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

The float's ability to shut the fuel off and maintain the proper fuel level is critically dependent on the volume. any float that does not look just like it came from the factory is junk. Another possible crush mechanism would be the hairline cracks nearly always present in old brass floats, the cracks allow air to leak out when the float is hot (expanding) but they may seal as the float cools (contracting) I find a fair amount of crushed floats in these old carbs, it's not rare.

xs650LA said:

Thanks for the compliments. It's been a work of love (and obsession ) I am literally learning all of this from scratch. I spent the whole last year methodically learning how to spray paint and airbrush I had this design in mind and I worked really hard to learn and buy all the right gear - lots of youtube, talking to experienced folks, trolling craigslist, and reading blogs to buy the cheap but good stuff. I posted the progress on Instagram https://www.instagram.com/jose.daveiga/ (you'll have to scroll through my other stuff to find those paint-related ones). All started with a "design" in mind and I went for it.
As for the pods I know, I was going for looks and someone told me those pods would work ... guess not... time to re-think that...

Click to expand...

You can make those work better with different carbs. It's your bike however if you are happy with it how it is, run it!

Thanks again @grizld1 @5twins @fredintoon @retiredgentleman @TwoManyXS1Bs @gggGary @Corndog @peanut for all the great advice!

Here is the progress report. I since I was waiting for the cylinder valve check gauge plates (arrived today late) I had time to yet again go in and clean both carbs, replace the floats with new ones, and adjust the height of the float. I had already adjusted the cam chain and next I will check the valve clearances.

However, having re-cleaned the carbs and the new floats helped. But oh-boy, setting the correct float height is like hairline precision on my bike. First seems like my initial problem was really carb float related. Since I re-set the (new) floats, the left-hand carb is working better now than the one on the right. However, setting it to 24mm was not cutting it because the float would not fully shut down the valve and the carb was still overflowing. I made a minimal (hairline) adjustment and it is now just right. Now, the right side carb, after I put in the new float is now somewhat strange. I see too much smoke coming out of the exhaust and it's kind of weird. The bike is perhaps not timed right which is not helping. So I am definitely going to stay the course with checking the valves next, then the points timing, etc.

Also, I have no idea how the bike was even running. Those Pods were the absolute worse. Now I am understanding a bit more about carbs, etc (I've spent a lot of time this weekend on videos, reading the carbs info on the tech site - great manual @grizld1 - and reading just about any other thing out there, including forums). Those pods are crap and at that they were just about closing some of the air intakes... that said, screw the looks and I am getting the Uni pods (ordered them already). Meanwhile, running the carbs without any pods has made a huge difference (duh ).

If I have time and energy tomorrow I will start the whole procedure of checking valve clearances... will report back with more questions. As before, feel free to comment on the above if you see something that jumps at you.

thats a lot of work ........well done.

Re the carbs overflowing the only thing that I would say is ....looking at your pics the tang is at too much of an oblique angle for ideal operation.

These floats ,like most replacement parts these days , are thrown together in some Far Eastern Country with little or no quality control procedures and requires the user to work them into a useable condition.

In your image the carb is inverted so the floats are practically in their final resting place for shutting off the fuel supply . If you look at the float tang it is set at almost a 45 degree angle in relation to the float needle valve. The problem with this is that the tang will be applying pressure on the needle valve from one side and the needle valve is likely to bind on the wall of the valve chamber on that side due to unequal pressure .

Ideally you need to adjust the tang so that when the needle valve is in the closed position against the valve seat , the tang is perpendicular to the valve needle so that there will be a uniform friction between the needlle valve and the valve chamber walls.

The other thing you need to check is that the float and float pivots don't have too much play or the float setting will be inaccurate

I explain how to achieve this in this video but it takes great patience and care not to break the floats .

Thanks! Ha! That's you?!?! I found your video and it's actually the exact one I used for reference. LOL. After all the reading and looking at the hose method I decided to at least start with yours... Great video btw! Thank you for going through the work of filming and posting it.

Yep, I think the pics you are looking at are before I adjusted it. I was thinking of showing the state and form of the carbs at that point. But after those photos I must have taken them out and put them back in at least 4 times before I had the right setting on that one side. The first two photos are of the left carb, the last one is of the right carb (which seems to be "pitted" inside on the upper side, not the bowl bottom, as in corrosion or something - unlike the left one which is smooth inside). And, as I said, I think on the other (right) side I am still going to have another 1 or 2 goes before it is set right...as you point out, it's a process when I go about it I will take photos of that one setup and share.

By the way, yes I did adjust the pivot as you advise with pliers so there's less play. I did not find it that fragile but I was like EXTRA careful when adjusting it.

