Carb Identification

[Anonymous]

When I bought my bike I also got an extra set of carbs but they look different than the stock carbs. They have a butterfly valve in the back and the top is round. I took the top off and it looks like some kind of diaphram. The guy I bought the bike from said they were 33mm and I would have to port the head to make them fit/work. Are these better than stock and are they worth trying to put on. I would have to rig a cable or something for the choke, they run vertically instead of horizontally. Thanks. Jkev.

 

[Dink]

It would help A LOT if we had any idea what you are trying to fit them too!!!
From your vague description it sounds like you have been given a set of 33mm smoothbore, IF you have a 1000cc or larger bike they would be great for it, but a ported head, 4 into ! etc is extremely advisable before trying to fit them, and IF they are smoothbore you will need a new twistgrip with push-pull cables.
Dink
Most members put the model and year of there bike in there signature block, which you can edot by going to your profile.

 

[Anonymous]

Carb Identification

Sorry, I have a 1978 GS 1000.The only performance modification is a Vance and Hines 4 into one. The bike already has a push pull throttle but these other carbs don't look like they are set up for that. There is no place for a second cable. The spring tension is very stiff. Maybe I can take them to work where I can take pictures of them. They don't look like the pictures sharpy sent of his 29mm smothbores. The top is flat and round and there are butterfly valves in the back.

 

[nert]

sounds like CV carbs. should be a number on the outer side of the end carb.

 

[Anonymous]

I don't see a number anywhere but I think you are right about them being CV's (constant velocity?). If they are CV's are they a good design?

 

[KEITH KRAUSE]

You need the head from a '80 1000 or newer. The CV's won't mount to the '78 head. The best carbs for your bike are the 29 smoothbores. The 33's need much better breathing. Maybe if you port/polish and bigger pistons/pods...the 29's with pipe/pods/pistons make a fast and better mannered street bike.

 

[Anonymous]

Thanks Keith. Since I already had them I thought they might be an easy upgrade instead of jetting the stock carbs. I think I'll just go ahead and jet the stock carbs. I just wish I could get the individual air cleaners to work good. Taking the carbs on and off with the stock box is such a pain. I'm afraid eventually the rubber boots will be damaged. Any ideas?

 

[KEITH KRAUSE]

I just wish I could get the individual air cleaners to work good. Taking the carbs on and off with the stock box is such a pain. I'm afraid eventually the rubber boots will be damaged. Any ideas?

Have you tried running pod filters with the pipe? What brand pods and what style of V&H pipe?
Because of past jetting problems, you put the stock airbox back on?

 

[Guest]

Here are my 33mm smoothies....

Do they look like this?

(pic deleted)

 

[Anonymous]

I bought the bike with pods on them and it would foul the plugs really fast and had bad throttle response. I had the same problem on my 750 and went to the stock air box and it cured the problem. On the 1000 I have now I took the pods off and went ttothe stock plenum with one pod out the back. Runs much better but lean. If I could get it to run good with the pods I would go back to them because the stock plenum is such a pain. I took the carbs off this morning and it has 15 pilot jets and 97.5 mains. Low end hestitates and the plugs are white with just a tad of brown.

 

[KEITH KRAUSE]

I can help with the jetting, but I'd like to know if the pods are K&N or a cheaper brand like Emgo. Also, is the V&H pipe a megaphone or Pro pipe?
Is the overall condition of the engine good, such as compression, spark, etc, except the poor jetting?

 

[Anonymous]

The pods are UNI foam but I would buy new pods if I knew I could get the thing to run right without having to put that stock box on. The pipe is not a megaphone although I do have an extra one of those brand new too. I got lots of extra parts with this bike. The pipe has a pattern of holes in the end. Sorry about all the vague descriptions it's hard to know what you have if you weren't the one who bought them.

 

[KEITH KRAUSE]

The pods are UNI foam but I would buy new pods if I knew I could get the thing to run right without having to put that stock box on.

Be aware that jetting is trial and error. It can take patience and you'll need to be able to work on these VM carbs. You'll also have to have them synched to be able to get accurate plug reads.
I also have better luck with a Dynojet kit for the stock carbs, but we can try to make the stock jet needle work, along with seperate jets.
What I really don't like are the Uni-pods. They're restrictive. This will make it more difficult to guess your initial re-jetting. Would you buy K&N's?

