No power over 3000RPM - Engine trouble - XS2 1972 XS650

sunk foam floats have been reported...................
I buy my genuine mikuni BS38 floats from 650central at least 8 sets so far.

Carb float-Genuine Mikuni
XS1/2, TX650/A, XS650 B/C/D/E/F/2F/SE/SF '70-79

#CSUDmi002.114 ..... $18.25 each
 
... remove advance cover.. physically expand the weights..... then release.. does the weights snap back...?....sometimes the weight springs grow weak...and/or the rod is gum'd up internally.... remove'n the advance rod isn't difficult... just remove the parts and lay them in order of assembly. NOTE: the advance unit has two small pins that inserts in the advance rod... they need to be removed to slide out the rod (there's one on the points side also)... clean the advance rod.. I use a Q tip to clean the bearing surface inside the head.. then grease the rod surface.. and also use another Q tip to add grease inside the head... you shouldn't need to remove the points plate.. just slide the rod out (left side)... don't go overboard on the grease.. clean up any excess.. grease'n your points isn't good...

...I always put the engine at TDC... the pins should be at 12 o'clock.... don't drop them in the open spark plug hole...a needle nose required to pull them. Order spare pins and advance weight springs... might as well replace them.
The only difficult part is getting the advance unit off.. remove 10mm nut and the advance unit drive collar...behind the weights.. you'll note a retaining ring that requires a heavy blade punch to loosen.. usually a sharp rap with a heavy hammer.. once it's loose... spin the ring and at the same time pull the advance unit out... the ring is between the weights and the advance unit housing.... once the advance unit is off.. you'll see the pins....NOTE: on the inside of the advance unit is a small notch, that's for pin placement...... carefully replace the springs.. don't over stretch them....once you hand start the advance unit back in place.. another sharp rap..or two.... on the retaining ring... I'v seen what happens if this comes loose at speed. Not pretty.

Once you have it tight... spin the engine over by hand several times.. make sure the advance unit isn't rubbing against the engine.

This MAY not be your problem.. ? but it should be done as basic maintenance .... most haven't be touched since they got off the boat. You could have weak coils.. ?
 
Yes, the Suzuki parts site pics are difficult to see, but the float hinge does curl away from the solder pads just like the Yamaha float. Here's a pic from eBay of an '81 GS450 float, much easier to see the float hinge curl in relation to the solder pads .....

G0uOelp.jpg


But, Gary seems to have found the best, cheapest float source, at least for the BS38s. I'm still looking at Suzuki for BS34 floats though. They're lots cheaper than Yamaha.
 
found an image for one of my 79 BS38 floats which clearly shows that the brass pivot has been curled the opposite direction to the floats supplied Mikesxs

Provided that the Mikes float diameters are no larger than the originals it should be possible to bend the float brackets sufficiently to level the tangs I should have thought.
 

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Yes, the Suzuki parts site pics are difficult to see, but the float hinge does curl away from the solder pads just like the Yamaha float.

But, Gary seems to have found the best, cheapest float source, at least for the BS38s...

... my 79 BS38 floats which clearly shows that the brass pivot has been curled the opposite direction to the floats...

Thanx, guys. Very interesting. I'll be looking at getting some BS38 floats, and this is on my radar...
 
... it should be possible to bend the float brackets sufficiently to level the tangs I should have thought...

I suppose one could put a tight Z-bend at the base of the tang, raising it enuff to make it perpendicular to the valve plunger. The bend would have to be very close to the hinge point, so that it doesn't contact the valve plunger...
 
Yep, those look like the ones I got from Mikes XS

Okay, took a look at Partzilla's float pics, for both the Suzuki and Yamaha, and I think I see a difference in the direction of the curled pivot.

The Suzuki float.
View attachment 107096

The Yamaha float.
View attachment 107097

Not sure if the pics can be trusted, but it looks like the Suzuki float hinge is curled to the same side as the floats' solder pads, and the Yamaha float hinge is curled to the opposite side of the solder pads.

What we need is good side view pics of these floats.

I wonder if MikesXS already detected this potential equivalence, and has been selling its customers the Suzuki floats. AND, if this IS the case, AND if the float hinge is indeed upside-down, then maybe this could answer the numerous postings about float setting difficulties.

Of course, 5twins will have the final say on this...
 
Those look right, mine look upside down (the curve).