Your points here are well taken. And, I might have set it the way you suggest (90 deg to the needle) without noticing. I was going for symmetry and equal balance of the whole float. As for the tang, I was going just for it to work so that it's set for the 24mm that is recommended (+/-2mm). But what was happening was that at the exact 24mm height (and boy, I pained over it and even made a jig to inspect the highest point of the float is right where it should as it barely touches the needle, etc) the float seems to touch the bottom of the carb. That did not set the needle all the way down. So I have it now at about 26mm and it seems to be working (as I said, actually it's more like 26mm minus a hair because at 26 it was leaking still a tad bit). With the tang set at 26mm the needle goes all the way down just as the floats seem to be about to touch the top of the cab walls. For the left carb it seems well set (I'm guessing and hoping, of course) and now the bike on that side seems to be working better than the other - the irony perhaps is that that was the side that was not working at all and that I thought maybe was a piston problem. Now the right side is the one that's not really dialed in - I had it set with the collapsed carbs, and when I placed this new one I clearly still don't have it where it ought to be (too lean?).

Not sure if this is wrong, but as I am looking at the whole experience it seems a good way is to just set them to the point where they start leaking only after running the engine a bit and letting them sit (seems like after a while it leaks but not right away). After that it's all about adjusting just a tad bit so it's a hair above where it was when it leaks that way. Another thing is, I have my bike on an angle since I work on it in my yard and am too lazy to put it on the jack (lift) I have. What happens is that when the bike is horizontal the floats don't leak (on the left/leaning side) but when I lean it on the footrest they start leaking - again this is the point where I have to adjust up a hair and seems to fix it. Is this right or should I not care they leak when at rest/leaning because they sure don't leak when the bike is running (even when leaning) - which I assume is there is just enough suction in place so that hair difference when working is taken away, but when the engine stops the float is not as compressed and there is a slight play and it leaks a bit (it's not a big flow)?

peanut said:

thats a lot of work ........well done.

Re the carbs overflowing the only thing that I would say is ....looking at your pics the tang is at too much of an oblique angle for ideal operation.

These floats ,like most replacement parts these days , are thrown together in some Far Eastern Country with little or no quality control procedures and requires the user to work them into a useable condition.

In your image the carb is inverted so the floats are practically in their final resting place for shutting off the fuel supply . If you look at the float tang it is set at almost a 45 degree angle in relation to the float needle valve. The problem with this is that the tang will be applying pressure on the needle valve from one side and the needle valve is likely to bind on the wall of the valve chamber on that side due to unequal pressure .

Ideally you need to adjust the tang so that when the needle valve is in the closed position against the valve seat , the tang is perpendicular to the valve needle so that there will be a uniform friction between the needlle valve and the valve chamber walls.

The other thing you need to check is that the float and float pivots don't have too much play or the float setting will be inaccurate

I explain how to achieve this in this video but it takes great patience and care not to break the floats .

Click to expand...

If your new floats and float needle/seat assemblies are aftermarket, that may explain the floats hitting the carb body. The new parts may not be fitting up exactly like the originals did. The float needle/seat assemblies may not be sitting as tall as the originals did. That would require setting the floats deeper into the body to get the spec measurement. Also, the spec measurement was taken with the carbs sitting upside down and the float gently resting on the float needle pin. It will depress it slightly but not fully. If you did your adjusting with the carb on it's side and the float swung in until the tang just touched the pin, your 26mm setting could very well be 24mm when checked correctly with the carb sitting upside down.

from your description it sounds like you may have a pair of Heinz 57 carbs made up out of bits .

If you still have your old floats I would measure the depth of the floats and compare with the replacement floats to see if there is any difference as 5Twins suggests but they would have to be quite a lot deeper to hit the roof of the float chamber at correct float setting.
There is nothing wrong with setting the float height to 26mm and testing it. you'll probably find that it has little if any effect on fuel delivery at WOT.

If you get the carbs off again try gently raising and lowering the floats with the carbs held the right way up with the floats hanging but hold the carbs at 45 degrees to the vertical and see if there is any friction or tendancy for the floats to stick

I know original parts are expensive but they really do work best. And they last. The originals from the factory got to this point. Factory replacements will probably outlast you. You really should do the clear tube test for the fuel levels. That's the only way to really tell where the fuel levels are at. Ideally, the level should be right around the bowl/body seam. Much higher and you could get overflowing problems, much lower and the bike could run lean and/or be hard to start.

It's been my experience that a bike (or any engine for that matter) that starts easily, idles good, but just won't make any revs or power has an advance that's stuck (or rusted) in the full retard position. I'd strongly suggest you look there. The advance allows retarded ignition for easy starting and then an advanced ignition as revs increase. No advance, no power.
Jim.
EDIT= I believe this was already pointed out but I just wanted to emphasize the point.

