Forum Donations
Search
VTF Google Search
 Click Here

Fouled plug(s) and no choke required

  • Advertisement

Post a reply

Fouled plug(s) and no choke required

PostAuthor: glegge » Thu Jun 06, 2019 10:16 am

Hi folks, recently purchased an 84 Virago 1000 which needed a bit of work, nothing major, mostly electrical related to the battery/starter circuit. About 50,000 km on the bike (30000 mi) The bike was laid up for a while, but in excellent appearance. I've done the normal maintenance, changed plugs, oil and filter, new battery installed, that sort of thing.

So once I got it running, things seemed pretty good, but I had some backfiring issues when I eased off on the throttle too quick, normal stuff from what I read on several forums. The bike has lots of power and runs smoother than I expected for a V-twin. After about 50km of driving, I started experiencing a miss in the front cylinder. Pulled the plugs and the front cylinder was fouled with sooty deposits. The plug in the back cylinder was greyish color with the insulator being white as new. So I pick up another set of plugs, this time opting to find the proper non-resistor plugs, as some people say the resistor plugs can cause a weak spark. I disconnected and capped the vacuum line running to the MCV, as many people have suggested, and I also tested the carb balance (but I may revisit that). I tossed some Seafoam in the tank as well, crossing my fingers that the problem would cure itself with little help from me. Haven't made it to 50km yet, but I'm starting to feel the missing on occasion once again. The backfiring is reduced though.

Strange thing I found is that in cold weather (around 5 Celsius or 40F), the bike starts easily with no choke applied. I've owned alot of bikes over the years and never had one yet that started without applying the choke at that temperature. Thats sort of suggests that the bike is running rich, when you combine that tidbit with the fouled plug. So I've been tempted to get a carb kit and do a rebuild, but I read so many horror stories on forums about bikes running worse after a rebuild that I wanted to see what others thought.

As for the carb sync, I used 2 older vacuum gauges but the needles move so erratically that pinching the lines off so that they are nearly closed is the only way to be able to get a reasonable reading. The reading was about 3" of Hg. for both cylinders, so it doesn't appear to be an imbalance. I checked the gauges against each other to make sure they are both reading the same, and they are. What i don't like is using a gauge which measures up to 30" to confirm they are balanced at 3", but thats the normal range of most vacuum gauges. So I'm thinking I may put together a hose/oil system which works by measuring the differential in vacuum, rather than the absolute vacuum. Seems to be a more logical way to go, as crude as the hose/oil systems are.

Just wanted to get some input to see if this is an unusual or if anyone has experienced something similar. The choke cable linkage all seems good, no signs of anything sticking. I suppose I should run a compression check as well, just to see if it's a larger mechanical issue, but the bike runs fantastic, up until the point the plugs foul. Install new plugs, and everything runs great again....for a while anyway.

Thoughts appreciated!!

glegge
Junior Membership
Junior Membership
 
Posts: 6
Joined: Thu Jun 06, 2019 9:25 am
Location: Newfoundland Flag
Bike year & model: 1984 XV1000 Virago
Sex: Male

Re: Fouled plug(s) and no choke required

PostAuthor: bstig60 » Thu Jun 06, 2019 12:14 pm

Check your pilot screw and see where it is set. It should be 2.5 turns out from a soft seat which is the nominal setting. The further out it is the more fuel it lets in. Also, check the choke on that carb and make sure it is fully closed. Check fuel levels using the clear tube method.
Bill
"It´s a friggen motorcycle, it´s not supposed to be comfortable, quiet or safe. The wind noise is supposed to hurt your ears, the seat should be hard and riding it should make you s**t your pants every now and then. "

Please take the time to edit your profile to show your location. City, State/Province, and Country.
It is easier to help you if we know where you are.


