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exhausted our brains


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okay...so My fellow Venture Rider buddy and I have exhausted our brains...

need help with 2 main issues.

 

Idles okay now...

 

bought a 88 VR last fall that would not run unless half choke..knew it needed carb work..this spring we pulled the carbs, put in new jets, new pilot jet, cleaned them up well, put in new idle air mix screws, 4 diaphrams are good..resistance through the caps is good. clipped wire ends and recapped at cylinder end

 

1. When air mixture needle is turned completely closed on cylinder 2 , nothing changes at all.. no change ....new plugs all seem look the same..seemed to work at one point, but now nothing

 

2.also stumbles the minute you give it throttle...especially when you twist it fast..not as much with gradual throttle. once you get above 2200 RPMs , it seems to clear up a bit..but something is still not right..

 

 

Not sure where to look next..totally baffled...any expert help requested and desired

 

Thanks

 

Clay

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1. When air mixture needle is turned completely closed on cylinder 2 , nothing changes at all.. no change ....new plugs all seem look the same..seemed to work at one point, but now nothing

 

"...once you get above 2200 RPMs , it seems to clear up a bit"

 

Classic symptom of a plugged carburetor pilot circuit.

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Something I think you overlooked. Hose going from fuel pump to carb!. Suggest replacing that hose. Sometimes the rubber inside that hose breaks down and causes nothing but troubles. So may I suggest, you once more remove and clean the carbs, making super sure you have the right jets in the proper spots, replace the hose and be happy. My guess is that you have a bit of rubber stuck in there,, wouldn't take much.

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Is it a to much fuel stumble when you wick on it (twist the throttle quickly) or is it a starvation stumble/bog? How is your air filter and are you trying to get it to run right without the air filter or airbox cover off - gotta have filter and cover on when tuning.. It is not uncommon for these old scoots to oblong the orvice that the metering rods ride in - this can result in a fattening up of the idle/mid range circuity and cause stumbling like you mention. You might take a couple minutes to read thru this: http://www.venturerider.org/forum/showthread.php?86325-Carb-metering-rod-question&highlight=tweeks+metering

If your machine is not Canadian it will not have the normal "E" clips and multiple slots for adjustments on the meter rods. You will need to shim the rods with nylon washers. My bike, Tweeks, had a similar problem and I found by dropping the meter rods .065 worked perfect. Canadian 1st Gens have normal E clip adjustment for doing the same thing.. Does any of this make sense to you?

If you problem is a lean condition you could also try raising the rods and see what happens.

Another issue that I have experienced in dealing with what your talking about has to do with high resistance in the plug caps.. Maybe try unscrewing the caps from the wire, trim the wire back a 1/2 inch and rescrew the caps back on.. Also. depending on the caps - they may have resistors in them you can clean up.. Of course, the best thing to do is replace the caps - nothing like new if you have an issue there.

You fellers got a set of gauges or a way to check carb sync? I would double check the diaphrams for pin holes, check the area where the diaphram attaches to the slides real well, triple check the slides for ease of movement in the throats, make sure the cover orings are in correct place and in good shape so its not sucking air and then drop a carb sync on it.. You might be surprised how far out it is after a dismantle of the carbs like you did..

 

edit - what a dork wad am I,,,,, I just reread your original post and noticed you had that covered already:doh: my bad:detective:

Edited by cowpuc
cause I told Chock to do something he already did - dahhh
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Reread your explaination of issues again Chock (I am really really thick skulled so sometimes it takes me FOREVER to comprehend - sorry bout that)... Another possibilty if its a "Fat" stumble is a float height adjustment or leaky float valve with a result of flooding a carb.. Did you guys check your float heights when you had it apart? Do you by any chance notice small dribbles of fuel on the overflow lines? If you look under the bike just in front of the swing arm you should notice the four over flow tubes hanging together. You might just check the ends of those four lines for dampness.. You could also centerstand the bike, turn the key on and off until the fuel pump stops pumping so the bowls are full - check the lines again, drain the bowls one at a time into baby food jars and see if you have one that shows over fueled.

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We have synced it with a carb tune...The sync is pretty close..

 

We have taken the carbs totally apart and cleaned things well twice....nothing plugged..really checked the pilot jet circuit ...

 

Hard to tell if its a too much gas or not enough...Just lots of backfire and popping while riding in just about any gear except 2nd.

 

checked the reistance in plug caps ..okay there...

 

Checked float height roughly when in the cars... no overflow for sure...not a stuff float either..

 

And yea...and taking it out on the road..it coughs and bacfires above 3000 too

 

This one has us both really stumped, and really disappointed...Usually we get stuff all worked out..

 

I'm thinking maybe taking it to a professional for an ultrasonic cleaning.

 

Going to order new wires and caps too.....really dont think thats it at all, but never can hurt

 

Clay

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Might try another set of new plugs - these D plugs are very sensitive. Put in new plugs, start - if it will - with no choke, use as little choke to start it as possible. Let it idle and spit check each header to see if its hitting on all four - see if you can chase it down to one cylinder acting up. How olds the gas? Check it for moisture? Do a compression check? - may have a tight valve or two. Any funny stuff going on with the tach? Any odor or hint of anti freeze in exhaust?

Also double check for vacuum leaks. Could be you have the spark advance vacuum line hooked up wrong or it is leaking? Top of my head thought - the 84 advances off the intake on #2 - same nipple you would use for syncing..

Any idea if the previous owner may have been fighting the same thing you are fighting? I only ask because its possible that someone roasted a TCI - picked up a TCI for an 83 thinking they were all the same. 83 had its own box, 84 to 89ish were the same. Only saying this cause it almost sounds like you could have something happening with spark advance..

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Thanks for the thoughts..

 

Had put in new plugs...Going to try new wires too , but really dont think that's it..

 

I've been thinking about the TCI possibly..wondering about a spark advance.don't know though..the PO was not really much of a rider..Did not know a whole lot..

 

did check for all possible vaccum leaks...checked the spark advance line too...seems to be working

 

Also thinking about a compression check, but bike only has 40,000 miles.. would not think valves could be too tight yet.

 

I'm thinking about taking carbs apart and having them ultrasonically cleaned, then try again..

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