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1996 XV750 First time cleaning carbs (New England USA)

Have a question about fixing something on a Yamaha Virago XV750? Post it here!

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MJanderson20
Posts: 57
Joined: Tue May 24, 2022 9:13 pm
Location: New England USA
What Virago you Own: 96' Virago XV750

Re: 1996 XV750 First time cleaning carbs (New England USA)

Post by MJanderson20 » Tue Aug 02, 2022 7:39 am

Thanks, was careful to try and makes both tubes (or both sides I guess) the same length, was concerned that if they werent that one would read different than the other, I'm glad you brought it up.
faffi wrote:
Mon Aug 01, 2022 5:29 pm
One more thing; if you want to make sure both tubes give the same reading, you must connect first one, then the other, to the same cylinder, marking the raised position of the oil on both with engine idling at a constant speed.
So to clarify, when I connect the tube, what do I do with the other one ..just leave it not connected to anything? Also the level will just rise a certain amount and just stay, not continually rise?

Something came up yesterday and I didn't end up getting a chance to do much, got the parts removed to check the valves and that's about it. But I have one question...most of the videos I see they remove the cam cover(name?) So that you can see if the little dot is at the top or bottom.
20220802_072721.jpg
The guide that I'm following doesn't say to do so. There's no reason I can't just take it off to double check the position of that dot right? This is the guide I'm following:
'Adjusting Virago Valves Forum'
app.php/adjusting-virago-valves
They tell u to make sure the valves wiggle when you are going to check/adjust, I'm assuming maybe they are saying to do that instead of checking to see if that dot is in the right position? But that's just a guess..
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faffi
Posts: 283
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Location: Norge
What Virago you Own: 1982 XV750 with XV1100 engine, Seca rear wheel, XT600Z shock, Seca 650 fuel tank

Re: 1996 XV750 First time cleaning carbs (New England USA)

Post by faffi » Tue Aug 02, 2022 9:57 am

Yes, normally just leave the other tube unconnected. However, I took another look at your system, and it appear that you have one long tube, not two tubes of equal length? If that is the case, there is no point check both sides since there really is just one tube formed as a U. In fact, if that is the way you have set the system, connecting just one end would probably cause the engine to suck in all the oil, since there will not be a vacuum with one open end.

One reason to remove the cam covers is to know if the cylinder is at TDC under compression, or on its exhaust stroke. Valves must me adjusted at TDC under compression. Another reason is if one does not want to turn the engine via the crank bolt and observe the timing marks in the window. Instead, you can remove the spark plugs, put the engine into high gear and use the rear wheel to bump the engine around.

If you turn the engine via the crank, not that the engine turn backwards. However, the plug covering the crank shaft nut is removed the conventional way, meaning counter-clockwise. Many have destroyed these plugs after observing the clockwise arrow on the cover, which actually indicate crank rotation. Using the rear wheel to turn the engine eliminate any potential error.

Note that these marks will match up every 360 degrees, but each piston will only be under compression every 720 degrees.

BTW, there is a simpler way to adjust the valves without being bothered by TDC or compression etc. Often, I just adjust the valve with clearance when the other is under tension. If the exhaust valve is pushed down and is open, the inlet is fully closed. And vice verse. Using this method, all you have to do is remove the valve covers and spark plugs, put the gearbox into 3rd or higher, and use the rear wheel to rotate the engine and observe the valves, and adjust the free ones until all four are done.
The journey of a thousand miles begins with a motorcycle.

MJanderson20
Posts: 57
Joined: Tue May 24, 2022 9:13 pm
Location: New England USA
What Virago you Own: 96' Virago XV750

Re: 1996 XV750 First time cleaning carbs (New England USA)

Post by MJanderson20 » Tue Aug 02, 2022 7:42 pm

Oh wow I did not realize there were so many options, thanks for the heads up! The way you described sounds much simpler. I may follow the guide this time just because it is so detailed and I am still not 100% grasping the concept of the valves and how they work, but would definitely like to try that much more simpler sounding way going forward. Glad to know that removing the cam covers can't hurt, and that the dot being at the top tells you that it is under compression, not on exhaust stroke. Knew you wanted it at the top, but was unclear of why. So I think I will add that as an extra step to double check that it's under compression.

