My 86 runs like crap

[Sheradan]

Put diaphams and slides in this newly aquired 1986. Fresh gas and it fires right up. Will only run with the choke on until fully warm. Then will idle nice (after sync) but coughs and backfires when I give it gas. Any ideas for me to check out when I work on it again tomorrow?

[Squidley]

Have you done a complete tune up? Wires Plugs and caps? Thats exactly where I would start if you haven't done it, and have you replaced the fuel filter?

[CrazyHorse]

Put diaphams and slides in this newly aquired 1986. Fresh gas and it fires right up. Will only run with the choke on until fully warm. Then will idle nice (after sync) but coughs and backfires when I give it gas. Any ideas for me to check out when I work on it again tomorrow?

 

Air leaks from the boots top and bottom make sure they are seated properly and the nipples are covered up and not leaking. Did you put diaphrams in right?

[Marcarl]

Are the little rubber o-rings in place under the tit on the cover of the diaphrams?

[Yammer Dan]

Sea-Foam Strong

[safetyguy]

Based on your symptoms --

 

I think the diaphragms aren't seated in the groove because they were pulled out when you put the carb side cover on. The spring applies a lot of force when you attach the cover and unless you have three hands, it is hard to keep the diaphragm seated.

 

Try doing reseating the diaphragms again but have a friend hold the slide with a screwdriver from top of the carb (through the air filter box) as you attach the side cover plate.

 

Look at step #8 in this older post

 

[ame=http://www.venturerider.org/forum/showthread.php?t=19269]Carb Diaphram Replacement - VentureRider.Org[/ame]

 

Good luck!

[Sheradan]

Diaphrams are all in right. Put my hand over the #2 carb while it was running and the RPM increased. I was working on body work today so didn't get a lot of time on the problem.

[yamadawg]

Just a suggestion since I am not even close to being as sharp or informed as most folks on here but have you checked to see that the emulsion tubes are seated and as tight as they should be? I had an issue with OK idle but crappy acceleration and mid to upper range rpm running on my '88VR during a Sturgis trip in '07. It would up being the emulsion tube in one carb. Being a layman it looks like the main jet to me. Looking down from the top in the air box you could see the tube (gold in color) following the needle on the end of the slide in and out when the engine was running and you accelerated. The thing is two piece and is held together from the other side and had came unscrewed. The fix was simple except I overtightened teh tube and had to replace it. No problem ever since. I thought I would share this, just in case...

[Sheradan]

What if the boost sensor is un plugged? I unplugged it to use the port for the carb stick. Could this be the problem? The 83 had a port on the #2 carb for the sensor. This is plugged into the intake manifold.

[Dano]

Usually doesn't hurt, plug it back in. The 83 was the only year they used the upper carb throat for the boost sensor, and the TCI has to match. I think your problems are in the carbs, tho.

 

Good luck

[GigaWhiskey]

Check the screws on the diaphragm covers. I forgot to tighten one or two on mine when I changed mine. It popped when I drove it but seemed to run fine at idle.

[MasterGuns]

Sheridan, Are you trying to run this thing without the airbox one, filter installed and the lid on and tight? This motors run like crap if you are running one with out the airbox installed. If you are, try installing the airbox, filter and the lid, and try it again.

[Sheradan]

Sheridan, Are you trying to run this thing without the airbox one, filter installed and the lid on and tight? This motors run like crap if you are running one with out the airbox installed. If you are, try installing the airbox, filter and the lid, and try it again.

 

Yes I am. The air box is off. Will try with it on.

[Harmonicashawn]

This may be worst case scenario, but if it has been sitting for a long time the carbs may be "Varnished". Meaning the internal passages and air bleeds are plugged up. The best solution in this case is to strip the carbs and dip all the cast pieces in a caustic (available at auto parts stores), then blow out the passages with compressed air. You can also run lots of "carb / fuel injector" cleaner through (the kind you mix in the tank). You can check for manifold boot leaks by spraying some ether around the base of the carbs when it is running (if the RPM rises there is a leak). Hope this is helpful---Shawn

[TexasFlyer]

Actually, MasterGuns makes a really good point - it will pop, backfire and make all kinds of ugly unless the airfilter and airbox is in position and tightened up. I used to get a kick out of looking down into the carbs from above and watching the sliders move when I revved the engine --- until a particularly nasty one of those "backfires" tried to reach up thru the opening and grab my face. Close call. Never again. Once is enough.

[GaryZ]

I agree with a couple others here.

Running without the air box will create a very lean condition with stock jetting.

The bike will seem to run OK at idle and at light throttle.

[Sheradan]

Here is what the problem was. Intake manifolds leaked. Somebody used some kind of sealant that looks like caulking. Took everything out, cleaned and sealed intakes properly. New plugs and plug wires. Somebody had tried to sync carbs with intake leak because they were so far out it idled at 3000 rpm. Got everything synced and now it runs like a Venture should. Really close to getting this thing on the road.