550 maxim carbs.

My first bike is 1981 xj550h maxim. I bought it in the spring of this year. Since I have had it, I have had trouble with the carbs. It has been synced a few times by bike mechanics and rebuilt/jetted.
When I first got it, it would not idle. It would stall at red lights if I didn't keep some throttle on it. One mechanic synced the carbs and then it began to have high rev problems going as high as 4000 RPM some of the time. I took it to an apparently better mechanic and he did the rebuilt. It worked great for a while.
On a wet day I took it in to service my front forks and another mechanic in the same shop decided to adjust the idle. The bike went berserk after that. It would have high rev issues, lunging forward like crazy or it would not throttle up. I had to walk it home one night because it would only go walking speed.
I brought it back in on the Monday and they synced it again. This time they told me that the crack on my air box was causing the problem. (I was earlier told the crack was nothing. It was covered in black duct tape to seal it.) This mechanic wanted me to repair it and they would sync it again. This was never mentioned as a problem before when they synced it. I could not find a new air box so I used the JB plastic repair. (worked like a charm BTW ). Again, I am gonna take it back in to sync it. However, I read the xj bike articles on syncing and everything I could to understand it better. I ordered a YICs eliminator tool for the mechanic. We chatted about it and he offered to buy it. At the moment, the bike hangs up at starts, it sometimes grabs and suddenly lunges forward. Once up to speed it seems to act fine until about a 40 min drive. Then the engines starts to get noisey and runs rough. Sometimes very jerky as I throttle up and down.
I am not sure the question, I am just hoping that someone may have some understanding as to what is happening. Will the syncing/Yics tool help.
Thank you for any help.

 

Fellow Canadian!
Lol
Have you checked your valve clearances? You can have perfect carbs but if your valves are out of whack it won't do anything.
I have a few links if you need them.
-EM

 

When you say the shop rebuilt the carbs what exactly does that mean. If they did not break the rack apart and replace the throttle shaft seals, then they really did not do a rebuild. They probably just took them apart and cleaned them out.
Hanging idle is a classic symptom of an air leak. The most commen place to have an air leak is at the throttle shaft seals. You can test for an air leak by holding an unlit propane torch by the shaft seals while the engine is running and see if your engine speed increases.

And EarMachine is right, all carburetor adjustment will be for nothing if the valves have not been adjusted correctly.

 

It is good to know Canadians are on here eh?
Until now it has not been checked. Most of my work is done by pros. So far the only mention of my problem has been the carbs. However, I can ask them to check them when I bring it back in again. Thank you.

 

Ha-ha-ha, now that's funny!

 

Most of your work is done by pros. That's too bad. They aren't really pros but more so people who are doing the job theyre paid for.
Alot of the time there work is generic.
Following advice from this site and the knowledgeable xj veterans you would be able to do a more thorough job on your own and and it would cost you less lol

Everyone says it over and over on this site so I didn't fight the power lol.
Checked my valves first and I have ONE in spec out of 8.
With a bike you haven't owned from new, checking airflow is huge.
-EM

 

Point taken Chacal. Thanks for the laugh as well. LOL. I take it you question my mechanics and think I should find a better one.

 

Unfortunately when it comes to 35 year old bikes it is extremely difficult to find a repair shop that has the knowledge and the will to fix these bikes correctly. You have already by your own account seen how having a shop who is not familiar with 35 year old bikes can take your money and leave you with a bike in worse condition than when you brought it in. Most shops just plain refuse to work on them.

So my advice is to buy a service manual and start working on it yourself. It's not going to be easy or fast, but you will learn a lot, save some cash, and have a bike you can be proud of because you put your own sweat, blood and tears into it.

 

When I drove bus for a living, I used to joke to my customers "I am a pro because I get paid for it, not because I am good at it."

 

When I first bought the bike, I decided I would not do my own home mechanics on it as I usually do on other things. I knew it was old and thought It needed special attention. And, if I choose to sell it in the future, I would have a service record of repair to go along with the bike. So far it seems that decision has cost me more than I paid for the bike and my next visit is gonna be another expensive one. I agree with you BigT. Maybe it is a decision I should retract. Getting the service manual is not that hard and I just need to roll up my sleeves and learn a little. And my wife also agrees with you. LOL

 

When I first got my bike about 6 years ago I had the same mentality you do. My mind began to change when I called a local motorcycle shop that I had been dealing with for years for atv parts. I even know the owner from school. I asked them if they had a YICS block off tool, when they said they had no idea what that was but bring it in anyway they would figure it out. That's when I decided to do the wrenching myself.

By the way my bike had the same problem as yours, ran ok until you come to a stop then have to rev the engine to keep it from stalling. Checked my valve clearance, only had one out of spec, broke down the carbs and went to the church of clean, replaced throttle shaft seals. Synced it up and it purrs like a kitten. Still need to do some fine tuning but very happy with the results.

 

My wife actually encouraged me to do my own wrenching (it was before I found this site) after a 40yr bike shop mech told me... "Man, i know these old bikes but you don't want to pay me what it's gonna cost to make this one run" (it was on it's way to a scrap yard). The only work i pay a shop to do is mount and balance the tires. Idk how many other bike forums are as legit but this one's pretty damn good. 17k then, 39k today...varoom, varoom!

Gary H.

 

Does your bike have pod filters? If not I'd re-visit the fuel jets. There are air jets under the carb hats. You'll need to make certain they are correctly oriented.

Gary H.

 

I am not sure what pod filters are.

 

Your bike doesn't have them then which is a good thing. They are the cone shaped air filters that are added to the air intake side of the carbs when the air box is removed. Re-jetting is required once they're installed. You said one of the mechs did some re-jetting. Your bike should idle with stock air and fuel jets and the stock airbox.

Gary H.

 

"With renewed vigor." (I just love that phrase) I decided to do my starter rebuild according to Tskaz pictures. My starter mounted slightly different but everything else worked the same.

I seen Dragsta's post and he mentioned the popping sound. Since my bikes last sync all it does is pop especially on de-cell. It does not bother me other than it is an indicator that something is not quite right. I have order a book and will look at taking off the carbs and also checking out the valve clearances. It will be a few days but I will post back my discoveries.

 

Got ya.