SERVICE MANUAL DOWNLOAD LINK
http://viragotechforum.com/viewtopic.php?f=220&t=31501#p279545

Image
User avatar
bstig60
Mod
Mod
 
Posts: 13443
Images: 38
Joined: Sun Jun 08, 2008 6:16 pm
Location: Sharpes, Florida Flag
Bike year & model: 1999 Yamaha Virago XV1100LC Cruiser,
2003 Honda Goldwing GL1800 Touring
2007 Honda ST1300A
1987 Honda TLR200
Sex: Male

Re: Fouled plug(s) and no choke required

PostAuthor: glegge » Fri Jun 07, 2019 9:38 am

I'll get a look at this 2nd set of plugs this weekend. As for the pilot screw, I'll look at that as well, but I think the caps are still in place so I will have to pull those out first. Does the choke on these carburetors actually control the air flow by positioning a butterfly valve? I have an XJ700 and the choke controls fuel in a mini enrichment cycle, rather than limiting air intake to the engine. See item 4 and 5 in this diagram. https://www.partzilla.com/catalog/yamah ... -xv1000l-n

glegge
Junior Membership
Junior Membership
 
Posts: 6
Joined: Thu Jun 06, 2019 9:25 am
Location: Newfoundland Flag
Bike year & model: 1984 XV1000 Virago
Sex: Male

Re: Fouled plug(s) and no choke required

PostAuthor: bstig60 » Fri Jun 07, 2019 12:08 pm

The Choke just adds more fuel to the air flow through a port in the carb venturi. If I remember correctly, the choke unscrews using a 10mm wrench. Then you can check the movement and the seal. If the pilot screw brass plugs are still in place, that means no one has ever touched the pilot screws. If your bike is completely stock, that's OK, if you have modified the air intake and/or the exhaust system, then you need to adjust the pilot screws to properly tune your carbs. The plugs must be drilled out, but if you attempt this, be very careful not to damage the pilot screw heads or their threads.
Bill
"It´s a friggen motorcycle, it´s not supposed to be comfortable, quiet or safe. The wind noise is supposed to hurt your ears, the seat should be hard and riding it should make you s**t your pants every now and then. "

Please take the time to edit your profile to show your location. City, State/Province, and Country.
It is easier to help you if we know where you are.


SERVICE MANUAL DOWNLOAD LINK
http://viragotechforum.com/viewtopic.php?f=220&t=31501#p279545

Image
User avatar
bstig60
Mod
Mod
 
Posts: 13443
Images: 38
Joined: Sun Jun 08, 2008 6:16 pm
Location: Sharpes, Florida Flag
Bike year & model: 1999 Yamaha Virago XV1100LC Cruiser,
2003 Honda Goldwing GL1800 Touring
2007 Honda ST1300A
1987 Honda TLR200
Sex: Male

Re: Fouled plug(s) and no choke required

PostAuthor: glegge » Fri Jun 28, 2019 6:17 pm

Took me a while get back at the bike. I decided to pull the carbs off and wanted to get the kits before going too far with things. This may sound like an unusual question, but which cylinder is considered the front? My manual specs says the rear cylinder uses a 124 main jet and the front a 132. The carburetors were disassembled before, so I don't trust that the jets were installed properly. Something I read previously confused me about which cylinder is the front. I would assume the one closest to the front wheel is the front cylinder?

Also, the pilot screws were adjusted about 2 and 2.25 turns. That is what is considered normal. Small amount of gunk in both carbs.

glegge
Junior Membership
Junior Membership
 
Posts: 6
Joined: Thu Jun 06, 2019 9:25 am
Location: Newfoundland Flag
Bike year & model: 1984 XV1000 Virago
Sex: Male

Re: Fouled plug(s) and no choke required

PostAuthor: Flyingdog » Fri Jun 28, 2019 6:52 pm

glegge wrote: Something I read previously confused me about which cylinder is the front. I would assume the one closest to the front wheel is the front cylinder?


Yep you assumed correctly...rear cylinder is by the saddle and front is by the front fender.

Factory OEM:

Rear cylinder...#1 with #124 jet
Front cylinder...#2 with #132 jet

If you look at the base of each cylinder you'll see these embossed numbers. Usually on the back side of each.

And yes..pilot screw is usually set 2 1/2 turns out from soft seat as a starting point.

