No low end power

Hey guys, I have been lurking around on the forums for a while, I have a 83 XJ750MK, the first thing I did was follow the great carb tear down and cleaning on this site and set all the pilot screws to 2 1/2 turns (they had been played with before by PO) The bike smokes a little blue smoke upon down shifiting, has 56,000 Km on it. It seems to start from cold with no choke, and adding choke kills the engine. I tired leaning the mixture some but it still does this. Could the lack of low end power ie. stumbles on takeoff untill the rpm's get up be caused by too rich of mixture?

Second question, the starter clutch engages fine when cold but slips and chatters if re-starting from hot, how serious is this issue and does it mean the starter cluctch is almost toast? or it has some life left in it. There is also a faint almost constant muffled click click click when running like a chain barelly running into something, maybe this is normal, never owned an xj before.

Any advice appreciated.

 

The Cam Chain on your bike has an automatic Tensioner.
Re-set it.
No. Dont remove it. It's Automatic.

Manually rotate the Engine 2 Full Revolutions in the Clockwise motion to present the Chain tightly in front of the Tensioner, coming to a slow halt.
There are Flats on the Crankshaft end of the Ignition Rotor for this purpose.
Remove the Left Side Cover to access the Crankshaft Roror Flats.

(The Chain is tight coming down off the Intake Cam Sprocket across the front of the Tensioner and under the Crankshaft Sprocket.

Then, ... Quickly ... Rotate the Engine Counter-clockwise ... bringing any slack up around the Crankshaft Sprocket and presenting it before the Auto-Tensioner on its way to the Intake Cam Sprocket.

The Auto-Tensioner will move out to tighten the Chain as is passes before the Tensioner up to the Intake Cam.

You may need to REPEAT the process a few times to get all the slack removed automatically.

On the second and third attempt (if necessary ... rotate the Crank at least 2 Turns Clockwise and then do a QUICK reset.)

 

Thanks, I will hopefully be able to crack it open this weekend and reset the tensioner.

 

I did the tensioner re-adjustment, don't know if it helped much or not. I pulled the plugs and it seems the 2nd cylinder has some issues. Here is a shot of the plugs.

 

hard work sets you free and so does Iridium Plugs...and they gottum for the XJ's (.028) gap......

 

#-1 = Looks OK

#-2 = Looks Oil Fouled -- (Lean Mixture to check)

#-3 = Too Clean and Too Lean ( Add some Richness )

#-4 = Too Clean and too Lean ( Add some Richness )

Left to Right

That 2 Hole looks Oily ... not sooty ... you can try running that hole a tiny bit lean to see if it will prevent that plug from fouling.

Not way too lean and causing a heat problem.

 

I adjusted the carbs today, I left #1 alone, leaned out #2 and adjusted #3 and #4 to 3 1/4 turns out on the pilot screws. I also synced the carbs today, which smoothed out the idle but any high reving still makes a good cloud of blue smoke, which I think is from the #2 cylinder judging by the plug.

 

sounds also like u might have a bad plug cap wire,and was not mentioned but do u have original exhaust,if you got 4 into ones on you need to get a kn airfilter and hog out the bike a bit imean adjust the air and gas screws out to 5.5 turns to get your power back,which will make the bike run alot smoother,i have a 650 xj maxim,and had same prob,good luck?

 

I checked the spark on all the wires, all of them fire good and don't seem to be shorting on the engine casing or anything. She smokes only on hard acceleration or high reving in neutral, so this is most likely valves or rings? I've got a feeling the starter clutch is on the way out as well.

 

Coming-up on 35,000 Miles.

Valve seals.
Valve adjustments.
Cam Chain Tension Check.

Shouldn't be rings yet.

 

I did some more fine tuning of the carbs again after checking the plugs. The bikes is running absolutly great, besides the blue smoke. It just hums along, almost no vibration at all, idles beautifully. The blue smoke actually got worse the better its tuned. I am going to run some feeler gauges on the valve shims when I get a chance. I am not sure what else could be causing the #2 cylinder to foul so bad.

 

Blue smoke usually means bad rings, black means rich mixture. sometimes if the OIL ring is bad it can foul out that plug.

 

Valve seals normally smoke at start up, then better.

Rings - consistently smoky.

Valve shims will not cause oil burning.

 

The compression is OK on the cylinder, the only way to tell if its seals or rings would be to pull the block apart I guess. The smoke gets a little better when it warms up but not much.

 

If compression is good I'd be tempted to pop new seals into it.

To check rings you'll need to pull the block off. Measure rings. Put whole thing back together. New head gasket. Etc.

I believe with the proper tools you can do valve seals without pulling the head. Cams will need to come out though. Not a small job.

 

if that starter clutch lets go that smoke will stop for sure, then you can pull the pistons out from the bottom

 

Well I am going to have to try and do something, in 300km the oil went from full to the high mark to oil light on. I suspose its not possible to replace the valve oil seals without removing the cams and re-timing the engine. I don't have a factory service manual to go by, just a haynes manual.

 

Over head cams you got to remove the cams - keepers - and valve springs to get to the seals. Also easyr to remove the head to do all this.
I just got done doing my 84 fj600. What a pain in the ars

 

Well I am going to start looking for some valve seals and a new valve cover gasket and get them on order. The ammout of oil consumption and how quickly it fouls the #2 cylinder is scary (but it runs so well). Removing everything is not a problem, its all the problems I keep reading about getting the cams re-timed after disassembly and the tools, have to purchase a valve spring compressor.

 

The first compression test was done with almost no km's on the bike since I purchased it. After running for several hundred Km's the blue smoke has gotten a lot worse and #2 is fouling even quicker than before. The most recent compression numbers are as follows:
#1 #2 #3 #4
Dry 120 90 120 110
Wet 140 120 145 150

I still think its a valve seal, the ammout of oil being burned seems to be a lot for it just to be a worn ring, and as RickoMatic said the Km's seem low for rings to be worn. Still waiting on parts for the valve seal job.