https://www.georgefixs.com/new-74-7...ers-intake-manifold-boots-gaskets-bs38-carbs/
No barbs, but OE quality.
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‘77 XS650 get it running
- Thread starter Woodrow31
- Start date
No barbs, but OE quality.
There was a Canadian Gentleman A week ago or so here -- .Tightening the intake Clamps and Flanges against cylinder .getting rid of air leaks getting rid of this
Isopropyl seems to be a good "wipe down" prior to "rattle can" touch up spraying. It leaves no residue that I know of and cuts petroleum residues of mineral spirits and other solvents.
Hey everyone.
Long post.
I uninstalled the carb and found the butterfly valves not centered correctly. I loosened the valve screws, flipped the throttle lever a few times and they lined themselves up. Tightened the screws back down. All set.
Then I did my best to sync the valves before reinstalling on the bike. I had noticed the right side valve, while all the way closed, was covering all 3 of the small holes, leaving only the 1 larger hole exposed. The left side valve was leaving one of the small holes exposed. I synced them so that all 3 holes were covered by both valves.
Next I found that I had some small cracks in the carb holders. I cleaned them up and sealed them with some RTV silicone. Let it set and dry for 24 hours. Reinstalled the carb holders and the carbs.
Next I repaired the air filters with some silicone and wrapped them with new filter.
Installed the air boxes and filters.
Hooked everything back up, hit the start button and it fired up on the 3rd roll over. Shut it off and went to bed.
This morning it fired right back up.
I adjusted the sync screw a hair and got the exhausts hitting very close to the same.
Adjusted the throttle screw until it was idling at 1200 rpm’s.
Adjusted the mixing screws to 1 1/2 turns out, then backed them out another 1/4 turn. This seemed to be the sweet spot where each cylinder was running well. Then adjusted the throttle screw until it was back down to 1200 rpm’s.
Let the bike idle for 20ish minutes and everything seemed well. Pretty proud of myself.
Until I wasn’t.
The rpms took off on me again, ran up to 3000 rpms and stayed there. I backed the throttle screw out a little bit and brought the rpms back down to 1200. At that point it would idle for a minute and then act like it was starved for fuel and die.
I would have to turn the throttle screw back in to get it to start again. After a few seconds the rpm’s would take back off.
I noticed once the bike was hot, there was a bit of smoke coming off of the motor. Hard to tell exactly where it was coming from but it seemed to be primarily on the left side, below the spark plug. Right under the spark plug there is a bolt, and below that bolt is what I assume the head gasket. I couldn’t tell if the smoke was coming from the gasket or the bolt. My assumption is the gasket, as it seemed like more smoke than what could come from the bolt.
So for anyone curious, that’s where things stand as of this afternoon.
Long post.
I uninstalled the carb and found the butterfly valves not centered correctly. I loosened the valve screws, flipped the throttle lever a few times and they lined themselves up. Tightened the screws back down. All set.
Then I did my best to sync the valves before reinstalling on the bike. I had noticed the right side valve, while all the way closed, was covering all 3 of the small holes, leaving only the 1 larger hole exposed. The left side valve was leaving one of the small holes exposed. I synced them so that all 3 holes were covered by both valves.
Next I found that I had some small cracks in the carb holders. I cleaned them up and sealed them with some RTV silicone. Let it set and dry for 24 hours. Reinstalled the carb holders and the carbs.
Next I repaired the air filters with some silicone and wrapped them with new filter.
Installed the air boxes and filters.
Hooked everything back up, hit the start button and it fired up on the 3rd roll over. Shut it off and went to bed.
This morning it fired right back up.
I adjusted the sync screw a hair and got the exhausts hitting very close to the same.
Adjusted the throttle screw until it was idling at 1200 rpm’s.
Adjusted the mixing screws to 1 1/2 turns out, then backed them out another 1/4 turn. This seemed to be the sweet spot where each cylinder was running well. Then adjusted the throttle screw until it was back down to 1200 rpm’s.
Let the bike idle for 20ish minutes and everything seemed well. Pretty proud of myself.
Until I wasn’t.
The rpms took off on me again, ran up to 3000 rpms and stayed there. I backed the throttle screw out a little bit and brought the rpms back down to 1200. At that point it would idle for a minute and then act like it was starved for fuel and die.
I would have to turn the throttle screw back in to get it to start again. After a few seconds the rpm’s would take back off.
I noticed once the bike was hot, there was a bit of smoke coming off of the motor. Hard to tell exactly where it was coming from but it seemed to be primarily on the left side, below the spark plug. Right under the spark plug there is a bolt, and below that bolt is what I assume the head gasket. I couldn’t tell if the smoke was coming from the gasket or the bolt. My assumption is the gasket, as it seemed like more smoke than what could come from the bolt.
So for anyone curious, that’s where things stand as of this afternoon.
I think you really need to change those carburettor inlet rubbers. At small throttle openings, there's significant vacuum in there. If the RTV silicone isn't already leaking, it soon will be.
Of course that's nothing to do with seeing smoke near the spark plug.
Of course that's nothing to do with seeing smoke near the spark plug.
