Question About Carbs

I have an '83 Venture. Just replaced the diaphragms and noticed some improvement. Now I know I need to sync the carbs.

Out of curiosity I opened the airbox and looking down at the carb throats, I was surprised to find that the needle valve tube extends into the throat of carb #2 about 1/4"+/-. Then in carbs #1, #3 and #4 the same tube is essential flush with the carb body wall. The images below may be helpful.

I've had the bike since 1986 and I've never worked on the carbs myself. Had a shop service them several times. So I don't know what they should look like inside.

My question is whether the tube extending into the throat of #2 is the way it should be. If not, should it be positioned so it is flush with the wall like the other carbs. Or perhaps this is the way it should be since #2 is the reference carb and it was engineered this way.

Thanks for your help. I've decided to spend some time, effort and money to get the old bike running better. It's got 61,000 miles on it and runs fairly good considering age.

Jan in Phoenix

In order for the 1st picture to happen, the mounting screw for the Main Nozzle, has to be loose, allowing nozzle to shift into venturi.

Picture attached., main nozzle at top with screw into it at very top of picture.

2nd picture shows nozzle with screw, washer& oring.

I think carbs are coming back off to fix this.

Gary

What's with the Canadian nickel, Eh???

I'm the OP. Thanks for the information and images.

I've looked at the diagram of the carbs in the Yamaha manual and it appears the screw that secures the main nozzle (needle jet tube) is inside the float housing. I assume I'd need to remove the float housing to tighten the screw. Is that correct?

Also I'm wondering if it might be physically possible to remove the float housing (four screws it looks like) while the carbs are still mounted on the bike after taking the airbox and intake tubes off. Is there enough clearance to get a tool in that area and remove the screws and the float housing?

Being a rookie, I'm trying to avoid removing the carbs completely if I can.

Thanks for your help.

Jan in Phoenix

To get the bowl off you need to split the rack. To split the rack you need to pull it off.

While you're in there you should give them a thorough go through. No point in doing it again next week.

As my father used to say: "You'll never learn any younger."

That's what I thought would be the case. I guess it's carb service time.

Thanks a lot.

Jan in Phoenix

Jan,

There are some good articles on removing the carbs. I can tell you it is a pain in the @$$. I have attached the verbiage of a thread that cover the removal. If I can find the actual thread I believe it has pictures embedded which may help. Also, your first question on syncing the carbs you need a Carbtune to do that. I have a Carbtune and the instructions how to use it on a 1st Gen. If you need to borrow it let me know and we'll figure out how to get it up to you.

Bill

Tucson

This is in reference to my 1983 Venture. I started my carb project yesterday after determining that cylinder #2 was not firing. That's the carb that has the main nozzle loose in the throat of the carb.

By the way I appreciate the very logical and simple trick of touching the exhaust pipes to determine which cylinder isn't firing. In my case #2 remained cool to the touch while the other three got hot normally. I also attached a spare spark plug to that cylinder and found that I did indeed have spark.

So I tackled the carb removal phase yesterday. After removing lots of parts, I had reasonable access to the carbs. The airbox came off easily after I loosened the clamps. The carbs themselves took a little persuasion with a hammer handle as a lever. I just gently worked one side and then the other and eventually the carbs popped out of their boots. It actually a little easier than I had expected. I finally finessed the throttle cables loose and then had the carbs off the bike.

To fix my loose part problem in carb #2 I had to separate the assembly into the left and right pairs. As had been expected getting the screws loose was a challenge. In some cases an appropriately sized phillips head in a racket did the trick. In others it took a pair of vise grips on the head of the screws to "wrench" the screws loose. But I was successful on all 8 screws.

On my problem carb I was able to open the float housing and found that the screw that holds the main nozzle in place had in fact come completely loose. I was able to push the nozzle back into position and secure it with the screw and washer.

