High idle after warming up?

Hello, I am riding a 550 maxim. While on my way back from work riding on the highway approximately 15 mins at 60-75mph, I came to a stop light and when I came to a stop my idle was hanging around 3k for about a minute, but by the time the light changed it had fallen to 1k. It kept hanging at a few other points when I was coming to a stop. The bike starts up beautifully with no choke, the mechanic I took it to last year does have it running rich. Not sure what would be causing this, I even tried to snap the throttle to see if it was sticking and that didn’t appear to make a difference

 

You most probably have a vacuum leak, spray some carb cleaner while running around the carb boots if RPM raises there is your leak . Also check the manifold plugs are in good order.

 

Yes, agreed, provided all your idle mixtures and carbs are balanced. I'd start there, then look for air leak. If all your carbs are set rich, you would expect the idle speed to come down when hot.

 

Ok, so I got home and I am out of carb cleaner but used propane and went over the boots, manifolds, and carbs without any noticeable increase of rpm. I did notice this though (see pic) could it be that when it is heating up that it is letting in a slight amount of air? One of the screws snapped off and I bought a replacement but it appears the mechanic didn’t replace it or bother securing its twin.

 

That is not cool that is above the cam chain tensioner and you are missing the nut and washer on the stud and missing stud on the other side.

 

Need to remove the head to get the broken stud out.

 

I have some experience doing that at this point. Could that be causing my idle issues?

 

Possibly, you should spray some carb spray directly at that joint starting the engine from cold and see what happens. I know you tried the gas torch but I would try it again to see if the revs change. Just covering the obvious, can you lower the idle when the engine is warm with the big idle screw located between carburettors 2 & 3?

 

Looking at this closer I believe it goes into the YICS and is could be part of your problem.

 

Okay so I tore down to the engine. Lots of things felt like they were only finger tight. I was able to install the double threaded bolt. Looks like I may be missing something though (see pic). Isn’t there supposed to be a metal or rubber piece there? Need to order a new gasket for that area anyway now. I am appreciative of this mechanic fixing the things I missed but when half the stuff isn’t fastened properly it begs the question of what is even the point?

 

You have a metal dowel missing there, same as the three on the other side. Just as well you removed the head. Sometimes they stick in the head or the block.

 

Any advice on putting the top of the engine back on and not messing up the rubber donuts or cylinder head gasket in the process? I pinched a donut a year ago and it was such a pain to undo all that work.

 

Can anyone confirm that the lower stud should not be there for an 82 xj 550 maxim?

 

Both studs need to be there.

 

I was under the impression that the lower one is supposed to be a bolt with a hex head. But I was able to get it back together no problem. On to the valve shims!

 

Was checking and adjusting the shim clearances and excitedly putting it back together when this happened. And the hole next to it was some how stripped after I finger tightened it and attempted to torque it.

 

Can you drill it with a left hand drill bit, and get an extractor in it? You used a combination left hand drill and screw thread like this.

https://www.ebay.co.uk/itm/35495720...YCPfCTmvLYZ3Al-9qYqdQuA6wmIICeboaAnoKEALw_wcB

 

Yes drill and then m5 LH tap should unscrew it. Don't be tempted to drill and retap, you will mess it up.

 

Any recommendations on new threads? Is helicoil the go to?

 

I've used Helicoil many times with great success. @Jetfixer will be happy to tell you that Helicoil is the only insert that's certified for aircraft use, which tells you a lot about reliability.

Having said that, if you drill and extract the stud you won't need new threads. Use a drill that's smaller than the stud. And give it a soak in penetrating oil (best is a 50/50 mix of automatic transmission fluid and acetone), then let it set a few hours to help free it up.

 

What do you mean by drill and retap? I haven’t tried this before, is there a good YouTube video you recommend?

 

Like thus, but you'll be using hand tools instead of a milling machine. Use a center punch on the broken stud to make sure the drill starts centered. You won't need to flatten the surface of the stud. It's being done in the video because that gearbox he's working on costs about as much as your whole bike.

 

This vid shows the same process using an electric hand drill.

