Reinstalling carbs

I just took out the carbs on my 550m1 for the first time :woohoo: and have a couple questions because I can't get it to start. It will crank but not catch.

1) I have two hoses I can't find where they go to. One comes from between # 1 & 2 and the other from between 3 & 4. The tip look a little stretched out so I assume they need to go somewhere. The both come out facing the rear of the bike. The aren't my overflow tubes because the 4 tubes weren't there when I took everything out in the first place.

2) Carbs 1 & 4 are connected by a T tube and go to the front of the bike (not the issue). Carb 3 runs a vacuum tube to the petcock while carb 2 has a couple inches in length of tube with a screw in the end to close it off. Should 2 & 3 be connected by a T as in 1 & 4 and then running to the petcock? Or doesn't really matter the one tube should do just fine?

Thank for the help

The lines between 1&2 and 3&4 sound like vents. Some run to the airbox and others just run to the back and hang there. Pics of where the T is located on the carb would help to be sure. One line to the petcock should be all it needs. The line with the screw in it is probably a home made cap for that vacuum port.

I am not sure how your bike differs from mine but as stated, you should have vents as well all fuel lines to the pitcock. For my bike, 2 carbs share a fuel line and a vent. Therefore, I have 2 lines leading to the pitcock and 2 that run up under the tank. Good luck. I have had my carbs off and apart so many times, I could do it in my sleep.

1... these are vents. They should not be obstructed. The hoses can route to the airbox or just route over the swingarm.
2....1&4 vacuum fittings are connected by small ID hose to a tee fitting. Out of the tee fitting another hose runs to your emissions vacuum switch. If you have the emissions stuff on your bike, these hoses MUST not have any leaks or holes. Either #2 or #3 carb vacuum fitting is connected to the petcock and the other carb's vacuum fitting MUST have a vacuum cap on the vacuum fitting.

Thanks for the info. I'll just route them over the airbox and get them out of the way.

I was able to finally get the engine to start but it sounds like I'm on the line at a drag strip, very high speed idle.
I checked the throttle cable and that moves cleanly and returns to position. Rechecked all the hoses and boots are in place. Not sure what else to check.

I guess too much to hope I could get them in and out my first time without issues.

If it is revving very high on the choke, but dies when you take it off choke, or try to open the throttles, you may have a vacuum leak somewhere. Are you sure the carbs are seated into their mounts properly!

Had exactly the same problem earlier this week after helping a friend (also a board member) change the throttle cable on a 750LTD - he didn't get the carbs back properly! Loosened clamps, pushed/wiggled 'em in place, tightened clamps and bingo!

P.S. - Does anybody know of an easier way to change the throttle cable on an '81 750LTD. Seems damn near impossible without taking the carbs off! What a PITA!

The engine doesn't rev, it starts high and runs high. I think I figured out what I might have done. I replaced the fuel line and I think I might have rerun it inside of the bar where you can adjust the idle with. I'll check it this afternoon, and if that's it I guess it's another learning point on my first attempt at carb work.

Limey wrote:

P.S. - Does anybody know of an easier way to change the throttle cable on an '81 750LTD. Seems damn near impossible without taking the carbs off! What a PITA!

Same thing on the 81 1000LTD. I forgot to connect the cable before installing the carbs once and it was a royal PITA to do but I finally made it. Replaced the cable this spring and another set of hands to hold the carb linkage in the full open position while I connected the cable was a little easier but still not something I'd want to do again.

It wasn't the fuel line but in checking I found I never tightened the clamps on the boots going from the carbs to the engine. I tightened those up but it still starts up at a screaming pace. Can't say I'm interested in doing it again but do I need to take everything out again?

The boots on both sides of the carbs seem to be in as far as they can go. Would the WD40 on each boot work? I'm just afraid of winding the engine up even higher without a load on it.

It's probably shop bound if I can't figure this out soon. Thanks

If not already done, has setting of the idle adjust screw been checked to assure it's not too high?

This is a confusing thread. You asked about hose connections but it seems to have gone somewhere else. You initially couldn't start the bike. It seems you can now start the bike. Please describe what happens when you start the bike and perhaps I can give you some help.

IT was initially a two parter but the question on the hoses has been solved as breather tubes.

The bike will now start but just at a very high idle. The following is what I've done or found

1) I forgot to tighten the clamps on the front boots - now nice and tight and the boots are well seated both front (carb to engine) and rear (airbox to carbs).
2) Rerouted fuel line so it's not going between # 2 & 3 carbs
3) Backed off idle screw (large thumb screw on back of carbs) - no real noticeable change when starting bike.
4) Just in trying things I ran it without the tank on since there was gas in the carbs and if I put my finger over the vacuum tube that would go to the petcock that would change the increase the idle speed.

Not sure what to check next. Throttle does work just increasing the speed even higher.