Forum Donations
Search
VTF Google Search
 Click Here

Shoot me NOW! BDS carbs driving me nuts.

  • Advertisement

Post a reply

Shoot me NOW! BDS carbs driving me nuts.

PostAuthor: Dario » Tue Jul 10, 2018 2:04 am

in February i decided to buy a "project" bike to help me while away time in retirement. It all seamed like a good idea seeings that i'm a veteran mechanic of years gone by.

I purchased a 1989 XV535 that had the carbs missing. before committing to the deal i had already found a set of BDS carbs of a 535 for about £110 so I sort of knew that I wouldn't get snookered with having to buy a bike cheap and very expensive carbs.

As of yesterday, i think i have had the carbs off and apart in excess of 10 times and the bike fully rebuilt with inlet trumpets and air filter/ tank in-place 5 times and road tested once.

the problem is as follows:-

1. the bike has a very rich idle. when i say rich i mean black smoke from the exhaust and spluttering to clear from low revs.
2. when the throttle is beyond the 1/8 - 1/4 opening it runs fairly well with relatively clean pickup in the upper rev range.
3. when the revs drop down to idle it all goes to pot again and you can visibly see the blackness of the exhaust.
4. the bike has been fitted with an aftermarket exhaust by MOTAD (no longer in existence) with this being a 2-1 exhaust so can differentiate from front or rear cylinder problems.
5. no amount of alteration of the pilot air screw / mixture screws causes the bike to run better. The bike running can be made worse, but not better.

Works carried out so far, but not listed in the order they may have been undertaken.
1. fuel tank under seat removed and cleaned 2 times.
2. fuel pump replaced
3. fuel filter replaced numerous times
4. spark plugs replaced numerous times
5. coil packs exchanged from another running 535 and originals left on the other bike, and no change (other bike runs fine with old coils).
6. fuel relay bypassed to allow constant fuel supply (to eliminate and temporary issues with this component)
7. pickup coils on the ignition circuit check for resistance and correct agains spec.
8. pickup coils removed and visually inspected for potential brake-down in wiring.
9. carbs fully stripped and cleaned with carb cleaner and compressed air half a dozen times.
10. carbs fully stripped and cleaned in ultrasonic bath with concentration of carb cleaning fluid and run for 2 hours each time at 80 degrees Centigrade.
11. all passages in the carbs checked with jet cleaning files/brushes.
12. main diaphragms in good condition
13. needle jet clips in the correct position. Tried jets in higher clip position to lower needle but not benefit effect.
14. check jet sizes against technical spec and no jets mixed in wrong locations.
15. checked choke mechanism and if fully closing (no evident problem found)
16. replaced pilot fuel jets (new jet (hole through it) look so much smaller) but not a scrap of difference.
17. fuel level in carbs checked, and sight tubes left in-place to see if the fuel level alters in running)
18. check charging and battery voltage whilst running (runs at between 12.5v and 13.5 v dc)
19. changed oil and filter after side cover removal for the hell of it lol.
20. rubber engine connectors checked and appear it be in good condition.
21. carb synchronised as bees as possible give the poor running at low revs.
22. carb gasket and seal kit installed
23. rubber bungs in the jet block have been replaced at they were brittle.
24. both main jets have been replaced with Uk spec jets. 137.5 front and 135 rear.
25. needles inspected and 10 in front carb and 9 in rear carb.
26. new fuel all the time as its using huge amounts under test.

the carbs came from europe, and i have no idea of their mileage, but under inspection all parts of the body and butterfly shaft appear un-worn.

SO, if anybody out the in Virago land has any experience that they can pass on to help me resolve this situation, i'd much appreciate it. failing this i'm going to have to take the carbs of my perfectly running other 535 and them them on this problem bike. this is my very last resort as i don't want to screw up anything on that bike as its a beauty.


Please help.

Dario

Dario
Junior Membership
Junior Membership
 
Posts: 4
Joined: Tue Mar 13, 2018 5:48 pm
  Flag
Bike year & model: 1990 virago 535 & 1994 Virago 535
Sex: Male

Re: Shoot me NOW! BDS carbs driving me nuts.

PostAuthor: bstig60 » Tue Jul 10, 2018 6:37 am

Check the choke to make sure it isn't dumping fuel into the mix. There are O rings in the pilot screws that should be replaced when you rebuild the carbs... If when you adjust the pilot screws clockwise and it doesn't shut that cylinder down or starve it of fuel enough that you can hear the change, then the O ring is probably bad or you have a vacuum leak somewhere.... Initial setting on the pilot screws should be 2.5 turns out from a soft seat. Also, check the pilot jet size to make sure it hasn't been changed from stock.
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: 12667
Images: 38
Joined: Sun Jun 08, 2008 6:16 pm
Location: Sharpes, Florida Flag
Bike year & model: 1999 Yamaha Virago XV1100LC Cruiser,
1982 Yamaha Seca XJ750RJ w/factory touring package
2003 Honda Goldwing GL1800 Touring
Sex: Male

Re: Shoot me NOW! BDS carbs driving me nuts.

PostAuthor: Dario » Tue Jul 10, 2018 7:41 am

bstig60 wrote:Check the choke to make sure it isn't dumping fuel into the mix. There are O rings in the pilot screws that should be replaced when you rebuild the carbs... If when you adjust the pilot screws clockwise and it doesn't shut that cylinder down or starve it of fuel enough that you can hear the change, then the O ring is probably bad or you have a vacuum leak somewhere.... Initial setting on the pilot screws should be 2.5 turns out from a soft seat. Also, check the pilot jet size to make sure it hasn't been changed from stock.



