Newbie here w/ '80 or '81 Maxim XJ550. Trials/Tribulations

Hi,

I would like to present my situation and look to the experienced XJ Veterans for their valued guidance and assistance. Apologies in advance as this might be lengthy and drone on.

Last week I picked up a title-less XJ550 (suspect '80 or '81) since the SN in 9-digit VIN is under 101xxx (5K5-0103xx).

It had been "bobbed" - rear springs removed and replaced with steel stock and paint job is courtesy of Krylon with NO clear coat. I mean, I breathe on a painted surface and it scratches.

Regardless, Im not worried as much about appearance and aesthetics as I am to just get this think to start and idle on its own.

First thing i did as soon as I got it home was to figure out exactly what this bike is (remember, i had no title, nothing). All I knew is that this was an early '80's Yamaha Maxim. Google became my friend.

I quickly learned that the carbs were a weak spot on this. The battery i had in it was purchased last year according to the previous owner.
It was deader than a rock. I charged it up @ 2A over night.
After a charge, I was happy to find the starter WORKS.. I tried starting the thing until the battery couldnt spin the starter any longer.
I charged the batt again.

After reading a couple of forums and write-ups, I got the guts to pull the carbs. I yanked the carbs out and i was not liking what I was seeing.
There were missing and severely stripped screws. I knew this wasnt going to be pretty.
I pulled the float bowls and man, did that gas stink. It was so old and nasty. I ended up doing a light carb cleaning and slapping the carbs back on the bike. My eagerness to get this running was killing me.

Guess what, no dice.

I ended up yanking the carbs off again, this time i took my time and visited each and every carb. I pulled all the jets, diaphram, screws, etc and doused anything not rubber with carb cleaner.

Some items refused to come out, such as the pilot jet on a couple carbs as the damn slots had been stripped. I did my best to clean what I could and replaced everything. Compared to what I started with, things were much cleaner, but far from perfect.

I managed to get the carbs back on the bike about 11pm at night. With a fully charged batt i tried starting for quite awhile after priming the clean carbs. and GUESS WHAT, the bike finally turned over and ran for a couple seconds. I was so excited that I stopped right there, shut off the garage lights, went inside and went to bed.

The next day I came home from work to play with the bike. I expected to start the bike and take her for a spin. NOPE.. I tried and tried and tried to start the bike and no go. FINALLY, I got her to start, but it would not continue to run unless I held the throttle. I immediately realized that I had a carb DUMPING gas out onto the floor as I was holding the throttle.

I started a couple times and just couldnt get past the raw fuel consistently being spewed onto the concrete below.

I suspected the float needle not closing and the bowl overfilling.

I yanked out the carbs, threw on the bench and went to bed.

The next day after work I opened the bowl on the pissing carb and adjusted the tang on the float. I cleaned a bit more with carb cleaner and put back together. I put back onto the bike and after a ton of tries to turn the bike over, it finally started and would only run when holding the throttle. GUESS WHAT, the carb i adjusted was no longer leaking. BUT, another carb was pissing gas out all over.

Start over again. I pulled the carbs and adjusted the tang on ALL floats.

I placed the carbs back onto the bike and now NO carbs leak. BONUS..

Now I am at a point where I am positive some tuning needs to take place with these carbs. While gas no longer dumps out from the carbs onto the floor, I have a hell of a time getting this bike to turn over. When she does turn over, it will not idle for anything longer than 5 seconds at the most.

Obviously this is a carb setting issue. I am seeking assistance from you experienced XJ peeps. What is the best way I can get this to start easy and run without the throttle held.

Are there basic setting i can set the carbs to then incrementally adjust from there? What would you do? I should also mention, I dont have ANY air filtration device. No pods, no stock air cleaner, nothing. So i imagine if pods are a PITA to get running, then not having anything might be my problem?

Thanks in advance and apologies for the long winded story. I know I could have summarized all this into a couple of paragraphs, but oh well.

Thanks again
BigjimCFH.

 

im not an expert.... but ive read enough questions to get you started to what they are going to say! yes... lol, you need some sort of filtration. pods end up causing more work than not. stocks the way to go if you can. a full cleaning of the carbs is crucial in order to do it once! (look at my signature.) next is going to be adjusting your valves, bench sync, and color tuning.... i have an 80 650 that runs great but not without holding the throttle for idle. there is a idle screw by the carbs, but im going to assume thats not your issue. im in the process of attempting to find someone to do my valve clearence as im scared as HELL!!!!!!!! good luck, and keep us up to date

 

oh and by the way....... WELCOME!

 

Way too much air flow if you have no air filter and you will be sucking in things that SHOULD NEVER be in a carb-that is why it won't run unless you are throttling it because it is lean, lean, LEAN. So there is no point in trying to run it at all until you get an air filter, and yes stock or very close to it will save you many hours of pain trying to tune it-pods can be done but they are labor intensive as these carbs require fine tuning to get the mix right.