 

[Anonymous]

I've worked on Mikuni carbs many times, mostly on the 78 750 I had. It had the same problem. Getting carbs in and out with the stock box on a 750 is much easier than on a 1000. So I know how to take the carbs apart and put them back together. I have synched the carbs according to the Mikuni tuning guide which says to use a piece of wire between the the throttle valve and the body and use it like a feeler gauge. Adjust each throttle valve to the wire (feeler gauge) and then the throttle valves will open the same amount at the same time. Mikuni says this is better than a vaccuum gauge for thesetype of carbs. I'm willing to buy a Dynojet kit and K&N pods if you think it will work. I'm trusting your expertise. What kit should I buy and which filters, the short tapered ones? Thanks.[/quote]

 

[KEITH KRAUSE]

I have synched the carbs according to the Mikuni tuning guide which says to use a piece of wire between the the throttle valve and the body and use it like a feeler gauge. Adjust each throttle valve to the wire (feeler gauge) and then the throttle valves will open the same amount at the same time. Mikuni says this is better than a vaccuum gauge for thesetype of carbs. I'm willing to buy a Dynojet kit and K&N pods if you think it will work. I'm trusting your expertise. What kit should I buy and which filters, the short tapered ones? Thanks.

The wire synch is used by some. I go by eye. In either case, this is just to get the bike started and make the vacuum synch easier. If Mikuni actually says that the wire method is better than doing a vacuum synch, they don't know their own carbs. These carbs require a good vacuum synch as a basic part of the jetting. It makes jetting and performance MUCH easier and better. VACUUM SYNCH THE CARBS. You won't be sorry. Motion Pro makes a simple but accurate mercury gauge for $40.
I bought the Dynojet kit, part # 3304. About $125.
The K&N chrome ovals, part # RC 2454, were about $120 for 4 a few years ago. They're quality and if taken care of, will last the life of the bike. Use K&N filter oil too.
I'm assuming the engine and electrical system is in good condition.
If you're going to order the parts, I suggest making sure the valve clearances are correct and the timing is correct while waiting for the parts. You may need shims.
I would also be certain the carbs are perfectly clean, floats adjusted to .94", be sure the floats are not tweaked. Measure each side of the floats to be sure they're even. Be sure the inside o-rings are all good. Robert Barr, a member here, sells o-ring kits for these carbs, $16 does all 4 carbs. You get EVERY o-ring. Make sure the manifolds are in good condition and BE SURE to install new manifold o-rings.
Also, be careful to count how much the pilot screws (underneath) are out. NEVER seat them tight, just lightly. You may find the pilot screws turned out differently from each other. Write it down. It can be important later.
Be careful not to strip the side air screws. They can be tight. Don't mix parts. Keep each throttle valve with its carb. Keep each float valve needle with its seat.
I know this is a lot of stuff to do (if needed) but it's necessary and will make possible trouble-shooting simpler down the road.
These were just some thought that may help you. Talk to you soon.

 

[Anonymous]

Thanks for the info Keith. A couple of questions. The manifold o rings?Are you talking about the rubber boots that go from the carb to the head? And the part # you gave for the Dynojet kit is that what I should use? I saw that they have a stage 3 kit for stock bikes with pipes but I didn't take note of the part #. Your bike is highly modified right?. I'll take a look through the carbs for condition of O rings. I have the carbs off now and the float bowls off and it is obvious that these carbs have been re built very recently. I know the timing is right I have checked and re checked it per the Dyna ignition instructions. I have checked the charging system and need a new regulator/ rectifier. I had planned on replacing the whole system with an Electrex system. It charges and runs okay but when you bypass the voltage regulator it still only puts out about 12v. Will it be neccessary to do that before doing all the jetting. Electrex kits are about $200 and the parts you listed are about $250 so it might be a couple of months before I can do all that. I'm willing to lay out the money if you say it can be done and done right. I'll check the valves although I've got a feeling they'll be okay, I have alot of receipts for maintanence on this bike. Looking forward to this project. Thanks.

 

[KEITH KRAUSE]

The manifolds are between the carb and head. When you take them off you'll see the o-rings in a groove on the engine side of the manifold. Replace (unless you can't see any cracking) and apply some hi-temp' bearing grease to help them last. If you get new Allen bolts to replace those Phillips, torque to 6 ft/lb.
The stage 3 DJ jet kit for your bike is # 3304. It's designed for use with K&N pod filters and a quality pipe.
I bought the Electrex Reg/Rec, part # RR10. It was $110 4 years ago. Just be sure you've got good spark before jetting is what I'm saying. I listed all those things to check because that's how I do things. Not knowing the true condition of your engine I have to mention anything that can effect the re-jetting and make it more difficult. The costs can stack up, but you have to at least check all the things I mentioned and if you have to spend money, that's the price you pay for tuning the engine for more power.
The up side is the money/time spent on re-jetting will make the bike run well and not be too lean or too rich, which would cost you a lot more down the road. There are so many people out there that slap pods and a pipe on a bike, change just the mains 8O , and say "done".