Forum Donations
Search
VTF Google Search
 Click Here

1 cylinder cutting in and out (SOLVED)

  • Advertisement

Post a reply

Re: 1 cylinder cutting in and out

PostAuthor: Billll » Fri Jul 05, 2019 5:46 pm

When the pilot screws are completely unscrewed, they remain about 1/2" down in the hole. I'm putting adhesive on my screwdriver to pull them out. Anybody got a better method? I mean without removing the carbs from the engine and pounding them on the bench to get the needles to finally fall out?

Billll
Junior Membership
Junior Membership
 
Posts: 46
Joined: Thu Jun 06, 2019 3:13 pm
Location: Littleton, CO Flag
Bike year & model: 87 xv535 Virago
Sex: Male

Re: 1 cylinder cutting in and out

PostAuthor: Flyingdog » Sat Jul 06, 2019 4:18 am

I find Bostik or Dap putty adhesive on a flat nosed punch works pretty good on somethings. Or better yet, forget the punch, just roll-up a chunk. Shop vac and/or air gun might work, too. All else fails...tip the bike and bang on or shake the carbs.
Thought the pvc for intakes was suppose to make those carbs almost fall out?
User avatar
Flyingdog
Silver Membership
Silver Membership
 
Posts: 2804
Joined: Fri Jun 23, 2017 2:31 am
Location: Colorado Flag
Bike year & model: 1985 xv1000 Virago
1981 xv750 Virago
Sex: Male

Re: 1 cylinder cutting in and out

PostAuthor: Billll » Sat Jul 06, 2019 2:42 pm

The carbs do pretty much fall out but the needles are still attached to the o-rings and do not want to drop out. I have them on the bench right now and got one screw out using a very small (#50) drill bit to get a grip inside the screw slot. Worked on one, but isn't working on the other. When I get both of them out, I'm drilling and tapping a blind hole in the tops of the needles so I can use another screw to pull the things out.
There should be a port somewhere in the carb where compressed air can be used to blow the things out once they're unscrewed but so far I can't find it.

Still haven't found any reason why both carbs should be running so rich. everything seems to be clear and clean. Very frustrating. The new up to date needles I ordered from Omaha are taking 2-3 weeks to get here as it seems that the shipping point of origin is Japan.

Billll
Junior Membership
Junior Membership
 
Posts: 46
Joined: Thu Jun 06, 2019 3:13 pm
Location: Littleton, CO Flag
Bike year & model: 87 xv535 Virago
Sex: Male

Re: 1 cylinder cutting in and out

PostAuthor: Flyingdog » Sat Jul 06, 2019 3:50 pm

Here's a cut - away so you can see what you're deal'n with:
(ignore the red arrow...pointing something out for someone else)

BDS34 Mikuni (2) - Copy.PNG
You do not have the required permissions to view the files attached to this post.
Last edited by Flyingdog on Sat Jul 06, 2019 4:10 pm, edited 2 times in total.
User avatar
Flyingdog
Silver Membership
Silver Membership
 
Posts: 2804
Joined: Fri Jun 23, 2017 2:31 am
Location: Colorado Flag
Bike year & model: 1985 xv1000 Virago
1981 xv750 Virago
Sex: Male

Re: 1 cylinder cutting in and out

PostAuthor: bstig60 » Sat Jul 06, 2019 4:06 pm

Billll wrote:The carbs do pretty much fall out but the needles are still attached to the o-rings and do not want to drop out. I have them on the bench right now and got one screw out using a very small (#50) drill bit to get a grip inside the screw slot. Worked on one, but isn't working on the other. When I get both of them out, I'm drilling and tapping a blind hole in the tops of the needles so I can use another screw to pull the things out.
There should be a port somewhere in the carb where compressed air can be used to blow the things out once they're unscrewed but so far I can't find it.

Still haven't found any reason why both carbs should be running so rich. everything seems to be clear and clean. Very frustrating. The new up to date needles I ordered from Omaha are taking 2-3 weeks to get here as it seems that the shipping point of origin is Japan.


The only port you can get compressed air to is the pilot jet. It's doubtful air will work to push out the pilot screw, but its worth a try.
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: 13448
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: 1 cylinder cutting in and out

PostAuthor: Flyingdog » Sat Jul 06, 2019 4:24 pm

Billll wrote:The carbs do pretty much fall out but the needles are still attached

Billll wrote:The new up to date needles I ordered from Omaha are taking 2-3 weeks to get here as it seems that the shipping point of origin is Japan.