I spent part of today cleaning the two left carbs (#1 and #2). I've used Sea Foam spray and carb cleaner. Everything seems to be cleaning up pretty good and the passages seem to be open. I used compressed air to blow through the passages. The floats appear to be in good shape with no apparent holes or splits. Also they are quiet when shaken indicating no leaks.

Everything else looks pretty good so far I think, but I did run into a couple of minor problems that I'd like some feedback on.

1. In the carbs the jet block inside the float chamber has the two black rubber plugs at the bottom...one smaller and one larger. In both cases the small one lost it's head while the stem of the plug remained in the jet block when I tried to remove the small plug. In one case I was able to remove the remaining stem but not the other at least so far. My question is whether the stem without the head is OK to leave in the jet block or should I replace the small plug? Is it correct to assume that the two plugs are required to be in place for correct operation?

2. In one carb the small "O" ring that fits around the main nozzle tube and that lies under the jet block looks kind of squished. Is this a part that I can replace from a source such as NAPA or do I need to order a Yamaha part?

3. I was able to loosen the drain screws on three carbs but wasn't able to do so on the fourth. That screw head has been more or less stripped. There's still some screwdriver slot left but I've elected to not destroy it further. Is there any need for removing that screw. I removed one of the others and I see that it's about 1/2 inch long with a pointed tip. Since that screw is recessed, I can't use my vise grips. I suppose I could drill out the faulty screw, but I wonder if it's necessary? In the 28 years that I've owned the bike I never knew the drains on the carbs existed until now.

4. Is it OK or advisable to apply silicon spray or lube to the rubber parts such as the "O" rings and float bowl gasket? Generally all the rubber parts appear to be in pretty good condition.

5. One final question. I plan on replacing many if not all of the fasteners on and in the carbs with stainless steel socket head fasteners. Is there any compatibility issues with using stainless steel with the carb metal and/or inside the carb such as fastening the jet block inside the float housing? Any reasons not to do this?

I appreciate all the information this forum has provided. It gave me the confidence to move forward. Thanks to everyone.

Jan in Phoenix

1. Rubber plugs are necessary. Get new, they're cheap.

2. Any fuel compatible o-ring will do the trick so long as it's sized right. I'd just order one from Yamaha along with the plugs so I was sure it fit properly.

3. Only real reason you need the drain screws open is to set the fuel level. I'd personally be real tempted to not risk damaging the carburetor removing it.

4. Couldn't hurt. I generally just assemble dry.

5. The stainless fasteners will be fine. Socket head has obvious advantages.

By the way, those screws are not Phillips. If you look at the heads they have a little punch mark on them which denotes they are JIS screws. Close, but not exactly Phillips. That's part of the reason you had trouble with them.

What's with the Canadian nickel, Eh???

If you use a Canadian nickel, you won't be losing as much money as if you used a US nickel. I think our nickel is worth about 4 US cents right now. But, we have a beaver. LOL

To fix my loose part problem in carb #2 I had to separate the assembly into the left and right pairs. As had been expected getting the screws loose was a challenge. In some cases an appropriately sized phillips head in a racket did the trick. In others it took a pair of vise grips on the head of the screws to "wrench" the screws loose. But I was successful on all 8 screws.

Don't play around with those phillips headed screws anymore. They're too tight and too soft. Save yourself the aggravation and cut a nice straight slot in the top of each one with a Dremel and cut-off wheel. Then you can put a fairly large straight screw driver in the slot and the screws will come out without much back-talk. Then throw away those screws and replace with hex socket cap screws. You can get the appropriate sizes at Home Depot, Lowes, Ace or True Value hardware. They come in stainless or black.

The next person to work on those carbs will either be very grateful or at least not pulling their hair out. http://www.venturerider.org/forum/images/smilies/bang%20head.gif

Better still, buy a good set of JIS (Japan Industrial Standard) screwdrivers and stop wrecking your screws. The angle for the JIS is different from the SAE and using an SAE strips the heads...