As with any carb work, specially installing kits, take into consideration your altitude. Plays big part in how these things work.
Last edited by Flyingdog on Fri Jun 28, 2019 7:10 pm, edited 1 time in total.
User avatar
Flyingdog
Silver Membership
Silver Membership
 
Posts: 2797
Joined: Fri Jun 23, 2017 2:31 am
Location: Colorado Flag
Bike year & model: 1985 xv1000 Virago
1981 xv750 Virago
Sex: Male

Re: Fouled plug(s) and no choke required

PostAuthor: glegge » Fri Jun 28, 2019 7:07 pm

OK. ..so front is front but is considered number 2. I had a look and seen the 1 and 2 you refer to. I was hoping to find a stupid problem like jets installed in the wrong carb, but it had 132 in the front. Never pulled the other carb fully apart yet. Job for tomorrow.

glegge
Junior Membership
Junior Membership
 
Posts: 6
Joined: Thu Jun 06, 2019 9:25 am
Location: Newfoundland Flag
Bike year & model: 1984 XV1000 Virago
Sex: Male

Re: Fouled plug(s) and no choke required

PostAuthor: glegge » Mon Jul 01, 2019 12:06 pm

So after stripping both carbs down, not much unusual to report, but the carb that's running rich did have a bad oring on the pilot screw. A little grunge in the choke circuit as well. The float level had to be adjusted but it was low, not high. Didn't check it before installing the new kit. Almost got it all reinstalled and then the rain started.

Note that I checked the float level with the carbs on the bench with the clear tube meThod. I read that it was OK to do that but some do it with the bike running. Anyone know if it makes much difference? Dont want to pull these off again, pain in the butt wrestling them back in.

glegge
Junior Membership
Junior Membership
 
Posts: 6
Joined: Thu Jun 06, 2019 9:25 am
Location: Newfoundland Flag
Bike year & model: 1984 XV1000 Virago
Sex: Male

Re: Fouled plug(s) and no choke required

PostAuthor: glegge » Fri Jul 12, 2019 11:23 am

Well things went from bad to worse. Got the bike running after getting the carbs back in. Took it for a short run and seemed to be running well. Pulled both plugs out and plugs were clean. A day later drove the bike to work but didn't make it. Started sputtering not far from work, pushed on forward and stopped firing on 1 cylinder. Figured it was the same thing again, but with all of the rattling coming from the engine I figured this was a new problem. To make a long story shorter, the rear plug melted! Stripped the thread in the cylinder pulling it out. Now I'm in for a big repair.

The bigger question is why did this happen. I hadn't finished adjusting things and didn't expect a 10km drive to be so detrimental. Had the pilot screw out 2 full turns. Did I create a lean condition that overheated the plug? Normally 2.5 turns out is the starting point. I had intermittent backfiring prior to doing the carbs, that had gone away after the carbs were done.
You do not have the required permissions to view the files attached to this post.

glegge
Junior Membership
Junior Membership
 
Posts: 6
Joined: Thu Jun 06, 2019 9:25 am
Location: Newfoundland Flag
Bike year & model: 1984 XV1000 Virago
Sex: Male

Re: Fouled plug(s) and no choke required

PostAuthor: bstig60 » Fri Jul 12, 2019 5:50 pm

Overheating for sure. What plugs are you using and what heat range?
Bill
"It´s a friggen motorcycle, it´s not supposed to be comfortable, quiet or safe. The wind noise is supposed to hurt your ears, the seat should be hard and riding it should make you s**t your pants every now and then. "

Please take the time to edit your profile to show your location. City, State/Province, and Country.
It is easier to help you if we know where you are.


SERVICE MANUAL DOWNLOAD LINK
http://viragotechforum.com/viewtopic.php?f=220&t=31501#p279545

Image
User avatar
bstig60
Mod
Mod
 
Posts: 13443
Images: 38
Joined: Sun Jun 08, 2008 6:16 pm
Location: Sharpes, Florida Flag
Bike year & model: 1999 Yamaha Virago XV1100LC Cruiser,
2003 Honda Goldwing GL1800 Touring
2007 Honda ST1300A
1987 Honda TLR200
Sex: Male

Re: Fouled plug(s) and no choke required

PostAuthor: Flyingdog » Fri Jul 12, 2019 5:57 pm

Plugs say BP7ES..that looks almost mechanical damage the way the ground strap is laid over.
User avatar
Flyingdog
Silver Membership
Silver Membership
 
Posts: 2797
Joined: Fri Jun 23, 2017 2:31 am
Location: Colorado Flag
Bike year & model: 1985 xv1000 Virago
1981 xv750 Virago
Sex: Male

Re: Fouled plug(s) and no choke required

PostAuthor: bstig60 » Fri Jul 12, 2019 6:02 pm

Flyingdog wrote:Plugs say BP7ES..that looks almost mechanical damage the way the ground strap is laid over.