Curious if you're referring to "needles" as the pilot screws or the jet needle? (aka: needle)

Should stick with referring pilot screws as pilot screw(s). Needles are normally referred to the vacuum piston needle or more accurately: Jet Needle. Was just curious, if it "was" the jet needles you ordered, why you think you needed them. They hardly ever wear out. The needle jet goes before the needle..(usually). Steel jet needle vs. Brass needle jet (aka: lets too much fuel in for given throttle) If it was the pilot screws you ordered...disregard this.


Ah hell...you could have driven to Omaha and back in 15hrs. Less if you drive like me. Better yet, could have had some relatives send them. Sounds like even snail mail would have been faster :bg:
Last edited by Flyingdog on Sun Jul 07, 2019 2:59 am, edited 2 times in total.
User avatar
Flyingdog
Silver Membership
Silver Membership
 
Posts: 2804
Joined: Fri Jun 23, 2017 2:31 am
Location: Colorado Flag
Bike year & model: 1985 xv1000 Virago
1981 xv750 Virago
Sex: Male

Re: 1 cylinder cutting in and out

PostAuthor: Billll » Sat Jul 06, 2019 5:19 pm

The site crashed just as I posted "submit" and my answer disappeared in the ether. The compressed air trick works, but the port you hit with the air is under the main jet block at about 8 O'clock from the Main needle jet. I drilled and tapped the pilot needles 2-56 and I'll put up a picture as soon as I find a 2-56 screw to install in one of them. Seems the hardware store has several small sizes mixed together. It behooves one to actually measure the screw before buying it.

The carbs are off the bike, and they do come off very easily now, and in pieces on my bench. I can't find anything wrong with them that would cause both of them to run so rich and it's quite frustrating.

Billll
Junior Membership
Junior Membership
 
Posts: 46
Joined: Thu Jun 06, 2019 3:13 pm
Location: Littleton, CO Flag
Bike year & model: 87 xv535 Virago
Sex: Male

Re: 1 cylinder cutting in and out

PostAuthor: Billll » Sat Jul 06, 2019 6:35 pm

OK here's a pilot needle with my removal tool installed. This is a 2-56 allen head screw with a bit of heat shrink applied to it. The pilot screw is tapped about 3/16" down as I don't need a whole lot of thread engagement to pull the part.
Needle and removal tool.JPG

I could have just drilled the screw 1/16" deep, then drilled a cross hole near the top so I could reach down with a bent piece of wire and pull the thing out, but that didn't occur to me until after I'd finished the thing.
You do not have the required permissions to view the files attached to this post.

Billll
Junior Membership
Junior Membership
 
Posts: 46
Joined: Thu Jun 06, 2019 3:13 pm
Location: Littleton, CO Flag
Bike year & model: 87 xv535 Virago
Sex: Male

Re: 1 cylinder cutting in and out

PostAuthor: Billll » Thu Jul 11, 2019 3:00 pm

I am not as familiar with the BS32 Mikunis as I am with some of the others so I gotta ask: Is there normally an insert of some sort at the bottom of the pilot screw passage below the o-ring? The needle looks very small and the hole it goes into seems rather large.

I can't find anything else wrong or missing and both carbs are dumping way too much gas into the engine. The fact that the o-rings and washers were missing from both carbs makes me wonder what else the previous "tuner" left out.

Billll
Junior Membership
Junior Membership
 
Posts: 46
Joined: Thu Jun 06, 2019 3:13 pm
Location: Littleton, CO Flag
Bike year & model: 87 xv535 Virago
Sex: Male

Re: 1 cylinder cutting in and out

PostAuthor: Billll » Fri Jul 12, 2019 2:20 pm

Progress (?) report: While testing the latest teardown and cleaning, a backfire in the front cylinder blew the pilot screw completely out of the carb. The motor immediately seemed to begin running better aside from backfiring at idle. Front plug no longer showing signs of fouling, back plug way too rich. I pulled the other pilot screw out and the motor runs fairly cleanly except at idle where it backfires a lot. So: runs very rich with the screws in, runs much leaner with the screws out.

It also seems the P.O. pretty much stripped the threads in the carb used by the pilot screws. I have some fixes for that which I'll post when I get the mixture settings closer to correct.

bstig60 was right to point to the pilot screws in the first place. Now I need to figure out exactly what the issue is here.

I'm so close I can almost taste the bugs in my teeth.