Better still, buy a good set of JIS (Japan Industrial Standard) screwdrivers and stop wrecking your screws. The angle for the JIS is different from the SAE and using an SAE strips the heads...

Were do you get them?

Many places online, but not many places in a local brick and mortar.

[ame=http://www.amazon.com/Hozan-JIS-4-JIS-Screwdriver-3rd/dp/B00A7WAHTU]Amazon.com: Hozan JIS-4 JIS Screwdriver Set (NEW 3rd. Gen): Home Improvement@@AMEPARAM@@http://ecx.images-amazon.com/images/I/413vva2sI3L.@@AMEPARAM@@413vva2sI3L[/ame]

I was successful in getting the fourth drain screw open. I used some penetrating oil and let it soak for a couple of days. Plus I found a "philips" style bit in my collection that was the correct size for the drain screw and was able to get it to release. At least I hadn't fully destroyed the head of the drain screw. It's mangled but functional.

You are right that the correct screw driver makes a difference.

I replaced most of the screws on the carbs and carb assembly with stainless steel socket heads including the two that hold the jet block inside the float boat.

I sourced my screws in Phoenix at Copperstate Nut and Bolt Supply. I asked the guys at the counter if they were familiar with the JIS screws head. One guy said he had heard of term, but didn't know any more than that.

I decided to go ahead and replace all the rubber plugs in the jet blocks as well as the "O" ring and gasket under the jet blocks. Waiting for those parts to come in.

Everything is cleaning up nicely and looking good. I plan on running though them one more time once I get the new parts in. I've found working on them is pretty straight forward. After the final run through then I'll tighten everything down and reassemble the brackets.

In the meantime I've got Skydoc's shim kit on the way. I've taken the valve covers off and will adjust the clearances when the kit arrives. I can see that it will be easier to do with the carbs off. This too will be another learning experience.

I ordered and received a Carbtune sync tool. It was ordered on April 15 and arrived on the 22nd. Great service considering it came from across the pond.

Thanks for the feedback.

Jan in Phoenix

For anybody who reads this this thread one trick I learned from this forum is to use a pair of wire dikes and grab the head of the screw and twist. I have used that trick on many screws now on several bikes and it works like a charm.

So do JIS screwdrivers!

So do JIS screwdrivers!

Yea..but all of my screws have been stripped out by previous owners/mechanics. I tried all types of screw drivers including an impact driver... the dikes worked when other stuff didn't...

Fair enough KIC!!

For anybody who reads this this thread one trick I learned from this forum is to use a pair of wire dikes and grab the head of the screw and twist. I have used that trick on many screws now on several bikes and it works like a charm.

Not sure I have ever seen them. I know I have never heard that term. What are they ? can you post a pic or a link?

Not sure I have ever seen them. I know I have never heard that term. What are they ? can you post a pic or a link?

I would guess that what he is talking about is what we call side cutters. i know how to do it, so don't mind sharing that with you when the time is right,,,, ya, I didn't come to the trick easily, Muffinman was the teacher.

Hi, again. I'm the OP.

I was successful in checking the clearances on my valves and ended up replacing 14 shims, all one size thinner. It was slow going and took a total of about five hours to check all the clearances and determine the existing shim sizes. Then I ordered my new shims and it took about four hours to install them and double check new clearances. Although time consuming it wasn't all that difficult once I figured out the technique. The only concerning part for me was extracting some of the shims. They can really get stuck in that bucket and it takes quite a bit of force to pop them up for removal. I think in one instance it took almost an hour.

But all is well that ends well.

Installing the valve covers was pretty straight forward. I obtained 2nd generation gaskets from Skydoc and lightly attached them to the covers with black RTV. As advised I let the cover and gasket assembly sit overnight. Then the next day they slipped into place without a hitch.

In the meantime I had completed my work on the carbs and reassembled the brackets using blue Loctite to secure the screws. I did install new stainless steel socket heads screws which worked out well.