Also thanks for the warning about removing the plug covering the crank shaft nut counter clockwise. Could see how that arrow above it could be misleading, and saw either a video or post (can't remember which) of somebody saying they were fooled by the arrow so definitely is a valid concern.

And yes, my manometer is only one tube wrapped all the way around.
I used this as a guide to make it, there is a link on that page to the original article. Hope that using all one piece of tubing will work well!
https://www.pbase.com/iamflagman/image/19233066

Long day, just got home and still haven't gotten a chance to get to valves. Getting so close and very anxious to finish! One quick question, my feeler guages only have thousands of an inch, not .00 MM , this isn't an issue is it? I noticed in the Haynes manual that the MM have a much wider range than the thousands of an inch, leading me to wonder if they'd give you a more exact reading?
Screenshot_20220802-194539_YouTube.jpg
Also found interesting, in this YouTube video, the guy mentions that a different manual (climber?) That it gives you different range. I wasn't even aware that there were other manuals than Haynes, good to know
https://youtu.be/r77smPpIe6Q
Screenshot_20220802-195054_YouTube.jpg
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faffi
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What Virago you Own: 1982 XV750 with XV1100 engine, Seca rear wheel, XT600Z shock, Seca 650 fuel tank

Re: 1996 XV750 First time cleaning carbs (New England USA)

Post by faffi » Wed Aug 03, 2022 12:53 pm

I set my inlets to at least 0.1 mm and exhaust to 0.15 mm. These are not critical to get exact, as you can see by the range given by Yamaha. If valves are within a tight 0.1 mm and less than 0.15 mm, I do not bother adjusting the inlets. Exhaust, I am happy between 0.15 mm and slightly roomy 0.20 mm. Exhaust valves need clearance to keep cool - too tight, and they can burn and pit their sealing surfaces. Inlets will not burn, but too little clearance will reduce compression. More clearance will give a better idle and a little more low-end power, less clearance will make starting a little harder and give a little more top-end power. Within the ranges given by Yamaha, you will not notice anything dramatic. Anyway, personally I tend to err on the roomy side of the specs.

You can use inches. IIRC 4/1000 = 0.10 mm and 6/1000 = 0.15 mm. If the bike was mine, I would set the inlets to 4/1000 to 5/1000, and exhaust to between 6/1000 and roomy 7/1000.
The journey of a thousand miles begins with a motorcycle.

MJanderson20
Posts: 57
Joined: Tue May 24, 2022 9:13 pm
Location: New England USA
What Virago you Own: 96' Virago XV750

Re: 1996 XV750 First time cleaning carbs (New England USA)

Post by MJanderson20 » Wed Aug 03, 2022 9:25 pm

Finally got to check the valves! Was quick and easy, other than having to chase down a 22mm socket which I didn't realize I didn't have. I tried putting in third gear and using the real wheel to turn, but wasn't having much luck. I couldn't get the wheel to turn the shaft and chain, other than a small fraction of an inch (barely at all) each time I tried to bounce it. But got a 22mm socket and checked everything..everything was within what you recommended for 'if it were your bike' other than the front cylinder exhaust valve. It was close, at .005, almost left it but figured I might as well get spot on while it was all apart, and also wanted some practice adjusting a valve since I've never done it. So made it the .006-roomy .007.

At that point it was too late to start the bike up, there are people that live above the shop, so I couldnt sync the carbs..but I put everything back together with the manometer hooked up to the intake boot vacuum lines so Ill be ready to sync the carbs tomorrow! Since the bike was running rough last time I started it, I'm almost hoping that the carbs are out of sync and that maybe this will get it running well. Hoping to not have to mess with the mixture screws, but I guess I'll have to see what happens. Both spark plugs looked good, but I put new ones in when I cleaned the carbs and only ran for few minutes after that.