I'll reiterate what peanut and 5twins are saying about the float tang and its relation to the float valve. Your tang is definitely hitting the valve at an angle. Bad.


It's almost as though the float was upside-down, or mis-manufactured, or wrong height of the float valve. Try as you might, no amount of float height changes and tang rebending will change that undesirable tang/valve angle.

It almost looks like the hinge portion of the float is curled in the wrong direction, forcing the tang surface to be too close to the valve body, forcing it to be bent up at that undesirable angle.

Peanut, remember running into this a few years ago? Are there any good pics of BS38 float tangs, valves, mounted to show the correct 90° angle?

As you suspected 2m. The pin part is curled the wrong way to the whole tang part of the floats.
BS38 Floats 78-79 carbs

Tomorrow or after I might have time to adjust them again once I am done with adjusting the timing. I think the end result looked very much like those pictures you just posted. I will confirm. If not, back to the drawing board

650Skull said:

As you suspected 2m. The pin part is curled the wrong way to the whole tang part of the floats.
BS38 Floats 78-79 carbs
View attachment 107057 View attachment 107058

Click to expand...

First, thanks all so much for the advice. Trust me, I am reading it all and I am working on it as per your advice.

With that in mind, today I did not have much time but I managed to adjust the valves. I followed all the advice to the T. I followed all your advice(s) about clearances, how to set the piston to the top, T mark, etc. And, I also followed this video
One thing is for sure, if I did this right, the clearances I had were waaaaayyyy too tight. If i got this right I would watch the exhaust valve go down and up and then the intake go down and up, once it was all the way up I would look down to line up the mark with the T mark. At that point the valves on the side I was adjusting both had some play and the piston on that same side was all the way up (I could clearly see it by shining a flashlight through the spark plug hole). Then I went about adjusting the inlet at 0.006 and the exhaust at 0.012 (my gauges also have metric). I made sure only the right dimension was passing through the gap, not the next one above. Again, on that note, when I started all valves were WAYYY too tight. Not sure what the guy before me was thinking.

So now it's another one down and a couple more to go. I've 1) adjusted the cam chain and 2) the valves to the right intake and exhaust clearances. Tomorrow I hope I will find some time to finish some engine cosmetic cleaning since I have the the tank out and the carbs out, and then I will attempt to adjust 3) the timing just with the light bulb method (sorry, no strobe yet - my budget is getting a bit tight). My hope is to finish that tomorrow and then find time Wednesday to check 4) the carbs again. I will report back then on the whole tang angle story. I will probably open both carbs back again and will take photos when I do - but right now, that's the last step. Thursday the pods arrive, and by then I ought to be able to wrap this up enough to go on a first test ride once I have it all more or less tuned (unlikely, the way this is going once I get to the carbs, it's not going to be only about the floats and I'll probably end up playing with rejetting and a bunch of other stuff ...kind of hoping not because of the work, and hoping for it because of what I will learn )

Again, cant' thank you all enough for all the help, information, going easy on me , and encouragement so far!

By the way, the floats I got were from MikesXS... wondering where I would get new ones that are legit if not from there... the original ones I was replacing are definetely not in good shape. So if I can't make it work with these ones from MikesXS...def have to get other ones

xs650LA said:

Tomorrow or after I might have time to adjust them again once I am done with adjusting the timing. I think the end result looked very much like those pictures you just posted. I will confirm. If not, back to the drawing board

Click to expand...

Your welcome, it's all up to yourself really, if you engage the response will reflect that..............Important to post pics as you have been doing. Things get picked up that normally wouldn't have without them, they are invaluable for diagnostics.

keep at it you'll soon be there..........

Hey xs650LA. I too had a bad experience with Mikes aftermarket floats. They are not the same quality as OEM parts. Swapped in a another pair from another set of carbs I had and all's good.

I see new OEM floats are available, they're not cheap but if they work, worth it IMHO.

http://www.boats.net/parts/detail/yamaha/Y-256-14985-00-00.html

These are what I believe to be the Suzuki equivalent part, much cheaper than the Yamaha one .....

http://www.partzilla.com/parts/detail/suzuki/SP-13252-31210.html

I plan on buying a couple eventually to make sure but until then I can say I'm only about 99% sure they're the same float. Take a look at the listed Suzuki carbs they fit. They're pretty much the same CV type BS series carbs as used on our 650s.

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.


The Yamaha float.


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...

TwoManyXS1Bs said:

2 known causes of collapsed brass floats (that I'm aware of), are extreme backfires, and a history of compressed air, jammed into ports/vents to clear blockages...

Click to expand...

Try to collapse a foam float. Reason 1001 Specials are better than standards

Are you talking about the 5 Special models with brass floats or the 4 Special models with foam floats...........lol