Billll
Junior Membership
Junior Membership
 
Posts: 46
Joined: Thu Jun 06, 2019 3:13 pm
Location: Littleton, CO Flag
Bike year & model: 87 xv535 Virago
Sex: Male

Re: 1 cylinder cutting in and out

PostAuthor: Billll » Tue Jul 16, 2019 10:26 pm

Close inspection of the pilot screw holes reveals that they have both been stripped out. The springs under the pilot screws were holding them well out, causing both cylinders to run very rich. The pilot screws have a 3mm dia stem with a tapered point to meter the idle fuel, and the pilot screw location holes are about .238" dia. M6 x .5 taps are impossible to find so with a bit of JB Weld down the holes, both are now tapped to 1/4-28. set screws in this size now screw all the way down to the bottom. Drilling out the set screws, and tapping the holes to M3 x .5, I made some needles from 3mm brazing rod, added a simple tapered point to the business end and threaded the other. Screwing the assemblies together, they replace the stock pilot screws, keeping in mind that instead of 2 turns out, one now goes only about 1/2 turn. The engine no longer runs rich, but is now running rather poorly with the front cylinder seeming to be running better than the rear. Perhaps I should not have been quite so eager to reduce the main jet size. The good news is that a main jet change does not require removing the carbs again.
Fwd Carb Pilot hole 1.jpg

Fwd carb pilot hole
Rear Carb Pilot Hole 1.jpg

Rear carb pilot hole. Note remains of original threads near the bottom of the hole, 1/4-20 threads near the top, 3.2mm needle passage, and fuel port.
You do not have the required permissions to view the files attached to this post.

Billll
Junior Membership
Junior Membership
 
Posts: 46
Joined: Thu Jun 06, 2019 3:13 pm
Location: Littleton, CO Flag
Bike year & model: 87 xv535 Virago
Sex: Male

Re: 1 cylinder cutting in and out

PostAuthor: Billll » Wed Jul 17, 2019 6:24 pm

Interesting: Fired it up just now to test the latest tweak, and it ran perfectly. Took it out on the street and zowie! lots of power and everything. Then it quit, out of gas. Quick dumb question: What kind of pressure does the stock Yamaha fuel pump deliver? P.O. had installed one from NAPA which as I remember puts out somewhere in the range of 5-10 psi, sufficient to fill a Holley 4-bbl from the far end of a full-sized car.

Billll
Junior Membership
Junior Membership
 
Posts: 46
Joined: Thu Jun 06, 2019 3:13 pm
Location: Littleton, CO Flag
Bike year & model: 87 xv535 Virago
Sex: Male

Re: 1 cylinder cutting in and out

PostAuthor: Billll » Wed Jul 17, 2019 10:12 pm

Fuel Pump Pressure Test: This quick test won't tell you what pressure your pump is delivering, but it will tell you if your aftermarket automobile pump is delivering too much. If you suffer from fouled plugs, black smoke, and generally poor performance, simply attach the Billlls Low Pressure Fuel Supply Module to your bike, after disconnecting the existing pump,
Fuel Pump Test.JPG

and fire that baby up. If the engine runs normally, does not smoke, does not foul plugs, etc, etc, then your pump is too enthusiastic and needs either some sort of pressure regulator, or a lower pressure replacement. I've seen OEM replacements on e-bay for as little as $15 so this is probably the ticket.

The pump that came with my bike is marked as a 2.5-5psi unit which qualifies as low pressure if you're using it in a car. Seems it's a bit high for the Yamaha.
You do not have the required permissions to view the files attached to this post.

Billll
Junior Membership
Junior Membership
 
Posts: 46
Joined: Thu Jun 06, 2019 3:13 pm
Location: Littleton, CO Flag
Bike year & model: 87 xv535 Virago
Sex: Male

Re: 1 cylinder cutting in and out

PostAuthor: Flyingdog » Thu Jul 18, 2019 2:29 am

Billll wrote: What kind of pressure does the stock Yamaha fuel pump deliver?


Generally 4-5 psi.

Billll wrote:The pump that came with my bike is marked as a 2.5-5psi unit which qualifies as low pressure if you're using it in a car. Seems it's a bit high for the Yamaha.


Hmmm..If the pump is marked: 2.5-5 psi, guess I'm not sure why someone would question it. Don't think Yamaha would use a fuel pump not designed for their bikes. They wouldn't sell.

VTstore sign.PNG
You do not have the required permissions to view the files attached to this post.
User avatar
Flyingdog
Silver Membership
Silver Membership
 
Posts: 2804
Joined: Fri Jun 23, 2017 2:31 am
Location: Colorado Flag
Bike year & model: 1985 xv1000 Virago
1981 xv750 Virago
Sex: Male

Re: 1 cylinder cutting in and out

PostAuthor: Billll » Sat Jul 20, 2019 8:14 pm

I built a pressure regulator and installed it. My gage says it's delivering 2 psi and the engine runs much better although it's still pretty rich, more so on the rear cylinder but then the rear cylinder needle is sized to run it a bit richer than the front. The pump is not a Yamaha pump, but an automotive one. I question everything. Once bitten, twice shy and all that.

