loosening screws, closing and retightening screws)....
If this also fails, pull the bowls and check that the jets are still in their holders and in place...(they have been known to vibrate out)......
Also, on the 500T, a defect in the "air-cut" valve diaphragm can cause this.......Check it too....
Let us know results so far........We'll go from there.... Steve

 

[Alfalfa]

great info thanks. I'll get right to it!

 

[djbrand1]

... Normal idle on a 450/500T is between 1100 and 1300 RPM......If it is "faster" than that, Check the condition of the rubber intake "boots" for cracks and air leaks.....make sure the "sync" tubes are sealed as well....( Hint: Carb cleaner spray will cause the idle to drop slightly when sprayed on a leak)
Also, on the 500T, a defect in the "air-cut" valve diaphragm can cause this.......Check it too....
Let us know results so far........We'll go from there.... Steve

Sorry to revive an old thread, but what are the "sync tubes" you are referring to? Having some running problems on my 75 CB500T, and this is the first I've heard of Sync Tubes. Thanks!

 

[tree fiddy]

Did you take the carbs all the way apart including the butterfly valves? If so then you might not have gotten the butterfly valve centered. I had a similar problem with my 350 and had to loosen the two screws and work the valve around until it closed completely.

bump.

Did anyone ever figure out if this can be done with just taking off the airboxes?

Now that I have spark I have crazy fast idle and symptoms described.


What else can I do with the carbs onboard. Seems the pilot jet cleaning did well now that the idle is screaming.

Can I get the main jets, needles or emulsion tubes out with carba onboard or do I have to hacksaw the brittle rubber holders and then find new ones?

Anyone got sizes for the pilot jet o-rings? (actually I think they're comming in a gasket kit).

 

[asdfqwer426]

you can't get to the butterfly valve screws from the air box side, as they are on the other side of the carb.

you may be able to get all that stuff out with carbs on board, but it would be very difficult. if your carb boots are really hard and dry from age, but you can get the carbs out without damaging them, I've read about people soaking them in different solutions to soften them back up. one i've read about is simply brake fluid, the other I forget but it's some sort of minty something. takes about a week+ of soaking, but it works great.

 

[tree fiddy]

you can't get to the butterfly valve screws from the air box side, as they are on the other side of the carb.

you may be able to get all that stuff out with carbs on board, but it would be very difficult. if your carb boots are really hard and dry from age, but you can get the carbs out without damaging them, I've read about people soaking them in different solutions to soften them back up. one i've read about is simply brake fluid, the other I forget but it's some sort of minty something. takes about a week+ of soaking, but it works great.

Thanks, I kind of figured the carbs would have to come ALL apart anyway just for good measure. I might pull the carbs off my parts bike first, I probably will find something makes the '71 carbs incompatible with '74 bike if I plan on swapping them all out.

The hardend carb boot remedy is wintergreen oil and xylene, and a little heat. I have first hand knowlege that it works great. I only had spray can xylene( goof off brand ) with just a bit left in it, so I was using the stuff sparingly and safely. I heated it on a gasl grill on low and cooked them for an hour or two on low setttings.

SOHC4 has a five page thread if not 2 or 3 on the wintergreen elixer and how people did theirs- this one guy definitely found the WRONG way...

http://forums.sohc4.net/index.php?topic ... #msg942399