problems with carbs any suggestions would be great!

[Shanefromwashington]

Greetings fellas! been working with my father in law on his 1986 venture that we got him for chrismas (sheriff) we removed the gas tank and treated it with the epoxy kit, we removed the exhaust system and cut open the collector and took the baffels out (they where shot) basically rebuilt the collector, pulled the carbs and cleaned them and reinstalled, also we pulled the front brake calipers and are in the process of replacing them with some rebuilt ones. Ok heres where we are at, Got the bike started last night, just put the fuel tank on and hooked up the fuel lines and started it, it started right up, but when you wick the throttle it wants to die, so..... I turn the choke up to about half, and let the rpms build, then when you wick the throttle it seems to run fine, it seems that the left rear carb has a slight backfire. We are going to sync the carbs today and see if that helps, I dont recall seeing the mixture screw when we took the carbs apart to clean them, where do i find them? this whole project started when my buddy (the previous owner) used sea foam, and the next thing ya know, he clogged the crap outta his carbs, so he cleaned the carbs twice it would run fine for about an hour and then start choking, so it was determined that the gas tank was quite rusty. anyways any ideas would be appreciated!

 

Shane

[Venturous Randy]

First of all Shane, welcome to our little family and we hope you join.

The biggie here is that you started with a rusty tank and will have rust particles throughout the plumbing. I did not see where you changed the fuel filter. If you didn't, you need to. It would have also helped to have blown out the fuel lines from one end to the other.

As far as the backfiring through a carb, is that with the air box off? These bikes run poorly without the air box. Another thing to check is the diaphragms. Did you look for any pin holes in the diaphragms when you had the carbs apart? Another thing to do is the slide pin adjustment, but it may be better to do that after you get your bugs worked out first.

Another biggie is these bikes like clean plugs and the Autolites from Advance Auto work just fine and are cheap. Also, check your spark plug caps. There is a resistor in the cap that can get corroded and make it run poorly.

Anyway, there are a few more things to think about.

RandyA

[warthogcrewchief]

Shane,

I had a similar problem...could only run decent with choke on. I don't recommend this because the fouls the plugs out quick.

 

I replaced the diaphragms and the carb boots.

 

The diaphragms run about $70 from a company that we have group buy with. I believe their name is Sirrus Consolidated Inc (SCI).

 

MiCarl owns Thunder Valley Powersports and gives a discount to Venture Rider members. Here's a link to view his carb boots.

 

You can email SCI at: sci@siriusconinc.com and indicate that this is a VentureRider order, for that price. Their part number is called SD-1.

 

You'll need four of them, and it's pretty easy to remove and reinstall the diaphragms from the sliders.

 

In order to get them to stay on the carb house as I install the outer cover, I used just a little bit of RTV in the groove for the diaphragm. It helps to keep the diaphragm in place and prevents a pinched point.

 

Good luck!

[Snaggletooth]

Hi Shane.

 

I was the guy that your father in law was talking to on the tank treatment. Sounded like that went well so we will eliminate most of that.

 

Like stated starting from the petcock you should have good fuel flow. We talked about the filter so I assume he replaced that. Now did he replace the fuel lines or at least rinse them out?

 

And did he clean out the fuel pump or rinse it out?

 

So onto the carbs. I assume he spilt the rack and opened the fuel bowls to clean them out. If so, are you getting good fuel level in all the carbs?

 

Ok, so the mix screws I expect you are looking for are on the outside of the carbs under the bottom of the diaphram covers. (pic) You will need a thin bladed standard screw driver and turn them in .....gently..... until they bottom out. Turn each one back out 2 1/4 turns. Good starting point most bikes run pretty good in that range.

 

If you haven't taken a good look at the diaphrams you might want to pull them out and look closely for pin holes. A bright flash light will show through them if there are. If you find any we can deal with that later.

 

Ok. The popping or chuffing from the exhaust is usally a sign of lean mix. Set your screws and fire it up. A sync will do wonders for the bike. If he split the carb rack a sync most likey will be needed. I hope he used an assembly plate to re-align the carbs as these bikes are pretty touchy about being off axis.

 

And I'm going the mention one more thing. When he did the tank we talked about the elbow that is the vent for the fuel tank at the top of the neck. Make sure he got that line blown out so there was no epoxy blocking it.

 

And as mentioned these bikes do not run well with the air box open. They will backfire and stutter. Close it up when adjusting the carbs and doing the sync.

 

So let us know how it goes.

 

Tell your father in law I said hey.

 

Mike

[frankd]

In addition to all the other good advice you received, I have a question to ask you. Is the bike warmed up?? What is the temperature where you were running it? As already mentioned, make sure the air cleaner top is on. These bikes need this to run properly.

 

Frank

[sheriff1112]

ok, Total tear down of the carbs - done, no holes in diaphrams everything looks great! fuel tank is fixed - no rust, all fuel lines blown and cleaned, new fuel filter, this morning we started again, first thing was to check out the mixture screws, i set them at 2 turns out, then i went on to do the sync, all carbs upon initial firing where good so dialed them in with the syncer, running much better, and now i can goose the throttle, starts with little or no choke (seattle wa) oh yeah all spark plugs have been replaced, and i cut and inch of each wire, anyways it starts right up, idles no problem and now i can goose it, upon heavy load though iam getting some slight back firing, i have the header pipes tighted on through to the cans, cans are just slid on and not tight, so.... iam thinking once i tighten everything up that may get rid of the back firing, or do you think iam still running lean? the airbox is back on by the way and it helped cleaned up things abit but like i said a slight back fire, do you think 2.5 turns to 3 would get rid of the back firing?