Very hopeful that I'll finally have my bike running well tomorrow, FINALLY! But then again don't want to get my hopes up too much.. I said that the bike had been running 'perfect' for a week or two before the carbs overflowed, but looking back on it that was probably an exaggeration, it wasnt exactly perfect..just had finally been running without issue for a week or two. Prior to that'd I'd been having idling problems, then misfiring, then stalled on me a couple times suddenly on the road. The couple weeks that it was 'perfect' it didn't have any of those issues, but it did seem to have a lack of power. Not 100% sure that it did because I didn't really have a steady baseline to go off of, but looking back I think that was probably the case. So I'm hopeful that syncing carbs and possibly adjusting mixture screws will finally get it running like it should, but definitely concerned that I may have other issues. Not sure what those might be but will cross that bridge if it comes to it, and I REALLY hope it doesn't since I've been SO eager to be riding all season and it's now August!😤😤😤🤣😂🤣

If I can get a little time to work on it tomorrow will update how it goes!!!

Also, thanks for the advice on where you'd adjust the valves to and why. Very helpful information!



Edit: Forgot I have to let the bike warm up before syncing carbs, guess I'll have to take manometer back off so I can do that before I sync

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faffi
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What Virago you Own: 1982 XV750 with XV1100 engine, Seca rear wheel, XT600Z shock, Seca 650 fuel tank

Re: 1996 XV750 First time cleaning carbs (New England USA)

Post by faffi » Thu Aug 04, 2022 7:16 am

Best to warm up without the manometer attached, yes.

Regarding turning the engine with the rear wheel, did you remove the spark plugs first? Otherwise, you are fighting compression.
The journey of a thousand miles begins with a motorcycle.

MJanderson20
Posts: 57
Joined: Tue May 24, 2022 9:13 pm
Location: New England USA
What Virago you Own: 96' Virago XV750

Re: 1996 XV750 First time cleaning carbs (New England USA)

Post by MJanderson20 » Thu Aug 04, 2022 10:42 am

Yeah I did take the plugs out before trying the rear wheel. With the small amount it was moving I would've had to have hit the wheel like 100 times, and stopped because it didn't feel right, like I might damage something. I must've been doing something wrong ..

MJanderson20
Posts: 57
Joined: Tue May 24, 2022 9:13 pm
Location: New England USA
What Virago you Own: 96' Virago XV750

Re: 1996 XV750 First time cleaning carbs (New England USA)

Post by MJanderson20 » Fri Aug 05, 2022 9:19 pm

So I FINALLY got a little time to sync my carbs! Not sure yet how happy I should be with the results..

I turned my bike on to warm it up, was running but not great. The exhaust pipe from the rear cylinder was shooting a little bit of smoke consistently, and bike was having mild popping, but was staying at a consistent idle. I left it on to warm up, and I'm wondering if maybe I let it run for too long. It was just sitting at idle, I didn't rev the engine or anything due to it running bad and holding the throttle just made the popping worse. I wanted to make sure it was warmed up enough and wasn't sure how long that would take, had it going for about 15 - 20 min before syncing, and when I started it the engine felt very hot. Could just be normal, I'm not sure. Looking back, I saw in a video someone put a fan blowing on the engine which I should've done but didn't think of it at the time.

Hooked up the manometer and started it up and the sync was way off..as I adjusted the bike started running better and better. By the time I got the fluid level it was running great. Did this at about 1300 RPMs, checked that it was still in sync holding the throttle to 2-3000 and it was. Went down to 1100 at idle and had to adjust sync again. At this point it was idling GREAT!!! Better than ever. No popping, sounded perfect. So I removed the manometer, remembered that I saw someone using a fan blowing on the engine in the video and did that to cool it down before taking for a ride.

