1983 Venture XVZ12 Mikuni Carb Help!!!

[Kemelito]

Hello everyone! I became a member just today. I am truly overwhelmed by the wealth and diversity of knowledge on this site!!

 

While rebuilding my Mikuni BS34 CV carbs, I broke a piece off of carb#1!!! To be more specific, it happened while removing the pilot air jet #1 from the top part (venturi) of the carb body. While applying downward pressure with the screw driver, the carb slipped from my grip and I broke a small piece of the "housing/port hole" (for lack of a better/proper term) where the pilot air jet #1 inserts in to.

 

My question is this..................... Will the larger opening caused by the break affect the airflow/vacuum (proper functioning) of carb #1??? My reasoning is that the air will still be "bottlenecked" through the hole in the pilot air jet (which I cleaned successfully and is not damaged) no matter the size of the top of the "housing/porthole". I need to know if the carb is ruined (junk) or if it will function properly.

 

I know there are good people here with much more knowledge on this subject than me! I would appreciate your impute to figure out if I have to start looking for a carb #1 replacement or not. I have attached two pictures of the broken section to make it easier for everyone to understand.

 

THANKS!!!!!!

[Venturous Randy]

I personally suspect that it will not make any difference at all. It probably just looks worse than it is. I would put it back together and go on.

RandyA

[Kemelito]

I agree!! I posted the thread as a precaution before I put the carb assembly back on. I would hate to not be able to synchronize carb #1 properly because of the damage. I'll wait to get more feedback before I proceed though.

Thanks!

[skydoc_17]

Hey Kemel,

Welcome to the VR.ORG Forum! I agree with Randy, from a visual standpoint, it looks bad, but from a functional standpoint, I'm sure that the #1 Carb. will have no problem moving air across that broken casting lug. Once you button the boots and air box up, YOU will be the only one to know that it is there. Most First Gen. owners have a few "skeletons" like this in their closets anyway.

Welcome again, and keep asking questions!

Earl

[Yammer Dan]

Don't think it will make any difference. If you wanted you could rebuild it with J B Weld. Use something to make a mold.

[Kemelito]

JB Weld! Good idea! Hadn't thought of that. Although it might not be necessary (from what you guys have posted so far) I'll probably do it anyway just to be sure. Also because..................... I know it will bug the heck out of me knowing the break is there even if it is not visible!!!

[Kemelito]

I'll wait to see if I get more feedback before I make a final decision. I appreciate all of you that have chimed in so far!

[Peder_y2k]

JB weld could break off and be sucked into the engine. Don't do it! Besides, the bulk of the repair can disrupt the air flow as CV carbs are very sensitive.

I'd use a dremel type grinder and round the broken edges. If you are anal about it, then do the same on the other carbs for consistency, and then you can claim the factory meant it to be that way.

-Pete, in Tacoma WA USA

[Kemelito]

This is exactly why I'm waiting for more feedback! I can see the risk that JB Weld poses. Wouldn't want a damaged valve or worse!! Thanks for the warning/observation! Believe it or not, I have never used JB Weld. Would it bond well enough to the surface of the porthole to prevent it from getting sucked into the engine? I would love to know if anyone has successfully repaired a carb body with JB Weld in an area of low stress/pressure................ more importantly, has the repair stayed intact over time??:confused24:

[Yammer Dan]

The JB Weld could break off. If I was going to use it I would make sure it had something to grip such as drilling small holes into the carb body to insure it got a good grip but that's putting a lot into a repair I don't think is necessary. Like you said its something I might do because I might feel it is holding back 1/100th Horse.....

Once it is in there and knitted good I can't see it breaking off but the more I think About it I think I would just let it go.

[Kemelito]

Thanks for you honest input Dan!! I will say that I bought some JB Weld already but seeing as it cost me less than $5, I will keep it for the next project!!

I'm leaning on the cautious side of leaving the break the way it is. Hopefully, it won't pose a problem when I synchronize the carbs! I'm open to more suggestions though.................

[Yammer Dan]

J B Weld is handy stuff. I've used it a lot with great success but in this case it does make you scratch your head. Drilling around the break with a very small bit and making sure the material got into these holes good and doing it all with one application have no doubt it would be there to stay. But in a case like this it would make you wonder:duck: Not worth the worry and though I would do it I will withdraw my recommendation. Try the J B Weld on a few things and maybe you will pull that thing out later and fix it:whistling: Put it back togather and enjoy!!

[dingy]

Ditto on not using JB Weld due to it possibly dislodging. It's good stuff if you need it and prep surfaces well.

 

This is only a air jet, and a rather small one at that, #80. Parts break down refers to it as a main jet. It isn't the important main jet, which is in the fuel bowl pocket. The air flow through the rather small jet orifice will not be disrupted much at all, and if it is, passing through the jet will correct any turbulence caused by small chunk missing.

 

Tweety has similar warts in places, and it runs OK.

 

Gary

[Kemelito]

ALLLRIGHTYYYYY GUYS! Taking into consideration all the info I have received, I will take your sound advice. I will leave the carb body as is!! Once I have put the carburetor assembly back on the bike and synchronized them, I will give you guys an update. Hopefully it will be good news!!!!!!!

Thanks again to all those who chimed in!!!

GREAT SITE! EVEN BETTER MEMBERS!!

[dfwthompson]

Welcome neighbor! Glad to have you.