[Squeeze]

Set the Mixture Screws at 2.5 Turns out (at least for now) and ride the Heck out of the Bike.

 

Exhaust Leaks may Cause Backfire on decel, you need to ride that Thing, hard ...

[Snaggletooth]

Hey Sheriff,

 

Sounds like you have been a busy camper since the last time we talked and you're close to having it whipped. Like Squeeze said, go ahead and open them up a bit more and get her out on the road. These bikes start to come into their own around 4,500 rpm. I run the Interstate a lot and I rarely go into 5th gear until I hit 75 mph. Tooling around at 3,000 to 3,500 rpm is not the way this engine likes to be run.

 

Some of these guys will attest to the fact that these old girls will top 100 mph in 3rd gear. Now...myself.....will never admit to it when speaking to a LEO current or not so you didn't hear that from me.

 

A 1/4 can of Sea Foam in the tank and let it work out what you didn't get during the clean up.

[Shanefromwashington]

Ok the bike is running and idling fine, I've never driven a venture with a good tune ( I drove this one last year for 50 or so miles and I noticed them that there was no snap anywhere ) so I'll give you my observations, 0-2500 rpms not real snappy kinda like a lawn mower building speed until it hits 3000 or so and then walaaa it opens up and screams quite nicely, any ideas on the slow rpm build up? Also still getting some sporadic sputtering down low (sounds like pops in the collector) I hAve not readjusted the fuel mix screw out from 2 yet but will next go around. Went ahead and put the subframe back on and tightned up the exhaust and moved on to the brakes (front calipers where locked up) we put new ones on and tried to get those dialed in ( please see new post ifvya gig some thoughts) we appreciate everyones help! I do want to say from 3000+ rpms this bike runs hard as good as my buddys old vmax (minus the vboost )

[Squeeze]

Sounds like the small Fuel Jets are clogged. Maybe SeaFoam can take care of that.

 

After you got your Brakes done, ride it like you stole it and hopefully this Issue will clear up. If not, there may be a second Carb Clean Job in Order.

[CrazyHorse]

Are all your carbs seated properly in their respective boots both top and bottom. Putting the carbs in when they are tightened together they sometimes do not sit perfectly in the boots. I usually set them in a little loose and tighten them while in the lower boots. Need angled screw driver for this though.

[Shanefromwashington]

Yeah, carbs are seated just fine, somebody put a k and n filter in the bike Iam wondering if that's screwing with the lower circuit?

[Condor]

Yeah, carbs are seated just fine, somebody put a k and n filter in the bike Iam wondering if that's screwing with the lower circuit?

 

The K&N shouldn't. Been runing one on the '83 and '87 without any problems...

[Shanefromwashington]

Can anyone send me a short video showing there bike starting and then slowly wicking the throttle? That would help beyond words my email is garcou@hotmail.com

[timgray]

In addition to all the other good advice you received, I have a question to ask you. Is the bike warmed up?? What is the temperature where you were running it? As already mentioned, make sure the air cleaner top is on. These bikes need this to run properly.

 

Frank

 

These bikes are incredibly cold blooded. it's 30 degrees out right now and if I were to go start mine it will take it at least 5 minutes before it would start to run right. even when it's 75 out it still took a minute for it to warm up enough to atomize the gasoline so it would run smooth at all throttle levels.

 

also check the line going to the boost sensor for plugging.

[camos]

The incredibly cold blooded is more likely a symptom of the 5 Bikes carb mod than a stock bike. I live just across the pond and it is not cold here, a bit cool, mid 40's. Had a look through the thread and did not see any mention of when the popping occurs. If it is on decel there are a few possible causes other than or in addition to carbs, vacuum leaks, exhaust leaks and poor connections at the TCI.

 

On a bike that has been sitting for a long time it is not unusual to have to clean the carbs more than twice before they are done right. There are some very small passages that will affect the pilot air mixture if they are not clean enough.

 

Just a few more things to look at, as if you didn't have enough to do already.

[Shanefromwashington]

Ok gents, fired up the bike today and let it warm up for about five minutes. Threw a leg over it and took off down the street, all I can say is wow! Don't know what happened, but everything seems to have smoothed out and power is excellent! (of course it could sound a whole log better with some nice mufflers any ideas? Stock ones are to quiet) I want to thank everyone for your help getting this bike dialed in, my father inlaw appreciates it as well, for some reason he won't quit smiling

got a few other issues to sort out..... Brakes there there but very light we bought a hand bleeder and will be using in the next few days and last but not least the electrical to the rear end, when we took off the subframe there where some wires that where taken off that need to be sorted out and we need to hook up the pump on the tail section (we have to put new o rings in first though) any words of advice to hook this system back up? Is there any procedures that I need to do? And also since this project began the radio and cb will not power up (they did before the tear down) any ideas? Is there a fuse for this system somewhere? Again your forum is great and I appreciate all your help!

[Dano]

Get a set of Mac mufflers for that puppy, you'll like the sound. Others like the Jardines, you may be able to find a decent set on flea-bay from time to time, or a member might come up with a new set on here every once in awhile...

 

 

 

 

 

You're REALLY gonna have some fun with that bike now!

[warthogcrewchief]

Just remember that when you bleed the hydraulic (brake or clutch) systems, it will take a little time. These systems are a real pain to bleed.

 

Remember that your brakes are linked. Your front master cylinder controls the front right brake caliper. Your brake (foot) pedal controls the left front and also the rear brake calipers. This, of course, is assuming the brakes haven't been modified or de-linked.

 

I don't remember who I got this from, but I did get a color coded wiring schematic for the MKII bikes. Both are the same, except one includes the (black) ground wires.