Didn't see the plug number. You may be right about the mechanical damage. At the very least, I would run a compression check if there are enough threads left to get a gauge to seal.
Bill
"It´s a friggen motorcycle, it´s not supposed to be comfortable, quiet or safe. The wind noise is supposed to hurt your ears, the seat should be hard and riding it should make you s**t your pants every now and then. "

Please take the time to edit your profile to show your location. City, State/Province, and Country.
It is easier to help you if we know where you are.


SERVICE MANUAL DOWNLOAD LINK
http://viragotechforum.com/viewtopic.php?f=220&t=31501#p279545

Image
User avatar
bstig60
Mod
Mod
 
Posts: 13443
Images: 38
Joined: Sun Jun 08, 2008 6:16 pm
Location: Sharpes, Florida Flag
Bike year & model: 1999 Yamaha Virago XV1100LC Cruiser,
2003 Honda Goldwing GL1800 Touring
2007 Honda ST1300A
1987 Honda TLR200
Sex: Male

Re: Fouled plug(s) and no choke required

PostAuthor: Flyingdog » Sat Jul 13, 2019 4:20 am

Personally, I'd be leary bout a compression check at this point, just incase it is mechanical. You'd be spinning the engine waaay to fast and could do more damage. If you "are" gutsy enough to turn it over, putting your finger over the spark plug hole will tell ya if there (some) compression. Worst case, you could remove the carbs, camshaft cover, valve covers, (even exhaust header), very slowly turn the engine over by hand and start looking at the valves/camchain/sprockets, listen for unusual noises. Ideally with a bores-cope or someway, just to check things out (piston/valves/cylinder walls etc). Don't know what kinda stores you have over that way, but if you got something equivalent to a Harbor Freight, bore-scopes can be had for less than $100. It would take quite a deal for a piston to get that high to slap a plug (using the correct plugs), but anything is possible. You'd think something would have to be "on top of" the piston, or connecting rod, letting loose to do something like that. Have no idea, but I'd be carefully look'n till you can narrow it down to a possible overheating problem. Just to be sure. That plug has a whole 1/2 of the top edge laid/smashed over..so weird. IMO... too much for just overheating.
User avatar
Flyingdog
Silver Membership
Silver Membership
 
Posts: 2797
Joined: Fri Jun 23, 2017 2:31 am
Location: Colorado Flag
Bike year & model: 1985 xv1000 Virago
1981 xv750 Virago
Sex: Male

Re: Fouled plug(s) and no choke required

PostAuthor: bstig60 » Sat Jul 13, 2019 11:44 am

Remove the plug from the other cylinder, then Pull the cover off the crankshaft bolt on the left side of the engine and use a socket wrench to turn the engine clockwise slowly. See if there is any mechanical noise. If you don't have access to the tools stated above, then the best thing to do at this point if you think something broke, a valve perhaps, is to pull the head off the bike.
Bill
"It´s a friggen motorcycle, it´s not supposed to be comfortable, quiet or safe. The wind noise is supposed to hurt your ears, the seat should be hard and riding it should make you s**t your pants every now and then. "

Please take the time to edit your profile to show your location. City, State/Province, and Country.
It is easier to help you if we know where you are.


SERVICE MANUAL DOWNLOAD LINK
http://viragotechforum.com/viewtopic.php?f=220&t=31501#p279545

Image
User avatar
bstig60
Mod
Mod
 
Posts: 13443
Images: 38
Joined: Sun Jun 08, 2008 6:16 pm
Location: Sharpes, Florida Flag
Bike year & model: 1999 Yamaha Virago XV1100LC Cruiser,
2003 Honda Goldwing GL1800 Touring
2007 Honda ST1300A
1987 Honda TLR200
Sex: Male



Post a reply


  • Advertisement

Return to Yamaha Virago XV1000

Who is online

Registered users: No registered users