Another '82 xj650 maxim running problem

My project bike is at the stage where I’m attempting to get it on the road. This is what I’ve done so far.

Adjusted the valves
Checked compression (#3 is a little lower and takes longer to heat up)
Build mufflers for the bike
Po replaced both coils and plugs
New air fitler and Stock air box
Carbs were disassembled and cleaned.
New needle and seats
Bench checked float levels. Several times!!!
Benchsync'ed using the paperclip method.
Mixture screws were set at 2-1/2 turns out from bottom.

Sunday I managed to get the bike to idle, but it would only do so with the petcock on the prime setting, it leaks like a seiv. (I’m ordering a new one today from Chacal), Then as soon as I touch the throttle it falls on its face; Even after I let It warm up for 5-10 minutes. If I turn the choke on a bit I can rev it up, but it still is slow to rev. Yesterday it fired right up and I let it warm up for 10 minutes; samething. I can play with the throttle/choke and get it to rev over 3,000 rpm.

Also I added a fuel filter, it never fills up all the way, there is a little air still in it. I checked the flow of gas and it comes out in an OK stream.
I thought it might be a vac leak, I sprayed a little starting fluid around the boots and nothing. I also did the propane tank test, nothing.
Sorry for the long post…
Whats next??
Any ideas?

p.s. (Sorry Toreadorranger, but we are on the same path.)

 

Tman 74
you got it to idle thats great now is time for adjustments, 2 1/2 turns out on carbs seems a little on the lean side thats why you have to keep choke (enriching valve) on, as soon as you hit throttle more air less fuel then dies. I would turn out to 2 3/4 to 3, look on this site as alot of info on carb adjustments. all 4 carbs will not be set exactly same turns out, need to do small adjustments on each, I turn in until i hear it falter(one at a time) than back out 1/8 to 1/4 turn
plus carbs need to be synched-look on site for this.
I tried taking short cuts but ended up starting over several times.
I thought my problems where float adjustment also but it will end up being carb adjustment and synching, both important and must be done.
Only one way to do, the right way.
good luck your getting close

 

I just printed the YCIS tool diagram and i am going to start gathering part!s! I will try to adjust the mix screws. I put them back where i found them, but the plugs were gone and the PO had bottles of starting fluid to get it to run!!!!

 

Link to the diagram?

 

YCIS tool
http://xjbikes.com/coppermine/displayim ... ize=1.html

 

It fired right up tonight, i let it warm up a bite and adjusted the air/fuel mix screws. It seeems to like 2 3/4 out, maybe a little more. Samething it falls on its face when you hit the throttle.

 

I have all the ycis tool parts, Saturday i am going to sync the carbs. Any other ideas??? What else do i need to check?? Where does fuel come from just off idle?? (what internal circut?) HELP!!!

 

Here is a pic of the fuel filter, It never fills all the way up. Is this normal??

 

Your fuel filter should fill up I'm pretty sure. Air bubble means high spot in the line, which equals a potential fuel-flow problem.

 

What should the flow be? What should the stream look like?

 

Ok lets try to hit one thing at a time

Fuel filter - Ideally it fills all the way up - mine has a small bubble a the top as it lays along top of carb. If it is mostly full it should not be a problem. (I'm sure others will disagree but my opinion). As long as enough fuel is flowing to keep the bowls fulled you are OK.

Next your lack of Rev from idle. Several issues to check

0) I almost forgot (Fitz will fuss) have you checked your valves? You have bigger issues right now but tuning with bad valve clearance is a waste of time.

1) are you sure your carbs are surgically clean? be honest with yourself

2) Check your float levels. If they are too low you will starve for fuel when you open it up.

3) if your carbs are clean and float levels correct check for air leaks. Use unlit propane torch to "probe" the carbs and boots while the bike is idling. If you have leaks it will speed up.

4) If all the above is OK - did you bench sync the carbs first? required first step after cleaning.

5) If you have done all the above and still have issues a sync may be in order. However you need to have a way to figure out if your mixture screws are set right. Plug color at idle is a good way as in a color tune plug. You really need to get a good idle setting before you sync.

I think that's most of it - word of caution when syncing lube your yics tool. Do not leave it in too long the rubber will melt. I remove mine and let it cool a bit every couple of minutes. RUN FANS on your engine while tuning - don't lose a head gasket to overheating...

Give it a go then post up your results - we'll knock em down

 

OK, valves are good, pulled the carbs, cleaned again (they are very very clean), set float levels, i also checked the compression, 105-110psi across all 4, I built my YCIS tool and i'm going to sync them tomorrow!!

 

You are getting there - any improvements?

 

i ran out of time and did not put the carbs back on, that will be this morn!!!

 

Success! Well sort of. I synced the carbs with my YCIS tool. It went ok. I will do it again when I have some more time to tinker. I also reset the mix screws. It runs, it comes off idle OK if I choke it just a bit. It pulls the plungers up maybe 1/16”. I took it for a quick spin down the road and it runs awesome!!! It pulls hard I only ran it up to 4,000 rpms. I am very happy!! Thanks to everyone for there help. I have some more tuning to do but I am closer!!!

 

If you still have to open the enrichment circuit, that makes me think you're still running lean. Could be you just need to back the mixtures out a hair more, which fortunately is a quick fix!

What color are your spark plugs if you do a chop?

 

2 plugs are white and 2 are black ill back out the white ones and turn in the black ones

 

I road the bike and pulled the plugs. 3 look good, one (#4) was black, I have had problems with the float sticking. How do i keep it from sticking?? i have adjusted it 4 times. it will be low or over flowing. I polished the tab, polished the New seat. How do i get it set correct.

 

I pulled my carbs, again, cleaned, cleaned and cleaned. They are spotless. Reassebled bench synced, installed on bike and it fired right up, runs awesome!!!! Im going to sync on the bike tomorrow, and RIDE!!!! I guess 4 times on the cleaning is the ticket!!!

 

Re: Another '82 xj650 maxim running problem (update)

OK, synced the carbs on the bike, tweeked the air/fuel mix, runs AWESOME, no misses, no smoke, all 4 pipes are hot. I went for a 5 mile ride and perfect!!!

 

Ok took it for a 40 mile ride. It runs great but, there is a hesitation just off idle, it has been idling well, it seems to like 1,200-1,500 rpms. it seems high but it will do for now. Pulled the plugs, they look white (lean).

A thought. the PO had a set of jardines, i installed them and made a set of baffels from 1.5" pipe cut some slits and pressed them in to impeed the exhaust gas flow and wrapped in muffler fiberglass wrap. I noticed this weekend that a stock exhaust has a very small hole, maybe 7/8-1". Is my exhaust 1.5" all the way out.

Would/could a lack of back pressure/excess flow cause an off idle hesitation?

 

Sounds like you're getting close. Off Idle hesitation is usually the mixture screws. You are looking to dial in a good idle without the transition hesitation. Different pipes, air filters, pods etc will effect your tuning but you should be able to tune around whatever difference you pipes have.

sounds like your a bit lean and your plugs are telling you the same thing. Rick is fond of saying to tune in degrees of turn, very small increments. That is good advice.

 

I am almost 3 turns out now, how far can I go? Or am i too far out. I ran it hard, shut it off and coasted into the drive, pulled the plugs and they were white. Taht would be lean on the top end. Do the air/fuel mis screws control the off idle, or across the entire throttle range? Also when I wrapped the baffles with fiberglass, I used some coated tie wire to secure the glass. It is tight now, should it be tight or looses for the best results?