The reinstallation of the carb assembly was slow going. It took awhile to get the throttle cables hooked into position and then the carbs were difficult to get seated in the carb mounts. It took some pretty solid pressure and rocking motion to get them to finally pop into place. The airbox installed easily although fussing with the crankcase vent hose was irritating. Eventually I got all the pieces put together.

After checking all my connections and clamps, etc., it was time to see if the bike would fire up. By the way I had switched out the fuel filter and installed a new gas line from the pump to the carb assembly. Easy to do when everything is opened up.

So with the key in the ignition, it was time to see if the bike would start. I was very happy when after a few cranks it started to fire. In fairly short order it started running, although rough. I hooked my Carbtune sync tool and was able to get the carbs synced roughly enough to improve the idle. As the bike warmed up and sounded better and I continued to work with the sync to the point that all the carbs were pretty well in line with each other.

I rapped the throttle and it was abundantly clear that this engine was performing at a much better level than it had for years. Between tight valves and semi-fouled carbs, it had been pretty doggy. But now it has great throttle response and tends to scream when I get a handful of throttle. I had forgotten how well this engine can perform.

After a week now and continued tuning the bike really appears to be running very good. I ran a rich mixture of Seafoam for about 80 miles. Then I added a two gallons of fuel and a rich mixture of Techron and have about 70 miles on that tank.

In the meantime I pulled the old spark plugs and put in new ones and replaced the plug wires and caps.

While the bike is running much better and I've got the carbs synced solidly, I do have a few issues.

1. When I pull the vacuum line cap on #1, the engine doesn't change pitch. When I pull that cap on the other three cylinders, the engine bogs. I suspect #1 has lean mixture at low speeds and doesn't fire a low speeds.

2. The attached images of the new plugs with about 70 miles on them seem light in color to me and implies that engine is running lean. I'm used to seeing darker colors.

3. When running in town and at low throttle, such as about 40 mph with 3,000 rpm, the bike seems to surge as if a cylinder isn't firing but does light up from time to time. Again maybe #1 is messing up. At highway speeds and heavier throttle, however, the bike seems solid. Lots of power and rapid response.

4. I've got one or two exhaust leaks one of which is associated with cylinder #1. I need to work on those. Perhaps another contributing factor to issues with #1.

I have suspected an intake leak on #1, but with a propane source, I haven't found anything obvious.

I will continue to ride the bike and use Seafoam and Techron to see if that helps to resolve these issues. I've been reading about the idle circuit and the pilot screw, etc. I may decide to do the "shotgun" process to make sure that those passages are clear.

Overall, however, the bikes idles smoothly and has lots of power when pushed hard on the freeway. An impressive improvement.

Thanks for the help and input from many of you and this forum as a resource. It gave me the confidence to tackle these projects and with a good outcome so far.

Jan in Phoenix

Good show, old chap!

I really like your concise and yet complete write-up of what has transpired.

By chance, could you elaborate on the pilot screw settings that are current? I agree that it seems as if one cylinder is dropping in and out (the surge) at low speeds, but a couple things I noted when I see the spark plugs:

Number 3 looks significantly richer than the rest; perhaps that is the cylinder that is flaky?

Number 2 appears to have melted aluminum bits on the electrode. That can't be good.

Time to 'tweak' the pilot screws and double check the synch. With warm engine idleing at 1000rpm, turn the pilot screws inward to a soft stop (closed), and if the engine does not noticeably slow down or stop, the pilot circuit of that carb is compromised. Same if you open the pilot screw way past the usual setting of 2-1/2 turns out, the engine should bog down and stumble. Final tweaking of the pilot screw will be close monitoring of the engine speed, adjust each screw for highest rpm when backing out from closed. If the driveability isn't right, meaning quick throttle response, and no backfire or exhaust pop, then turn the screw out 1/8 turn at a time testing between adjustments as this richens the mixture.

-Pete, in Tacoma WA USA