Also, i re-adjusted the one on the right and here is how it looks (attach/images).

However, I am kind of stuck with these for now and I inverted the carb with the float and tested it. When the float is all the way up it is pretty much at 90 degrees (the tang is).

In any case, see my next post. I really don't think my issue right now is float related....I wish...



A 650 central float and two out of bs38s probably factory, the one good looking used one probably came out of the 5K mile bike, I replaced it with new.

View attachment 107131 View attachment 107132 View attachment 107133
 

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Gents, I need your expert help...

So I followed the plan and the program.
- I adjusted the cam chain (flush, etc).
- I adjusted the valves as per the intake and outake dimensions I had been told (INLET 0.006" EXHAUST 0.012)
- I set the points clearance (0.016 to 0.012) and the timing (to middle of the F marks).
- I charged the battery (actually I pretty much have it always on a tender) and used a steel brush to polish/brush the spark plugs
- I also cleaned the carbs (3 times now) and I re-adjusted the one that I suspected was too lean (the right)
- To top it all off, I gave it a good cleaning with degreaser and water and then used my air hose and waited a whole night and part of the day for it all to dry (this took restraint).

What am I doing wrong? Why? well, before all this I had a working bike but my carbs seemed not so adjusted. Then i fiddled with it and installed new floats and is worked better, except the right side seemed a bit lean now and i needed to make a hair adjustment. So before I adjusted the valve clearances and the points it was working...

...And now it won't even start. I rechecked the freaking points 3 times. In the process I got fed up of my 40 year old screws so even went and bought a bunch of new (metric) screws for the points system (the adjustment screws). In the process I cleaned the heck out of this. Granted I used the light bulb static method to adjust the points as seen on this video and the link below:
http://www.650central.com/fsetting_pointstype_ignition_on.htm

Some information. As I adjusted the valves, they were way too tight. As in, the clearances when dead top end were minimal. How did I do it? I rotated the engine counter clockwise until the piston hit maximum height on the side I was adjusting (watch the exhaust go down and then up, then the intake down and then stop when it's up at the max compression). At this point there is play on both of the valves (in and out) and I adjusted the clearances. Repeat for the other side, and that's it.

For the points, I followed the video above to the T but I also put my finger in the hole to make sure it was at top of compression (when I felt my finger was being pushed out of the spark plug hole I'd stop and then rotate until I saw the F mark, and then gently rotate until it was at the middle). I then adjusted the top points first (for the right side cylinder) by moving the whole jig. I quadruple checked, so that every time the turn came to the right place that bulb would light up smack at the middle of the F mark. I now see how hard it is to get this right with a bulb, but I thought to get it good enough this way and then, once i got it working, I'd get a strobe... same thing for the left side, I adjusted the lower part of the jig etc. Same thing, rotate the engine, when the piston on the left side was getting to the top of the compression stroke (feeling the hole on that side) I'd go about the same thing.

But all that done, I go and I try and run it and it wont even sputter. Electrical seems fine, all else is same as 48 hours before when I started adjusting the valve clearances. So the question is? Do I have to go further back and adjust the advance mechanism? Granted, my engine was running but my valve clearances were completely off and the point at which the mark would hit the F the light had been long on... could it be my engine was set differently and this guy had it running right even though he was not following the marks? WTF... problem now is, I am a bit lost because I feel like I followed painstakingly every direction and the right steps and now my bike won't even fire up... :( Help is welcome!
 
Nice closeup pics of the floats there, xs650LA.
Maybe I'm seeing things. Dunno.

I see some red things on the bowl gaskets. If that's remnants of red silicone sealer, you've got to get all that out of there.

A closeup of GggGary's floats pic.
It almost looks like the float arms are aimed differently, relative to the float bodies.
BS38-Floats-Edge02.jpg


The only pic I have of my float. Oriented as it would be in gasoline, the pivot weighted down with a drillbit resting on a stop. 13mm of float body should appear above the fuel level.
XS1B-Carbs-FuelLevel01.jpg


Note that there's almost no bend to the valve tang. I saw your finger on the float in your pics. Just to be sure, float height is set with only the weight of the float gently resting on the valve's spring-loaded plunger, just barely compressing it, no assist from a finger, no pressure holding it down all the way...
 
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On your ignition issue, you could remove the plugs, plug the plug wires back in, rest them on the head fins, so you can see any spark. Then, kick it thru and watch if you're getting any spark.

