Author grazingazer Date Mon Jun 16, 2008 8:19 am Type KB Fix
Category Tech Tips
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Posted: Mon 06 16, 2008 12:33 am Post subject: Carb problem on XV750/XV700 - read this if you have problems

Came across a situation that all Virago owners should be aware of - defective/failed floats causing carbs to run rich. The floats I found the problem in are PN 10L-14985-01-00 and are used in the following:
-XV1100 '86-'87
-XV700 '84-'87
-XV750 '81, '83 (not '82)
-XV920 '83
-XV750 '88
-XV1000 '84-'85

A '85 XV700 came into my small shop a while back... owner said he had tried to rebuild carbs and couldn't get 'em to work right. I snickered, thinking "rookie" - but sometimes even a pro doesn't figure it out the first go around

I began the usual - pull those carbs, rebuild, install...test according to the book, all good, go for a ride. Hand keys over to customer... and have him return in a week complaining of fouling plugs. Start over at step one. Repeat about 3 times

After WAAAAAY too much time spent piddling with these carbs I finally decided just to drop the floats into a bowl of gas to see what happened. This is not a test in the book, I guess they expect the floats to last forever. At first I could not believe my eyes... one set of floats (the ones on the cyl that was causing all the problems) sank on one side. Half of the float stayed above the fuel, half fell below the surface.

I have handled quite a few of these solid polymer floats, but never seen one fail...till now. Unlike the old brass floats, these always seem to be functional... but this set failed sure as hell.

I even tried to dry out the floats...left them on top of my A/C condensor outside during a recent heat wave... when tossed back into the bowl, they floated a bit more, perhaps 5% of one float above surface, the other holding it's own. I let it sit for over 48 hrs, no change. I then tossed in some STP carb cleaner, making the mixture in the bowl about 50% carbcleaner/gas... after another day, no change. I don't know why it failed, all I know is it doesn't float any more.

so ...bottom line...
- when rebuilding these carbs this is a simple test... toss the floats pivot down into fuel... they should remail 25-40% above the surface, and both sides should float the same amount.

- when setting up carbs that have been rebuilt, use clear fuel line (avail at my local parts store as lawn mower fuel line) to attach to the drain and check float bowl fuel level... a most valuable check on how the innards are working, even though it is a pain

HINT - if you read this far you deserve something ... so here are some tips for testing/adjusting float bowl level

- when you rebuild the carbs, leave out the float bowl screws that are inside and furthest from the intake. Get one of the right angle screwdrivers and an extended phillips tip to pull/install the other three screws. For testing only 2 screws are needed, I installed the back outer and the front inner screw, easily done with the rt-angle drive

- in order to install the rear inner screw, use hemostats (surgical clamps/roach pliers) to hold the screw by the washer. Push it up into the hole, then use a thin small tip screwdriver to screw it in. Difficult, but not impossible to do. Keeps from having to pull the carbs, saves hours. Float bowl screws do not (and should not) need to be super tight, just snug and a pinch.

The factory manual says you must adjust float level on rebuilt carbs... but it's hard to believe they expected you to pull the carbs each time you adjust the floats... it can be done, after practice I can do it in 5 min on each side. When you have the float level correct, then install final 2 screws on each carb and GO FOR A RIDE

Good luck - hope this problem doesn't bite you, but the test is VERY simple, so do it when you have the carbs apart and off the bike

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grazingazer Posted: Mon Jun 16, 2008 8:19 am    Post subject [ KB ]

[ Article updated...grazingazer ]

Category: Tech Tips
Type: KB Fix

Author: grazingazer

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