 

I would try and extract the broken stud first. Keeping drill bit square is critical.

 

LH drill bit is a good start, sometimes the best tool, as long as you can get your centre bang on - point being take as much time or tries as you need, once you start drilling its (almost) too late. If you get close to the thread and it doesn't shift, the LH tap is the next option.
The next, and least best option is to drill and retap, usually next size up and fit a helicoil or similar insert. This assumes your hole is still on centre etc.
Hope all this helps to keep these old things going.

 

One broken LH drill bit later… it is finally out!

 

So I have the hole next to it which appears to be partially stripped, planning to use an M6 helicoil for that hole! Found an earlier thread of someone in the same issue that I will be following

 

How much thread is left? You may have enough to torque the bolt down. You can always helicoil if it fails. Then again you don't want another broken bolt.

 

I will try that and hope and pray!

 

Status update is everything worked like a charm! Broken bolt is out, the other hole that stripped is replaced with helicoil. @chacal sent me the necessary replacement parts. I will be putting the rest of it back together soon (ending on a high note today) and will see if my original problem is fixed.

 

Great you got it fixed.

 

Now it’s not starting haha! Turns over but won’t ignite. I did not touch the carbs besides removing them

 

Okay so after having let it sit and taking the dogs for a walk it started right up, just rode to the nearest gas station to fill her up and so far so good!

 

550s seem to be notorious for flooding when hot. Carbs are packed in tighter to the case than other models, and they are the only ones with the heat shield as far as I know. Symptoms are not starting when warm after sitting a minute or two...you can immediately restart, or let it cool (take the dogs for a walk). To restart between these time periods, if flooded, give it about half throttle and crank till it clears itself out.

I believe the heat shield was an unsuccessful attempt by Yamaha to eliminate this known issue.

 

I also do not have the heat shield on them, I am not certain where I put it actually. Should I find it and install it?

 

I'm not sure they made a difference. In fact, I'm not even absolutely certain that the heat caused the issue. But from my own experience, which included trying it with and without the heat shield, a cardboard shield after the bike was shut off, blowing a fan on the carbs, etc, plus reading about the experiences of others and their speculation, that's the conclusion I came to.

And this identical problem gets mentioned a lot regarding 550s.

Specifically, I think the gas expanded or boiled and pushed a slug of fuel up the pilot and main jets and flooded it.

But anyhow, if you wanted to do your own experiment with the heat shield and can't find yours, message me and I'll ship one to you.

They unfortunately bolt under all 8 of the front carb screws, so you have to pull the carbs to install. They make setting float levels a pain, probably the reason why most of them disappear after a while. If you got creative you could make some extended bolts/studs with spacers and attach it slightly lower using only the two outside screws, making it removable while the carbs are mounted. Heck, it might even work then with a bigger air gap under the bowls.

 

Ok so big update.

I just did my very first sync and colortune. Overall it was a pretty fun and straight forward process.Except for the not so fun part:

- My gas line broke off where it met the petcock but that was a panicked simple fix that I had prepared for just in case.

-I was able to get close to that Bunsen blue but my air mixture screws were all the way in! The mechanic said he jetted it rich! The plug was cleaned via flame method and put in before riding the bike, Neighborhood trip ~8mins and it’s that black.

-I synched again and forgot to replace the caps on the manifolds and freaked out when the bike wouldn’t start.

-Idle went from a 1200 to 2000 by the time the process was over but the idle screw was adjusted and now it hovers around 1200. It died on me once but I think I have it’s sweet spot (time will tell)

Big advice is don’t be worried about a project like this. It was easy, I read the forums, bought the tools and had a plan.

and of course as soon as I post this it won’t hold an idle and dies. Thoughts? Should I back out the air mixture screws a half turn?

 

Is it worth it to reset the jets if the bike is too rich? It currently runs fine right now but I haven’t gone on a trip longer than 15 minutes. I have some oil leaking from the valve cover part with the little half moon, and want to patch some holes on the exhaust collector this winter so rejetting might be worth my while? Just looking for some friendly advice!