That 1200 RPM idle spec is for a hot engine. If you set it at that on a cold engine, once it warms up, the idle speed will begin to climb. Once it gets to 1500 or 1800, the ignition will start advancing, and that will increase the idle speed even more. This is a "self feeding" problem. As the ignition advances, the RPMs climb, which causes more ignition advance, and more RPM increase. The bike can end up at 3K RPM without you even touching the throttle.
How would you suggest setting the rpm’s on the start up then? Just wait until it gets hot and then set it to 1200? Once it’s hot, and I adjust the rpm’s down to 1200 it stalls. I’m not sure how to keep it running at that point.
When the bike is warm is when you want to adjust the mixing screws.
You have to kinda "nurse" it along with throttle blips to keep it running while it's still cold. The idle speed will be lower, and maybe too low for it to keep running on it's own. Finding the perfect idle speed setting may take some tinkering. You want it slow enough so hot, it won't start into the advance curve but cold it will still be fast enough to run.
That being said, your carbs may need some additional tuning. Are your float heights correct? If the fuel level is too low in the bowls, the bike can stall while idling.
That being said, your carbs may need some additional tuning. Are your float heights correct? If the fuel level is too low in the bowls, the bike can stall while idling.
I've often wondered how my bike performed when new.
I turn my idle screw (the one that adjusts the butterfly, not the mixture) in (more throttle) 1 1/2 turns before I start the bike. With the choke on, I can kick start it and it usually starts up right away. I let it warm up and the idle climbs to over 2K then adjust the idle screw to drop the idle down to about 1200 then start the ride. After say 5 miles, when I hit a stop light, I"m usually over 1500 RPMs at idle, so I drop it down a little again. Is that typical? By the end when fully warmed up I'm usually about 1 1/2 turns out each time.
This is helpful. Thanks.
I believe the floats are set correctly. I had to make a minor adjustment to them when I had them torn apart and cleaned them. I mean, how close do they need to be? I set them both to 25mm per spec, however I remember one being at 25 on one side and 26 on the other.
The float height spec usually has a "+/-" factor attached, in your case +/- 1mm. That would mean that anywhere from 24 to 26mm is acceptable. However, I've experimented with them set to the limits and find the bike seems happiest at the spec. Also, when setting them, you need to measure both sides or bulbs. The floats are often twisted on their bracket and one side sits higher or lower than the other. You won't catch that unless you check both sides. And if they are off side to side, the level you set on one side may not be what the actual level ends up being.
Melnic, you should eventually be able to find one setting that works both hot and cold, and not need to go through all that adjusting as the bike warms up. Granted, you may need to keep it running when cold with some throttle blips, until it warms enough to idle on it's own. I do have to "tweak" my setting a couple times during the season it seems, turning it up a little when it's colder out and back down a little when the weather gets hot.
When I first got my 650, I thought that 1200 idle sounded a little "busy" or fast, so I turned it down to around 1000. But then the bike would randomly stall at stops, so it seems it really needs that 1100 to 1200 idle speed. I've gotten used to it and it sounds normal to me now.
Melnic, you should eventually be able to find one setting that works both hot and cold, and not need to go through all that adjusting as the bike warms up. Granted, you may need to keep it running when cold with some throttle blips, until it warms enough to idle on it's own. I do have to "tweak" my setting a couple times during the season it seems, turning it up a little when it's colder out and back down a little when the weather gets hot.
When I first got my 650, I thought that 1200 idle sounded a little "busy" or fast, so I turned it down to around 1000. But then the bike would randomly stall at stops, so it seems it really needs that 1100 to 1200 idle speed. I've gotten used to it and it sounds normal to me now.
Mikey
got muscles in his head that ain't never been used
"Checking fork tubes goes on your list. It's a worthy project you have if you're into it."
ggggggggggary ( sorry my finger got stuck) has a good YouTube video on checking to see if your fork tubes are bent
It's easy as in if I could do it it's got to be easy (and my tubes weren't bent )
And when your done with the video give him a like and subscribe too
I'm hoping to monetize his channel
Oh and the guy can sure roll a log too
Yes, one float was right on spec. The other was slightly twisted. One bulb was at spec, the other was 1mm higher. I wasn’t comfortable trying to twist it so they were even.
Perhaps I should.
Yes, it's a rather common issue and easy to remedy. Remove the float, grab both bulbs, and gently twist them in the direction they need to go.
That would also make sense as to why I have had a bike that I could leave the petcock on and never spill a drop while another bike would pee a little gas on the floor to remind you to shut it off.
VM34s will idle nicely down arround 800-900 rpm when warm but I set them higher so the cold idle doesn't randomly die. There is no charging at these low rims but I ride very little in places I may need to idle for more than 30 sec or a minute. YRMV
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Hey everyone.
I pulled the carbs back off.
Adjusted the floats.
Installed new carb holders.
Reinstalled everything and she started right back up and ran pretty well.
However, now I have kind of a jingling coins sound coming from the top of the motor that I did not have before.
Is this a common thing that maybe is an easy fix?
Thanks again everyone.
I pulled the carbs back off.
Adjusted the floats.
Installed new carb holders.
Reinstalled everything and she started right back up and ran pretty well.
However, now I have kind of a jingling coins sound coming from the top of the motor that I did not have before.
Is this a common thing that maybe is an easy fix?
Thanks again everyone.