I only went down the road and back, 5 minute ride tops. I had probly twice as much power as I did right before my carbs overflowed, was very happy about that. But the bike immediately was popping loudly and a lot on deceleration. Other than that ran great. But then when I got back to the shop, it was idling rough. Mild popping like before I had synched the carbs, no smoke though. I barely had time to even take it for a ride, so after I got back to the shop I only had time to let it sit for another few minutes.

Got home about an hour ago and haven't had a chance to look into why I might be still having these issues yet, but figured I'd give an update. I'm confused as to why it ran so great before the ride, then had the issues at deceleration. Also don't get why idle was so rough after the ride when it was so good before. Is this maybe a sign that I need to adjust the mixture screws? Not sure where to go from here. Wondering if maybe I synced the carbs with the bike too hot? Not sure if that could even be a possibility, just a guess. Also my tubing on my manometer slid over the attachment on the intake manifold quite easily, maybe I should've added a hose clamp and that led to a bad sync?

Going to look into these issues tonight.. any input would be greatly appreciated!!! Happy that the bike had way more power and the fact that it was idling great for a while makes me very hopeful.. At that point it had been idling better than it ever had by far! Definitely a little bit of a letdown that there's still work to be done, but feel like I'm closer than ever to getting back on the road!

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faffi
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What Virago you Own: 1982 XV750 with XV1100 engine, Seca rear wheel, XT600Z shock, Seca 650 fuel tank

Re: 1996 XV750 First time cleaning carbs (New England USA)

Post by faffi » Sat Aug 06, 2022 5:00 am

If you let the engine idle for 15-20 minutes (I think I suggested 3 minutes at 2-3000 rpm? but maybe that was in another topic) in high temps (80F or more), you have not done your engine any good. Nor should it be damaged, but the oil will have noticeably reduced it's life and should be changed sooner than originally planned.

A fan during the warmup and adjustment period would have been good, but it would have likely been better to just get riding when you did rather than use a fan for 5 minutes first. Also, other than making the engine very hot, it sounds like you did an excellent job getting the carbs sync'ed - well done!

Before you do anything more, I would suggest you go for a solid ride of at least 30 minutes, a ride that will allow the engine to stretch its leg a little, meaning not constant stop and go city riding. Throughout that ride, and especially at the end of it, make mental notes of how it reacts. Personally, I believe the popping and other issues you had came from the engine being so hot, fuel was boiling in the carbs, and that the next ride should verify that everything is just fine - but you need to ride it to be sure ;)
The journey of a thousand miles begins with a motorcycle.

MJanderson20
Posts: 57
Joined: Tue May 24, 2022 9:13 pm
Location: New England USA
What Virago you Own: 96' Virago XV750

Re: 1996 XV750 First time cleaning carbs (New England USA)

Post by MJanderson20 » Sat Aug 06, 2022 7:27 am

Can I take that prescription for 30 minutes of riding to my boss ? 😂😂 That will definitely be the easiest test yet!

Yeah I definitely screwed up leaving it warming up for so long, I did remember you said 3 min at 2-3000 rpm, I figured 5-7 ish at idle would do the trick, but got a phone call while I was waiting and lost track of time. Although I didn't realize it was so serious that I potentially could've damaged the bike! Will keep in mind that the oil could be compromised, that is too bad I just changed it. Do you think it could've also compromised the results of the carb sync?

Will take your advice and try a longer ride and see how that goes. I did let the bike cool for a while though with a big floor fan on it before I went for the test ride. Maybe 15 min if I had to guess. Should I re-sync the carbs quick before the ride? Can do the 3 min at 2-3000 RPMs now, just didnt want to rev it for that long the way it was running last time.

The popping on deceleration was pretty significant, hope this goes away. Will be great if it was just too hot!! Also just out of curiosity, why is it more important to take notes towards end of ride?

Thanks!

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