Your efforts to not be afraid and try and tackle the issues are great, but if you don't put things in order then you will be chasing your tail for a long time. From the sound of things you will either need new carbs or will need to do surgery on your current ones, and replace some parts. But first you need to check and likely adjust your valves. Transform your eagerness for it run now into eagerness to fix it right then ride. Sorry if I bummed you out but we've all been through this before. And we've all dealt with various degrees of what dumb%$#! thing a PO has done to a bike and sounds like yours did his best to create a challenge for you.

And definitely welcome to XJBikes! Your gonna love it here.

Check this out to get you started:

http://xjbikes.com/Forums/viewtopic/t=14827.html

Also if I'm reading your VIN# right then your bike came off the assembly line about the same time as mine, maybe even in the same week. Mine is a 1981 XJ550 Maxim, black & chrome, and run's scary fast for a 1/2 liter bike! Check it out in the gallery.

 

Thanks for the warm welcome!! I appreciate it.

It seems things are going from bad to worse.

I did a boneheaded thing. In an effort to improve things, i made things worse. I messed with the pilot mix screw and the big main screw that sits between carbs #2 and #3.

I had read a few places that said to take them out, clean them and then place them in and screw in all the way then back out 2 1/2 turns. Well, before i took the screws out, i drove them in and it was a whole lot more turns that 2 1/2. (i should have kept better track).

Anyways, now after messing with these two items, i cant even get the bike to turn over. Now that I know that it wont idle on its own without a filter, i am kicking myself and woudnt have messed with these things. hmm..

after the 2.5 turn thing didnt work, i drove back in and backed each out .5 turns while trying to start after each turn and no luck.

These are what I fudged with:


and



any ideas about these things??

Thanks!!!!!!!!!

 

Thanks MercuryMan. Then I must have an '81 if the VIN is that close to yours. I cant wait to see if mine goes scary fast!

 

Fit an air cleaner then have another go....this link may help?

http://forum.highlifter.com/Basic-CV-Ca ... 72049.aspx

 

Re: Newbie here w/ '80 or '81 Maxim XJ550. Trials/Tribulatio

Thanks for all the info guys. So I read quite a bit more about the pilot mixture screw and the big screw which I found to be the idle adjustment screw. Apparently these were unlikely to be the cause of my starting issues.

I then realized that I had adjusted the tab on the floats to seat closer to the needle to stop gas from dumping out of the carbs. I think I might have bent the tabs too much and no gas is getting in there when the bowls are full.

I took the carbs of to do my best to adjust the float height. Carbs 45 degrees (barely resting on needle). I grabbed a engineers ruler and marked 21.5mm on a stick and used that as a gauge to check float height.

Based on my reading, 21.5mm I understand to be the float height for mikuni bs28 carbs.

I had a hard time adjusting one floss. I later realized that the float seat and needle must be from something else. The needle had a much longer springy top and no tiny metal hanger that hangs on the float tab. I pulled the float seat and the rubber washer was trashed. It had crumbled off.

So, I ask you great people of xjbikes; its apparent I need carb replacement parts.
I have made a list. I understand my carbs to be in fact the BS28 x 4
- 1ea top pilot mixture screw (threads coming off)
- 1 ea main jet washer (yeah, one was missing)
- 2 ea float needle seats with seals
- 2 ea float needles
- 2 ea pilot fuel jet (stripped)

Anyone have a reliable place to snag carb part at reasonable prices?

I tried sourcing a factory air cleaner housing. Someone on eBay wants $90 for one. That seems a bit outrageous to me.

Regardless? If anyone can point me in the right direction, I would sure appreciate it.

 

STOP. Before all else, get a service manual, you're gonna need it.

First off, float heights need to be "wet-set" you can dry set them all day and it's just a starting point. http://www.xj4ever.com/setting%20fuel%20levels.pdf

The best place for the correct parts at reasonable prices is XJ4Ever, our resident parts source. PM member chacal, or send an email to "info AT XJ4Ever DOT com" with your needs. His "catalog" forum is linked via the logo in the site banner at upper right.

You have Mikuni BS28s like all of the 550s. Exploded: http://xjbikes.com/Forums/viewtopic/t=31061.html

You should be able to find an airbox on eBay for way less than $90. I have a replacement here for my '81, it cost me a whopping $10.

Here's what you're going to HAVE to do if you want the bike to run right:

Field-strip, CLEAN and service those carbs. DO NOT submerge still partially assembled (with the butterflies and shafts still in) carbs or you can damage the throttle shaft seals. You have about a 40/60 shot that the shaft seals might still be good; don't make it 0/100 against.

Replace all of the rubber parts-- the tiny o-rings on the pilot screws, the o-rings on the outside of the float valve seats, etc.

WET set the float levels. As above, dry setting is only the beginning.

Do an accurate bench sync. Set the mixture screws at 3 turns out.

GET YOUR VALVES IN SPEC. You won't be able to vacuum sync the carbs if the valves aren't in spec. http://xjbikes.com/Forums/viewtopic/t=14827.html and http://xjbikes.com/Forums/viewtopic/t=29209.html

Vacuum sync the carbs with YICS blocked.

THEN and only then do you mess with the mixture screws. Use a ColorTune or adjust by ear.

Re-check the vac sync.

IN ORDER. Take shortcuts or leave anything out and you'll be at it until you do it right. Heed the words of those who have been there, done that.