If you replaced any points plate screws, ensure that they don't protrude so far out the backside as to hit the aluminum housing...
 
LA, first off... there's a valuable lesson here for you to learn, one that some people never learn. It's this... When solving a problem/troubleshooting/tweaking ALWAYS test for results after each step. In other words... adjust the points, fire the engine up. Adjust valves, fire the engine up... etc. That way, when things go south, you know exactly where to look. It's a lesson you just learned the hard way (those are the best lessons), but never forget it. On to your problem....

As 2M said above, take the plugs out reattach the plug wires, rest the plugs on the head, kick the engine over and see if they spark. if they do, you can put a wrench on the crank and rotate it and watch to see if they fire when the F mark aligns. If all that's good, I'd be suspicious of you valve clearance. You said they were way too tight "before" yet the engine ran "before". That sounds suspect to me. If all that's good, it's back to the carbs. Good luck and keep us posted.
Jim.
 
That .006" and .012" valve clearance spec was only for the 1st model year. Yamaha revised it down to .003" and .006" in a tech bulletin early in 1972. That is what most of us run. So, your P.O. probably didn't have the settings too tight, he was just following the accepted newer settings. Some claim the larger clearances are better, producing less wear and more power, so I tried them. All I got was a terrible racket and clatter, no power or performance increase that I could discern.

If you used a feeler gauge to gap your points and didn't thoroughly clean the blade first, you may have contaminated the points faces with oil. That could cause them to misfire, weakly fire, or not fire at all. Also, if your points are used and have some pits, you can't accurately set the gap with a feeler gauge. The spark jumps between the pits so the gap will actually be larger than what the feeler gauge measures. When gapping used points, it's best to set them closer to the bottom of the spec range, say around .012"
 
Hi xs650LA,
you have big fat blue sparks but it won't fire up at all even if you squirt ether-based instant start into the carbs?
Is it possible that with all the fussing and fiddling with your points you've gotten them firing on the wrong TDCs?
 
@grizld1 @5twins @fredintoon @retiredgentleman @TwoManyXS1Bs @gggGary @Corndog @peanut @650Skull @xjwmx @robinc

THANK YOU! It runs and it's running pretty much better than ever now. And I haven't even fine tuned it.

Ok, so this has been quite the ride (pun intended). I redid it all 3x times (carbs actually 4x). And it would just not start. I mean, I set the cam chain right, I set the valve clearances right (or so I thought), I set the points....and I triple checked all this crap over and over... BTW @JimD54 I did fire it up after each check and even adjusted the carbs before touching the points just to make sure they were rich enough without leaking (no leaks now so far, but seems rich enough - at least for my non-expert level of knowledge). But after I checked the timing and adjusted the points, it would not start. So I scratched my head and scratched (lost a few more hairs in the process and got a lot grays too), and decided I had to go even further back...

Soo, it was the advance system. The short is that it was 180 degrees wrong. So I looked and looked for instructions on how to figure the advance system out and turns out those damn lines need to line up and they were exactly 180deg wrong. So I unscrewed it, took the weights out, turned it 180deg, put the screw back and TADDDAAA....hummm hummm hummm. Clearly I was feeling the hole wrong and the compression I was feeling was at the opposite piston - or something like that, because when I was doing the points adjustments something was not totally clear. So I turned it off and checked the points yet one more time. This time I had no changes to make. The mark is hitting the F right between the lines ;) and the compression feels right for the right side now. So I guess my flipping advance was all wrong to begin with. I have no idea how the last guy got this thing to work. But I swear it was (I even posted a video). No idea. The valve clearances were super tight. The Points were super tight. The timing looked all wrong (duh, he must have set it upside down or something like that for it all to work with the advance upside down), etc.

Took it for a spin. So I got the new UNI pods and it runs great. It idles great and it has power in 1st, 2nd, and 3rd (that's as high as I went) and up to the higher revs and at the lowest too. Feels...good :)

But of course, there are some issues still. The carb on the right is somehow sputtering. And a minor amount of smoke is coming out. Suggestions on why this is happening are welcome. Also, next I will probably get a strobe (next month's budget) and fine tune it with it. Also, all is fine but when I turn the engine off it pops, I think only from one of the sides (probably the one that's smoking)...a loud final POW. Please send comments on this. I will post a video tomorrow when there is light to show what's happening.
 

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