[Huggy]

Kemelito if it does not work out for you I may have a carb body you can have once my replacement carbs get here. May be a while. There at bongobobny's place and need to be picked up. The cage needs some repairs so right now I don't dare drive it too far. But once I have them I have no problem with breaking up the set if you need a body.

[dna9656]

I have seen JB Weld used is a LOT or applications in my 20 year USAF career, HOWEVER using it in the air stream of the intake system is a little scary to me too.

So far as drilling holes to get the JB down in the part to assure a good bond; I'm a painter by trade and we have a standard we call "profile" it's the roughed up surface needed for good paint to substrate bond. We measure it in Mils. 3-5 mils. is good. Having said THAT as to drilling a hole for bonding purposes; the sides of the hole would be too smooth and if it's very deep at all you would have to be sure there was no air under the JB Weld compound.

Ever hear about some one in a altitude chamber that has air under a filing in their teeth? The air expands with the lower ambient air pressure and hurts like hell! In your case the metal could expand with heat, any air under the fill could (heat again) expand, and you could have inadequate profile on your glue surfaces and then the engine just sucked up the piece....I would follow the advice you got here OR get a replacement part...better safer than broke down someplace AT night, in a galaxy far, far, away because believe me it won't go South in your driveway.

Edited November 25, 2013 by dna9656
grammar

[Kemelito]

Ok guys! I haven't posted anything on the thread in over six weeks because I've been.........let's just say..........busy with my 83!!!! I've done many repairs including a complete rebuild on the carbs, which is why I started the thread in the first place.

I am glad to report that the break I caused on the carb body did not affect a thing! You guys got it right. I adjusted and synchronized the carburetors and "she" idles and runs beautifully! I attached pictures of some of the steps in the rebuild process if you guys want to check them out.

Here is a list of what I did/replaced on the carburetors:

- complete disassembly of all four carburetor bodies

- a detailed & deep cleaning of all parts, jets & passageways using varies methods

(soaking & spraying w/cleaner, compressed air, media blasting w/baking soda, brushing)

- 4 new gasket/o-ring kits

- 4 new diaphragms (old ones had tears and pin sized holes)

- one new float in carb #2 (old one was deteriorated & taking in gasoline)

- new (Allen) bolts on all 4 slide/diaphragm covers (the stock Phillips heads tend to strip)

- new hex head bolts on all four support brackets

(this enables you to get much better torque when attaching carbs back together)

- all new fuel lines and hose clamps

- all new (4) fuel bowl drain hoses

- checked (and calibrated when needed) float heights with digital calipers

(1.025in. worked great for me in achieving the next step)

- set fuel levels on all 4 carbs to 14mm (+/- .05mm) below piston valve center mark

- synchronized carbs with vaccum gauges

(I will say that it took me almost an hour and a half but I got it right on the money!!!!)

- adjusted all four air mixture screws to approximately 2.5/3 turns out

(this also worked great for me; not too rich or too lean)

It is possible that I forgot to list a few other things/steps I did to the carbs but overall my 83 runs and idles very well (I set idle right at 1,000rpm). I had read and heard the difference that a full rebuild would make but I was blown away at the results!!!!

[Prairiehammer]

Good job! Makes one feel very satisfied, doesn't it?

 

One point: On some 1983 Venture carbs, there was a sharp edge on the inner side of the diaphragm covers that tended to wear and cut the diaphragms. It was explained in Tech Bulletin M85-012. Check your diaphragm covers and utilize an abrasive to smooth the inner shoulder to prevent cutting your new diaphragms.

[Kemelito]

Thanks for the heads up. That is one of the steps that I forgot to put on the list! I checked for that and the PO must have wet sanded them down because the edges were very smooth!

[Venturous Randy]

Once you get some riding time, you may want to do a needle adjustment on the slides. Several of us have had great luck in going from 40 mpg to 45 mpg and if cruising two up through the mountains, I have got as good as 50 mpg. This is also without loosing any power. Also, do you have your YICS still hooked up? If you do, blocking that off can help your bike run better.

RandyA

[Peder_y2k]

Congrats on completing a lengthy and involved motorcycle chore. Been there and done that several times myself.

 

FYI, more important than the float height physical measurement is the actual fluid level inside the carbs. This confirmation is achieved using a clear tube from the drain port and comparing the fluid level seen in the tube to the reference mark on the outside of the carb body. This method is more reliable because an older float can be compromised looking physicly OK, but actually sink because it can absorb fuel when the surface breaks down from age or surface scratch, and can possible hang up if not aligned perfectly. Fluid level is critical in CV carbs because they are very sensitive to vacuum, and vacuum is the energy source for moving fluid inside the carb. If the fluid level is low, slow or delayed throttle response is the result, and if high, the engine runs rich.

 

-Pete, in Tacoma WA USA

[Kemelito]

I agree! Earlier in the thread I posted details and pictures of how I checked fuel levels in each of the four fuel bowls that you might have missed. I set levels right at 14mm (+/- .05mm) below the center mark per the service manual. I made a line with a permanent marker on the side of the carb body to make it easier. Here are a few pictures.

[MikeWa]

The break should have no affect on the air flow. I agree though, use your dremel to clean it up a bit and make it look nice.

 

Mike

[Peder_y2k]

"I agree! Earlier in the thread I posted details and pictures of how I checked fuel levels "

 

Good boy!!! You can come work on my carbs anytime, just leave the hammer behind.

 

-Pete, in Tacoma WA