Trying to reason my way through this, The bike starts easily enough but has a slight hesitation when I roll on throttle from a modest cruise which suggests that the pilot screws need to come out just a smidge. This leaves the main jets as the culprit for the sooty spark plugs and based on past experience I'd say the front could go down one more size, and the rear down 2. The problem with this is that it's a pretty good bet the bike ran fine with the original jets and stuff in it so there's some other problem causing the rich condition and I'd hate to fix it with small jets, then have it go away by itself and leave me with burned exhaust valves.

The main jet needles have been revised 3 times since 87 and the new ones I ordered from Omaha are being shipped direct to me from Japan. This is making for a really long wait and leaves me with visions of some old Japanese fisherman poling a sampan across the Pacific while pausing occasionally to catch some squid for meals. :bg:

Billll
Junior Membership
Junior Membership
 
Posts: 46
Joined: Thu Jun 06, 2019 3:13 pm
Location: Littleton, CO Flag
Bike year & model: 87 xv535 Virago
Sex: Male

Re: 1 cylinder cutting in and out

PostAuthor: Billll » Tue Jul 23, 2019 10:33 pm

More stuff and pictures: Here's the pressure regulator
Fuel Press Reg.JPG

Primary fuel flow is through the lower passage marked with arrows. The mid-level passage is drilled about 2/3 of the way through from the right, and the line is routed back to the fuel tank using the tank vent line connection. I figure the tank cap probably vents the tank just fine. I drilled 1/8" down from the top, through the mid line and into the lower line. Drilled again to the return line,and tapped 1/4-28, and installed a 3/16 ball bearing and a soft spring to hold it in place. Apply sealant to the set screw, and screw it most of the way in. Test the rig and find fuel supply to the carbs is holding at 2 psi. Perfect.

This helped the rich condition, but didn't solve it. Somewhere in the carbs, there is a leak dumping gas into the engine. I have now jetted 3 stages leaner and the plugs are still black. At this point I'm grasping at straws. What about those rubber plugs on the bottom of the jet block? If they were old, stiff, and not perfectly tight, would this have an effect? I suppose it would be easy enough to pull the blocks out and re-seat the plugs with a bit of sealant, but if this doesn't actually have any effect, why do it? OTOH those plugs must serve some function or the factory wouldn't have put them in there.

One other thing, here are the carb to air chamber stack I built.
Inlet tube 1.JPG

Inlet tube 2.JPG

I wrote the dimensions on them so no one would have to memorize them, just print the pic and go. These are made from 2" nominal black PVC schedule 40 pipe. They fit closely in the air box and over the carbs. To remove the carbs, simply slide them up. When done, install the carbs and slide them down.
You do not have the required permissions to view the files attached to this post.

Billll
Junior Membership
Junior Membership
 
Posts: 46
Joined: Thu Jun 06, 2019 3:13 pm
Location: Littleton, CO Flag
Bike year & model: 87 xv535 Virago
Sex: Male

Re: 1 cylinder cutting in and out

PostAuthor: Billll » Thu Aug 01, 2019 6:27 pm

Fixed? I gave up on the original carbs and threw together a single carb manifold. If there is demand I'll go through all the dirty details, but bottom line I've mounted one of those Chinese flat slide Kehin knock-offs. 32mm which is close enough to 1-1/4 as not to matter. The manifold is crude for sure with no graceful curves, but it seems to work fine. Bike starts easy, runs strong, idles slow, and no backfire. I'll be checking the mixture today and tomorrow to see how close I am, and start looking for one of those 90 degree inlet adapters for an air filter. At low speed and wide open throttle, it spits a bit of gas out the inlet, but no obvious problems through the rest of the range.

Shades of the old Triumph 500 Tiger!
Single Carb Right 4.JPG

Here's the other side:
Single Carb Right 3.JPG

Fed through the pressure regulator at 2 psi.
You do not have the required permissions to view the files attached to this post.

Billll
Junior Membership
Junior Membership
 
Posts: 46
Joined: Thu Jun 06, 2019 3:13 pm
Location: Littleton, CO Flag
Bike year & model: 87 xv535 Virago
Sex: Male


Previous

Post a reply


  • Advertisement

Return to Yamaha Virago XV535

Who is online

Registered users: abidali69, Cusstout 1100, gswatson, rchawaii