Thats for the feed back on this.

1. yes pilot screw is fitted with new spring, metal washer and rubber o ring and as of the last few hours it was definitely there and in place.

2. yes to the pilot screw setting at 2-2.5 out from a soft seat, but no the i cannot get the engine to stop running via the pilot screws! I have another 535 that runs beautiful and yes the either screw will shut down the respective cylinder. this one doesn't!

3. it is difficult to see the mercury on the vacuums gauges, but i've sprayed the manifolds with carb cleaner and i can't find any appreciable change in engine speed when spraying.

4. just changed the pilot fuel jet for new one (correct size) and in comparison to the old jet it looks about 2-3 times smaller.

5. i haven't tried blanking off the choke just yet (its on my list) but under inspection i have not found any fuel in the galleries associated with either coke.

what i have just discovered (like 20 minutes ago) when i closed off both pilot screws there was no change in engine speed or anything. It just kept running fairly roughly. now because it almost impossible to see in to the inlet of the carb because of the design of the air box/frame etc, however i did set my phone to video and stuck it in there!

What i did discover was the fuel was passing the closed needle jet and the engine was running on this un-metered fuel. Now i don't know at the moment if with the throttle closed, the slide down against its seat if this should stop fuel from coming out of the float chamber. my guess its it shouldn't. If i can clarify this, and its supposed not to allow fuel through, its highly lightly the the needle and associated main nozzle is excessively worn.

[http]https://photos.google.com/share/AF1QipP7U1odZSyRpSdbKJQzO6rh0jqy4tT1ElgKRoBOyig0ceTw6SLEVGg_W7x0gJBuGw/photo/AF1QipNEnrpYMj11G0ivKvvq345OlClG-UUvF78lf2dk?key=SjY1VjFIWk52QkM4eEFPd1JFd0pfUFJCS2F1UFF3[/http]

Dario

Dario
Junior Membership
Junior Membership
 
Posts: 4
Joined: Tue Mar 13, 2018 5:48 pm
  Flag
Bike year & model: 1990 virago 535 & 1994 Virago 535
Sex: Male

Re: Shoot me NOW! BDS carbs driving me nuts.

PostAuthor: bstig60 » Tue Jul 10, 2018 8:09 am

If I understand correctly, fuel is coming from the Main Jet to let the engine run. If that is true, either the slides are not closing all the way or the needle jet is set too high....
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: 12667
Images: 38
Joined: Sun Jun 08, 2008 6:16 pm
Location: Sharpes, Florida Flag
Bike year & model: 1999 Yamaha Virago XV1100LC Cruiser,
1982 Yamaha Seca XJ750RJ w/factory touring package
2003 Honda Goldwing GL1800 Touring
Sex: Male

Re: Shoot me NOW! BDS carbs driving me nuts.

PostAuthor: Dario » Tue Jul 10, 2018 8:17 am

bstig60 wrote:If I understand correctly, fuel is coming from the Main Jet to let the engine run. If that is true, either the slides are not closing all the way or the needle jet is set too high....



Yes that what it looks like to me! I have check the clip setting and its set to the middle of five positions which is standard as per the manual.

I've measured the needle valve and there is not real difference in the valve taper for the first half inch ( just under the clip measured towards the tapered end) both needles measure the same.

regarding the slides, each appear to be bottoming out.

Given that the history of the carbs is unknown to me, and the condition of the pilot fuel Jet (if you check the link i attached to my initial post) its most likely that the emulsion tubes are worn to an egg shape. This i can't see with the naked eye.

what do you think?

Dario

Dario
Junior Membership
Junior Membership
 
Posts: 4
Joined: Tue Mar 13, 2018 5:48 pm
  Flag
Bike year & model: 1990 virago 535 & 1994 Virago 535
Sex: Male

Re: Shoot me NOW! BDS carbs driving me nuts.

PostAuthor: Dario » Tue Jul 10, 2018 3:08 pm

i think i found the problem finally.

https://youtu.be/ivqb3V6qXzA

looks like the needle jet / nozzle/ emulsion tube is excessively worn and is letting by un-metered fuel.

Dario
Junior Membership
Junior Membership
 
Posts: 4
Joined: Tue Mar 13, 2018 5:48 pm
  Flag
Bike year & model: 1990 virago 535 & 1994 Virago 535
Sex: Male

Re: Shoot me NOW! BDS carbs driving me nuts.

PostAuthor: Flyingdog » Tue Jul 10, 2018 5:01 pm

Pretty common..hardly never-ever looked at. I would say the majority of home mechanics overlook how vital this part is.. :GJ: And..as you've seen, can drive ya nuts, cuz nothings' making sense. With that needle fairly loose in the slide, pretty damn easy for it to become bias to one side or the other in the needle jet. Will wear faster than the needle, for sure. Gixxers always seem the worst. Real crappy material.

http://www.factorypro.com/
http://www.jetsrus.com/

Mikuni-left...Hitachi-right
You do not have the required permissions to view the files attached to this post.
User avatar
Flyingdog
Silver Membership
Silver Membership
 
Posts: 1785
Joined: Fri Jun 23, 2017 2:31 am
Location: Colorado Flag
Bike year & model: 1985 xv1000 Virago
1981 xv750 Virago
Sex: Male



Post a reply


  • Advertisement

Return to Yamaha Virago XV535

Who is online

Registered users: califbikeguy, Google [Bot], patspiercing, RMSIII