high idle and emissions bits missing

[totty]

Hi,

I'm working my way through what is more or less an extended service to get a 550 back on the road after 7 years of being stood in the back of someones garage, it's going fairly well but there's a couple of things I can't get my head around.

The bike now starts quite easily but takes a little coaxing to keep it running until it's warmed up. Once warmed up and ticking over at 1,000rpm if you blip the throttle it ticks over at 3,000. It you then put a bit of pressure on the grip a little in the closed direction there is no movement but it will drop back to 1,000rpm. Everything feels free, there resistance from the spring feels even throughout the range of the throttle.

There is a missing pipe from the airbox between the carbs and the airfilter housing and there is nothing below the airfilter in it's housing. I believe there should be a breather system and oil separator. As this is before the carbs I can't see how this could affect the idle but it's the only parts that stand out as missing.

The carbs have been blasted through with carb cleaner and don't appear to have any blockages. The rubber boots are hard but have no cracks, given the amount of force it took to push the carbs back into them I think/hope that they will be sealing. I don't think I'll be able to get good results from the usual spray something flammable in the area and listen for idle change vacuum leak test due to the nearby openings into the airbox from the missing breather system.

Any ideas?

Cheers

Allan

[Bryanj]

what year is the 550?

[totty]

79 reg, I think it's a k3.

[Yoshi823]

It sounds to me like the bob weights on the auto advance retard unit arn't returning once the revs have picked up. If you remove this unit there are two positions that the cam could go back into place. It's a good idea to make a mark so's to put it back the same way after the cam has been removed, cleaned up & offered back up to it's correct place.
If it's the K3 that you have there are some small screws just ahead of the float bowls. These should be about 1.5 turns out, but make sure that the very small washers are in place together with the minute 'O' rings & the spring. If the 'O' ring is missing it can cause all sorts of problems trying to balance the carbs up.

[totty]

Hi,

I hadn't even considered that it might be ignition related, I'll clean it up as you suggest at the weekend.

The screws are all 1.5 turns out, but I haven't removed them. I'll take them out and have a look. I haven't made any attempt to balance the carbs yet as I only have a single vacuum gauge.

Cheers

Allan

[Bryanj]

Have you removed the press in pilot jets, they are notorious for blocking and can give similar symptoms. Just blowing through dont do it the cross drillings need to be clear.

It wil be an old stock 77 if its a UK model, possibly a 78 if its US

[totty]

No I didn't remove them, just blew through. I found the carbs to be a right pain to remove and refit so I'll keep this in mind but try the easier to access bits first.

I'll lookup the chassis number to check at some stage.

[Bryanj]

Sorry but without removing and thoroughly cleaning the pilots you will get nowhere fast

[Yoshi823]

I had to have the carbs apart on the wifes 550F2 as it wouldn't start on all four cylinders. I tried to squirt carb cleaner spray up through the pilot jet, but one or two just wouldn't clear. I managed to do it in the end by stripping the carbs down & poking a bit of wire through the pilots. It was only these that were blocked.

[totty]

They appeared to be clear when I stripped the carbs, but I didn't remove them so they may not be as clear as I thought. The bike idles nicely, definitely running on all four, it just holds at 3k after being revved. I don't recall it doing this before I cleaned the carbs but I had only hared it running twice at the time, I also set the points and timing up on the same day so that doesn't really narrow it down.

[Seamus]

May be a silly comment, but are you sure the cables are returning fully?

[totty]

I was but but I'll certainly double check before pulling anything else apart.

[totty]

It now drops back to tick over itself but there is a little bit of a lag from 2.5k down over. I don't know if this is a normal characteristic or a side effect of something, possibly the carbs not being balanced yet.
The bracket that holds the outer part of the throttle cable was misaligned and there was barely any detectable slack on the cable. It's also had fresh fuel. Ran out of daylight.

Cheers

Allan